Intertek Testing Services Page 1 of 13 9/28/2010



### North American and European Wood-Fired Boiler Testing Comparison

Rick Curkeet, PE Chief Engineer – Hearth Products

INTRODUCTION

The following is a comparison of EN 303-5 to EPA Method 28 WHH, ASTM

E2618 and CSA B415.1-2010. These are t he currently active standard test

methods for evaluation of emissions and heating performance of hydronic central heating appliances that use wood or other bio-mass (primarily wood based pellets) as fuel.

EN 303-5 is roughly equivalent to t he combined requirem ents of the ASME Pressure Vessel Code for heating boilers, UL or CSA appliance safety standards and EPA , ASTM or CSA Emissions and Efficiency test procedures. This paper will focus only on the emissions and efficien cy related testing procedures in these

standards.

I am not too concerned about issues rela ted to pellet burning appliances. These products are relatively easy to engineer for clean combustion and control of output rate. Control over the fuel feed rate and combustion air have led to very few problems in meeting emissions require ments. I am ther efore confining my comments to manually fuel ed cordwood appliances.

EN 303-5 provides only very general guidance and virtually no detailed procedures or calculations for emissions and efficiency measurements. I think

I understand the basics that are being specified, but it's a very different test than we do under EPA, ASTM or CSA methods. Perhaps there are detailed test methods for emissions measurement proc edures in other documents, but I found no references to such procedures in EN 303-5.

It has already been well documented that t he test methods currently published

have several substantial technical and philosophical differences. The primary philosophical difference is that in NA we tend to try to envision typical or worstcase behavior of the user and design tests to make sure performance is acceptable even when the user does not follow the manufacturer’s recommended operating procedures. The EU standards appear to assume that

users do follow manufacturer’s recommendations closely.

The following is a summary of those tec hnical differences that I believe need to

be addressed. I do not think that it is reasonable to expect that tests run under the EN 303-5 procedure to be comparable or correlate to those obtained from the North American standards currently in use. I, therefore, belie ve that the most expeditious route to inter national compatibility in em issions and efficiency testing of these appliances is the development of a harmonized inter national standard.Intertek Testing Services Page 2 of 13 9/28/2010

Before discussing differences and sim ilarities between EN 303-5 and North American standards, the differences betwe en the three NA standards should be

understood.

NORTH AMERICAN TEST METHODS

First, EPA Method 28 OWHH was issued while the ASTM E2618 standard was in its early development stage. In fact, M28 OWHH was essentially “draft 4” of what ultimately became ASTM E2618. The fi rst published edition of ASTM E2618 was “draft 12” which went through the rigorous ASTM consensus balloting process. There are, therefor e, many differences between the EPA version and the ASTM Standard. Many are minor, but a few are quite significant. These include the use of oak cordwood, measurement of dire ct heat output on the load side of the system and an appendix for testing therma l mass storage units in the ASTM

standard. The EPA M28 OWHH requires the use of oak 4 x 4 cribs, heat output measurement on the supply side 1 of the system and has no thermal mass storage procedure.

CSA B415.1-2010 specifies the use of ASTM E2618 for hydronic unit testing, but modifies the heat output categories and we ighting of the results to be less focused on the lower heat output rate s than the ASTM and EPA methods. Table 1 is a compilation of some of the more significant differences

1 At high output rates load vs. supply side meas urements tend to agree well, but at low output rates the temperature difference (delta-T) betw een supply outlet and return become very small while the load side delta-T gets larger. Since accu rate delta-T measurement is critical, the larger the delta-T, the more accurate the heat output determination for any specific measurement accuracy. In addition, the load side water flow ra te and temperature used to remove heat through a water-to-water heat exchanger tend to be very constant. Supply side water temperature

fluctuates and calibration of the water flow me ter at elevated temperatures adds uncertainty. Thus, load side measurements are significantly more accurate for lower output rates. The loss in the piping between the unit and the heat exchange r should be the only difference between load and supply side outputs and this has be shown to be relatively insignificant due to small surface areas and use of insulated piping.Intertek Testing Services Page 3 of 13 9/28/2010

Table 1

Parameter M 28 OWHH ASTM E2618 CSA B415.1

Fuel Oak 4 x 4 crib – 10

lb/ft 3 Oak Cordwood – *10

or more lb/ft 3 Cordwood w/ sp. g. of

0.6-0.73 – *10 or more
lb/ft 3
Output Rates <15%, 16-24%, 25-

50% and 100% <15%, 16-24%, 25-

50% and 100% <35%, 35-53%,53-76%,

100%

Emissions/ Efficiency Average Weightings **Low- 43.7%

Med Low – 23.8% Med High – 27.5% High – 5% **Low- 43.7%

Med Low – 23.8% Med High – 27.5% High – 5% ***Low – 25%

Med Low – 25% Med High – 25% High – 25% Output

Measurement Delivered at supply

side. Delivered at load

side. Delivered at load side and Overall by Stack

Loss.

Particulate Limits 0.32 lb/MMBtu Del. Output (0.138 g/MJ) Not Specified. 0.137 g/MJ Del. Output.

Thermal Storage Not Addressed Covered for units

with sufficient storage for 100% of fuel load output. Not Addressed directly, but covered by reference
to ASTM E2618.

Fuel M.C. (dry basis) 19-25% 18-28% 18-28%

Coal Bed Weight 10-20% of test load 10-20% of test load 10- 25% of test load

Emissions

Measurement

Method ASTM E2515 ASTM E2515 ASTM E2515

Efficiency Input

Basis HHV & LHV HHV & LHV HHV

Draft Natural w/15’ Height Natural w/15’ Height Natural w/15’ Height

* 10 lb/ft 3 is the default, larger loads are used if specified by the manufacturer. ** Year Round operation weightings as currently required by EPA Voluntary Program (Phase 2). Heat Season Only Weightings are: Low- 17.5%, Med. Low – 27.5%, Med. High – 45%, High – 10%. *** Weightings per B415/EPA NSPS Probability Distributi on if maximum burn rate is less than 5.3 kg/hr.

The ASTM E06.54 subcommittee currently has a task group working on revisions to E2618 which will likely include ha rmonization with CSA B415.1 and the addition of test procedures for appliances linked to remote or partial heat storage systems.

There has been a substantial amount of work done through both ASTM and CSA in the development of c onsensus standards for eval uation of emissions and efficiency performance of wood fire hydroni c heaters. This work included severalIntertek Testing Services Page 4 of 13 9/28/2010

significant research programs to validat e the procedures. Thus, EPA Method 28 WHH should, in my view, be considered obsolete and not be used as a basis for further research testing.

EN 303-5 vs. EPA M28 OWHH, AS TM E2618-09 & CSA B415.1-10

There are many important differences between the method of measuring

emissions between EN 303-5 and t he EPA/ASTM/CSA Standards. These include what is measured, how it’s m easured and how the appliance is operated.

I will not address the sections of EN 303- 5 that deal with safety testing or pressure vessel construction as these have been well documented elsewhere.

(See “Biomass Boiler &Furnace Emissions and Sa fety Regulations In the Northeast States Evaluation and Options for Regional Consistency”, CONEG Policy Research Center, Inc., June 2009.)

WHAT IS MEASURED?

The most obvious difference is that EN 303-5 measures particulate (dust) as only material that is solid at the flue gas te mperature or on a filt er at a temperature that is about the same as the flue gas te mperature ~ 180 oC ( 356 oF). In the NA methods, particulate is measured by t he dilution tunnel method (ASTM E2515)

and includes both solid material and organic compounds which condense to liquid or solid form at temperatures of 20 to 32 oC (68 to 90 oF). Thus, in terms of solid particulate, NA standards collect signif icantly more material than is reported as “dust” per EN 303-5. EN 303-5 does , however, also require measurement and reporting of Organically Bound Ca rbon (OGC) which would exclude the “dust” but presumably include all organic material that passes through the heated

filter. This would therefore include material that remains in gas form at lower temperatures which would not be collected in the NA measurements.

In theory, the relationship between w hat is measured by ASTM E2515 and what is measured by EN 303-5 should look like:

ASTM E2515 = EN 303-5 Dust + EN 303-5 OGC – Non-Condensable Gases,

or,

ASTM E2515 + Non-Condensable Gase s = EN 303-5 Dust + EN 303-5 OGC

Unfortunately, there is considerable ev idence that the production of relative amounts of solid, condensable and gaseous organics from wood combustion is highly variable relative to combustion conditions. Poor combustion tends to produce higher levels of gaseous and condensable hydrocarbons and lower proportions of solids. As combustion im proves, light hydrocarbons (gases) tend to be reduced the most and the proportions of solids and condensables

increases while the total amount decreases . Very clean combustion producesIntertek Testing Services Page 5 of 13 9/28/2010

almost no hydrocarbons and only sma ll amounts of soot – mostly carbon particles. Under some conditions fine as h particles may be entrained in the flue gas stream and contribute to the solid parti culate catch. However, ash particles typically are larger that the PM 2.5 or PM 10 material of most interest in air quality regulation and do not remain sus pended in the air shed for a significant

time. None of the methods I know of provide a method of segregating organic from inorganic (i.e . ash) particles.

I would not expect that it will be feasible to relate the EN 303-5 and ASTM E2515

emissions measurements unless t he procedure include s a means of measurement the “non-condensable gas” propor tion of the overall emissions. I am not aware of any data that would indicate what the re lative proportions of this component of emissions might be or whether the relationship would be

consistent.

I believe that it is well under stood that the term “particu late” as used in air quality management is defined by the measurem ent method applied. That is, “particulate” is essentially what the s pecified measurement pr ocess captures.

METHOD PRECISION

We should not be “getting the cart before the horse” in this proce ss. For any test method that produces quant itative results it is critic ally important to have some idea of the variability or “precision” in re sults that the method produces. This is statistically referred to as Repeatabilit y (within lab) and R eproducibility (between labs). Perhaps this has been eval uated for EN 303-5 and our Swedish colleagues can enlighten us as to the m agnitude of expected variation within and

between laboratories.

Precision is typically evaluated thr ough an Interlaboratory Study (ILS) where multiple labs run replicate tests on ident ical artifacts. A bare-bones ILS requires a minimum of 6 labs, 6 materials or pr oducts representative of the anticipated range of expected results and at least 3 replic ate tests of each. This would result in a minimum of 108 data points wher e each data point would represent one complete test series of each product. It seems clear that funding for a project of this magnitude is unlikely to materialize anytime soon.

Intertek has done some work in several research programs, in support of the ASTM and CSA standards development, on repeatability (within lab) and the

results indicate that variation in result s can be quite significant. It will be very difficult to attempt to quant ify a relationship between test methods if the variability in test results is close to magnitude of the differences in results between the

methods. In statistical terms, one must be able to distinguish between “random” and “systematic” differences. If random vari ability is large, it becomes impossible to determine the magnitude of systematic differences. My best estimate basedIntertek Testing Services Page 6 of 13 9/28/2010

on data available is that repeatability in par ticulate emissions measurements is at best ± 20% and more typically ± 60- 80% of the value reported.

APPLIANCE OPERATION DIFFERENCES

Setting aside the differences in what is measured, the most obvious differences between EN 303-5 and the NA procedures are the differences in appliance operation. Key differences are summarized in table 4.

Table 4

Parameter EN 303-5 M28 OWHH/E2618/B415.1 Emissions Test Output Rate –

Dust/Particulate 100% Four rates from <30% to 100% (Weighted Ave.)

Emissions – OGC Appliance Output Rate for Tests 100% and Mfgr. Specified

minimum no less than 30% (Average or Individual Run compliance not specified) Not measured.

Emissions – CO Appliance Output Rate for Tests 100% Mfgr. Specified

minimum no less than 30% (Average or Individual Run compliance not specified) Measured in B415.1 at 4 output rates but no limit specified.

Efficiency Tests Appliance Output Rate for Tests 100% and Mfgr. Specified

minimum no less than 30% All 4 output rates.

Sampling Time Four 30 minute periods (2 hrs) w/ 2 fuel loads. Full duration of each test.

Sampling location In Stack or D.T. Dilution Tunnel Fuel Load Size Per Manufacturer Specified by Standard

Fuel Moisture 13.6 – 25% 18-25% Efficiency Input Basis Lower Heating Value Higher Heating Value Emissions reporting units mg/M 3 (@10% O 2 ) g/MJ (lb/MMBtu Output) Flue Draught Regulated to specified

maximum. Natural from specified chimney. Coal bed size. Visual judgment 10-20% of test load weight

Test Duration Unclear as a scale is not required. Scale used to determine when

100% of test load is consumed. Heat Storage (Accumulator) Recommended if minimum heat output is > 30% of max. Size calculated, but not

used in tests. If specified, requires test with heat storage. (No current coverage for partial heat storage) Emissions Regulated CO, OGC, Dust ParticulateIntertek Testing Services Page 7 of 13 9/28/2010

FLUE DRAUGHT

Draught regulators (baromet ric dampers) are rarely used on wood burning equipment in North America. A draught limiter can hav e a significant impact on the burn rate profile of the appliances wh ich could in turn affect performance. The requirement to use a dr aught limiter as specified dr aft in EN 303-5 therefore has the potential to alter the burn characteristics and performance when compared to the NA test procedures.

SAMPLING LOCATION

In-stack emissions sampling for small scale wood heating equipment cannot, in my experience, be done accurately. EPA Method 5, from which EPA Method 5H was derived, was developed for industrial and commercial scale systems characterized by relatively constant and high velocity stack flow conditions. This allows for the use of a pitot tube to meas ure flow rate and provides the basis for a reasonably accurate means of setting a known proportional sampling rate.

In smaller scale residential appliances, st ack flow velocities are typically much smaller and quite variable. Flow rate s are often too low to be measured by a pitot tube. Many attempts have been m ade to use other methods to determine stack flow rates. These include inject ion of tracer gases and measurement of dilution ratio in the stack, carbon mass balance calculation based on stack CO

and CO 2 concentrations and fuel carbon content and CO 2 dilution ratio from stack

concentration to dilution tunnel concentration.

When compared to each other, these te chniques virtually always give substantially different results. None has been demonstrated to be accurate. If we cannot accurately measure stack flow rates in real time, we cannot know accurately what proportion of that flow is being collected by the sampling system. And if we do not know what proportion of the flow has be en sampled we do not know what the actual emissions rate really is.

This is the problem that led to the use of a dilution tunnel for emissions
measurement which is now embodied in AS TM E2515 and is used in all recent North American solid fuel appliance emi ssions test methods. Any comparison

between EN 303-5 and North American methods should, therefore, be limited to the dilution tunnel opti on within EN 303-5.

SAMPLING TIME

EN 303-5 (5.9.1.1) specifies emissions co llection for Dust for 4 thirty minute periods over the course of two fuel burning down cycles with the unit operating atIntertek Testing Services Page 8 of 13 9/28/2010

nominal output. If, for ex ample, one fueling results in 3 hours of burning down time, the sampling would occur from w hen the fuel is loaded to 30 minutes, form 90 to 120 minutes, from 180 to 210 minutes (beginning of second fuel load) and

from 270 to 300 minutes. This would resu lt in sampling for 2 hours out of the 6 the unit operates. It would also result in no sampling during the second 1⁄2 hour after fuel is loaded. In my experience this part of a burning cycle is frequently where the most particulate emissions are produced. Thus, EN 303-5 would seem to have the potential to miss a potent ially very significant proportion of the emissions production. In the NA st andards sampling is conducted through the entire burning process and therefore accura tely measures the total emissions produced.

HEAT STORAGE SYSTEMS

By far the most significant operationa l difference is the measurement of particulate emissions only at full output l oad under EN 303-5 (5.7.3). Virtually all wood fired boilers with reasonably we ll design combustion chambers and properly proportion combustion air will pr oduce their lowest emissions and highest efficiency when run at full output load. However, all appliances I have seen must incorporate tem perature limiting controls that substantially reduce combustion air supplies to prevent ov erheating when the heating load is small

and firebox is full. EN 303-5 does reco mmend the use of a heat accumulator (a.k.a. “thermal storage”) to reduce t he potential for the appliance to cycle between high and low combustion rates, but does not specif y testing with the

recommended heat accumulator included.

In the colder regions of the US, the ru le of thumb is that central heating equipment in single family homes will ty pically be called on to provide less than 60% of their nominal output for more t han 80% of the heating season. Output of

more than 80% of the nominal output is typically required less than 3% of the heating season. (See Figure 1 for ASHRAE Bin Data for Ch icago, IL.) This reality leads to some complexity in the proper sizing and use of heat accumulators. A

unit that can sustain its nominal heat output for several hours on a full load of wood will need to store a substantial porti on of its heat output if refueled when the building heat demand happens to be low. To avoid over heating and still burn most of the load on high leads to r equirements for much larger heat storage capacity that is commonly specified or the use of a heat di ssipation system to dump excess heat and prevent over heating. If the user happens to reload the appliance while the heat stor age is already near its uppe r temperature limit, the appliance will quickly go into a cycling mode which may incl ude extended periods of operation at its reduced rate. (See Appendix 1 for an example.)Intertek Testing Services Page 9 of 13 9/28/2010

Figure 1

Assuming that the heat storage provided is adequate, it will cert ainly be true that at normally lower heat demand levels, t he storage will supply the required heat demand for many hours after a fuel load has been consumed. This means that most fires will require a “col d-start”. That is, the user will need to start a new fire

as there will not be a coal bed left from the previous fire. This will certainly have an impact on potential emissions which is not a factor in “hot-to-hot” test cycles. As indicated by typical heat demand dat a, appliances with large heat storage capacity will rarely be operated on a hot-to-ho t fueling cycle with full wood loads.

For a heat accumulator type system, it w ould seem to be imperative to provide

the user with direction on when to fire the appliance. This would typically require a temperature indication of t he heat storage media and inst ructions to fire the unit only when the storage temperatur e approaches the lower recommended operating level. E.g. “Fire unit only w hen the heat storage temperature is below 60 oC.” In reality, it would, of cour se, be acceptable to provide direction that might include fueling with heat storage at higher temper atures using less fuel. Perhaps recommending a half load if t he temperature is 65 to 70 oC.

In general, I do not think standards should be design restrictive. They should be performance based and provide only an appr opriate and accurate measurement process and reasonable performance requi rements. We have already seen ASHRAE BIN DATA -Chicago

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

% of Heating Season% of Nominal LoadIntertek Testing Services Page 10 of 13 9/28/2010

wood fired boilers that achieve remark ably low emissions results over a broad range of heat outputs that do not require heat accumulators. These units are able to modulate heat outputs to matc h applied demand and still burn very cleanly. There may well be many design st rategies that could prove to be as good or better that we do not currently know of. If a regulatory standard requires a specific type of technology, the effect is to stifle innovation and development of potentially even more effective designs . I have no doubt that heat storage systems are effective, but they have an associated added cost and space burden that might be avoided with other solutions.

EMISSIONS RATING UNITS

I believe emissions should be reported in terms of mass per unit of useful heat output – g/MJ or lb s/MMBtu. The mg/m 3 @ 10% O 2 used in EN 303-5 does not provide a readily understood me asurement. It also does not give direct credit to higher efficiency designs. That is, the value would not change if the heat exchange efficiency of an appliance were si gnificantly increased. Emissions in terms of mass per heat output also provi des a basis for fair comparison between wood heating appliances of different types – e.g. room heaters, furnaces, boilers etc. can be compared directly in terms of their impact on air quality versus the useful heat they supply.

EFFICIENCY REPORTING

I am fundamentally opposed to the use of Lower Heat ing Value (LHV) as the basis for efficiency determinations. In North America virtually all fuel burning heating appliances are rat ed for heating efficiency expr essed as a percentage of the fuel’s Higher Heating Va lue. Propane, natural gas and fuel oil all have some hydrogen content and thus also have a difference between higher and lower heating values.

The use of LHV as a basis for efficiency reporting is predica ted on the argument

that latent heat of wate r produced in the combustion process is unrecoverable and thus all that can be transferred is sensible heat. The issue becomes quite

clear if we look at the t heoretical process that would result in 100% efficiency.

Using the Higher Heating Value we could achieve 100% efficiency with complete combustion (e.g. 100% of f uel converted to water and CO 2 ) and simply venting the product into the heated space. All t he available heat would be released and

none would be lost to areas outside the heated space (unvented gas-fired heaters approach this condition). Thus, all the fuel’s Higher Heating Value would be captured. This condition could al so be approached with a vented appliance with sufficient heat exchange capacity to cool the flue gas to close to the ambient room temperature. But water would cond ense in the system in this process.Intertek Testing Services Page 11 of 13 9/28/2010

For a LHV based 100% efficiency we w ould also need to achieve complete combustion and then capture 100% of the sensible hea t, but none of the latent heat. This would mean cooling the flue products back to ambient temperature, but not allowing water to condense. Since the dew point of the flue gases would typically be well over 60 oC, this would be a physical impossibi lity. A unit that was capable of nearly full recovery of bot h sensible and latent heat could, thus, result in an LHV efficiency of more than 100%. This, of course, appears to defy

the first law of thermal dynamics — you cannot get more energy out of a system than goes into it (conservation of energy). While an expert in the subject would

understand that more than 100% efficiency ratings are possible due to the use of LHV, it would seem to be an issue that w ould result in some challenges to the credibility of such ratings.

There is certainly no scientific or physi cal barrier to designing a “condensing” wood fired appliance. There are many condensing gas and oil appliances on the

market with HHV efficiencies that are we ll into the 90% -98% range. It is probably only a matter of time before we see wood-fired appliances that would be

rated at over 100% based on LHV if th is remains the basis for efficiency reporting.

See: Well-to-Wheel Studies, Heating Values, and the Energy Conservation Principle, Ulf Bossel, European Fuel Cell Forum, Morgenacherstrasse 2F CH-5452 Oberrohrdorf / Switzerland, forum@efcf.com, www.efcf.com

29 October 2003 for a discussion of this issue.

OVERALL HEAT OUTPUT

CSA B415.1-2010 includes an effective “Sta ck-Loss” efficiency method that is capable of determining the total heat output from t he appliance – both through the heated water delivery and through radiation and convection directly to the space around the appliance. This is impor tant in that the di rect heating of the space around the appliance constitutes us eful heating in many applications, but wasted heat when the appliance is installed outdoors or in an unheated space. Emissions requirements based on mass per useful heat output should include provisions to determine which heat output should be the basis for the emissions requirement. i.e. “Total H eat Output” for indoor units vs. “Delivered Heat Output”

for outdoor units.

SUMMARY

It is my view that the EN 303-5 procedur es and those currently used by EPA are seriously flawed as well as being inco mpatible. The differences are both philosophical and technical. We do not cu rrently have a completely sufficient test method that is capable of properly m easuring and rating emissions performance for all product types either in the EU or North America. Ho wever, between ASTM E2618, E2515 and CSA B415.1-2010, we do have most of what we need in terms of well developed and carefully defined test procedures. These areIntertek Testing Services Page 12 of 13 9/28/2010

international consensus standards and c an be revised and improved to deal with technical challenges on an on-going basis. I urge consideration of using these forums as a readily available platform for development of international standards.

We currently lack a good understanding of va riability in emissions and efficiency

test results related to all forms of w ood heating equipment. It is clear that the process can be highly variable, but we do not yet have sufficient information to determine how much variability might be controlled or reduced by various technological advances in product design or improvements to test methods.

Research into this area has not been s ubstantial to date and significant funding will surely be needed if we are going to quantify variability and explore methods of reducing it. However, it appears likely t hat a substantial variability is simply inherent in the wood combustion process and results from interactions between

numerous variables that we neither under stand nor can readily control.

It has always been challenging to harmonize product standards used in government regulations on an inte rnational basis. It is cl ear to me that there is virtually zero chance of establishing a simple relationship between EN 303-5 emissions ratings and compliance with regul ations that EPA would likely impose under the forthcoming revised NSPS. That is, if an appliance achieves an emissions rating of “X” under EN 303-5 it would meet a rating of “Y” under the EPA specified procedure or vice versa.

GOING FORWARD

In my view, the way forward must in volve development of new or revised consensus test methods that fully address th e needs of all stakehol ders. I think it will require considerable work to create internationally acceptable standards and

test methods.

There are a few basic principles of per formance test method development that I think must be kept in mind. These are:

 Measure performance that is meaningful.

 Test methods must adequately simulate actual product use.

 Test results must be sufficient ly repeatable and reproducible (i.e. “precise”) to assure that compliance issues can be fairly resolved. (“Validated”).

 Results provided to the end user must be clear and easily understood.

 Procedures must be clearly defined and unambiguous.

 Keep the process as simple as possibl e while allowing as much flexibility as possible.

 The costs of the process must not be so high that they are unaffordable or result in increasing the price of the end products sufficiently to make them non-competitive in the market.Intertek Testing Services Page 13 of 13 9/28/2010

Respectfully Submitted: Rick Curkeet, PE INTERTEK – Chief Engineer



### Appendix 1

EN 303-5 Heat Accumulator

Example:

Unit output (Q N ): 30 kW (102 000 Btu/h) Burn duration at full load (T B ): 3 hours. Total output: 90 kWh (306 000 Btu) Low output rate (Q min ): 10 kW (34 120 Btu/hr) Heat Load (Q H ): = 7.5 kW (25 590 Btu/hr)

EN 303-5 Heat accumulator size: V sp = 15 x T B x Q N (1-0.3(Q H /Q min ))

V sp = 15 x 3 x 30 (1-0.3(7.5/10 )) = 1046.25 l (277 gal., 2306 lbs H 2 O)

Storage Capacity:

Lower Temp. limit: 60 oC (140 oF) Upper Temp. Limit: 90 oC (194 oF)

Heat Storage Capacity: 1046 l x 1 kg/l x (90-60) x 1.1622 Wh/kg-cal / 1000 W/kW

= 36.478 kWh (1046 l x 2.204 lb/l x (194-140) = 124 491 Btu)

At nominal output: 7.5 kW (25 590 Btu/hr) to load, 22.5 kW (76 770 Btu/hr) to storage.

36.478/22.5 = 1.62 hours to upper storage temperature limit.

After 1.62 hours – Output drops to 10 kW . 2.5 kW higher than load. Unit operates in this mode for additional 4. 14 hours. 2.5 x 4.14 = 10.25 kWh (34 973 Btu), or 11.4% of the a ppliance output must be diverted to heat dissipater (wasted).

After fuel is consumed, heat stored will satisfy 7.5 kW load for 4.86 hours before returning to starting temper ature. Total heating time: 10.63 hours

.