Furnace short cycle question
 

Hello

I've got a fairly new (5 year) York gas furnace in my home, high efficiency.
Also a cooling "A" coil in the uprising plenum, installed at the same time.

I'm getting a short-cycling condition when it gets cold. I've checked the
various cutoffs, and I think it's a combustion chamber over heat limit
switch that's kicking out. It's done it on and off since I got the
furnace, but I usually just notice it on the coldest days. I've run it
with filters out just to see if they were restricting the airflow, and they
don't seem to be the problem.

I'm suspecting an air flow problem. The A coil, which is a new cooling coil
spans the entire length and width of the plenum, in other words, air can't
get around it in the winter...it has to go through it. I've seen some
furnaces where the plenum is wider than the coil, and in the winter, you
can open up a louver to let air around the coil. I've also seen coils held
up by two sheet metal straps so that air could get around it, but this one
is in a tray that blocks any air from getting around it. The coil is about
3 inches less than the diameter of the plenum, so this tray makes up the
difference to complete block any air from getting around the A coil.

Any comments on this type of installation? Could this be the source of my
short-cycle problem? Any tests or solution? Any way to clean the coils
in-place (can't imagine doing that, everything would drip onto the motor).

Thanks

Harry

"Harry" wrote in message
...
Hello

I've got a fairly new (5 year) York gas furnace in my home, high
efficiency.
Also a cooling "A" coil in the uprising plenum, installed at the same
time.

I'm getting a short-cycling condition when it gets cold. I've checked the
various cutoffs, and I think it's a combustion chamber over heat limit
switch that's kicking out. It's done it on and off since I got the
furnace, but I usually just notice it on the coldest days. I've run it
with filters out just to see if they were restricting the airflow, and
they
don't seem to be the problem.

I'm suspecting an air flow problem. The A coil, which is a new cooling
coil
spans the entire length and width of the plenum, in other words, air can't
get around it in the winter...it has to go through it. I've seen some
furnaces where the plenum is wider than the coil, and in the winter, you
can open up a louver to let air around the coil. I've also seen coils
held
up by two sheet metal straps so that air could get around it, but this one
is in a tray that blocks any air from getting around it. The coil is
about
3 inches less than the diameter of the plenum, so this tray makes up the
difference to complete block any air from getting around the A coil.

Any comments on this type of installation? Could this be the source of my
short-cycle problem? Any tests or solution? Any way to clean the coils
in-place (can't imagine doing that, everything would drip onto the motor).

Yes

"Harry" wrote in message
...
Hello

I've got a fairly new (5 year) York gas furnace in my home, high
efficiency.
Also a cooling "A" coil in the uprising plenum, installed at the same
time.

I'm getting a short-cycling condition when it gets cold. I've checked the
various cutoffs, and I think it's a combustion chamber over heat limit
switch that's kicking out. It's done it on and off since I got the
furnace, but I usually just notice it on the coldest days. I've run it
with filters out just to see if they were restricting the airflow, and
they
don't seem to be the problem.

I'm suspecting an air flow problem. The A coil, which is a new cooling
coil
spans the entire length and width of the plenum, in other words, air can't
get around it in the winter...it has to go through it. I've seen some
furnaces where the plenum is wider than the coil, and in the winter, you
can open up a louver to let air around the coil. I've also seen coils
held
up by two sheet metal straps so that air could get around it, but this one
is in a tray that blocks any air from getting around it. The coil is
about
3 inches less than the diameter of the plenum, so this tray makes up the
difference to complete block any air from getting around the A coil.

Any comments on this type of installation? Could this be the source of my
short-cycle problem? Any tests or solution? Any way to clean the coils
in-place (can't imagine doing that, everything would drip onto the motor).

Thanks

Harry

Sounds pretty typical installation to me.

If this situation is only on the coldest days. (long run times) And it has
been that way since the installation. The issue is/was in the installation
of the unit originally. Screwing with the A coil will only serve to play
havoc with your air this summer.

It is impossible to troubleshoot remotely. Hire a pro and be done with the
problem