*
Ok I know this has nothing to do with
homebuilding but my gas furnace is
acting strange.
The fan motor cuts in for short (10-15
secs) periods of time without the
thermostat being “on”. I looked inside
the furnace and there is a Honeywell
control box which has a “Fan Limit” dial
that looks sort of like an plug-in
electric timer. It has temps marked in
degrees from 80 to 250 degrees. The
range from 100-150 degrees is marked
“Off” and “On” with “Off” being the 100
deg. end and “On” at the 150 deg. end.
Way up at 250 deg. end there is
another “Off” mark. For each “Off” and
“On” mark there is a movable
pointer. The pointers are set within the
ranges.
I assume this controls the temps at
which the fan starts after the
thermostat cuts in so that the fan
starts when the air in the firebox is
actually warm instead of starting when
the burners first light and blowing
ice cold air which gradually gets
warmer.
The pilot in the furnace is always on
and I wonder if it is so warm that the
control thinks that the firebox is warm
enough for the fan to start?
I have tried raising the “On” pointer
past 150 deg. thinking I would raise
the level that the fan would start. It
made no difference.
Any comments before I call in a service
person?
Many thanks in advance,
David
Replies
*
I think you really know you're fooling with fire, literally. You shouldn't be messing with those temperature controls. Call a HVAC professional.
*Do you have a heating/cooling system, or heating only? If the former, then there could be other controls affecting the fan ......Lee
*In mild weather it is normal for the fan to cycle back on after the thermostat has turned the burner off and the fan has stopped. This is because air movement over the fan control cools it enough to turn the fan off then the residual heat warms the control up and causes it to start the fan again, this is especialy true if the fan "on" temperature is set at a low range.
*
Ok I know this has nothing to do with
homebuilding but my gas furnace is
acting strange.
The fan motor cuts in for short (10-15
secs) periods of time without the
thermostat being "on". I looked inside
the furnace and there is a Honeywell
control box which has a "Fan Limit" dial
that looks sort of like an plug-in
electric timer. It has temps marked in
degrees from 80 to 250 degrees. The
range from 100-150 degrees is marked
"Off" and "On" with "Off" being the 100
deg. end and "On" at the 150 deg. end.
Way up at 250 deg. end there is
another "Off" mark. For each "Off" and
"On" mark there is a movable
pointer. The pointers are set within the
ranges.
I assume this controls the temps at
which the fan starts after the
thermostat cuts in so that the fan
starts when the air in the firebox is
actually warm instead of starting when
the burners first light and blowing
ice cold air which gradually gets
warmer.
The pilot in the furnace is always on
and I wonder if it is so warm that the
control thinks that the firebox is warm
enough for the fan to start?
I have tried raising the "On" pointer
past 150 deg. thinking I would raise
the level that the fan would start. It
made no difference.
Any comments before I call in a service
person?
Many thanks in advance,
David