Quote:
Originally Posted by JRMichler
I built an economizer into my new (at the time) house 15 years ago. A forced air system with a damper in the return air duct, a duct from the outside with a damper, and a switch (normal / economizer). In normal mode, the heating and central air worked normally. In economizer mode, the return air damper closed, the outside air damper opened, the AC was shut off, and the furnace blower ran until room temperature met the cooling setpoint.
When we first started it up, no air came out of the registers. Tried to open an outside door. It did not open. A two handed pull got it open. Then we got air out of the registers. Then closed the door and opened a window. Less than several inches open, the window howled. Fully open, everything was was good. It ran until the house got down to setpoint, then the blower shut off. Everything worked as planned.
EXCEPT, Wisconsin is humid during the summer. And the relative humidity is highest at night. We woke up to a house at setpoint, about 72 degrees, and very high humidity. It was a swamp inside.
Then I thought "what will happen if the outside air damper fails open in winter at -20 degrees F outside". So I removed the outside air duct and put in a dehumidifier.
Also, the house is so well insulated that the central AC gets very little use.
In dry climate with large day to night temperature swings, an economizer system can work extremely well. When I was in the Air Force at March AFB, CA in the 1970's, our barracks air conditioner failed one summer. We kept the barracks comfortable by running the ventilation fan all night and shutting it down during the day. Typical night low temperature 60 to 70 deg F, typical day high temperature 100 to 110 deg F.
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Your system sounds exactly like the one I had in mind.
Here in SE New Mexico the day and night temperatures are about the same as your summer temps, but no humidity.
My house is well insulated, doubled the wall thickness then put in R30 fiberglass batts and a separate plastic vapor barrier. When the outside and inside temps are the same we close all the windows and turn on the AC, let it run for an hour then it's turned off and we don't need it until early afternoon.
I'm hoping that by using your example to extend that time to late afternoon or ideally, not need the AC until morning.