Any HVAC guys on here?

   #1  

rumble phish

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Just installed a Honeywell RTH7500 programmable thermostat and my blower fan won't shut off.
 
   #4  

Austin_F

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My system has a setting to be always on at very low speed, set by the installer. Not accessible to the homeowner. Supposedly uses less electricity to let it run like that and speed up on demand rather than getting it going from a dead stop.

Not sure I believe it. I told him to set mine to turn all the way off. We have short time periods where we have the windows open.
 
   #5  

Wretch

amazingly graceful
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is overrated
The more you bend a piece of metal back and forth, the sooner in fatigues and fails.

The same with cycling electrical and electronic circuits.

Heat, cool, heat, cool physically works the metals.

Just ask Hagrid.
 
   #8  
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on the back of the thermostat is the 4 digit installer master code. use it to log in under installer settings and adjust as needed, though this shoulnt be necessary. fan settings are attached to time periods in your schedule. you should try that first before you fuck up your dead band etc.
 
   #9  

fr0st

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My system has a setting to be always on at very low speed, set by the installer. Not accessible to the homeowner. Supposedly uses less electricity to let it run like that and speed up on demand rather than getting it going from a dead stop.

Not sure I believe it. I told him to set mine to turn all the way off. We have short time periods where we have the windows open.
Dont believe that shit..

If it doesnt need to run make it stop

You'll wear out the bearing and other parts for reason..

Doesnt cost much to start stop a fan if its not a 50 hp motor.
 
   #12  
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rumble phish

rumble phish

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Have you tried turning it off and turning it back on again?
Yep, first thing I tried :lol: Didn't work. The only way I can get the blower motor to shut off right now is to flip the breaker.

Mind has a "fan on" setting. Turn that off.
There is no "off". Only "Auto", "On", and "Circ". It is currently set to "Auto" and the system is "Off" (no heat, no AC) and the fan is STILL on.

My system has a setting to be always on at very low speed, set by the installer. Not accessible to the homeowner. Supposedly uses less electricity to let it run like that and speed up on demand rather than getting it going from a dead stop.

Not sure I believe it. I told him to set mine to turn all the way off. We have short time periods where we have the windows open.
Yeah, that's the "Circ" setting on mine. Runs the fan at 33% load at various times. I do not have that enabled at this time.

Fan has to be set to auto.
It is set to "Auto". The fan will not shut off even when I pull the thermostat off the wall.

on the back of the thermostat is the 4 digit installer master code. use it to log in under installer settings and adjust as needed, though this shoulnt be necessary. fan settings are attached to time periods in your schedule. you should try that first before you fuck up your dead band etc.
I went in under "ISU" which is system set up options. I also went through the programming options and there are no options to turn the fan on or off. It stays on "Auto" during the program sequence.

A little back story - My system only has 4 wires. W (White), Y (Yellow), G (Green) and R (Red). I snapped a pic of how these wires were set up on the original thermo and copied that set up to the new one (per the instructions). Turned off the mains before fucking with the wires, installed the new thermo and it worked great. AC kicked on right when it should've along with the blower. Except that when it got to temp (78 F) the blower kept on blowing. Thought it would kick off in a few second, maybe a minute but it ran all night. No matter what I did, short of flipping the breaker, it would just run. This morning I went back through everything, double checked the wiring, flipped the breaker on and off and it's still running. At this point I'm thinking it might be a bad relay on the blower motor itself.


Guess it's time to call the HVAC guy :mad2:
 
   #13  

DaCat

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How competent are you at fault finding? Do you have a multimeter?

If both questions have a positive response, then your last paragraph gave a good hint. Check that the relay does not have closed contacts when the power is off. That will eliminate the faulty relay theory or prove it.

If the relay contacts are open it means it is coming on when the system is energized, ie. control signal to the relay coil to start the fan.

I don't know the system as it is most likely not sold here, but the logic to fault finding will be the same.

Next step to be advised...

PS. No, I'm not a HVAC guy, but I know a little which could be dangerous.
 
   #15  
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rumble phish

rumble phish

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Got it figured out. My old thermostat didn't use the C (common) wire, which is blue. I pulled the cover off of the blower and saw that it did have the C-wire hooked up. Pulled the thermostat off the wall and pulled the wire bundle through a bit and found that, sure enough, the C-wire was never used. Trimmed back the wire, hooked it up to the C terminal and BAM! Everything works now.


Guess sometimes you just need to think out loud to see the issue right in front of you. Thanks all for the advice (and chuckles).
 
   #16  

Rusty Nuts

Building things in Paradise, and drinking JD
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I love it when a question is asked and tons of advise is given, but there’s one little bit of info not out there. Solved!!! By the guy asking......😎
 
   #21  

sailUSVI

Tripping on the road and buying stuff
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We have or had, 2 HVAC guys in Florida...?

Need more info on your unit, heat pump? How old is it? Brand?
 
   #23  

sailUSVI

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Probably a stuck or bad relay.
 
   #28  
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rumble phish

rumble phish

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I'm not reading through this whole thread. Have you checked the blue wire? It's not used on some older thermostats, but probably will be needed on this new one.
Yep, that was the one. It's all fixed now. The old thermostat didn't use the blue (common) wire, so when I wired up the new one there was no
 
   #30  

Z

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aside from banging it...check blue wire. Also PM @Z he has nothing better to do. He taught Master-Cylinder Master-Cylinder all about hvac

:razz: Wrongo,, dere,,,,,,,, :turboblew:boy :smashtard:

I ran,,,,,,,,,, a,, commercial REFRIGERATION. biz.. :lol:

Neva laid a hand on,,,,,,,,,,,,, residential a/c.. :mad2:

Cept,,,,,,,, my own,,,, a course,,, :yahoo:
 
   #32  
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My system has a setting to be always on at very low speed, set by the installer. Not accessible to the homeowner. Supposedly uses less electricity to let it run like that and speed up on demand rather than getting it going from a dead stop.

Not sure I believe it. I told him to set mine to turn all the way off. We have short time periods where we have the windows open.
Well you can be sure the installer is not up to speed. If the fan stays on all of the time it is actually costing you money. How? Do not know where you live but the heat load in the summer on the duct work and equipment in the attic is transferred and put back into your home. Same happens in the winter just the opposite.

The "new" not really that new thing now is for the compressor (ac) to run at low speed on a 2 speed compressor and a "lower" speed on a variable speed compressor to more effectively manage humidity which has a significant impact on how comfortable the body feels at a given temperature. It does work have several friends and a relative who went that route vs the zoning approach I use in my house. Personally for me zoning is much better but much more expensive to install.
 
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