Evaluation of an Infra-Red Two-Stage Heating System in a Commercial Application R.D. MacDonald, P.Eng., Member AHSRAE M.E. Armstrong, P.Eng., K.G. Boyd, P.Eng Appreciation for technical support and funding from Union Gas, Chatham, ON and Brant Radiant Heaters Ltd., Paris, ON, is gratefully acknowledged. ASHRAE Research Project Number: 4643

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INFRARED HEATING SYSTEM	FORCED AIR HEATING SYSTEM

OBJECTIVE:

• To determine effectiveness (fuel utilization and comfort) of a two-stage heating system designed to provide space heating and offset elevated losses from overhead door usage.
  
• To determine how a two-stage heat system better meets heat requirements vs. forced air heat system.

IR vs. FA Temperature Cycling

SITE DESCRIPTIONS:

Commercial facility with frequent overhead door opening facilitating the movement of supplies.

Installed a forced-air unit heater (FA) and a tube-type infrared heater (IR) that operate by a common thermostat with a manual override switch to allow either FA or IR operation.


PROCEDURES & METHODS:

• Measure temperatures at 10 minute intervals, outside and a variety of inside and slab locations.
• Measure gas usage daily at designated times, conduct regular interview with staff on comfort.
• Predetermined operating cycles for FA and IR heater (i.e. alternate weeks, etc.).

RESULTS:

Test 1
October 1, 1999 - February 17, 2000.  Target set point was 17șC

• To establish a test methodology using the systems and verifying the controls.
• Systems operated during the heating season at 1-2 week alternating equal intervals, FA then IR.
• Energy savings comparing FA and IR proved minimal

Test 2

February 18 - April 28, 2000.  Target set point for IR 16șC and FA 19șC.

(Actual average 13.2șC IR and 17.7șC FA)

• Systems operated during the heating season at 1 week alternating intervals.
• IR savings measured 19.5%, savings influenced by the lower set point of IR.

Test 3

October 16, 2000 - April 12, 2001.  Target set point for IR 14șC and FA 17șC.

(Actual average 21.2șC IR and 18.9șC FA)

• Systems operated during the heating season at 1 week alternating intervals.
• IR savings measured 23%, (note: average temperature higher for IR).

Test 4

December 15 - March 25, 2000-2001 and 2001-2002.  Target set point for IR 17șC.

(Actual delta T inside to outside for two time periods was 21.3șC IR and 21.8șC)

• IR and FA systems cycled weekly 2000-2001.
• IR only 2001-2002.
• Saved 25.4%with continuous infrared vs. weekly interval IR and FA.

Slab Temperature Changes of FA and IR

Average IR Low / High Fire vs. FA Opening Time

IR Total On-Time vs. High Fire

CONCLUSION:

• IR heating saved up to 23% over a conventional FA heating system.
• The thermal flywheel effect in the slab contributes to energy use efficiency.
• A weekly cycle of FA vs. IR is not a useful method of evaluating potential in either system due to the flywheel effect.
• Two stage infrared heat system ran on low fire longer than FA per on-cycle; plus only used high fire 8-23% of the total on-time for heating.

FA vs. IR Energy Usage

Alternating IR vs. Continuous Energy Usage