John Maurice; South Paris, Maine wrote:
on Thursday, January 4, 2001 at 09:20:50
> Brand: Miller
> type: hot air furnace
> fuel: kerosene
> location: living quarters
> Problem: temperature
Hi:
> My furnace is running through it's cycle and heating
the house as it should, however, the burner turns off and on about 3 times
during it's normal cycle. We had the furnace checked recently, and I think
the serviceman may have accidentally bumped the temp controls. We can't
pay to have him come out here again. I see three controls labeled off-on-off,
with
(I assume) a temperature setting label. The first off
is set to 100, the on is set to 160, and the off is set to 200. How should
I change these to make the burner run once during the cycle? Thank you
very much for your time and this service!
>
> -John
Date: Thus, 04 Jan 2001 17:38:38 -0500
I am not sure why it would go off on high limit unless
you have a clogged filter. 200 degrees is plenty high for the high limit.
If it does cycle on high limit it should be no cause for concern.
Sometimes the gas companies change the btu content of
the gas too. Check your thermostat under the cover is a little electric
heater called the anticipator. its job is to cause the thermostat to turn
off the burner before the temperature can over shoot. You will find them
on forced air systems that use gas, oil or electric. Some hot water (hydronic)
systems don't have them and most heat pump systems do not use them except
for the backup heat function. Usually it is set to the current draw on
the gas valve or oil primary. If it has been moved to a lower number that
would cause the burner to short cycle. The way to know is to remove the
cover on the thermostat and watch the mercury bulb to see if it is falling
to the off position. If it is not check to see if the limit (shown below)
is opening.
The correct way to set the anticipator
is to measure the current draw of the gas valve/oil burner plus the heat
assist device (show below) if it has one. If you have a clamp
on ammeter wrap 10 (ten) turns of wire around the pick up and read
the current and divide by 10. Ex: 6 amps =600MA or .6 amps. Set the scale
on your thermostat to this number but don't be afraid to change it if you
have too short or long a cycle.
WARNING: If you short circuit the gas valve terminals
or oil burner W terminal you will burn out the heat anticipator. You will
have to replace the thermostat! This is how a service
person can sell you a new thermostat too.
Scott 240-460-3820
This fan/limit has an "assist heater" the wires
in the center. Which adds load to the heat anticipator and must be compensated
for or short cycling of the valve or burner will result. If you do not
see the wires in the center then you have a conventional control. The two
wires you see in the center are connected across the gas valve in this
system.
If your heat pump forms
ice outside in the heat mode click
here.
If your air conditioner or heat pump ices
up
in the cooling mode click
here.
If you have
water leaking problems with your air conditioner
click here to solve it.
For other heat pump problems click
here. For other heating system problems click
here.
Any other questions feel free to contact us by
any of the means below. good luck Scott.
Written By: Scott
Meenen N3SJH of: G&S MECHANICAL SERVICES. Specializing in Mechanical, Controls
and Electrical Modifications Of
Heating, Air-conditioning, Refrigeration,
Cold storage,
Ice Production and Food preservation.
Anything having to do with Heat
and Energy.
Serving MD, DC, and Northern
VA. Contact us by pager: 1-877-467-2914 Page
us by e-mail 4103560613.3732505@pagenet.net 240Chrs max.
