Home>Discussions>INSULATION & HVAC>heat system cycling on and off
20 posts / 0 new
Last post
JLMCDANIEL
Re: heat system cycling on and off

Sten,
Unless these systems work differently than other systems, you can have the blower on continuously and the heat heat strips are still controlled by by the thermostat being in the heat position and calling for heat, you can also run the blower on continuous mode and have the cooling turning on and off as the thermostat calls for cooling. The thermostat fan auto/on control and it's heating/ cooling control are separate.
Jack

Sten
Re: heat system cycling on and off

So your saying the blower is on 24/7 with both heat and A/C, OK

JLMCDANIEL
Re: heat system cycling on and off

No, I'm saying that the fan can be turned to the on position, the blower will run as long as it is in the "on" condition and it has no affect on the heat/cooling cycle control. The heat or cooling will cycle on and off with the fan continuously running. The fan is either in the auto or the on position, in "auto" it is controlled by the call for conditioning and the limit switches in the "on" position it runs by passing the other controls but it does not affect the call for conditioning.
Jack

Sten
Re: heat system cycling on and off

That's right but the OP said it works in the on pos. but not the auto pos., clearly sounds like a wiring issue to me. Some units have two transformers, if this one does maybe he should check that

Then again some say all I know is duct sealing

JLMCDANIEL
Re: heat system cycling on and off

Sten,
Consider this. It is a 3 ton unit hooked to the ductwork in probably a 620 sg.ft. mobile home. The thermostat calls for heat the strips come on and the heat exchanger reaches 80 degrees, the low limit then turns on the fan. With the restricted duct system it would take a while to get much air moving. The heat exchanger reaches say 110 degrees and the high limit opens cutting power to the strips. because the unit is out side and the fan is running it cools below the low limit very rapidly, the fan stops. It then recycles and goes through the same thing.

With the fan in the on position, the fan is running so when the strips turn on there is enough airflow to prevent the heat exchanger from reaching the high limit.
Jack

Sten
Re: heat system cycling on and off
JLMCDANIEL wrote:

Sten,
Consider this. It is a 3 ton unit hooked to the ductwork in probably a 620 sg.ft. mobile home. The thermostat calls for heat the strips come on and the heat exchanger reaches 80 degrees, the low limit then turns on the fan. With the restricted duct system it would take a while to get much air moving. The heat exchanger reaches say 110 degrees and the high limit opens cutting power to the strips. because the unit is out side and the fan is running it cools below the low limit very rapidly, the fan stops. It then recycles and goes through the same thing.

With the fan in the on position, the fan is running so when the strips turn on there is enough airflow to prevent the heat exchanger from reaching the high limit.
Jack

Hi Jack
It seems like your temp diff. is kind of close. When the blower comes on it starts pulling air (some say air can't be pulled), IMHO I don't think it takes so long that it would hit high limit.
On the other hand, since the unit is a three ton and 1 ton would be good for say 400 sq. ft. depending on area (I'll get flack for that one), it makes me wonder if they have the right sized heating element in there or if it's oversized and putting out to much heat. Then it would hit high limit.

garywood
Re: heat system cycling on and off

in regard to my heat system cycling, i have solved the problem. i purchased a digital thermastat, programed it so that the thermastat controls the fan instead of the unit controlling it. the heat system is working perfectly now. the thermastat i had on it before was a cheap mechanical thermastat and that seems to be the problem. thank you all for your suggestions.

Robert
Re: heat system cycling on and off

how do i run my ac after the winter do i need to reset something to get my ac to come on?

canuk
Re: heat system cycling on and off
rdennis wrote:

how do i run my ac after the winter do i need to reset something to get my ac to come on?

On the thermostat move the mode switch from "Heat" to "A/C"

Pages

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.