NBSIR 87-3656

Research Information Center

National Bureau of Standards

Gaithersburg, Maryland 2 GB >9

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Experimental Plan for

Investigation of Lighting and

HVAC Interactions

Stephen J. Treado

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Physics Division

Gaithersburg, MD 20899

October 1 987

Issued February 1988

Prepared for: U.S. Department of Energy

NBSIR 87-3656

EXPERIMENTAL PLAN FOR

INVESTIGATION OF LIGHTING AND

HVAC INTERACTIONS

Stephen J. Treado

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Physics Division

Gaithersburg, MD 20899

October 1987

Issued February 1988

Prepared for: U.S. Department of Energy

U.S. DEPARTMENT OF COMMERCE, C. William Verity, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
Abstract

This report describes the experimental plan for the investigation of the

interaction of lighting and HVAC systems, including the purpose and scope

of the research, the test facility and instrumentation system, -and the

data collection and analysis procedures. The research focuses on the

relationship between lighting system design and performance, room design,

and HVAC system design for typical office-type construction.

A test facility will be constructed and instrumented to enable variation

of lighting, room and HVAC design. Testing will be performed for various

configurations. The results will be used to develop design guidelines

and modeling procedures, particularly for incorporation into building

energy analysis computer programs.

Keywords

:

building energy performance; cooling load; lighting; thermal performance;

weighting factors

ii
FORWARD

This report is an initial report in a series of reports by the National

Bureau of Standards on the interaction of lighting an HVAC system. The

NBS research was supported by the U.S. Department of Energy (DoE) under

contract No. DE-A1D1-76 PR06010, Task 008, Mod. No. 56.

ACKNOWLEDGMENTS

The author wishes to acknowledge the active encouragement and support

provided by the Department of Energy technical representatives, Mr.

Robert Boettner, Jean Boulin, Carol Gardner and John Ryan.

DISCLAIMER

Any commercial products or tradenames mentioned in this report are included for informational purposes only and do not constitute any

endorsement or recommendation by the National Bureau of Standards.

iii
Table of Contents

Page

1 . Introduction . . : 1

2 . Background . . . 3-

3 . Summary of Experimental Plan 8

4, Design of Test Facility .10

4.1 Physical (Architectural) Design ..10

4.2 Electrical and Mechanical 11

4.3 Selection of Luminaires for Testing ^ 12

5. Instrumentation System. 14

5.1 Measurement Parameters 14

5.1.1 Lighting Power 14

5.1.2 Cooling (or Heating) Load 15

5.1.3 Surface Temperatures 17

5.1.4 Air Temperatures .17

5.1.5 Heat Flows 18

5.1.6 Light Levels 18

5.1.7 Long-Wave Infrared Radiation 18

5.2 Data Collection and Analysis ..18

6 . Testing Procedure 20

7. Calibration and Testing .....21

7.1 Initial Calibration and Testing 21

7.2 Periodic Calibration and Testing .21

8. Testing Schedule 22

9. References ....26

iv
List of Tables

Paee

Table 1. Description of the Six Luminaire Types 13

Table 2. Listing of Variable Parameters ".....22

Table 3. Schedule for Sensitivity Testing ...23

Table 4. Schedule for Primary Testing. . . . . 24

v
List of Figures

Page

Figure 1 . Schematic of Test Facility . .

.- .... 27

Figure 2. Control room roof supports HVAC equipment. ................ 28-

Figure 3 . Test room slabs and steel support frame ................... 29

Figure 4 . Guard air spaces 30

Figure 5 . Access doors .31

Figure 6. Air Handling Unit #1, test room and #2, Guard Air ......... 32

Figure 7. Air Handling Unit #3, lower plenun. ....................... 33

Figure 8. Supply and return ductwork for test room. .34

Figure 9. Electrical plan .35

Figure 10. Schematic of guard air temperature control... .36

Figure 11. Locations of surface temperature measurements.... .37

Figure 12 . Air temperature measurement locations ..................... 38

Figure 13 . Locations of heat flux transducers 39

vi
1 . INTRODUCTION

This project is a combined, cooperative effort between the U.S.

Department of Energy (DoE) , the Electric Power Research Institute

(EPRI) , Dubin-Bloom Associates and Ross & Baruzzini, Inc. (DB-RB);

and the National Bureau of Standards (NBS).

The purpose of this research is to obtain the interaction

characteristics of HVAC and lighting systems by studying the heat

distribution characteristics of various lighting systems in

typical room thermal environments. This is to assist both HVAC

and lighting engineers by developing a database for detailed

lighting heat transfer calculations, to enable analysis of the

components of lighting heat transfer, and to evaluate the

influence of wall and floor construction and HVAC design on lighting and cooling/heating loads.

The research specifically will examine the relationships among

electrical power input, lighting output and cooling load, and the

methods used to determine the air conditioning and heating load

impacts of lighting, so that design professionals can more

accurately quantify the heat from lighting. Improvements in the

quantification of the distribution of energy from lighting (e.g.,

to plenum and occupied space) promotes innovation in controlling

and directing lighting heat. The project team will present

innovative methods for rejecting or using the heat from lights.

Experimental testing will present . a platform whereby HVAC

engineers and lighting designers can work together to consider the

complex interaction between HVAC and lighting systems for various

lighting systems in typical room thermal environments. As a result, illumination engineers will have a quantitative evaluation

of the influence of wall floor, ceiling and fenestration

construction and HVAC design on lighting and cooling/heating

loads

.

The test facility will be designed to allow various testing

configurations and measurements, including the following studies

to be carried out:

o the thermal interaction between light fixtures, room

components, and HVAC systems; and

o the exchange of energy by conduction, convection, and

radiation exchange within the room;

o the performance of the air-conditioning terminal units and

other heating and cooling devices.

o heat transfer by conduction, convection, and radiation

through building envelope sections exposed to a variety of

weather conditions;

1
The research program consists of three basic elements. These are:

1) detailed full-scale measurements of lighting and HVAC

system performance

2) the detailed modeling of test facility

3) the generation of simplified models, algorithms and

guidelines

2
2. BACKGROUND

ASHRAE studies indicate that electric energy consumption in

commercial buildings can range from 25 to 50% of total building

energy use. Since the early 1970' s efforts have been made to

reduce the lighting energy consumption without reducing its

illumination performance, such as the development of high

efficiency ballasts, high efficacy light tubes, and the use of

daylighting.

The heat dissipated by luminaires is a major element of the

year-round cooling load in the building interior zone. It also

provides a major portion of the necessary winter heating energy in

the perimeter zone. Unless the fixture is adequately cooled,

decreases in luminous efficacy and shortened life result. Both

air and water cooled fixtures are available; however, a recommended practice for evaluating performance is available only

for the air cooled type. Since it dominates the market place at

present, the air cooled type will be the focus of this project.

Current cooling procedures can involve the introduction of as much

as 50 CFM of room air or return air into the luminaire. The

efficiency with which the removed heat is applied to the winter

heating requirement, and the effect on cooling loads, Is

influenced by the design of the lighting and HVAC systems. An

optimization design method is needed whereby net annual energy

consumption, illumination performance and peak load performance

are considered. An important element of such an optimization

design procedure is an improved understanding of the heat transfer

from the lighting system.

Hour-by-hour simulation of energy consumption requires

consideration of the fact that heat from the lighting fixture is

dissipated into the air before it adds cooling load in the summer

or reduces the heating requirements in winter.

The heat emitted by the lighting fixture is dissipated in the

following manner:

1 . Part of the heat is released by convection into the air

that either surrounds the fixture or is circulated

through it by means of connections to the ventilation

system.

2. If the heated air leaving the lighting fixture is not

vented into the ceiling plenum space, and eventually to

the central HVAC system, it tends to increase the room

air temperature. Depending upon the mode of the heating

and cooling operation at the time of lighting, this

increased room temperature either activates the cooling

thermostat or deactivates the heating thermostat. In

other words, the heat convected away from the lighting

fixture becomes an instantaneous cooling load.

3
3.

Part of the heat emitted from lighting fixtures is

radiated out to the surface that "see" the light sources.

The heat radiated to the room surfaces in turn can be reflected

back onto other surfaces, where it can be conducted away from the

room, convected back into the room air or stored within the

component. The process is complex and requires detailed heat

balance calculations.

If the outdoor temperature is constant, and if there are no other

heat sources in the room, the cooling load Q approaches the

steady- state Q®, which is equal to the total power supplied to the

lighting fixture P minus the envelope heat loss, or:

Q=o = p - (EUk Ak ATk + G C AT) (1)

where

:

Uk and Ak

ATk

G

C

AT

overall heat transfer coefficient and area

of the k-th surfaces that are exposed to

outside environment,

temperature difference across the k-th

surface

,

the room air leakage

,

specific heat of air, and

temperature difference between indoor and

outdoor air.

The time required for Q to approach the steady- state value Q®

depends upon several factors, such as:

1. air flow rate through or near the lighting fixture,

2. thermal storage characteristics of the surfaces that are irradiated by the light,

3. heat conduction characteristics of the surfaces,

4. radiation heat exchange characteristics of the lighting

fixture

,

5. outdoor temperature, and

6. power density of the lighting systems (watt/sq. ft. of

floor area)

.

If, for example, the heat receiving surfaces are highly conductive

and have a large thermal capacity, it will take many hours before

Q® is reached. On the other hand, if the heat receiving surfaces

are all adiabatic, Q becomes Q® instantly.

The exact treatment of the heat transfer process associated with

the lighting fixture is extremely complex. It involves transient

and three-dimensional convection, conduction, and radiation heat

transfer processes surrounding the lighting fixture. An extensive*

literature search on this and related subjects was conducted by H.

Ball. Among all of the previous work in this area, the most

notable contributions were made by Sowell, Mitalas/Kimura , and H.

4
Ball. While Sowell treated the radiative heat transfer effects in

detail [1], Ball et al. [2] provided detailed and comprehensive

analysis of the transient heat conduction phenomenon. Kimura and

Stephenson [3] , on the other hand, developed a simplified heat

transfer model based on the experimental observation that the

trend for Q to become Q

00 is a simple exponential function.

For example, if there is no envelope heat loss, the relationship

between Q and P may be approximated by:

Q(t) = P [1 - Cj. exp - (C2 t)] (2)

Empirical constants such as and C 2 can readily be determined

from measurements by monitoring the change of Q(t) with respect to

time in a test room. In this expression C 2 represents the rate of

reduction for the quantity P-Q with respect to time and 1-C^

represents the instantaneous cooling load fraction of P when the

lights are suddenly turned on. can be determined by the intercept of the Q vs time t plot at t-0 as follows:

Ci .

P-Q(°)

(3 ) p

While equation (1) is appropriate for predicting the change of Q

with respect to time as long as P remains constant, Mitalas and

Kimura developed an autoregressive relation between time varying Q

and P by introducing three conduction transfer functions, V^, V2 , and w as follows:

Ql = vlPt - A + V2 Pt - 2A + WQt

- A (4)

where P t _A and Pt

_ 2 A indicate power inputs to the lighting fixture

at time t -A and t

- 2A, while Q t and Qt-At are the cooling loads at

time t and t -A, respectively. V]_, V2 , and w are the transfer

functions and can be calculated using and C2 by the following

equations

w = exp (-C2

A

V1 = 1 - exp (InC - C 2 a

) (5)

V2 = 1 - Vi - w

Three sets of these transfer functions were generated by Mitalas

and Kimura by their calorimetric tests [4-7] for typical offices

having "light", "medium", and "heavy" thermal mass and are presented in the 1977 ASHRAE Handbook of Fundamentals.

Ball extended the Mitalas/Kimura sets of conduction transfer

functions by using a computer simulated Q-P relationship [8].

Having those conduction transfer functions available, one can now

determine the cooling load due to lighting while the power input

to the luminaire is changing continuously, in hourly steps.

5
In spite of these notable achievements of previous workers, there

are, however, several shortcomings to the current ASHRAE transfer

function approach:

1. They cannot be extrapolated for specific types of

buildings which may not be similar to the test configurations that were used for the development of the current

data. All of the current measured data were obtained

for an interior office space with no exterior walls.

2. The ASHRAE transfer functions are not suitable for

detailed heat balance calculations. This is especially

true when light heat dissipation is a function of the

luminaire temperature, as is the case for some modern

luminaires [9], and when the time increment for the

dynamic simulation is other than one hour, as is the case

for control simulation.

3. The current transfer function data are unable to account

for energy losses through the building envelope,

especially during the winter. The conduction transfer

function approach inherently assumes that all the heat

dissipated by the luminaire will eventually be picked up

by the room air.

This assumption is the result of another more fundamental

assumption that the instantaneous ratio between the

radiative heat dissipation, Rand the power input to the

luminaire, P is constant

„ R

or = _

P

r-Qo

p

( 6 )

regardless of the environmental condition.

The heat dissipation process of a luminaire having the power input

P can be expressed as radiative heat loss R and convective heat

loss C such. that:

P = R + C (7)

On the other hand R and C can be expressed by:

R = hr A (Tg - Thrt) ( 8 )

C = he A (TB

- Ta ) (9)

hr = radiation heat transfer coefficient,

he = convective heat transfer coefficient,

Tb = fixture surface temperature,

Tj^rt = mean radiant temperature of the environment arouncf

the fixture,

and

Ta = air temperature surrounding the lighting fixture.

6
Equations (7), (8), and (9) can be used to arrive at:

C = 5

1 P h + h

r c

1 +

T - T

MRT A

h

c + h

r TB

- T

MRT

( 10 )

Since

T - T

MRT A

h

r + h

c T

B

T

MRT < < 1

C

1 = h + h

1 +

h + h

r c c r In many instances, is approximated by:

Ci =

hr

hr+hc

which is only valid when Ta = T^rt

T - T

A MRT

T - T

B MRT

(ID

( 12 )

In reality, especially during the heating season, Ta

is considerably different from T^rt* and is also a strong function of outside

temperature T0

.

In order to understand the nature and magnitude of energy flows

associated with lighting systems, and their interactions with HVAC

systems and room design, several issues must be addressed. Of

particular importance are the following.

A. Convective heat transfer from the luminaire to the return

air.

B. Convective heat transfer from the luminaire to the room

air.

C. The distribution of infrared radiant energy from the

luminaire

.

D. The distribution of short wave radiant energy from the

luminaire

.

E. The influence of outdoor air temperature.

F. The influence of air duct design.

G. The effect of wall and floor thermal properties.

H. Luminous efficacy vs luminaire heat balance.

This research will address these issues and develop improved

and/or extended weighting factors or calculation procedures

suitable for annual energy and peak load analysis, as well as for

short-time control simulation, to determine the impact on the HVAC

system due to operation of lights.

7
3 . SUMMARY OF EXPERIMENTAL PLAN

A test facility will be constructed within the large NBS environmental chamber. The test facility will consist of an outer

insulated shell enclosing a simulated office space, with an attached instrumentation room. The simulated office space will

consist of a steel structural frame, and concrete floor and

ceiling slabs, surrounded by guard air spaces for temperature

control. The test room will be configured with or without a plenum space, with an identical configuration below the floor.

Identical lighting systems will be installed in both the test room

and the lower space

.

Conditioning of guard air spaces and test room will be accom- plished using separate fan, cooling coil and electric reheat

systems. The guard air space temperature conditions will be

controlled to maintain zero surface-to-surface temperature

difference across the interior walls of the test room, and

symmetric conditions between the ceiling and floor.

An extensive microcomputer-based data acquisition system will be

used to monitor the various measurement parameters, including

electric power, heat and mass flows, and temperatures. Data will

be collected and stored every two minutes. Preliminary data

reduction will be performed immediately following collection and

suspect data will be flagged and warning messages issued.

The basic test run will consist of suddenly energizing the

lighting system and waiting for steady state conditions to be

achieved or operating the lighting on a daily cycle with steady

periodic conditions. Each test will begin with a period to allow

the room temperatures to stabilize with the lights off. When

steady-state conditions are achieved, the lighting system will be

energized and cooling load monitored until it stabilizes. In the

lighting daily cycle tests, the lights will be energized for a set

period, then turned off for the remaining portion of the day.

This cycle will be continued until steady-periodic conditions are achieved (i.e. until cooling load and surface temperature daily

profiles do not change)

.

The current ASHRAE-type weighting factors can be determined from

the step change test or the first test cycle. Similar factors can

be determined from each successive cycle, although the room temperature conditions will be different for each cycle as the room gradually achieves steady-periodic conditions. The

difference in weighting factors determined from each cycle will be

a useful indicator of the potential variations in lighting and

HVAC performance due to slight variations in room temperature

conditions

.

The relationship between lighting energy and cooling load for

steady periodic conditions will provide the basis for incorporating dynamic lighting system performance within the context of

a room heat balance calculation. When the lighting system is

8
included in the room heat balance, it is usually necessary to

determine lighting energy consumption, which varies with minimum

lamp wall temperature, and the fractions of lighting energy which

end up being emitted as visible light, emitted as infrared thermal

radiation, convected to the plenum, and convected to the room air-.

The direct measurement of each of these components in an actual

installation would be extremely difficult, if not impossible.

However, some of the important elements can be measured, and other

related parameters, particularly surface temperatures, can be

measured and used to verify a numerical model which can in turn be

used to determine the various energy fractions.

Thus, a detailed computer model will be generated and adjusted so that the predicted cooling loads and temperature distributions

match those observed experimentally. The model will include

detailed radiant and convective exchange calculations.

9
4. DESIGN OF TEST FACILITY

The test facility was designed to emulate an office space with one exterior wall, surrounded on the other -five sides by similar

spaces. Details of the architectural, electrical and mechanical

design are contained in the following sections.

4.1 Physical (Architectural ) Design

The test facility will be constructed on a slab 30 ft. 6 in. by 21

ft. 4 in., within a large environmental chamber. The facility is

divided into two sections, a large insulated shell enclosing the

test room, and a smaller attached control room for housing

instrumentation, as shown in Figure 1. The overall height of the

facility is 20 ft. 10-1/2 in. , while the control room ceiling

height is 13 ft. 2-1/2 in. The roof of the control room serves as

a platform to support some of the HVAC systems (see figure 2)

.

The test room, which is within the insulated shell, consists of

floor and ceiling slabs on steel decking, supported by a steel

framework. The space below the floor slab will be operated

identically to the test room (i.e. both will have same plenum and

lighting configuration) (see figure 3)

.

Initially, the test room will have four interior walls,

constructed of drywall and framing. One interior wall will be

removed to reveal an exterior wall part-way through the testing

schedule. The opposite sides of each of the test room walls will

face guard air spaces (see figure 4)

.

One of the guard air spaces will have the capability of being

operated to simulate exterior conditions. Also, large access

doors between one guard air space and the chamber can be opened to

allow the use of the environmental chamber to provide the exterior

temperature conditions, and to allow the use of a solar simulator

to incorporate solar effects. Smaller access doors will

facilitate entry into the side and top guard air spaces, as shown

in figure 5. A door will connect the test room/guard air portion

of the facility to the control room, with steps leading from the

test room height to the floor of the control room. All of the

instrumentation and control equipment will be housed in this

space. Chilled water for cooling and electric power will be

obtained from the environmental chamber hookups.

The construction specifications call for extreme care in

assembling the test room, particularly regarding air tightness,

uniformity and insulation concerns. The test room will be as air

and vapor-tight as possible, as will the exterior insulated shell.

All doors will have gaskets and all joints will be sealed.

Measures for verifying air tightness are detailed in the calibration section of this plan.

10
Thermal bridges between the test room and the guard air spaces

will be minimized, sealed, and insulated. Special attention will

be given to the structural elements such as the slab-frame

interface

.

4.2 Electrical and Mechanical

The electrical and mechanical systems in the test facility are essentially similar to typical office building systems, except

that there are three air handling units servicing several small

spaces. Each of the major air handling systems consists of a fan,

a chilled water cooling coil and electric reheat unit. The main

system serves the test room, and has a variable speed fan.

Temperature control is achieved through electric reheat. Room air

temperature will be the control parameter for the test room air

handling system. The other air handling systems serve the guard

air spaces. Their temperature control is described below.

Details of the HVAC systems are shown in figures 6, 7 and 8.

The electrical system is essentially standard except for extensive

sub-metering of fan, lighting and reheat power consumptions.

Pulse generating watt-hour meters will be used to monitor electrical usages. Six different luminaire types will be available for

testing, as listed in table 1. Figure 9 shows the electrical

plan.

The temperature of the guard air will be controlled to maintain

equal surface temperatures on both sides of each* wall. Temperature control will be accomplished using electric reheat, with

separate control for each wall. The equal surface temperature

condition simulates an adjacent identical room. In such a case,

there would be no net heat flow through an interior wall, but heat

storage in the wall could occur.

Multi- junction thermopiles will be used to measure the average

temperature difference across each wall, producing a voltage

proportional to temperature difference. This voltage signal will

serve as input to a Proportional Integral Derivative (PID)

controller which will vary heat addition to the supply air through

electric reheat. The system is shown schematically in figure 10.

The temperature control for the ceiling and floor slabs is

slightly more complicated, however the control strategy remains

basically the same as for the walls.

The main difference between the interior walls and the ceiling and

floor slabs is that net heat flow can and does occur through the

slabs. Net heat flow occurs because the thermal conditions on the

bottom of the ceiling are different from the conditions on the top

of the ceiling, since the top of the ceiling is really just

another floor surface. A floor surface is exposed to the downward

fraction of the lighting energy and the room air flow and temperature conditions, while the bottom of the ceiling frequently is

contained within a plenum space, and sees the upward fraction of

11
the lighting energy. However, vertical symmetry can be obtained

by controlling the surface temperature of the top of the ceiling

to match the measured floor surface temperature, which is floating

with test conditions. The average temperature difference between

the top of the ceiling and floor surface will be measured with a multijunction thermopile, the output signal being used to drive a PID controller regulating the level of electric reheat for the top

guard air space.

In a similar manner, the temperature of the bottom of the floor

(the ceiling of the lower plenum) is controlled to match the

bottom of the test room ceiling, which is floating with test

conditions. It should be noted that each of the thermopiles will

be measuring the average temperature difference between two

surface without regard to any variations in temperature across the

plane of each surface. This does not present a particularly

serious problem for the interior walls, since their surface

temperatures will not vary vary rapidly or through a wide range

spatially. However, variations in temperature can be expected on

the floor and ceiling slabs due to the lighting systems. It is

for this reason that a duplicate, identical lighting system will

be installed in the lower plenum space. This should provide

essentially the same temperature distributions in both slabs.

All of the ductwork will be sealed and insulated. All

penetrations due to electrical and mechanical systems will be

sealed.

4.3 Selection of Luminaires for Testing

A representative selection of luminaire types has been made in an attempt to enable evaluation of the critical design parameters

while covering the broad range of potential design options. This

initial selection of luminaires is intended to address the primary

objective of the overall research program, that of the evaluation

of the performance of commercial office lighting systems, thus the

evaluation will initially focus on fluorescent luminaires, with

various mounting and air- flow configurations.

Table 1 contains a description of the six luminaire types

initially selected for testing:

12
Table 1

LI 2' x 4' Fluorescent Fixture; 4 lamp, recessed',

combination troffer, static and air handling;

ballasts, high power factor, rapid start;

diffuser, acrylic, .125 inches thick; with

lamps; with side slot closures, and heat removal

dampers; with written directions for alternate

operations; Lithonia 2 GCD440-ACS, 120 volt.

L2 1' x 4' 2 lamp Fluorescent Fixture; similar to LI

L3 2' x 4' Fluorescent Fixture; similar to LI except with

3" parabolic louver, air pattern control blades,

and heat removal dampers ; Lithonia 2PM3GCD440

L4 1

' x 4' 2 lamp Fluorescent Fixture similar to L3

L5 2' x 4' Fluorescent Fixture; wrap around diffuser,

acrylic; with 4 lamps; ballasts same as LI; with

surface and stem mount hardware; Lithonia LB 440

or equal

L6 1' x 4' Fluorescent Fixture, 2 lamp, similar to L5

13
5 . INSTRUMENTATION SYSTEM

The instrumentation system serves three basic purposes, namely

data collection, data analysis and experimental control. A

microcomputer-based data acquisition system will be utilized to

execute the testing, collect and store the data and to perform

initial data analysis. It is possible that some or all of the

data will be transferred to a main frame computer for subsequent

processing, if that seems useful. Most of the data analysis will

be performed on a microcomputer dedicated to that use.

The testing revolves around two primary variables, cooling (or

heating) load and lighting power. The traditional ASHRAE-type

weighting factor approach is based on determining the relationship

between cooling load and lighting load following a step change in

lighting load, with all other environmental conditions remaining

constant. The ASHRAE method is also based on the assumption that

all of the lighting energy eventually becomes cooling load, thus

not accounting for heat gain or loss through exterior wall or window. The ASHRAE method primarily accounts for heat storage in

the floor and ceiling slabs.

The current measurements will allow determination of lighting and

cooling relationship for a variety of HVAC and exterior conditions, but the primary variables will still be cooling load and

lighting energy. Many other measurements will be made to support

the primary measurements, to characterize the test room conditions

and for model validation. Where possible, redundant measurement

systems will be implemented.

The measurement sensors will be connected to a data acquisition

system under the control of a network consisting of three microcomputers. The data acquisition system will perform signal

conditioning and analog- to-digital conversion form, while the

microcomputers will process, store and analyze the measured data.

Initial data processing will involve built in checks for data

accuracy and experimental system performance. Additional

real-time processing will include computation of ASHRAE-type

weighting factors and other statistical information related to the

testing results.

5 . 1 Measurement Parameters

5.1.1 LiEhting Power

This is one of the primary measurement parameters and, fortunately, one of the easier measurements to make accurately.

Lighting power consumption will be measured using pulse-generating

watt-hour meters, sized to produce about one count per 10 seconds.

Both lighting energy usage, the total number of counts in an

interval, and instantaneous lighting power, the pulse rate, can be

determined to within one percent.

14
5.1.2 Cooling (or Heating) Load

This is the second primary measurement parameter, one which

presents more difficulties than the measurement of lighting power.

Within the context of this testing program, room cooling load

represents the energy which must be extracted from the room,

including plenum space, in order to maintain the desired temperature condition. Of course, if heat must be added to the room the

load is actually a heating load; however, for simplicity the term

cooling load will be used to describe the room thermal load.

The determination of cooling load requires the measurement of more

than one variable, and can be accomplished in several ways, each

with its own advantages and disadvantages. One method would be tb

measure the supply and return air flow rates , and the temperature

change of the air between the supply and return. Then, the change

in enthalpy of the air could be calculated using the appropriate

thermal property data, according to:

Qc = h = m Cp AT

where

:

Qc = room cooling load

Ah = enthapy change

m = mass flow rate of air

Cp = constant pressure specific heat

AT — temperature change of air

This method will be the primary means of determining room cooling

load. Since the room is airtight, except for supply and return

air, then the air flow rate need be measured only at the supply.

The temperature change between the supply and return air will be

measured using multijunction thermopiles, located at the room

boundary. An additional thermopile will be used to measure air

temperature change within the plenum, when a plenum is used. The

ratio of these two measurements will indicate the percentage of

heat pickup above the plenum.

Multij unction thermopiles of Type T (copper-constantan) wire can

be designed to be very sensitive when many junctions are used. In

addition, the multiple junctions allow measurements over a large area to determine the true average temperature difference.

Air flow rate will be measured using a commercially available

anemometer, consisting of a flow straightener and thermister

15
array. The stated uncertainty of the sensor is less than three

percent. The sensor output is a voltage signal which is proportional to mass flow. The mass flow rate can be determined from:

M = Av

where

:

A = flow area

v = mass flow velocity

The instantaneous cooling load due to lighting, Ql, is determined

by subtracting any other heat sources from the room load Q^.

thus

:

Ql =Qc - Qe ' Qi

where

:

Qe = heat gain from exterior

Qj = heat gain from interior equipment

As a supporting measurement the product mCp for the supply air

will be determined by measuring the temperature rise AT of the

air across the electric reheat unit, according to:

mC

p = JL

AT

where

:

E = heat addition by electric reheat

The product mCp can be determined from measurement during fairly

stable conditions. Thus, room cooling load can be determined by

two direct measurement methods. A third method will also be used, one which provides additional information about the system

performance. This third method is based on cooling coil load at

the water-to air heat exchanger in the test room air circulation

loop. The heat extracted from the return air by the cooling coil

consists of heat gain from lighting and electric equipment, heat

gain through exterior surfaces , heat gain from lighting and

electric equipment, heat gain through exterior surfaces, heat gain

from the circulation fan and heat gain from the electric reheat.

16
Thus, under steady state conditions,

Qcc = Ql + Qe + Qi + Qf + Qr + Qd

where

:

Qcc = cooling coil load

Qp = heat gain from fan

Qp = heat gain from reheat

Qp = duct heat gain

The cooling coil load can be determined from measurement of water

flow rate and temperature rise across the heat exchanger,

accounting for thermal storage effects. The other electric heat

sources, Qj , Qp and Qp, will be measured with pulse-generating

watt hour meters. Then Ql can be determined from

Ql = Qcc ~ Qe ~ Qi ~ Qf ' Qr “ Qd

provided that Qp is known. Initially, Qp will be zero. During

subsequent tests under summer and winter conditions, Qp will be

measured using heat flow meters. Duct heat gain will be small,

but a correction for the effect can be made from a combination of

temperature and heat flow measurements.

5.1.3 Surface Temperatures

Extensive measurements will be made of surface temperatures

throughout the test facility. The measurements will serve three

purposes. First, they will allow the characterization of the test

conditions, supporting the basic measurements. Second, they will

be used to generate and validate the computer simulation models.

Third, they will allow real-time diagnosing of control system

performance

.

Temperature measurements will be made using type T thermocouples,

whenever precision temperature difference measurements are needed,

multijunction thermopiles will be used.

Since the test room is symmetric about an axis in the center of

the room normal to the window wall, temperatures and heat flows

should be nearly equal in the east and west halves of the test

room. Thus, detailed measurements only need to be made over one half of the test room. Figure 11 shows the locations of the wall,

floor and ceiling thermocouples. Only two luminaires need to be

measured. Each will be instrumented with 16 thermocouples,

distributed on the fluorescent tube and fixture.

5.1.4 Air Temperatures

Thermocouples will be used to measure room air temperature’

distribution, according to figure 12. Temperature will be

measured at four heights at each location. Radiation shields will

be used to minimize radiative coupling. Additional air tempera17
ture measurements will be made throughout the guard air spaces and

the air handling systems.

5.1.5 Heat Flows

Heat flow at the interior surface of the test room envelope will

be measured using heat flux transducers. These transducers will

be located as shown in figure 13. Each transducer develops a low-level dc voltage proportional to heat flow at the measurement

location. Total heat flow through each component of the room envelope will be determined by suitable area-weighted averaging of

the individual measured heat flows.

5.1.6 Light Levels

The illuminance incident upon each room surface will be measured

with photovoltaic silicon cells. Single cells will be permanently

located at the center of each surface. An additional movable

array of cells will be used to evaluate illuminance distributions.

5.1.7 Long-Wave Infrared Radiation

The long-wave radiant energy incident upon each room surface will

be measured using pyrgeometers . Thermographic imaging equipment

and spot radiometers will be used to evaluate radiant interchange

conditions and temperature distributions for different luminaire

designs

.

5.2 Data Collection and Analysis

Measurements will be recorded at two minute intervals for the

entire set of measurement parameters. The recorded value will

consist of the average of ten equally spaced readings during the

two minute interval, for a twelve second sampling interval. Each

twelve second reading will be computed as the average of a number

sequential measurements. Error detection and correction programs

will be used to improve measurement accuracy.

A few important parameters will be stored at twelve second

intervals for modeling, control and analysis purposes. These

parameters include lighting power, cooling load, minimum lamp wall

temperature and room air temperature.

Each measurement input will be checked for accuracy and to verify

proper operation of the sensor and data acquisition system. This

checking will involve intercomparisons of related measurement

parameters, and checks against theoretical constraints. Any

anomalous data will be flagged and an error message will be issued

to the control monitor and automatically recorded in the testing

log.

Each test will consist of up to a week of measurements. The data

recorded for each test will be stored individually on magnetic

media for subsequent processing. Real time data analysis will

18
include the calculation of ASHRAE-type weighting factors during

each daily cycle, heat balance analysis of lighting/room system

and other heat transfer calculations.

'

.

19
6 . TESTING PROCEDURE

The general testing procedure consists of initially establishing a set of wall and lighting conditions. That configuration would

then be tested by operating the lighting on a step change of

cyclic schedule until room thermal loads and temperature

conditions achieve steady periodic state. At that point, one or more of the design parameters will be changed and the new

configuration will be tested as before. While testing continues,

previously collected data will be analyzed.

The list of variable parameters includes the following:

o luminaire type

o air flow configuration

o interior wall type

o exterior condition

o carpeting

o lighting schedule

o electric equipment load

o furnishings

o constant or variable air volume

o floor mass

Some of these parameters are easily altered, such as lighting

schedule or electric equipment load. Others, such as interior

wall type, are difficult to change, so changes will be made only

infrequently.

20
7. CALIBRATION AND TESTING

Several calibration procedures will be utilized, both during

shakedown testing and periodically as required.

7.1 Initial Calibration and Testing

The initial testing efforts will be aimed towards verifying air

tightness of the test room, ducts and insulated shell, and

locating any thermal bridges or construction defects. Once any

problems are identified, corrective action will taken. Air

tightness will be measured using sulfur-hexafluoride (SFg) tracer

gas measurements . The leakage rates for each air zone and air

handling system will be measured. Thermographic imaging equipment

will be used to search for thermal anomalies. Air flow rates and

distributions will be measured in each of the zones.

The control systems will be set to maintain steady-state conditions, so that an overall heat-balance analysis can be performed

on the test room, both with lights on and off.

The measurement transducers will be calibrated before installation, and their performance will be rechecked periodically. The

primary calibration efforts will involve the air flow sensor,

electric power meters, heat flux transducers and water flow meter.

7.2 Periodic Calibration and Testing

Real-time analysis of the measurement data will help the identification of sensor malfunctions. The flow sensors and electric

meters will be periodically recalibrated. Additional air tight- ness measurements will also be performed periodically.

21
8 . TESTING SCHEDULE

Testing will begin following the completion of the test facility

construction. An initial period of four months will be used for

calibration and shakedown testing. This will also provide a chance for some sensitivity testing and analysis. Due to the

large number of potential test configurations, only a small

percentage of configurations can be tested, so it is important

that the test configurations be chosen so that the significant

effects of each important variable can be evaluated. Thus, during

the sensitivity and shakedown testing, each easily varied

parameter will be varied at least once from baseline conditions.

The following table contains a listing of each variable parameter,

including an identification code for reference in the testing

schedule variation of parameters.

Table 2 Listing of Variable Parameters

Parameter Code

1. Luminaire type

o 2 x 4, 4 lamp, recessed LI

o 1x4, 2 lamp, recessed L2

o 2 x 4, 4 lamp, parabolic L3

o 1x4, 2 lamp, parabolic L4

o 2 x 4, 4 lamp, surface L5

o 1 x 4, 2 lamp, surface L6

2. Supply Air

o ceiling SI

o luminaire S2

3. Return Air

o ceiling plenum, no duct R1

o ceiling plenum, with duct R2

o luminaire, no duct R3

o luminaire, with duct R4

o high sidewall, no plenum R5

4. Walls

o four foil covered foam W1

o four interior drywall W2

o three interior drywall, one exterior curtain W3

o three interior block, one exterior block W4

5. Exterior Condition

o none El

o summer E2

o winter E3

22
6. HVAC

o constant air volume HI

o variable air volume H2

o fan coil unit H3

7. Floor

o 2-1/2" concrete, bare FI

o 2-1/2" concrete, carpet F2

o 4" concrete, bare F3

o 4" concrete, carpet F4

Due the necessary construction changes, option W4 (block walls)

will not be undertaken until all other testing is completed, and

options F3 and F4 will also be deferred.

Also, the fan coil unit tests (H3) will be run following the other

numerous HVAC design combinations.

\ Four months time has been allotted for calibration and shakedown

testing. This should allow for about 12 sensitivity tests. This

testing will allow for preliminary analysis of the sensitivity of

the measurements to the variable parameters, while at the same

time allowing tuning and adjustment of the various control and

data collection systems. Table 3 presents the schedule for

shakedown testing.

Table 3. Schedule for Sensitivity Testing.

Test Number Configuration Code

1 LI, si, Rl, Wl, El, HI, FI

2 L2, SI, R2

,

Wl, El, HI, FI

3 LI, si, R3, Wl, El, HI, FI

4 LI, si, R4, Wl, El, HI, FI

5 LI, si, Rl, Wl, El, H2

,

FI

6 LI, si, R2

,

Wl, El, H2

,

FI

7 LI, SI, R3, Wl, El, H2, FI

8 LI, si, R4, Wl, El, H2

,

FI

9 L3, si, Rl, Wl, El, HI, FI

10 L3

,

si, R2

,

Wl, El, HI, FI

11 LI

,

si, Rl, Wl, El, HI, F2

12 LI, S2

,

Rl, Wl, El, HI, FI

The schedule for the primary testing will depend in part on

results of the sensitivity testing and related computer simulations and indeed on the results obtained from the initial primary

testing. An optimistic testing schedule would call for about 50

tests, each lasting roughly a week. Given this target, table 4

lists a tentative schedule for the primary testing.

23
Table 4. Schedule for Primary Testing

Test Number Configuration Code

1 L2

,

SI, Rl, Wl, El, HI, FI

2 L5

,

SI, R5

,

W2, El, HI, FI

3 L5

,

SI, R5

,

W2, El, H2

,

FI

4 L5

,

SI, R5

,

W2

,

El, HI, F2

5 L5

,

SI, R5, W2, El

,

H2

,

F2

6 L2

,

SI, Rl, W2, El, HI, FI

7 L2

,

SI, R3

,

W2

,

El

,

H2

,

FI

8 L2

,

SI, Rl, W2, El, H2

,

FI

9 L2

,

SI, Rl, W2, El, HI, F2

10 L2

,

SI, Rl, W2, El, H2

,

F2

11 L2

,

SI, Rl, W3

,

E2

,

HI

,

FI

12 L2

,

SI, R2

,

W3

,

E2

,

HI, FI

13 L2

,

SI, R3

,

W3

,

E2

,

HI, FI

14 L2

,

SI, R4

,

W3

,

E2

,

HI, FI

15 L2

,

SI, Rl, W3

,

E2, H2

,

FI

16 L2, SI, R2

,

W3, E2, H2

,

FI

17 L2, SI, R3

,

W3

,

E2, H2

,

FI

18 L2, si, R4

,

W3

,

E2

,

H2

,

FI

19 L4

,

SI

,

Rl, W3, E2

,

HI, FI

20 LA, SI, R2

,

W3

,

E2

,

HI, FI

21 LA, si, R3

,

W3, E2

,

HI

,

FI

22 LA, SI

,

R4, W3

,

E2

,

HI, FI

23 LA

,

si, Rl, W3

,

E2, H2

,

FI

24 LA, SI, R2

,

W3

,

E2

,

H2

,

FI

25 LA

,

SI, R3

,

W3

,

E2

,

H2

,

FI

26 LA, si, R4, W3, El, H2

,

FI

27 L2

,

si, Rl, W3

,

E2

,

HI, F2

28 L2

,

si, R3

,

W3, E2

,

HI, F2

29 L2 , SI, Rl, W3

,

E2

,

H2

,

F2

30 L2

,

si, R3

,

W3

,

E2, H2

,

F2

31 LI, SI

,

Rl, W3, E2

,

HI, FI

32 LI, si, R3

,

W3

,

E2

,

HI, FI

33 L3, si , Rl, W3, E2, HI, FI

34 L3

,

SI, R3

,

W3

,

E2

,

HI

,

FI

35 L4

,

si, Rl, W3

,

E2

,

HI, F2

36 L4

,

si, R3

,

W3

,

E2, HI, F2

37 L4

,

si, Rl, W3, E2

,

H2

,

F2

38 L4

,

si, R3

,

W3, E2

,

H2

,

F2

39 L2, si, Rl, W3

,

E3

,

HI, FI

40 L2

,

si, R2

,

W3, E3

,

HI

,

FI

41 L2

,

si, R3

,

W3, E3

,

HI, FI

42 L2

,

si, R4

,

W3

,

E3

,

HI, FI

43 L4

,

si, Rl, W3

,

E3

,

HI, FI

44 LA

,

si, R2

,

W3

,

F3

,

HI, FI

45 L4

,

si, R3

,

W3, E3

,

HI, FI

46 L4, SI, R4, W3, E3, HI, FI

47 L2

,

si, Rl, W3

,

E3

,

HI

,

F2

48 L2

,

si, Rl, W3, E3

,

H2

,

F2

49 L2

,

si, R4, W3

,

E3

,

HI, F2

50 L2

,

si, R4, W3, E3

,

H2

,

F2

24
As is seen from the preceding schedule, the changeover to block

walls is not included in the first 50 configurations. This is

because such a changeover involves disassembling the gypsum walls

and building the block walls in place, thus preventing anymore

tests with drywall. This construction work will prevent testing

during the changeover, and it is felt that the wall change should

be delayed as long as possible. If necessary for contractural

reasons, the wall changeover could be moved up, at the expense of

testing time.

25
9. REFERENCES

1. Sowell, E. , "A General Model for the Transport of Lighting

Thermal Power," California State University.

2. Ball, H. , Green, D. , "The Impact of Lighting Fixtures on Heating and Cooling Loads - Mathematical Model," ASHRAE

Transactions, Vol. 89, 1983.

3. Kimura, K. , Stephenson, D. , "Theoretical Study of Cooling

Load Caused by Lights," ASHRAE Transactions, Vol. 74, Part

II, 1968.

4. Mitalas, G., "A Calorimeter to Determine Cooling Load Caused

by Lights," ASHRAE Transactions, Vol. 77, Part II, 1971.

5. Mitalas, G. , "Transfer Function Method of Calculating Cooling

Loads, Heat Extraction and Space Temperature," ASHRAE

Journal, Vol. 14, No. 12, Dec. 1972.

6. Mitalas, G. , "Cooling Load Caused by Lights," Transactions of

Canadian Society for Mechanical Engineering, Vol. 2, No. 3,

1973.

7. Mitalas, G., "Calculating Cooling Load Caused by Lights,"

ASHRAE Journal, Vol. 15, No. 6, June 1973.

8. Ball, H. , "The Impact of Lighting Fixtures on Heating and

Cooling Loads - Application to Design," ASHRAE Transactions,

Vol. 89, 1983.

9. Siminovitch, M. , Rubinstein, F. , Clark, T. , Verderber, R. , "A

Luminaire/Plenum HVAC Simulator," Proceedings IEES-IAS,

Conference, Toronto, Oct. 1985.

26
Lighting/HVAC

Test

Facility

Figure 1. Schematic of Test Facility

t 27

Floorslab
A jhIj L©Jn1 SI t

• h

' t- ? i» st *» r

1 \\

^-VlftRATlON

ISOLATORS

Figure 2. Control room roof supports HVAC equipment

28
Figure 3. Test room slabs and steel support frame

29
Figure 4. Guard air spaces

PLAN

VIEW

OF

LIGHTING

TEST

FACILITY
Figure 5. Access doors

31
Figure 6. Air Handling Unit #1, test room and #2, Guard Air.

32

TEST

ROOM

PLAN
33
1

1

1

s

M H~

ot

o;

r

•- •

*4

-

" s' t

. \

' s'

. \

0

• B- S

^

i

^

J ^

34

^

0H 1 r

L ,\kk

Figure 8. Supply and return ductwork for test room

34
/toes' « ausauafe vwi S *»* |w> «

J*(lUwV*» Mrvc# 1#' <•&*.

a^-1

!*• I .%> c^A, AtfftC. feo* ^ «^«9»4s f^r i» «a#f

C-STf MOniu^J C«M»Tm

©* »l»viCt BiW W MU# CnACK BAfc&T •©»wt •» au*

^Stayr.gjgy- H£tS>

^±gjf r* — “*

cfac^a clacks Jeiacifsclacks

(suT*IJ /v /y mm r<* ue Af jfTtr)**»rT ** i

<*M» Ml a^*6

ii>llaMICi MW« TO J»»

•uqjuf nrtfr 1 1 aqtol (M.1 1) UarfuU i* 4 < «7^0P M M>«*% U,Maj.t US •«« mCTtl ’4J6

I MUU «,»?&=, 6=©ffl

tu»»<« aU, «•«’» storsos Welusn U««n ^uU teuTM •u%r8au«Jr >Nrtf IM' nr aSuBM W»*#

^•uhm wane <es ^rfuct 'to'UAT'®** uarj »fc <T*n* ®*>.y (s^l i/

s A*W

’4*±k> M4L4W6 ««M «%*?»« TO 3&

*V\MBLCItfMl«i4

yMMH

la±HHliriIl

POWER R'SEtt PiAGCAH

»»*\‘>

Figure 9. Electrical plan

35
CONTROL

OF

GUARD

AIR

TEMPERATURE

5

tt

Figure 10. Schematic of guard air temperature control

36

•

Thermopile

Junctions

Thermopile

output

Is

dc

voltage

fmvl

proportional

to

average

temperature

difference

across

wall
West Watt • •

Figure 11.

• •

North Wall • •

Floor

• • •

East Watt

South W*

• Measurement Station

Locations of surface temperature measurements

37
Figure 12. Air temperature measurement locations

38
Figure 13. Locations of heat flux transducers

39
NBS-1 14A (rev. 2®0C

)

U.S. DEPT, OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NB S I R 8 7 - 3 6 5 6

2c Performing Organ. Report No

3. Publication Date JANUARY 1988

4.

TITLE AND SUBTITLE

5.Experimental Plan for Investigation of Lighting and HVAC Interactions

AUTHOR(S)

Stephen J. Treado

6.

PERFORMING ORGANIZATION (If joint or other than NBS, see in struction s)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7c Contract/Grant No.

8. Type of Report & Period Covered

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

National Bureau of Standards

Gaithersburg, MD 20899

10.

SUPPLEMENTARY NOTES

_

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200~word or less factual summary of mdst significant information. If document includes a significant

bibliography or literature survey, mention it here) This report describes the experimental plan for the investigation of the interaction

of lighting and HVAC systems, including the purpose and scope of the research, the

test facility and instrumentation system, and the data collection and analysis

procedures. The research focuses on the relationship between lighting system design

and performance, room design, and HVAC system design for typical office-type

construction .

A test facility will be constructed and instrumented to enable variation of lighting room and HVAC design. Testing will be performed for various configurations. The

results will be used to develop design guidelines and modeling procedures,

particularly for incorporation into building energy analysis computer programs.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) building energy performance; cooling load; lighting; thermal performance; weighting

factors

13. AVAILABILITY

Uni i ml ted |~] For Official Distribution. Do Not Release to NTIS

[~~] Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

' 20402. K

! Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

47

15. Price $11.95

USCOMM-DC 6043-P80