Quick question regarding my Amana Propane furnace

[snookered]

One programmable Honeywell t-stat will stop calling for heat 2*F below the set point........... then after a few minutes, kick the furnace back on for the last 2*F until the T-stat is satisfied. Only happens on cycles that require a larger rise in temperature. I don't remember which model this occurs with.

[mrmichaeljmoore]

what type of thermostat?

is whole unit shutting down like a normal cycle or does blower keep running?

on a big recovery thermostat could be cycling furnace so it does not overshoot temp setting.

follow up....

I came home from work today.
Wife had already turned up the thermostat to the usual 68 degrees. She said the temperature on the thermostat when she came home read 62 degrees. (I turned the thermostat down to 55 degrees when I left the hose this morning).
I checked the thermostat. It read 66 degrees.
I ran downstairs to check the furnace.
It was off. completely off.....no blower....no nothing....and it hadn't yet reached the 68 degrees setting.
It kicked back on a few minutes later and then went to 68 degrees.

SO.....the furnace couldn't go from 62 degrees to 68 degrees without shutting down at least once.

so.....since everyone says this is not proper operation (that is, the furnace should run constantly until it reaches the set temperature), I will be calling the installer tomorrow.

i'll keep you posted.

UGH!

[pulaskihvacr]

Anticipator/cycle rate?

[mrmichaeljmoore]

Well, I am gonna try and change the thermostat to see if that is the problem....

but, even that is not a simple job.

that saga is detailed here:

http://hvac-talk.com/vbb/showthread.php?t=234312

ugh.

[mrmichaeljmoore]

I installed a new thermostat (Honeywell Focus Pro 600 #TH6110D1005) last night, but before I did I ran the furnace on the old Honeywell stat to see what happened...

Here's what happened:

Got home.
Stat read 63 degree house temp.
Set the heat at 73 degrees and furnace fired up.
Took about 9 minutes to get to 64 degrees.
Approximately 20 minutes later, with the temp at 66 degrees, furnace shut off.
Blower ran for approximately 2:30 then the furnace was completely off.
Furnace fired up approximately 2 minutes later.
Furnace ran for approximately 29 minutes then turned off. Temp was 71 degrees.
Blower ran for approximately 2 minutes then furnace was completely off.
Furnace fired up about 1 minute 15 seconds later.
Furnace ran for approximately 10 minutes and then turned off. Temp at 71 degrees.
Blower ran for approximately 2 mim 30 seconds then furnace was completely off.
Furnace fired back up approximately 1 minute later.
73 degrees obtained some time later. (lost track of how long it ran to get from 71 degrees to 73.)

Each time the furnace shut down, I went downstairs and checked the peephole on the furnace to see if the little red light was blinking any codes. It wasn't.

So I then changed the stat and hopefully that will fix it. If not, then the installer will be coming out.

anyone have any thoughts on my problem??

thanks.
mike

[superheatrman]

Mrmjmoore,
your filter is making the temperature rise thru the heat exchanger higher. to high for the furnace to stay on, your are reaching the high limit when the furnace shuts down the burner, and the blower continues to run to cool it. when the limit cools the furnaces restarts the heating cycle. this is the stopping and starting you hear. this will eventually wear out alot of parts prematurely. A cheap filter{fiberglass} will help, but not fix this issue. Most cases require increasing the blower speed and lowering the gas pressure to the burnners. to lower the overall heat input. temperature rise is how you determine how much you need to lower the gas pressure to meet your air flow, with your endust{very restrictive} filter in place. You need to take accurate supply and return temps, find the temp rise rating on manufactures rating plate. make, model numbers , pics of furnace and ductwork. are also helpful...

can you see the diagnostic light at all?

[mrmichaeljmoore]

Well, it seems to have been a thermostat problem, as my installer thought it was.

With his help, I installed a new thermostat.
Installed a Honeywell Focus Pro 6000 (TH6110D1005).

Since installing the thermostat, the furnace has run continuously until it reaches the set temperature.
Most times it has been from about 62 degrees to 68 degrees......runs non stop, no problems.
But I finally went a away for a weekend and gave the house a chance to cool down to 55 degrees.
Set the temp to 68 degrees when I got home and the furnace ran non-stop until it reached 68 degrees. Took the furnace about 45 minutes or so.

Problem solved. Excellent.
Thanks to everyone who helped.