So the compressor runs and then at some point the A/C decides to turn on the blower fan. Mine works fine for awhile, but then it starts turning the fan on and then off again, within a few seconds, as if it can't decide whether the coil is cold enough.
On Wednesday, June 18, 2014 10:16:26 PM UTC-4, Davej wrote:
Are we talking about a central AC system that's part of
a furnace? A window unit? A mini-split?
IDK what the latter does, but in all the first two types
that I've seen, the coil temp doesn't control the blower.
The blower is turned on and the compressor start at the
same time. When it shuts off, the blower typically stays
on for another minute or two after the compressor goes
On Thursday, June 19, 2014 6:39:38 AM UTC-5, trader_4 wrote:
Hmmm, you're right. I thought it worked identical to the furnace but apparently not. I've had this strange blower fan operation ever since the furnace was installed and have used continuous fan to avoid it, but now even continuous fan has strange behavior.
On Thursday, June 19, 2014 7:50:37 AM UTC-4, Davej wrote:
rently not. I've had this strange blower fan operation ever since the furna
ce was installed and have used continuous fan to avoid it, but now even con
tinuous fan has strange behavior.
You need to put a meter on it and see if it's getting power but not running
or if the control board is not keeping it powered.
On Thursday, June 19, 2014 8:25:22 AM UTC-4, jamesgang wrote:
parently not. I've had this strange blower fan operation ever since the fur
nace was installed and have used continuous fan to avoid it, but now even c
ontinuous fan has strange behavior.
ng or if the control board is not keeping it powered.
Agree, that would be a good place to start. Also, if it;s a modern unit,
they have LEDs that light to indicate OK or identify faults if the CPU
board knows there is one.
Running the fan constantly may not be such a good idea either. In furnaces
from 25 years ago, putting the fan on all the time put it on high, the
same speed as for cooling. Which is OK, except that those motors were
not efficient and it's going to run up $$$, running when it doesn't need to
Newer furnaces, the blower when set to run all the time, doesn't run
at high speed. Mine runs closer to the heating speed. That isn't going
to produce maximum cooling. With mine, if the AC kicks on, then it goes
up to high. With the OP system with the problem, without knowing how
it operates no way to know what it does.
On Thursday, June 19, 2014 8:16:15 AM UTC-5, trader_4 wrote:
The symptom has cured itself for the past few days. When the symptom was oc
curring I could hear a relay clicking on the furnace board, so it was defin
itely deciding to turn the blower fan on and off. Also the blower fan motor
was cool to the touch. The furnace controller terminal voltages never chan
ged: Red had 26VAC and Green had 20VAC continuously.
I think the first thing I should do is get the thing wired correctly becaus
e I suspect that it has never been wired correctly.
The way the companies dick around with settings to meet certain seer
ratings, it would not surprise me that the blower is set up to only come on
when a certain head pressure or coil temperature is reached. Probably not
your case, but could be.
That is one reason why the fans ramp up in speed instead of comming on and
just have one speed for heating and anther for cooling in a heat pump.
On Thursday, June 19, 2014 11:39:52 AM UTC-4, Ralph Mowery wrote:
I've never seen such a thing and doubt it exists.
It certainly wouldn't be based on temperature or
pressure, because the controller in the furnace isn't
measuring either of those. It could have a time delay,
but every system I've seen the blower starts at the same
time as the compressor. My new Rheem ramps up over
about 30 secs, but it starts same time as the compressor.
The coil is cold very quickly. Without knowing exactly
how they calculate the SEER, it's just speculation that
a 30 sec or 1 min delay would even have any effect at all
on the SEER.
Your source for that? I thought the reason variable
speeds ramp up is because they can and it makes the
blower far less noticeable when it starts up.
IDK about heat pumps, but my Rheem has multiple jumper selectable
speeds for both heating and cooling. The heating speed in
every furnace I've seen has always been less than for cooling.
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