Quote:
Originally Posted by jrref
The Solar Guys install two models. RM1500 and RM2400. There is a chart on their web site used to determine how many of each fan you need depending on the square footage of your home. AC powered fans will give you more CFM but the solar fans produce more than enough air flow. Initially, I had them install two RM2400s but it was too much for my 2600 sqft home. At peak times I could head the RM2400 in my living room if it was quiet so I had them replace one RM2400 with a RM1500 and that solved the problem. Now my attic never gets more than 10 degrees hotter than the outside air. I have temperature sensors in my attic with the data that shows this. Before the attic fans, my attic would superheat to around 150 degrees on a 90 degree+ day here in the Villages. The typical thought is that you need a huge attic fan to evacuate the hot air but assuming your soffit vents are not clogged and you have adequate air circulation in your attic, all you need is a fan with a moderate CFM to move the hot air out of the attic. A fan that's too large will start sucking air from the living space and you don't want that either.
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How do you know that the fan is not sucking conditioned air from your living space? If the fan creates a negative pressure in your attic, air will be sucked out from any ceiling leak or other opening, not just through the soffit vents.