Squeezing cold air from A/C

[auger66]

This is a minor one, but I noticed the Venstar thermostat has an option to let the fan run for up to 90 seconds after the cooling call is satisfied.

 

So I did some testing on my commercial fluid heat pump and found cool air comes out for about four minutes after the compressor is shut off. So I wrote a simple program to keep the fan running for four minutes. I enabled the option in the thermostat to keep the fan from quickly cycling off and on.

 

I've never turn my heater on so this is just for A/C.

 

 

If

Status 'Thermostat / Main' is Mode Cool

And Control 'Thermostat / Main / Cool Control' is switched Off

 

Then

Set 'Thermostat / Main' Fan On

Wait 4 minutes

Set 'Thermostat / Main' Fan Auto

 

Else

- No actions

[Mark Sanctuary]

Squeezing all the last cooled air out of the ducts. This is a good idea I will have to experiment with.

[apostolakisl]

The difference that makes will depend on where your unit is.

 

If the air handling unit and ducts are all inside the conditioned space (like in a closet in the house) it will slightly decrease efficiency becuase you will be running the fan (producing heat and burning electricity) without actually moving any heat that is inside the house to outside (only from inside your house in one area to inside your house in another area). The freon has to be moving for heat to get moved from inside the house to outside and that won't be happening after the compressor shuts down.

 

If the unit is in an attic (that is not in the conditioned space), you will increase your efficiency since you will be capturing what is left of the heat sink (the freon) before it gets wasted to the inferno knows as the summer attic.