[TobyWan]

I have had this condition for several years now and my repair/installer company has attended to it several times, charged me steeply and, while the condition may be temporarily improved, they have never fully solved the problem. Here is what happens:

My 1988 Bryant Day & Night furnace will come on, begin to heat up the chamber for maybe a minute, I hear some multiple & rapid clicks then shuts down. Sometimes a secondary noise occurs (fan I think) and shortly thereafter everything shuts down. The duration of this process may last from 30 seconds to perhaps a minute & a half.

Eventually the furnace will go through the entire sequence and the blower will come on and warm the house. I imagine there's quite a bit of gas wasted when it repeatedly fails to complete the cycle.

I notice this mostly in the early mornings when the thermostat is set to a low temperature setting.

I would appreciate any suggestions you may have.

Thank you!

Toby

[hvac1000]

Exact model number?

Brand and exact model of thermostat. Could be a heat anticipator problem.

[TobyWan]

The Bryant furnace model # is: 398AAW036080AFJA

The thermostat is a Honeywell with the numbers T87F 2873 3
(below) 9502

[hvac1000]

Inside the thermostat just behind the outer cover of these types of thermostats you will see a heat anticipator. It looks something similar to one of these two:


These adjustments are the heat anticipator. They are for the length of the cycle of the heating, but sometimes there is one for the cooling. But almost always, the cooling anticipator is a fixed resistor on the subbase. It's a very critical measurement with special instruments for the professional. Don't worry, you can set a replacement thermostat heat anticipator just like the old one or you can make adjustments in very small increments as instructed here.

1. HEAT CYCLE TOO LONG--Set adjustable heater to a slightly lower dial setting. (1/2 division)
2. HEAT CYCLE TOO SHORT--Set adjustable heater to a slightly higher dial setting (1/2) division)
3. YOUR thermostat should look like the picture on the left inside. Use the directions in number 2 since your heat cycle is to short causing a problem with your system. Move the lever just a little bit at a time to the longer side on the little dial till the unit works correctly. It may take a few furnace cycles to ballance so do not rush the job by moving the lever to fast. Move the lever and wait 15-30 minutes for the results.

There is a professional way to do this adjustment but involves a meter which you do not have.

[TobyWan]

Thanks for your recommendation. I've not been home much recently but I've made one adjustment so far and will let you know if this works.

[hvac1000]

Hope it works out for you.

[TobyWan]

Thank you for your generosity in sharing your expertise.

Yes, my furnace now comes on as designed with no premature shut-down. This is so great!
May I offer some form of compensation?

[hvac1000]

As long as you are happy with the results that is all that counts. If you happen to find a charity that helps feed the homeless during the Thanks Giving season or Christmas and you feel like helping them out will a few $$ that would be all the compensation I could think of. Many of or less fortunate citizens will be forever grateful for your generosity. Have a happy holiday season.

[TobyWan]

Thank you Masked Man!