I'm having a problem with my furnace short cycling.
I have a Honeywell T87F thermostat. I have the heat anticipator maxed
1.2 and it still short cycles. The thermostats on my other zones
don't have this problem.
How do I tell if the thermostat has gone bad and needs to be replaced?
You check the stat,and if its bad, replace it...check your calibration
first, and level, then insure that you didnt fry the anticipation wiring
when you moved the slider..since you only adjust that with the power
off..and finally, insure that the anticipation resistor on the backside is
in working order.
If thats all fine, then you have other issues.
The T87F is a bulletproof stat. Rare for them to give a moments issue ever.
Are you sure you don't have a furnace that is over heating and short
cycling? (Make sure you have replace your filter.)You may also have a
problem with your furnace that is causing a high amp draw on the heat
anticipator and causing your short cycling problem. You can replace the
t-stat, but if that doesn't take care of your problem then you will have to
call a Pro out to fix the problem. You could have a bad heat anticipator,
but you could also have a problem with your furnace that makes it look like
a problem with the heat anticipator.
This is Turtle.
I take it you have a Natural gas or a Propane furnace by what you have said but
I can't see it from here.
If it is Natural gas furnace. Set the Antisipator on the scale at .4 amps.
If it is Propane Furnace . Set the Antisipator on .5 amps.
If it is all electric not heat pump , set the needle to the lowest point on the
scale. I have did it so much that i can't remember if it is the 1.2 amps or .01
amps at the bottom of the scale on the T-87.
Then adjust as to the cycle length you want.
Now like other's have said check to see about too many vents being cut off or a
dirty filter causing short cycling the high limit switch. If you set it as above
and it still does the same thing. It could be any thing and call a service
company to come see.
Its a natural gas, hydronic system. There are 3 zones, and the
thermostat that is the furthest from the furnace is the one
misbehaving. I don't know if distance matters. The other 2
thermostats are fine.
I had the anticipator maxed out at 1.2 and the furnace would cycle off
after about 2 minutes. I experimented with a lower setting (.8 ??)
and the furnace cut off in a matter of seconds.
I have Teco zone valves. Can anyone suggest a digital,
non-programmable thermostat that is compatible with Teco zone valves
and widely available?
I picked up a Honeywell CT8775A digital stat today. But its not
compatible with Taco zone valves, so I'm back to square one.
We can't see it from here, but I am guessing the thermostat controls
the zone valve, not the boiler. The boiler has it's own temperature
Gary R. Lloyd CMS
HVACR Troubleshooting Books/Software
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