demonstration of tankless water heaters in army family ... · temperature. tankless water heaters...

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FEAP-TR-FE-93/11 REPORT November 1992 FACILIES ENGINEERING APPLICATIONS PROGRAM AD-A262 413 Demonstration of Tankless Water Heaters in Army Family Housing D"TIC ,/IAN?, Z,'3 .1993 by Lee A. Edgarons / U.S. Army Construction Engineering Resear :h Laboratoies Champaign, IL 61826-900b IL. Approved for Public Release; Distribution Is Unlimited. 0.4-a Qooq co•s 93-05850 Fort Belvoir, VA 22060-5516 9& i ) 9 8 3 y. •v Ideas for, the Opiwltion, Mainteonance, I; Repair of Army Fai:rl Itie

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Page 1: Demonstration of Tankless Water Heaters in Army Family ... · temperature. Tankless water heaters provide several advantages over conventional water heaters. Since tankless water

FEAP-TR-FE-93/11 REPORTNovember 1992

FACILIES ENGINEERINGAPPLICATIONS PROGRAM

AD-A262 413

Demonstration of Tankless WaterHeaters in Army Family Housing

D"TIC,/IAN?, Z,'3 .1993

by

Lee A. Edgarons /U.S. Army Construction Engineering Resear :h Laboratoies

Champaign, IL 61826-900b

IL.

Approved for Public Release; Distribution Is Unlimited.0.4-a

Qooq co•s 93-05850

Fort Belvoir, VA 22060-5516

9& i )

9 8 3 y. •v Ideas for, the Opiwltion, Mainteonance, I; Repair of Army Fai:rl Itie

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The contents of this report are not to be used for advertising, publication,or promotional purposes. Citation of trade names does not constitute anofficial endorsement or approval of the use of such commercial products.The fir~dings of this report are not to be construed as an officialDepartment of the Army position, unless so designated by other authorizeddocuments.

DESTROY THIS REPORT WHEN IT IS NO LONGER NEEDED

DO NOT RETURN IT TO THE ORIGINATOR

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USER EVALUATION OF REPORT

REFERENCE: USACERL FEAP Technical Report FE-93/1 1, Demonstration of Tankless Water Heatersin Army Family Housing

Please take a few minutes to answer the questions below, tear out this sheet, and return it to USACERL.As user of this report, your customer comments will provide USACERL with information essential forimproving future reports.

1. Does this report satisfy a need? (Comment on purpose, related project, or other area of interest forwhich report will be used.)

2. How, specifically, is the report being used? (Information source, design data or procedure,management procedure, source of ideas, etc.)

3. Has the information in this report led to any quantitative savings as far as manhours/contract dollarssaved, operating costs avoided, efficiencies achieved, etc.? If so, please elaborate.

4. What is iour evaluation of this report in the following areas?

a. Presettation:

b. Comp eteness:

c. Easy t• Understand:

d. Easy to Implement:_

e. Adequa e Reference Material:

f. Relates to Area of Interest:_

g. Did the report meet your expectations?_

/

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i. General Comments. (Indicate what you think should be changed to make this report and futurereports of this type more responsive to your needs, more usable, improve readability, etc.)

5. If you would like to he contacted by the personnel who prepared this report to raise specific questions

or discuss the topic, please fill in the following information.

Name:

Telephone Number:

Organization Address:

6. Please mail the completed form to:

Department of the ArmyCONSTRUCTION ENGINEERING RESEARCH LABORATORIESATTN: CECER-IMTP.O. Box 9005Champaign, IL 61826-9005

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. EREPORT DOCUMENTATION PAGE Form ApprovedOMB No. 070"-188

Public reporing WidJen for this colleodion of information is estirrated to ave-age I hour per responsa, including the time for reviewing instructions, searching airsing data sources.gathering and maintaining the data needed, and comnpleting and reviewing the collection of information. Send comments regarihng this burden estimate or any other aspect of thiscollection of information,. jitclud, ng suggestions for reducing this burden. to Washington Headquarters Services, Di rectorate for information Operations and RW. Is. 1215 Jecfferson

Davis Highway, Suits 1204. Arlington• VA 22202-4302. and to the Offica8 of Management andl Sudget. Paperwork Redluction Project 10704-0188). Washingtor OC 20503.

1. AGENCY USE 0O.NLY (Leave Blank) 1 'REPORT DAr'Eoem r 1992 13. REPORT TYPE AND DATES COVERED~ia

4. TITLE AND SUBTITLE 5. FUNDING NUMBERSDemonstration of Tankless Water Heaters in Army Family Housing

FEAP6. AUTHOR(S)

Lee A. Edgar

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATIONREPORT NUMBER

US Army Construction Engineering Research Laboratories (USACERL) FEAPPO Box 9005Champaign, IL 61826-9005 TR FE-93/11

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORINGAGENCY REPORT NUMBER

US Army Engineering and Housing Support CenterATTN: CEHSC-FU-MFort Belvoir, VA 2206-5580

11. SUPPLEMFNTARY NOTESCopies are available from the National Technical Information Service, 5285 Port Royal Road,Springfield, VA 22161

12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE

Approved for public release; distribution is unlimited.

13. ABSTRACT (Maximum 200 words)

Tankless water heater technology is used widely thrughout Europe and Japan to reduce the amount of energy required to produce a steady supplyof hot water. Because this technology does not employ a water storage tank, standb) heat losses are avoided, saving up to 25 percent of the energyconsumed by conventional water heaters. The U.S. Army Construction Engineering Research Laboratories (USACERL) demonstrated two types oftankless water heaters in Army family housing at Fort Sill, OK, through the Facilities Engineering Applications Program (FEAP). U.S.-made gasand electric tankless water heaters were laboratory tested, and five units of each type were installed in 10 similir residences. Five new conventionalg.s water heaters and five new conventional electric units were installed in another 10 residences for comparison. All demonstration units wereevaluated for (1) ability to provide a safe, steady supply of hot water and (2) energy costs.

The only U.S-made tankless gas water heater available for the demonstration was a unit designed for commercial applications. Initial resultsdemonstrated that the unit tended to overheat water at low flow rates, making it unable to provide a safe supply of hot water. No further data onthe unit were collected.

The tankless electric water heater provided a safe, sustained hot water supply, but the flow rate was lower than desirable. The average energy costfor the tankless unit was about 26 percent lower than for the conventional electric water heater. However, the tankless electric water heater requireda costly electric service upgrade for each residence in which it was installed, and one unit malfunctioned early in the demonstration. Theconventional gas water heater provided the most economical hot water of all units demonstrated, and no safety or performance problems wereobserved.

14. SUBJECT TERMS 15. NUMBER OF PAGEStankless water heater electric water heater 28FEAP gas water heater 1s. PRICE CODE

17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATICN 20. LIMITATION OF ABSTRACTOF REPORT OF THIS PAGE OF ABSTRACTUnclassified Unclassified Unclassified SAR

NSN 7540-01-280-5500 SWad Formn 298 (Rev. 2-MPresorae byANSI Sid 239-18211-102

• .• ' ... , :- •-• :• ... • " -

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FOREWORD

This research was performed for the U.S. Army Engineering and Housing Support Center(USAEHSC) under the Facilities Engineering Applications Program (FEAP) work unit "Tankless WaterHeaters." The USAEHSC technical monitor was B. Wasserman, CEFSC-FU-M.

The work was performed by the Fuels and Power Systems Team (FEP) of the Energy and UtilitySystems Division (FE), Jnfrastructure Laboratory (FL), U.S. Army Construction Engineering ResearchLaboratories (USACERL). The team leader is Gary Schanche, CECER-FEP. Dr. David M. Joncich isChief, CECER-FE. Dr. Michael J. O'Connor is Chief, CECER-FL. The USACERL technical editor wasGordon L. Cohen, Information Management Office.

Appreciation is expressed to Kevin Heyen and Daiva Tamulaitis for assistance in performing tests.

COL Daniel Waldo, Jr., is Commander and Director of USACERL, and Dr. L.R. Shaffer isTechnical Director.

Accesion For

NTIS CRA&IlDTIC TAB1Unannounced LJJustification..............

D BY ution'........................ ..................

Distribution~Availability Codes

Avail aiid/orDist Special

DTIC QUAIXl Ini"•-"2EC.. D I

2

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CONTENTSPage

SF 298 1FOREWORD 2LIST OF FIGURES AND TABLES 4

INTRODUCTION .................................................... 5BackgroundObjectiveApproachScopeMode of Technology Transfer

2 DESCRIPTION OF WATER HEATERS USED IN DEMONSTRATION ........... 7Conventionar Water HeatersThe Hot Box Tankless Electric Water HeaterThe Hotomatic Tankless Gas Water Heater

3 INSTALLATION OF DEMONSTRATION UNITS .......................... 10Laboratory InstallationField Installation

4 WATER HEATER EVALUATION ...................................... 14Laboratory TestingField TestingData Collcrtion and Analysis

5 SUMMARY ....................................................... 23

METRIC CONVERSION FACTORS 23

ABBREVIATIONS AND ACRONYMS 24

DISTRIBUTION

3

-yf

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FIGURES

Number Page

I The Hot Box Tankless Electric Water Heater 8

2 The Hotomatic Tankless Gas Water Heater 9

3 Laboratory Setup for Tankless Electric Water Heater II

4 Laboratory Setup for Tankless Gas Water Heater 1

5 Family Housing Area at Fort Sill 12

6 Field Setup for Demonstration Water Heaters 13

7 Water Temperature versus Flow Rate for Laboratory Test of Hot Box 15

8 Power Consumption versus Flow Rate for Laboratory Test of Hot Box 15

• 9 Water Temperature versus Flow Rate for Laboratory Test of Hotomatic #3 16

10 Discharge from Hotomatic Temperature-Pressure Relief Valve 17

I I Original Flow in Upstairs Shower, Residence 2072N 18

12 Reduced Flow in Upstairs Shower Due to Hot Box, Residence 2072N 18

13 Damaged Wires on Hot Box Installed at Residence 2071N 19

14 Effect of Changing Gas Prices on Cost of Heating 100 Gallons of Water WithStandard Gas Water Heaters at Fort Sill 22

15 Effect of Changing Electricity Prices on Cost of Heating 100 Gallons of Water WithConventional and Tankless Electric Water Heaters at Fort Sill 22

TABLES

Hot Water Consumption and Energy Data for 20 Fort Sill Residences,November 1991 to January 1992 20

2 Costs of Heating 100 Gallons of Water 21

4

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DEMONSTRATION OF TANKLESS WATER HEATERS IN ARMY FAMILY HOUSING

1 INTRODUCTION

Background

Tankless water heater technology has been available for several years, and is used widely throughoutEurope and Japan. Tankless water heaters do not use a water storage tank, as do conventional watetheaters. Instead, they instantaneously heat water flowing through their coils to a desired deliverytemperature. Tankless water heaters provide several advantages over conventional water heaters. Sincetankless water heaters do not have a tank, they are more compact than conventional water heaters.Another benefit of tankless technology is that standby heat losses-the cooling of water standing in thestorage tank-are avoided. Standby heat losses can account for up to 25 percent of the energy consumedby a conventional water heater (Herbert 1986). Such energy savings would be expected to result incorresponding dollar savings or utility bills.

Recognizing the energy-saving potential of tankless water heaters in Army family housing, the U.S.Army Engineering and Housing Support Center (USAEHSC) tasked the U.S. Army ConstructionEngineering Research Laboratories (USACERL) to demonstrate the technology. This demonstration,conducted through the Facilities Engineering Application Program (FEAP), required tankless water heaterscapable of replacing 40-gallon' conventional water heaters. The tankless water heaters would have to becapable of providing a safe, dependable hot water supply that fully meets the needs of family housingoccupants. The requirement to purchase products manufactured in the United States limited the numberof options available to demonstrate, because most tankless water heaters are made in Europe or Japan.

Objective

The objective of this study was to determine the performance characteristics of tankless gas- andelectric-powered water heaters in Army family housing.

Approach

Twenty family housing units at Fort Sill, OK, were selected for the demonstration. Tankless gaswater heaters were installed in five units and tankless electric water heaters were installed in another fiveunits. Conventional gas water heaters were installed in five units, and conventional electric units wereinstalled in the remaining five housing units. All of the water heaters were new. Before the tanklesswater heaters were turned on in the test residences, one of each kind was installed in the laboratory andtested by USACERL.

The performance of all water heaters was monitored, and performance of the four types of waterheaters was compared to determine which one provides the best service and economy.

"U.S. standard units of measure am used throughout this reporL A table of metric conversion factors may be found on page23.

5

-'. 1 '. - : : . . :. _ "• •...

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Scope

This report covers the findings from the FEAP demonstration L.- '..nkless and conventional waterheaters at Fort Sill, OK. Only equipment manufactured in the United States was used in thedemonstration. The manufacturer of the tankless gas water heater originally selected for the demonstrationwent out of business before the equipment was acquired. The only other U.S.-made tankless gas unitavailable was designed for commercial applications. Testing of the unit uncovered a problem with itstemperature controls that made it unsuitable for further consideration in a residential application. For thisreason, no energy-use data for the tankless gas water heater wcre collected. Also, for reasons discussedin Chapter 4, test data were collected for a relatively short period of time between November 1991 andJanuary 1992. Due to the short duration of the demonstration, therefore. this rcport does not cover aspectsof the equipment's long-term reliability.

Mode of Technology Transfer

The findings of this research will be reported in the DEH Digest, and may be the subject of aninformational flier or fact sheet distributed through the FEAP Information Center at USACERL. Thisresearch may also be reported in an issue of the EIRS" Bulletin. Additionally, it may be appropriate topublish an Engineer Technical Note on lessons learned through this research.

"Engineering Improvement Recommendation System.

6

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2 DESCRIPTION OF WATER HEATERS USED IN DEMONSTRATION

Conventional Water Heaters

The conventional gas- and electric-powered tank water heateirs used in this demonstration were high-efficiency units by Rheem Mfg. Co. The gas-powered model was the Rheemglas Fury 81GX40D, witha 40 gallon holding tank. The electri!- water heater was the Rheem Tri-Power Imperial 21 V40-7, also witha 40 gallon holding tank. These two water heaters rely on thermostats to control the temperature cf thewater in the holding tank. If water tetperature drops below the level set on the thermostat setpoint, theunit's heating system is switched on. When the water temperature reaches the setpoint, the main gasburner or electric elements are switched off. The Rheemglas Fury (gas) has an energy factor of 0.55 anda first-hour rating of 62 gallons. The Imperial (electric) has an energy factor of 3.96 and a first-hourrating of 49 gallons. The energy factor indicates the unit's overall efficiency, taking into account themodel's recovery efficiency, energy input, and standby losses. The first-hour rating refers to the volumeof heated water the unit can supply in its first hour of operation after a cold start, and is based on themodel's tank size and heating rate. Both of these water heaters meet the criteria in American Society ofHeating, Refrigerating, and Air-Conditioning. Engineers (ASHRAE) Standard 90A - 1980, EnergyConservation in New Building Design.

The Hot Box Tankless Electric Water Heater

The tankless electric water heater used in this .,nonstration was.the Hot Box, manufactured byHurriSystems, Inc. (see Figure 1). The Hot Box uses electric resistance elements to instantaneously heatwater to a specified delivery temperature. A flow switch in the Hot Box turns on the heating elementswhen tht.re is demand fir hot water. When ,he user turns on the water, 'he Hot Box detects the flow andenergizes the element to heat the water passing through the unit. The unit's heating elements are arrangedin stages so the unit can change the water temperature as the flow rate changes.

Tankiess water heaters are rated on the basis of the temperature rise the unit is capable of producing.If a tanldess watcr heater is capable of p,-'ducing a 60 *F Aise at 2 gallons per minute (gpm) and the inlettemperature is 55 'F, then the outlet temperature would be 115 'F.

At rates below the specified flow rate, the unit provides a larger temperature rise, while at higherflow rates, the unit provides a smaller temperature rise. Because the Hot Box is designed to provide atemperature rise of 60 degrees at 2 gpm, it can produce 120 gallons of hot water per hour (2 gpm x 60minutes/hour). At the same time, the Hot Box is very compact, measuring only 19.5 in. x 14 in. x 4.5in., and is designed to be wall mounted. The Hot Box cost $250 at the time of the demonstration.

The Hotomatic Tankless Gas Water Heater

The tankless gas water heater used in this demonstration was the Hotomatic #3, manufactured byLittdc Giant Mfg. Co. The Hotomatic, a cylinder measuring 41 in. tall and 14 in. in diameter (see Figure2), is designed to provide a 60 OF temperature rise at 2.5 gpm, for 150 gallons per hour recovery. TheHotontac uses a thermostat and temperature sensor to conmrol water temperature. When the user turnson the hot water, cold water flows into thl. Hotomatic and cools the temperature sensor be!ow thetemperature set on the thermostat. This cooling trigges the thermostat to fire the main burner, whichheats Incoming cold water. However, when the user shuts off the hot water, the main burner continuesto operate, rapidly heating water in the coils to the set-point temperature (even though the user no longer

7

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needs the hot watcr Vhen the set-point temperatum is reached, the thermostat then shuts off the mainburner. In this resi- Ce Hotomatic's design requires the main burner to cycle continuously to maintainwater temperature, just as con% er':ional water heaters do. (This design characteiistic is related to systemcontrol difficulties reported in Chapter 4.)

The Hotomatic is approved by the Internationai Gas Association, and retailed for $550 at the timeof the demonstration.

Figure 1. The Hot Box Tankless Electric Water Heater.

8

/.

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Figure 2. The Hotomatic Tankless Gas Water Heater.

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3 INSTALLATION OF DEMONSTRATION UNITS

Laboratory Instaliation

One Hotomatic #3 and one Hot Box were installed at USACERL for testing under controlledconditions. The tankless water heaters are designed to provide a specified temperature rise at a specificflow rate, but the temperature rise changes as the flow rate changes, Laboratory testing was designed tomeasure the temperature rise over a wide range of flow rates.

Temperature sensors were placed on the iatlet and the oiftlet of each tankiess water heater todetermine the temperature rise. A water meter was installed at the inlet of each water heater so the flowrate could be measured. In order to determine each water heate,'!, energy consumption, gas and electricityusage were monitored. A gas meter was installed on the gas line to the Hotomatic, and current andpotential transformers were inst,"Jled in the circuit feeding the Hot Box to record the electrical demand andconsumption. The laboratory test apparatus used a Synergistic Control Systems C- 180 data logger torecord data from the various sensors and meters. Figure 3 shows the laboratory setup for the electrictankless water heater. Figure 4 shows the laboratory setup for the tankless gas water heater, whichrequired a pulscd-output gas meter. A temperature- and pressure-relief valve was installed on the oudetside of both water heaters. These valves were set at 150 pounds per square inch (psi) for pressure and210 *F for temperature.

Field Installation

The family housing area at Fort Sill (the 2000 area) was selected for the demonstration because itincludes many duplex housing units of similar layout and design (see Figure 5). Each duplex is dividedinto a north and a south residence. The water heaters for eacti residence is in the basement, next to thecommon wall. By running the sensor wires from south basement to the north one, a single data loggerwas used to monitor both sides. All of the demonstration water heaters, except the conventional gas-fueledones, were plumbed in parallel with the existing water heaters.' Isolation valves were installed so the hotwater supply in each residence could easily be switched from the old water heater to the demonstrationunit. Thermoiwells for temperature sensors were installed on the inlet and outlet of each new water heater.A water meter with pulsed output was installed on the inlet side, and a temperature. and pressure reliefvalve was installed on the outlet side. Figure 6 shows the plumbing details for the new water heaters.The field installation also included 0 to 200 *F dial-reading temperature gauges on the inlet and outlet ofeach demonstration water heater. These gauges allo.,ed visual verification Gf the water heater operation.New gas water heaters were installed with a gas meter on the gas line to measure the amount of gas used.Current transformers and potential transformers for measuring the amounts of electricity used wereinstalled on the electrical circuits to the demonstration electric water heaters.

7The residences in which a Hot Box was installed required extensive changes in electrical service tohandle the new unit. The large electrical demand of the Hot Box--over 60 amps at 240 VAC (volts,alternating current)-dictated an upgrade of the existing 100 amp service to 200 amps. This requiredinstallation of a new panel, a new wire drop with an increase in size, and a new transformer. The requiredchanges resulted in the Pot Box installations costing 20 to 30 times the installation cost of a conventionalelectric water heater. Although the cost of this upgrade was not documented, it is reasonable to assumethat it was expensive enough to significantly diminish the appeal of the Hot Box as a cost-saving device.

SThe conventional gas units were intended to remain in the test residence after the demonstration, so there was no reason to keepthe existing umt instal'ed and standing by.

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TemperatureRTD ,and PressureRelief Valve RTD

Water Meter IO

BOX

240 VAC 1-8

Electric Tankless Water Heater C

S PIT

Figure 3. Laboratory Setup for Tankless Electric Water Heater.

TemperatureRTD and Pressure

Relief Valve RTD

Hotomat ic C-180O

Gas Meter 03 Dt

Gas Line F

Gas Tankless Water Heater

C2-180

Figure 4. Laboratory Setup for Tankless Gas Water Heater.

II

i ili/

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-- I.

.0a uj10

I U310 It*O : .5

zz

121

z 4AO z /

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THERMOWELL , TEMPRES

HOW WATER 4" --METE VHEATER

CONNECT TOE

CONNECT TO34 CNEXITINtIPN EXISTING EXISTING PIPINGEXISTING PIPING •HOT WATER

HEATER NOTE:TYPICAL FOR INSTALLATIONOF GAS TANKLESS AND ELECTRIC

TANKLESS AND TANK TYPE HOT

WATER HEATERS

Figure 6. Field Setup for Demonstration Water Heaters. Note: for reasons explained in text, thissetup was not used for the conventional gas water heaters in the demonstration.

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4 WATER HEATER EVALUATION

Laboratory Testing

The tankless water heaters were tested at USACERL to evaluate the units under controlledconditions. Data were collected to determine the temperature rise versus flow rate for both tankless waterheaters. Inlet and outlet tcmperatures were recorded over a wide range of flow rates.

The tankless electric water heater (Hot Box) was tested first. Inlet and outlet temperatures versusflow data are shown in Figure 7. At flow rates lower than 0.5 gpm, the water outlet temperatures rangefrom 150 °F to 175 °F. The Hot Box is designed to restrict water flow, and is limited to a maximum flowrate of between 2.0 and 2.25 gpm. Figure 8 shows the power consumption versus flow rate for the sametest, and reveals an increase in electrical demand as the hot water flow rate increases. At its maximumflow rate, the Hot Box required 16 kW (240 VAC) to heat the water. Such high demand could lead toincreased demand charges on an Army installation if a large number of Hot Boxes were installed. Forexample, if 1000 units were installed, and only 10 percent of the units were operating during the periodof peak demand, the H't Boxes would add 1.6 MW to the installation's peak demand (1000 x 0.1 x 16kW).

The tankless gas water heater (Hotomatic #3) was tested next. The temperature versus flow dataare shown in Figure 9. Comparison of Figure 9 to Figure 7 shows that the Hotomatic unit provided hotwater at higher flows than the Hot Box. Although the Hotomatic unit is capable of providing a 60 OFtemperature rise at 2.5 gpm, as advertised in its specifications, this tankless gas water heater producedsome alarming results. At flow rates between 0.25 and 0.75 gpm, the outlet temperature wouldinappropriately rise to 185 OF, activating the temperature-pressure relief valve. When activated, the valvereleases hot water out a second pipe onto the floor or into a drain. When the temperature and pressuredropped to safe levels, the valve closed and the system returned to normal operation.

The reason for this problem appears to be related to a design characteristic of the unit. TheHotomatic uses a temperature sensor located near the inlet to prevent quantities of cold water from flowingout of the faucet before the unit is up to temperature. This design scheme may work correctly at highflow rates for large-scale applications like car washes, where the hot water is tapped off as fast as it isheated. In residential-scale flow rates of 0.25 to 0.75 gpm, however, the Hotomatic's powerful burnerheats water faster than it can be used. At such low flow rates, the burner tended to overheat the waterin the coils, which activated the relief valve.

Field Testing

As discussed earlier, the new water heaters used in this demonstration were plumbed in parallel withthe original water heaters. This approach allowed for switching from the original water heater to thedemonstration unit without interrupting the resident's hot water service. The power for the new waterheater-gas or electric-was switched on, the unit was given time to warm up, the isolation valves wereset to direct the hot water service from the old water heater to the demonstration unit, and then the oldwater heater was shut down by turning off its gas supply. The data logging equipment was checked tomake sure it was collecting and record; ig data properly.

Hotomatic Results

Echoing the results of the laboratory investigation discussed earlier, the tanidess gas water heatersproved to be the most troublesome. The Hotomatic unit at residence 2057S was started and tested witha short-duration, low flow rate load. Tle load was repeated every few minutes while the dial temperaturegauge on the water heater's ouwlet was monitored. During each load the temperature would climb 10 to

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TEMPERATURE VS FLOW RITE

180

1 6 0 - [

140

120LW

S100 U I MLETLu0

OUTLET~80

- 80 I I I l II . n I i U * * m "1 U

60

40

20

0 I I I t I I IIt

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

FLOW RATE (GPM)

Figure 7. Water Temperature versus Flow Rate for Laboratory Test of Hot Box.

POWER VS FLOW RATE

18

S10

16-, , . "- !

I I

6 I II

2 3u0* I I I I I I

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 .2

FLOW RATE (GPM)

Figure 8. Power Consumption versus Flow Rate for Laboratory Test of Hot Box.

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TEMPERATURE VS FLOW RATE

200

03 a O~ 0 0n00 0180 n 0

160 0 00 0o 0

140 o

i 120 0 0 0 n INLETS100-L0 0 0 OUTLET

680

60 I uUnUn n a i n m * Ei I Ui

40

20

0 I I I I

0 0.5 1 1.5 2 2.5 3

FLOW RATE (GPM)

Figure 9. Water Temperature versus Flow Rate for Laboratory Test of Hotomatic #3.

15 OF. After several repeated tests, the temperature-pressure relief valve was activated, spraying hot wateron the floor (Figure 10) before the gas was shut off. The outlet temperature reached 190 OF, as observedon the outlet temperature gauge.

Next, the Hotomatic in residence 2068N was started. After the new hot water system was turnedon, the resident was asked to run some hot water. The outlet temperature was monitored on the large-dialgauges. After running for a few minutes, the water temperature climbed to 185 OF, the level at which thetemperature-pressure relief valve should have activated. The gas was shut off but the temperaturecontinued to climb for a few seconds, finally reaching 197 *F. The temperature-pressure relief valve failedto activate. At this point, the researchers determined that the low-flow operating characteristics of theHotomatic unit made it unsafe for use in family housing. The Hotomatic unit in residence 2068N wasshut down, and all other Hotomatic units installed for this demonstration at Fort Sill were left off line.All of these residences continued to use their original water heating systems.

Hot Box Results

The tankless electric water heater (Hot Box) performed somewhat better than the Hotomatic, butsignificant problems were reported nevertheless. Two residents reported that they had no hot water theday after the switchover. At residence 2073N, the two valves used to isolate the original water heaterfrom the demonstration system were not closing off the water flow as intended. Instead of drawing waterthrough the Hot Box, the system was pulling water from the cold tank of the original water heater. Whenthe system was switched over the evening before, it had not been obvious that the hot water was stillbeing drawn from the tank of the original heater. The residence was switched back to its original waterheater until the faulty isolation valve could be replaced.

16

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* Figure 10. Discharge from Hotomatic Temperature-Pressure Relief Valve.

The residents at 2072N also reported insufficient hot water early in the demonstration. The* 'I residence had hot water, but the flow rate in the upstairs shower was much lower than it had been under

the old system. Figure 11 shows the original flow of the shower and Figure 12 shows how the Hot Boxreduced the flow. This reduction of flow was apparently due to the smaller diameter pipe used inside theHot Box to reduce the maximum flow rate to about 2.5 gpmn. To address the resident's complaint aboutthe low flow rate, the hot water service was switched back to the original system.

During a second site visit by the researcher to collect data in January 1992, the residents of 2071 Nreported problems with the Hot Box. Several weeks after the Hot Box had been switched on, the residentsnoticed a burning smell in the basement. The residents were unable to contact anyone at Family Housing,so they called the base fire department. The residents did not know what the fire department did toresolve the problem, but when the system was examined it was found that the Hot Box had been switchedoff and the conventional gas water heater was operating once again. When the cover of the Hot Box wasopened, burned insulation was found on several wires. Insulation on the two wires supplying power fromthe circuit panel had melted 2 to 3 in. from the Hot Box terminal, and insulation on the wire that carriesthe power from that same terminal to the interior of the Hot Box had melted back 4 to 6 in. Figure 13shows the damaged wires from several angles. Investigation of the problem and speculation on its causeare beyond the scope of this research. However, any future use of the Hot Box should be conditional oninvestigation of the unit's failure and correction of' the cause by the manufacturer.

17

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-- :5 -Figure 11. Original Flow in Upstairs Shower, Residence 2072N.

/ Figure 12. Reduced Flow in Upstairs Shower Due to Hot Box, Residence 2072N.

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Wir:s supplying power tothe Hot Box from the panel

VWirs with insulation rmeltedone inch back from terminal

Terminals for connectingpower to the Hot Box~x

Wire with insulation melted~8inches from terminal

ON-OFF power switch

Figure 13. Damaged Wires on Hot Box Installed at Residence 2071N.

Data Collection and Analysis

Data were collected for the field test over 2 months, from November 1991 to January 1992. Thetotal amount of hot water consumed and the total amount of energy required to heat that water wererecorded. Table I summarizes the data. The table lists the residence number, type of water heater,amount of energy consumption, total hot water consumption, average daily hot water consumption, andthe cost of heating 100 gallons of water.

As indicated previously, technical problems prevented the collectien of a complete data set for allwater heaters installed for this demonstration. There are no field data for the Hotomatic units because theywere judged too unsafe to use. Also, the data logger at residence 2072N malfunctioned, providing onlyreadings of "0." This was the residence where the original hot water service was restored after occupantscomplained of insufficient hot water flow in the upstairs shower the day after the Hot Box was switchedon. There are also incomplete data for: residence 2073N, where faulty isolation valves prevented testingof the Hot Box during the demonstration period; residence 2074N, which was vacant during most of thedemonstration period; and residence 2071N, where the Hot Box was shut down in late November afterinsulation on the unit's wiring began to melt. The calculation of average daily hot water consumption wasbased on data collected over 79 days from all properly functioning demonstration water heaters (exceptresidence 2071N, whose taikless water heater operated for only 22 days).

The average daily amount of hot water used by the residences with conventional water heatersranged from 38 to 138 gallons, with an overall average of 82 gallons per day. The cost for 100 gallonsof hot water was based on Fort Sill's costs of $ .00584 per kiloWatt-hour for electricity and $ 0.216 perhundred cubic freet (ccf) for gas.

19

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Page 24: Demonstration of Tankless Water Heaters in Army Family ... · temperature. Tankless water heaters provide several advantages over conventional water heaters. Since tankless water

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The cost of heating 100 gallons of water using the conventional gas water heater ranged from $ 0.22to $ 0.28, with an average of $ 0.26. For the reasons previously discussed, no costs could be calculatedfor the tankless gas water heater technology.

The cost for the conventional electric water heaters to heat 100 gallons varied from $0.14 to $0.19,with an average of $0.16. The cost of heating 100 gallons of water with the Hot Box ranged from $0.11to $0.13," with an average of $0.12 (Table 2). Therefore, the average cost for heating water using the HotBox was 26 percent lower than with conventional electric water heaters.

Figares 14 and 15 show the relative costs of heating water with gas and electricity at Fort Sill.Figure 14 includes no data for tankless gas technology because testing was canceled due to safetyconsiderations, as previously discussed. Figure 15 shows the relative savir.gs possible by using the HotBox in place of conventional electric water heater technology. Note that the savings increase as the costper kiloWatt-hour increases.

In regions where electricity is less expensive than gas for heating water, the Hot Box could savemoney compared to conventional electric water heaters.

Table 2

Costs of Heating 100 Gallons of Water

Heater Type Low High Average

Conventional Gas $0.22 $0.28 $0.26

Tankless Gas n/a n/a n/a

Conventional $0.14 $0.19 $0.16Electric

Tankless $0.11 $0.13 $0.12Electric

"This was the cost for the init at residence 2071N, for which data were gathered over only 22 days.

21

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1.2

J 0.I- 0.0

cs 0.2

C.

0 -0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9'

DOLLARS PER THERN

Figure 14. E!'Tect of Changing Gas Prices on Cost of Heating 100 G alions or Water With StandardGas Water Heaters at Fort Sill.

°

2.5

02.

S• al----Not Box

0.5

0.02 0.03 0.04 0.05 0. 0. 0.6 0..09 0.1

DOLLARS PER IW

Figure 14. Effect of Changing lectricity Prices on Cost of Heating 100 Gallons or Water WithConventional and Tankless Electric Water Heaters at Fort Sill.

22

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5 SUMMARY

In this FEAP demonstration, tankless gas- and electric-powered water heaters were to be tested andcompared with conventional gas- and electric-powered water heaters in terms of performance andeconomy. Due to problems related to the design of the temperature controls on the Hotomatic #3 tanklessgas water heater early in the project, however, it was determined that the Hotomatic could not provide asafe source of hot water at low flow rates. Therefore, only the tankless electric unit-the HotBox-operated long enough to provide data for comparing tankless and conventional water heatingtechnologies.

The Hot Box reduced the amount of electricity needed to provide hot water as compared to the newconventional electric water heaters tested in the demonstration. In areas where electricity is moreeconomical than gas. the Hot Box could provide dollar savings on 'energy costs when replacing aconventional electric water heater. The !'nt Box's small size and wall-mounted design provided for acompact installation that did not use any floor space in the residents' basements. Th-e Hot Box performedadequately in the field except for two problems:

a The lower flow rate was the subject of complaints by some residents* One unit-the Hot Box installed at residence 2071N-malfunctioned, melting the insulation on

some of its wires.

The costs of installing a Hot Box in many of the Army's older family housing units, such as theones in the Fort Sill demonstration, would be prohibitively high wherever it was necessary to upgrade the240 VAC electrical service from 100 amp to 200 amp. Also, it could be counterproductive to install alarge number of Hot Boxes on any Army installation that is attcmpting to reduce electrical demand andthe associated charges.

As noted above, the Hotomatic tankless gas water heater failed to provide safe hot water service forthe residences in which it was installed. As currently designed, the Hotomatic would require extensiveplumbing modifications to make it safe for residential use. However, it should be remembered that theHotomatic was designed for commercial-scale application by users who do not depend on the unit'sperformance at low flow rates. Therefore, it should not be concluded that there is something inherentlyunsafe about the unit, just that its current design is not appropriate for low-flow residential applications.

The conventional gas and electric water heaters installed for this demonstration both successfullyprovided residents hot water service. The residents with these water heaters used an average 82 gallonsof ho. water per day. The cost to heat 100 gallons of water using the electric units averaged $0.16 whileheating the same quantity of water with the gas units averaged $0.26. The conventional electric waterheater would have to be the choice to use at Fort Sill, due to its lower operating cost. The cost of heating100 gallons of water with the hot box was lower than the cost of heating water with the conventionalelectric water heater: $0.12 versus $0.16, respectively. The Hot Box also cost more to install than theelectric water heater due to the requirement for a new panel, new wire drop, and new transformer toupgrade the existing electrical service.

METRIC CONVERSION FACTORS

I in. - 25.4 mm

I cu (I w 0.002832 mr'I psi a 6.89 kPaI lb a 0.453 kgI gal a 3.78 1"OF a VC + 17.78) x 1.8

23

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ABBREVIATIONS AND ACRONYMS

AC alternating current

ASHRAE American Society of Heating, Refrigerating, and Air-Conditioning Engineers

ccf hundred cubic feet

FEAP Facilities Engineering Applications Program

gpm gallons per minute

psi pounds per square inch

USACERL U.S. Army Construction Engineering Research Laboratories

USAEHSC U.S. Army Engineering and Housing Support Center

VAC volts, alternating current

1

24

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DATE:i