I'm writing to see if anyone can help solve a mystery regarding Heat Pumps.
I have a two story house with 2, 2-ton Lennox Heat Pumps. I have owned the house for nearly 2 years and have noticed some efficiency problems. I have had the units serviced (no problems) and embarked on some research into why the units run all the time and cost a fortune to operate even with the thermostat set on 79 or 80.
Here's what I found. Some of the research involved multiple units being installed too close together. I measured the distance between mine and it is at about 8". That seemed close to me - so I called a local hvac contractor and was told that 8" shouldn't make a difference in the efficiency of the units. I decided to contact the manufacturer, Lennox to get their thoughts on the matter. I was told by their consumer affairs folks that most definitely having only 8" between the units would negatively effect their efficiency. They said that they recommend 24" between multiple units (and that was substantiated by the fact that it is in the engineering data for the model).
Puzzled, I called another HVAC contractor that I have used in the past (40 years of experience) and he said that "while he wouldn't say separating the units wouldn't help the problem, he didn't think it would solve it entirely". In my discussion with the Lennox rep, he said that being so close together, the units are essentially "competing for air". It is widely known and accepted that you are not supposed to obstruct hvac equipment. So, how could it not be an issue that an entire air intake surface of each unit are 8" apart? Additionally, if they are both running simultaneously, wouldn't they both be trying to draw in air on the obstructed sides and "fighting against each other"
so to speak?
I would greatly appreciate some professional insight into the matter. I understand that hvac contractors and engineers have completely different perspectives - but they can't both be right about this!