# Presentation: 233798

## HVAC Provisions

*Mick Schwedler, PE *
*The Trane Company*
*Member, SSPC 90.1 **Mechanical Subcommittee*

## HVAC Section

- 3 paths to compliance ...
- Simplified approach
- Mandatory plus prescriptive
- Mandatory plus ECB

*There’s more ...*

**Notes:**
The HVAC (Heating, Ventilating and Air-Conditioning) section provides three different paths for compliance. There is a simplified approach, satisfying mandatory plus prescriptive requirements, and The Mandatory plus Energy Cost Budget” approach. We’ll discuss the first two in some detail.
The ECB method is a computerized method to arrive at an “Energy Cost Budget” for a base building. Your proposed building must have an energy cost budget equal to or less than the base building. Because of time, we will not be discussing the ECB method in this broadcast.
Let’s look at the other available paths.

## Simplified Approach

- Limited Scope
- Same requirements
- Fits on two pages

**Notes:**
The Simplified Approach was included so that small buildings could comply with the standard with minimal effort, but be subjected to the same stringency as is in the rest of the standard. Since the requirements fit on two pages it is ideal for a small commercial building. The committee included this simplified approach because 80 to 85% of the building stock is this type of building. 

## Simplified Approach (Cont’d)

- Limited to ...
- Buildings with 1 or 2 stories
- Buildings less than 25,000 ft2
- Single-zone system
- Air-cooled or evaporatively cooled only

**Notes:**
The simplified approach is restricted in the size of building allowed, building zoning and air conditioning system type. 
The building must be 2 stories or less and less than 25,000 square feet. 
Each system must serve a single HVAC zone — for example, the face of a building. Minimum equipment efficiency is still a requirement. The equipment must also be air-cooled or evaporatively cooled. An equipment example is a single zone rooftop.

## Simplified Approach (Cont’d)

- Requirements
- Economizer as necessary
- Heat pump, fuel-fired furnace, electric resistance, or baseboard/boiler for heat
- OA < 3000 cfm and 70%
- Manual changeover or dual set-point thermostat

**Notes:**
The simplified approach also defines limits which, when exceeded, necessitate economizers. 
The heating type selection is fairly broad. 
Outdoor air must be less than 3000 cfm and 70% of the supply air quantity. Therefore heat recovery requirements are not a part of the simplified approach. 
To minimize the possibility of simultaneous heating and cooling a change over or dual setpoint thermostat is required.

## Simplified Approach (Cont’d)

- Supplemental heat controls on heat pumps
- No reheat for humidity controls
- Night setback controls
- Piping and ductwork insulated

**Notes:**
If heat pumps are used they are required to have controls that use the heat pump to satisfy heating loads if possible. This keeps the system operating at its most efficient point.
If humidity is being controlled directly by using reheat the simplified approach may not be used.
There are also requirements for night setback and insulation.

## Simplified Approach (Cont’d)

- Balancing within 10% of design airflow rates
- Interlocked thermostats if heating and cooling equipment are separate
- Exhaust > 300 cfm, gravity or motorize dampers
- System > 10,000 cfm, optimum start controls

**Notes:**
Balancing of the system is required in accordance with industry accepted practices. 
If there is separate heating and cooling equipment the thermostats must be interlocked to prevent simultaneous heating and cooling.
Either gravity or motorized dampers are required once exhaust reaches 300 cfm and optimal start controls are required above 10,000 cfm. 
It is important to remember that the simplified approach has the same stringency as the rest of the standard, they have just been put on two pages for single-zone air- or evaporatively-cooled systems. In doing this the committee had to balance simplicity (fewer pages) with which requirements to include. Therefore some systems, such as those requiring heat recovery or water cooled systems are not included in the simplified approach.
Now let’s move on to the mandatory plus prescriptive requirements.

## Mandatory Requirements

- Requirements address ...
- Equipment efficiencies
- Controls
- Construction and insulation
- Drawings, manuals, and commissioning
- Required in both prescriptive and ECB compliance paths

**Notes:**

The standard’s mandatory requirements address the subjects shown here. We’ll look at all of these mandatory requirements individually.  Remember that whether you choose the prescriptive or ECB compliance “path” the mandatory requirements must be met. 

## MandatoryEquipment Covered

- Packaged air conditioners
- Heat pumps
- Chillers
- Packaged terminal/room air conditioners
- Furnaces
- Boilers
- Heat rejection equipment

**Notes:**
Shown here are several of the HVAC equipment types with minimum requirements in the standard. It’s obvious that most of the heating and cooling equipment that is installed in normal applications is covered. The efficiency tables that list these requirements have two columns:
One column identifies those requirements that took effect when the standard was published. The other column shows requirements, usually more stringent, that take effect on October 29, 2001. (This gives manufacturers lead time to design, develop and retool plants to produce higher efficiency equipment.)
It’s also very important to understand that pieces of equipment that are not listed have NO requirements. For example, there are no testing standards in place for engine driven chillers. Since they are not rated and tested, the committee put no requirement for them in the standard. They may still be used.

## MandatoryEquipment Examples

_**Equipment**__**	**__**Present**__**	**__**    10/29/2001**_
**15-ton rooftop**	8.5 EER		9.7 EER
**300-ton WC** 	5.20 COP		6.10 COP
**centrifugal** 	5.30 IPLV		6.10 IPLV

**Notes:**
This slide gives two examples of required equipment efficiencies. Note the two columns we just discussed. The first  is the existing efficiency. For those pieces of equipment previously covered under 90.1-1989, the numbers have not changed. For pieces of equipment that were not covered under the 1989 standard the minimum efficiency requirement is generally blank.
The second column is the efficiency requirement beginning October 29, 2001.
So the rooftop efficiency requirements increased 14% and the large chiller requirements over 17%.
 Note that for a water cooled centrifugal chiller over 300 tons this coefficient of performance (COP) equates to  0.576 kW/ton at ARI standard rating conditions.

## MandatoryEquipment Covered for the First Time

- Ground-source heat pumps
- Single- and double-effect absorption chillers
- Heat rejection equipment
- New categories for
- Hot water and Steam boilers
- Replacement PTAC’s, PTHP’s

**Notes:**
Several types of equipment didn’t previously have efficiency requirements, some of them are shown here.
Ground source heat pumps, absorption chillers, cooling towers and air-cooled condensers. There are also new categories for some boilers and a separate efficiency requirement for replacements of packaged terminal air conditioners and heat pumps.
Generally the stringency isn’t as high for equipment being covered for the first time. 
During the public review process, extensive work went on with the heat rejection equipment manufacturers and ASHRAE’s technical committee on Cooling Towers to ensure the new efficiency requirements were reasonable.

## MandatoryLoad Calculations

- Only requires calculations to be done
- No longer a sizing restriction

**Notes:**
Load calculations are required to be performed using “...generally accepted engineering standards and handbooks acceptable to the adopting authorities (for example, ASHRAE Handbook -- Fundamentals).”
Another difference from the 1989 standard should be noted. It allowed a load safety factor of 10%. To give designers latitude, for example when expansions are planned, there is no longer an oversizing restriction.

## MandatoryThermostatic Controls

- Required for each zone –perimeter can be treated differently
- 5° F deadband
- Dual setpoint or deadband(can be software for DDC)

**75**

**Notes:**
Thermostatic controls are required for each zone, although the perimeter can be treated differently. There’s a very good example of its treatment in the User’s Manual. If I may digress, the User’s Manual is a very valuable companion to the standard. It answers many of the common questions people pose and also gives good examples of common usage.
There is also a thermostatic requirement for the capability to have a 5 F deadband, that is the difference between when cooling takes place and heating takes place. This can be met by mechanical means or through software. 

## MandatoryOff-Hour Controls> 65,000 Btuh and 3⁄4 hp

- Automatic shutdown via
- Automatic time clock w/10 hour battery back up, or
- Occupancy sensor, or
- Manually-operated timer w/max. 2 hr duration, or
- Interlock to security system

**Notes:**
Once a system reaches 65,000 Btuh and 3/4 horsepower of fan off-hour controls come into play. These controls can be initiated using a time clock, occupancy sensors, manual override or even be interlocked with the security system so that when people leave, sections of the system may be turned off to reduce energy consumption.
One confusion noted during the public review process is that some people felt that ALL of these off-hour controls were required. That’s not true. The standard states that at least one of the off-hour control strategies listed on the slide must be available. 

## MandatoryOff-Hour Controls> 65,000 Btuh and 3⁄4 hp (Cont’d)

- Setback, except radiant floor or ceiling
- Optimum start if > 10,000 cfm

**Notes:**
There are exceptions for setback of radiant heating systems. This is because it can be hard to bring the space up to requirements because of large pickup or pulldown loads.
Another requirement is that optimum start is required above 10,000 cfm. Optimal start can be a complex algorithm that “learns” from building operation how long it takes to bring a building to its setpoint in the morning. Alternatively it can be as simple as controls that begin the warmup (or cooldown) two hours prior to the building being occupied and ramping the temperatures appropriately.

## MandatoryOff-Hour Controls (Cont’d)

- Shut-off dampers controls
- Zone isolation
- Isolation area maximum 25,000 ft2 zone size on one floor
- Ability to shut off airflow to isolation area
- Central systems capable of stable operation for smallest isolation area

**Notes:**
During off-hours, there needs to be the capability to reduce the airflow in a system. This is so that the entire air conditioning system doesn’t have to function to satisfy a small area of the building. As an example, we have a large building and one person comes in to work. The entire building shouldn’t have to be conditioned to provide comfort to that one person. This zone isolation is required once an area of 25,000 square feet is exceeded on a single floor
As it can be seen we need to be able to reduce airflow and be able to stably operate at these reduced airflows.

## MandatoryHeat Pump Auxiliary Heat Control

- Heat pump with internal electric heaters need to use heat pump alone when load can be met
- Exception for NAECA products

**Notes:**
If a heat pump is being used, and it has internal electric heaters, the first source of heat needs to be the heat pump, rather than the resistance heat. This is because the COP of a heat pump can be in the range of 3 or higher.
There is an exceptions for NAECA equipment where the rating already includes the electric resistance heating.

## MandatoryConstruction & Insulation

- Leakage tests(>3 in. w.c.)
- Piping insulation
- Duct insulation

**Notes:**
There are specific requirements for insulation. They are dependent on where the pipe or ductwork is located (in the conditioned space, in an attic, etc.) and also the climate. In addition, the insulation needs to be able to hold up to its environment. If it’s outside, it must hold up to the sun, rain and other elements.
Some of the insulation requirements are actually lower than those required in Standard 90.1-1989. This is because the 1999 standard is based on cost-effectiveness.
There are also system sealing levels with leakage tests required on ducts where the static pressure is intended to operate in excess of 3” w.c.

## MandatoryCompletion Requirements

- Drawings
- Manuals
- Operating
- Maintenance

**Notes:**
It’s important that the design team’s knowledge and intent is actually passed to the building owner. Drawings, manuals and a narrative of the intended system operation are required to be delivered within 90 days of construction. This can really help the building owner and operator to run the system as it was intended to be run. If you think of it, this should be done on all jobs, because if the system isn’t run properly, energy won’t be saved.
There are also balancing requirements that are mandatory once certain thresholds are reached. Let’s look at them.

## MandatoryCompletion Requirements (Cont’d)

- Balancing
- Written report conditioned spaces > 5000 ft2
- Measured and adjusted within 10% of design
- Airside > 1hp – except calibrated VAV
- Hydronic pumps > 10 hp

**Notes:**
Balancing is required once the conditioned space is greater than 5000 square feet. This means that the system flows must be measured and adjusted within 10% of design.
There is an exception as shown.
The balancing requirements take effect if the airside is greater than 1 hp or the water side is greater than 10 hp. 

## MandatoryCompletion Requirements (Cont’d)

- Commissioning
- Control elements calibrated, adjusted and in working order
- > 50,000 ft2 requires commissioning plan (Appendix E)

**Notes:**
System commissioning is also required once the building area exceeds 50,000 square feet. Commissioning as used here is to make sure the system is calibrated, adjusted and working. It is the designer’s responsibility to provide detailed instructions so that proper commissioning can be performed. 
All of the requirements we’ve just discussed are mandatory. 

Let’s now discuss the Prescriptive path. Remember that if you are using this path you must comply with the mandatory requirements as well as the prescriptive requirements.

## Prescriptive

- Requirements address ...
- Economizers
- Simultaneous heating and cooling
- Air system design and control
- Hydronic system design and control
- Heat rejection equipment control and limitations
- Heat recovery
- Exhaust hoods

**Notes:**
If you want to use the prescriptive path, all prescriptive requirements must be met. Here’s a thumbnail sketch of what’s entailed: They
Require economizers in specified climates.
Limit how much simultaneous heating and cooling can be done.
Restrict fan power based on nameplate horsepower.
Provide specifications for hydronic system design and control.
State heat recovery requirements for systems with large amounts of outdoor air.
Reduce energy consumption in kitchen or fume exhaust hoods.
Let’s look at each or these requirements in more detail.

## PrescriptiveEconomizers

- Climate and size dependent
- Numerous exceptions
- Including efficiency trade-off
- Integrated control
- High limit controls are climate dependent
- No increase in heating

**Notes:**
Economizers are not required in all climates. In fact, the requirement is both size and climate dependent. It is a function of local humidity and number of hours during which an economizer would be effective. For example, Denver, CO must have an economizer once system capacity reaches 65,000 Btuh, Chicago requires one above 135,000 Btuh and New Orleans, LA has no economizer requirement.
There are also numerous exceptions including:
Systems with condenser heat recovery
Systems that operate less than 20 hours per week
Supermarket systems
Where the equipment efficiency has been increased.
Integrated control is a requirement. That means that the economizer and mechanical cooling must be able to operate simultaneously.
The control types vary depending if it’s a humid (>73F wb), Intermediate (69-73 wb, < 100 db) or dry climate (<69 and db <75 or >=100)
The designer may select either an air or water economizer. If an air economizer is selected it must be able to handle the entire system airflow.
For all economizers, there is a requirement to not increase the heating energy in the system. In effect, this does not allow systems such as single-fan double-duct, since they can greatly increase the heating energy usage.

## PrescriptiveEconomizers (Cont’d)

- Waterside economizers allowed w/
- Performance requirement
- Limited pressure drop effect

**Notes:**
If a waterside economizer is chosen, it must satisfy the loads when ambient conditions are 50db/45wb. If the waterside coil pressure drop is >= 15 feet, the economizer must be “bypassed” when it is not being used. Many designers and manufacturers already pipe the economizer this way. Remember, that a waterside economizer must be piped so that mechanical cooling can operate at the same time. Again, the User’s Manual gives a great example of one way to accomplish this.

## PrescriptiveSimultaneous Heating and Cooling Limitation

- Limits recooling, reheating or mixing of air
- 0.4 cfm/sf or 300 cfm/zone or min ventilation
- Hydronic systems
- Three pipe not allowed
- Two pipe changeover control
- Water loop heat pump systems controls

**Notes:**
There are limits on simultaneous heating and cooling. Note that reheating or recooling (in the case of a desiccant system) are NOT banned, just limited.There are also exceptions based on the zone airflow. 
For example the system much reduce it airflow .4 cfm per square foot, 300 cfm or the zone’s minimum ventilation before reheating or recooling with new energy is allowed.
However, if 75% of the reheating or recooling is done with site-recovered or solar energy, there are no limits.
Three pipe hydronic systems are no longer allowed, and in a two pipe system there must be a deadband and time delay of four hours between the temperatures at which heating and cooling of the loop take place. 
Hydronic heat pump systems need to have two position valves when pump power is > 10 hp.

## Dehumidification

- Humidistatic controls shall prevent
- Reheating
- Mixing of hot and cold air streams
- Heating and cooling of same air stream

**Notes:**
When humidistatic controls are being used to directly control space humidity it also makes sense to reduce the amount of reheat, mixing of hot and cold air streams or heating and cooling the same air stream. 

As in the “normal” reheat, there are a number of exceptions

## Dehumidification Exceptions

- Systems capable of reducing supply air flow to 50%, or to min. ventilation
- Systems under 6.67 tons that can unload at least 50%
- Systems smaller than 3.3 tons
- Process applications
- 75% of reheat or recool energy is recovered or solar

**Notes:**
The exceptions are shown on the slide. For most units, there must be a way to reduce either airflow or cooling capacity. Small units less than 40,000 Btuh are also excepted.
The process applications include uses such as computer rooms, museums, surgical suites, supermarket, refrigerated warehouses and ice arenas.
Again if 75% of the reheat or recool energy is recovered or site solar, any amount may be used.
These are the requirements. What might they mean to a designer? In my opinion the reduction of new energy reheat will lead designers to use heat recovery more often. One option is condenser heat recovery. This might be from a chiller’s condenser bundle or its auxiliary heat recovery condenser, or from a heat recovery refrigerant coil in a direct expansion system.

## PrescriptiveAir System Design and Control

- Fan system power limitation
- Applies to systems > 5 hp
- Limits based on nameplate hp of fans
- Cold air, relief fan and some pressure credits available

**Notes:**
There are fan power limitations. They are different depending on system size (above or below 20,000 cfm) and system type -- constant or variable volume. As an example, a VAV system delivering 25,000 cfm allows 1.5 horsepower per 1000 cfm -- or 37.5 horsepower.
One change from the 1989 standard is that now the fan power limitation is based on nameplate hp. The committee increased the allowable power to account for the fact that we can’t pick a fan with a 22.8 hp nameplate motor.
There are also credits available for filtration above 1”, relief rather than return fans, or using cold air distribution systems.

## PrescriptiveAir System Design and Control (Cont’d)

- VAV fan control for motors 30 hp
- Provide for 30% design wattage at 50% air volume
- DDC: Fan Pressure Optimization

**Notes:**
It should also be noted that with fan motors 30 hp and above in a VAV system, the part load power consumption must be as shown. At 50% of design airflow the fan must consume 30% or less of its design wattage. Most people feel this will lead to using variable frequency drives (VFD’s) or vane axial fans. Some feel that other fan types may be able to reach these power levels.

Finally, for VAV systems with direct digital control (DDC), fan pressure optimization is required. This means that the control system must look at the box requiring the most static pressure and reset the fan’s control point so that that “critical” box is almost fully open. In this way the pressure the fan is working against is optimized at each point in time. This requires coordination between the VAV boxes, the fan and the DDC system.

## PrescriptiveHydronic System Design and Control

- Variable flow required for systems
- > 75 total hp
- More than 3 control valves
- Performance req. for pumps >               100 ft head, > 50 hp
- 30% design wattage at 50% flow

**Notes:**
Variable water flow is required in systems with pump power greater than 75 hp with more than three control valves.
If an individual pumps is designed to operate at 100 feet of head and draws 50 hp, it is required to operate at 30% of its design wattage when flow is at 50%.
Again, many feel that this will lead to designers using variable frequency drives.

## PrescriptiveHydronic System Design and Control (Cont’d)

- Pump isolation for chillers or boilers piped in parallel
-  provide for flow reduction when one of multiple chiller or boilers is  shut down

**Notes:**
Basically pump isolation says that when a chiller is turned off, the pumping power must be reduced. This can be done by turning pumps off or reducing the flow rate some other way, such as reducing the speed of a variable speed pump. The same reduction applies for boilers.
For this section chillers piped in series are treated as a single chiller.

## PrescriptiveHydronic System Design and Control (Cont’d)

- Chilled and hot water resetfor > 300,000 Btu/h, exceptions:
- Result in improper operation
- Variable flow systems

**Notes:**
Chilled and hot water reset is required once the system size exceeds 300,000 Btuh (for cooling, that’s 25 tons.) However reset is not required for variable flow systems (where it doesn’t make sense) or if the reset will cause improper operation (e.g., poor dehumidification).

## PrescriptiveHeat Rejection Equipment

- Fan speed control for motors 7.5 hp and up

**Notes:**
In addition to efficiency requirements for heat rejection equipment, there are also prescriptive requirements.
Once a cooling tower fan reaches 7.5 horsepower it needs to have a way to reduce its speed to 2/3 or less. This could be pony motor, a two speed fan or variable frequency drive. There are exceptions.

## PrescriptiveHeat Rejection Equipment (Cont’d)

- Exceptions
- Condenser fans on multiple circuits
- Condenser fans on flooded condensers
- Very warm climates
- 1/3 of the fans on a multiple fan application speed controlled

**Notes:**
As an example, if you have 3 tower cells, at least two of them need something such as pony motors, half speed control or VFD’s to reduce their speed.
Other exceptions are shown, either for specific equipment configurations or in very warm climates. Most of these exceptions were included in response to comments during the public review process.

## PrescriptiveEnergy Recovery

- Airside
- 70% OA and 5000 cfm total
- 50% effectiveness
- Condenser recovery for service water heating if
- 24 hrs per day **and**
- Heat rejection > 6 MMBtuh **and**
- SWH load 1 MMBtuh

**Notes:**
Heat recovery with 50% effectiveness is required on the airside when individual fan systems have 5000 cfm and at least 70% outside air. So if a makeup air unit is being added to a system it is likely that heat recovery will be required. Again there are exceptions.
One exception that I’d like to point out is that if the largest exhaust airstream is less than 75% of the outdoor airflow, heat recovery is not required. For example, if there are many small exhaust sources in a building and none of them is 75% of the outdoor airflow, the designer is not required to bring them all together. However if there is a single, large exhaust source, it makes sense to recover its heat.
Condenser heat recovery for service water heating is required where there are simultaneous heating and cooling loads all day and where those loads are fairly sizeable.

## PrescriptiveExhaust Hoods

- Kitchen hoods makeup air req. if > 5,000 cfm
- Fume hood systems > 15,000 cfm
- Operation to < 50% design flow or ...
- Direct make-up at least 75% of exhaust rate at specified conditions or ...
- Heat recovery for make-up air

**Notes:**
Kitchen hoods above 5000 cfm require 50% make up air that is untreated or only heated to 60F.  
Fume hoods require part load operation capabilities, the use of untreated air for make-up purposes or heat recovery for the make up air. In the case of using heat recovery the effectiveness needs to be 50%.

## PrescriptiveRadiant Heating

- Req. for unenclosed spaces except loading dock w/ air curtain

**Notes:**
Heating for unenclosed spaces (such as the outdoors) requires radiant heating to be used. One exception is that on a loading dock an air curtain may be used instead.

## PrescriptiveHot Gas Bypass Limitation

- > 7.5 tons
- Multiple steps or continuous unloading

- 	Rated Capacity		Max. Hot Gas 						Bypass Capacity 					(% of Total Capacity)
-  240,000 Btu/h (70 kW)			50%
- > 240,000 Btu/h (70 kW)			25%

**Notes:**
There is also a limitation on hot gas bypass -- it’s based on system size. This applies to systems over 7.5 tons. Note that the hot gas bypass limitation applies to packaged units and chillers.

## Service Water Heating

- Equipment Efficiency
- Insulation
- Service water heating system controls

**Notes:**
Service water heating equipment has efficiency, insulation and control requirements.

## Service Water Heating (Cont’d)

- Pool heaters and covers
- Prescriptive for
- Space and water heating
- Service water heating

**Notes:**
There are also requirements for pool heaters and covers. In addition, there are prescriptive requirements depending on whether the heating is combined (for water and space) or is only for service water heating.

In the past 30 minutes we’ve tried to give a thumbnail sketch of the mechanical section requirements. Since time was limited it’s obvious that we couldn’t mention all the requirements. We also didn’t have time to go into many of the exceptions available to designers. It’s important for you to examine the standard and review the User’s Manual if you have particular questions or concerns.
A final word. The Mechanical Subcommittee was made up of designers, code officials, users and manufacturers with practical experience. Not only did we look at requirements from a theoretical standpoint, but also tested those requirements against the  on-the-job knowledge of the committee members. We also worked with many commenters during the public review process to make the standard more practical, easier to use and more clear. We thank those who took the time to comment and improve the standard for ASHRAE and IESNA.
With that said, we’ll attempt to answer your questions.