I've been looking at a lot of dual fuel heat pumps and I'll have to say that the configurations are a puzzle to a lot of us. First of all, you're dealing with a heat pump. That means that the same unit is used for heating and cooling. You have a reversing valve that makes it like turning a window ac unit around and blowing the hot exhaust into the house to heat it. A clever idea and very efficient.
Q;Why does my heat pump have ice and periodically make groaning sounds?
A:: Not only groaning sounds, but the outdoor unit fan stops and the ice thaws. This is a normal occurence because the condensed moisture on the outside unit needs thawing for the heat pump to work.Steam happens.
Q:My air supply blows cold while the outside unit is in this defrost cycle. Is that normal?
A:Your wiring may be wrong Your auxiliary heat should be compensating for the unit going into cooling mode(reversing)by heating the inside air.
Q: My Heat Pump has an outdoor sensor that is set to lock out the heat pump below 40 degrees and only use the furnace. Why is that?
A; At a certain point, Heat pumps become less efficient and also the icing and defrosting is not appealing to some.
Here are two ways of setting up dual fuel heat pumps
1. In the restricted mode of operation an outdoor
temperature sensor is used to cause the unit to operate in the
heat pump mode above a selected outdoor temperature and to
operate in the gas heating mode below the selected outdoor
temperature. The gas heat will operate with the heat pump when
the unit requires a defrost cycle. The gas heat is used to offset
the effect of the unit going into the cooling mode during defrost.
The unit will be commanded to transition to
gas heat even when the outdoor temperature is above the
selected outdoor temperature changeover point if the heat
pump capacity is not enough to maintain the indoor temperature
at the desired heating setpoint.
2. A non-restricted mode of operation allows the unit to
operate in the heat pump mode during the first or second call, or
stage, of heat commanded by the indoor thermostat. During the
first stage of heat pump mode the heat pump will operate on low
speed. During the second stage, the heat pump will operate on
high speed. If the heat pump capacity is sufficient, gas heat will
not be required. If the heat pump capacity is not enough to
maintain the indoor temperature at the desired heating setpoint,
the thermostat will call for the third stage of heat. At that point,
the gas heat will begin to operate and the heat pump will be
locked out. As in the restricted mode, the gas heat will act as
supplementary heat during the unit’s defrost cycle.
If the outdoor sensor is set high enough, the heat pump would not need the defrost cycle but efficieny would be lost.
If your heat pump is not using auxiliary heat to compensate for the defrost cyle (blowing cold air) or the emergency heat will no coming on, you might have a simple and cheap to fix wiring situation. I have seen systems that had NEVER used their furnaces and noticed the problem when it got so cold. If your unit is a block of ice....
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