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47
Performance Specifications
(
cont.
)
G. Protection Circuits:
Compressor shall have automatic reset, over tempera-
ture and over current protection. The fan motor shall
have an inherent, automatic reset over temperature
protection. The electric heater shall have two over
temperature protectors.
4.0.1 heAt pump operAtIon
Heat pump units shall have the selected room tempera-
ture maintained by cycling either in the heat pump mode
or electric strip heat. A heat pump unit with electric heat
is switched from the heat pump mode to electric strip
heat when the outdoor coil temperature is 20 °F or when
the heat pump cannot keep up with the heating load and
a two-stage thermostat is used.
For heat pump operation, a room thermostat with a B**
(heating changeover) terminal is required. This will
mean that some “auto changeover” thermostats cannot be
used, as many of them either do not have a B** terminal,
or else energize the B** terminal continuously when in
the “auto” position.
4.0.2 electrIc heAt overrIde
For heat pump applications, electric heat comes on only
when the outdoor coil temperature is below 28 °F, maxi-
mizing the amount of time the unit operates in the more
efficient heat pump mode. The minimum COP for heat
pumps, at 47 °F DB outdoor, must be 2.9 for all sizes.
(Heat pump models shall also include reversing valve).
4.0.3 reverse cycle
A Heat Pump WITH back-up electric heat –
The reversing valve, the compressor, the outdoor
condenser fan motor and the indoor fan motor shall
be energized. Reverse cycle heating shall occur when
the outdoor coil temperature is 28 °F and above. If
outdoor coil temperature drops below 28 °F or the
Outdoor air temperature drops to 35 °F or less,
electric heat is the only source of heat. When the
outdoor coil temperature rises back to 40 °F or above,
the Compressor or electric heater is used.
A temperature-sensing device shall be used to
monitor the outdoor coil temperature to limit frost
buildup. Defrosting of the outdoor coil will be
activated when outdoor coil temperature drops below
28 °F or outdoor air temperature drops to 35 °F or
less. Defrosting is terminated when outdoor coil
temperature rises back to 40 °F. During defrosting,
both compressor and the outdoor fan are turned off.
The indoor fan will run at its set speed.
Condensation accumulated during reverse cycle
heating must NOT be evaporated against the indoor
coil so as to prevent contamination of the indoor air
with pollutants and odors. Condensation must be
disposed of using a (external/internal) drain system as
shown on plans.
