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Old 12-18-2009, 11:06 AM   #1
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Fresh Air Controls / Economizer


I'm looking for advice on a thermostat or custom controls for the following situation:

Location: Central Florida
System: 2.5 ton AC/Heat Pump, 1150 square feet

I recently added a fresh air draw to the return side of my system to save on running the compressor. I used a Honeywell damper on a manual switch located near the thermostat to control it, however I have to manually engage the switch, turn off cooling, and turn on the air handler.

I understand that economizer controls should be able to do this automatically, however given $400 electric bills I've had to up the thermostat to 76-78. I'd like some control that when the outside temperature permits, to cool the house to 72 using fresh air, and only engage cooling for humidity control or when fresh air can't cool below 76.

My high electrical load is attributed to running 6 computers in one of the bedrooms. I have a dedicated 10k BTU portable unit that handles that room so the load on the central unit is minimized. I have added a 12x12 return to this room to be able to use the heat generated to warm the rest of the house (I've only run the heat pump ~20 hours last 12 months).

I've explored the home automation (communicating) thermostats. None of them seem to offer any way to interact with the sensors and control the unit directly. My ideal solution would be a thermostat that I can interface to a computer to and write my own logic (I'm a programmer by trade).

Edit: Added square footage to description


Last edited by Bobberly; 12-18-2009 at 03:57 PM.
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Old 12-18-2009, 12:28 PM   #2
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Fresh Air Controls / Economizer


How big of a fresh air duct?
Ain't gonna do much cooling with a little 8" round duct.
Also. How big is the exhaust duct. needs to be atleast as large. And sometimes larger then the intake.

Can't bring in more air then is being exhausted.
Guessing your talking about when outdoor temps are around 70, is when you want to use this system.

It would be easier to just go out and by an economizer control. Install it, set it up for what you want. And forget it.

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Old 12-18-2009, 03:46 PM   #3
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Fresh Air Controls / Economizer


The house is 1150 sq feet. The fresh air duct is 12", it mixes into a 16" duct that has the computer room return (10"). The 16" and a 20x20 return feed into the air handler. I have air filters on the inside returns and just a bug screen on the outside, so it sucks in air pretty good and does a decent job cooling whenever the temperature outside is < 68.

I don't have an exhaust system in place yet. The plan is to branch the return from the computer room to an attic vent whenever it is warmer than the outside air (in cooling mode).

Is there a particular brand economizer control you'd recommend for this?

Edit: I usually have a window/sliding glass door opened anytime the outside temp is < 70, so exhaust hasn't been an issue yet. My house was also contructed with vents over every doorway to equalize pressure.

Last edited by Bobberly; 12-18-2009 at 03:50 PM.
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Old 12-18-2009, 05:07 PM   #4
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Fresh Air Controls / Economizer


Honeywell makes a good one.

http://customer.honeywell.com/TechLi...0s/63-8586.pdf
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