Testing back-up heat

Air Conditioning and Heat Pumps · Heat Pumps in Practice · printed page 229 (PDF page 230)

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Book index entries

Back Up Heat for Heat Pumps – Testing Heat Pump – Testing Back Up Heat

Text in the illustration

supply plenum
heating elements (typically 5 kw each)
electrical supply
indoor coil
blower
air return
A
clamp the amp-meter around one of the main wires at the heat pump or electrical panel to check that all of the heating elements are working (e.g., 15 kw of auxiliary heat should draw 62.5 amps at 240 volts)
B
individual heater element lead wires can be tested to determine which one (or more) is inoperative if the overall current draw is less than expected
make sure all the elements have had ample time to come on and watch out for staged auxiliary heat
note:
this test goes beyond the Standards

Generated explanation

A cutaway indoor heat-pump air handler shows a bottom air return and blower, an indoor coil above, and electric back-up heating elements in the supply plenum. Two clamp-on ammeters illustrate measuring current around a main supply wire and an individual heater element lead wire. The annotations explain checking total current draw to verify operation of all elements, then testing individual leads if the total draw is lower than expected. They also caution that elements need time to energize and that auxiliary heat may be staged. A note states that this test goes beyond the Standards.

Components

indoor air handler supply plenum electric resistance heating elements heater element lead wires electrical supply wiring indoor coil blower air return clamp-on ammeters

Materials

sheet metal insulated electrical wiring