I’m sitting listening to the fan in our HVAC system at here at work. The fan is running constantly and doesn’t shut off.
It seems to have a mind of it’s own. The fan will run continually for several weeks. Then for the next few weeks it won’t run unless the furnace or AC kick in.
The thermostat is a programable one but we have no manual. I tried changing the switch settings, but that seems to make no difference.
There’s a button that says: “Fan” that has an “AUTO” and “ON” setting. But moving that switch does nothing.
The other switch says “AC-OFF-HEAT”. The fan runs continuously regardless of what position that switch is in.
So I basically have no clue how the system determines when the fan run or when it doesn’t.
Most of the time it’s no big deal. But when the weather is mild I need the air circulation. I work in a small back-room office, and the thermostat is out front in the main office. When the fan isn’t running it gets pretty miserable back here.
Any thoughts would be appreciated…
I go pantyless in jeans all the time. But in a skirt it’s kind of gross. [Tara Reid]
Replies
My furnace in my home would also kick on when it wasn't supposed to as well during the summers. I can't explain all of the odd behaviour you see, but this might explain why it comes on and doesn't turn off:
Old furnaces like the one I had have a temprature switch inside that will kick on the fan after the gas has heated the exchanger up past a certain point... this also keeps it running after the gas has been turned off for a few moments until it cools down again. On a hot summer day, that sensor thought that the exchanger was hot enough to need air blowing past it. I pulled pull all the wires out of the thermostat and the blower fan would continue to run! Funny thing, my furnace didn't even have a "Fan Only" option.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
More details, Boss
What kind of furnace.....
Can you pop the t-stat off the wall & see how many wires to it? (the programmable ones usually just pop off a base plate)
If it's two wire, it's most likely a problem at the furnace (maybe what the 1st reply said, though it seems a stretch)
If it's 3 wire, & one is connected to the fan slide Auto/On switch, you might be seeing an intermittent short in that circuit....
"What kind of furnace....."
Don't really know. I won't be back at work again until Wednesday. I'll see what I can find out then and post back.
Who is General Failure and why is he reading my hard drive?
I kinda let this slip for a few days - Kept forgetting about it. The tags on both the inside and outside parts of the furnace have the "Arcoaire" brand on them. The thermostat says "White-Rodgers".I pulled the front of the thermostat off. There are 6 wires coming out of the wall that are hooked to screws.
A small town that cannot support one lawyer can always support two.
I'm not an HVAC tech, but the wiring from t-stat to unit is pretty much standard
G=Fan
Y=Cooling
W= Heat
R=Furnace power 24V
Rc= Air Cond. Power 24V
Typical installation is a five wire, not six..there may be a common ground wire on your White Rodgers....which would tie to a common ground terminal at the furnace logic board.On Honeywell t-stat, the R & Rc terminals are jumpered together with a brass tab (just like a typical 110 duplex outlet). Unless the furnace/AC has separate 24V transformers for heat and cool sides, the jumper stays intact, and the 24V signal for heat or cool is powered from the red terminal. It may be that your installer should have removed the jumper & didn't, but I doubt that's the problem.The Fan Auto/On function is probably a separate slide switch on the t-stat...no digital logic involved...when you switch to on, if the t-stat is wired properly, it sends 24V from the red down the green wire to the fan relay, & the fan goes on. If you are comfortable with getting inside, turn off power to the unit, pop the cover off the furnace, you may find a second cover, pop it and note that it has a safety interlock switch, mark all the t-stat wires, disconnect them, make up a jumper from the red to green terminals, turn the power back on, hold the safety switch down & the fan should go on. If it goes on, your t-stat is probably wired wrong or the wiring to it is shorting out intermittently. If it doesn't go on, and you are sure you had power on, and the right terminals connected at the furnace, either the logic board or the fan relay are bad.Honeywell was happy to send me a manual for my t-stat N/C.....you may want to see if White-Rodgers will do the same, before troubleshooting, but at this level it's pretty straight forward.
Thanks for the suggestions. I'll look at it when I'm back at work on Monday.
A lie can travel halfway around the world while the truth is putting on it's shoes. [Mark Twain]
On a "basic" furnance and setback thermostate the fan in cool mode the fan is controlled by a fan relay that runs when the AC is on. And the Fan auto/on switch just feeds the fan relay with power even when the AC is not called on.
In heat mode the fan is controlled by either a thermostat in the heat exchanger or a time delay relay.
Fancer digital thermostats have programable controls of the fan.
The fact that the fan won't run in ON indicates that the system ASU (all screwed up).
One possibility is that the fan wire is pulled off the terminal on either the furnace or the thermostat and randomly makes contact wwith the hot wire.
"The fact that the fan won't run in ON indicates that the system ASU (all screwed up)."
Wouldn't surprise me at all.
When the AC quit 2 years ago in August, they searched far and wide to find the best possible HVAC contractor and the highest efficiency unit possible. Money was no object.
O.K. - I'm yankin' your chain. (-:
They hired a guy who looked to be about 20 years old. He had just gotten fired from a job with a HVAC contractor, and had decided to go out on his own. The company had to front him the money to buy the unit.
His extensive calcs of the size of the unit we needed centered on how they had put on like this in another office once, so he figured it was O.K.
Took him 5 or 6 days to install it. Two days later the fan fell off of the shaft on the condenser unit.
The guy came back to mess with it a couple of times. Eventually he quit returning calls.
Last winter when the temps got down to about zero, the office wouldn't get above about 55°.
Other than that, the unit works great...
Any connection between your reality and mine is purely coincidental.