Quote:
Originally Posted by Ormston
Unless those other heat sources are outside the thermal envelope of the house you're stealing heat from one part of the house to give to another.
So no net gain.
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The Net gain comes from the infiltrated air temps vs. The discharge air temps.
Basically the Unit brings in outdoor air at say 72ºF and discharges it at 32ºF, so basically there are 40ºF worth of BTUs in that infiltrated air. If we want the indoor air to be 76ºF then 10% of those BTUs are used to heat up the infiltrated air and the rest of the BTUs are used to heat up the rest of the house.
COP is the efficiency of the Unit itself not a measure of efficiency of the entire house. Basically the unit can cause a net loss of heat to the house (this happens when the recoverable BTUs are greater than the BTUs needed to warm the infiltrated air up to warm temperature) and the unit will still operate at its COP.