Furnace control problem


  #1  
Old 11-25-05, 08:48 AM
handyinnh
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Angry Furnace control problem

I have a Fordham forced hot water furnace with 5 zones using Taco valves and a Honeywell furnace control. The system has two circulating valves that splits the zones; 3 zones on one circulator and two on the other. My problem is that one of the circulators is finicky. I think it's the furnace controller itself, since I can hear a relay buzz and tapping the controller box slightly makes the buzz go away. Also turning the furnace switch on and off makes the finicky circulator operate properly for a while. Any suggestions as to narrowing down the problem to either the circulator or controller? Or is there something else going on that I should check out?

 
  #2  
Old 11-25-05, 09:25 AM
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Control Problem

The next time it gives you trouble, use a volt meter to check the terminals on the control for power. The terminals you want to check are the ones to which the circulator wires connect. If you have 120 volts & the circulator does not run, the circulator is the problem. If 120 volts are not present, & turning the switch off & back on or tapping the control causes the circ to run, the problem is in the control.
 
  #3  
Old 11-25-05, 01:57 PM
handyinnh
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Arrow Furnace control

Thanks Grady. I suspect it's the controller, but it appears to be working OK for the moment. I'll give the voltage testing a try, next time it acts up.

handyinnh
 
  #4  
Old 11-26-05, 09:07 AM
handyinnh
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Furnace control problem

Grady,

Iwas able to verify that the controller appears to be at fault. With the thermostat up, there is no AC voltage to the circulator. Turning the furnace switch off and back on applies 120v to the circulator and it does it's function. It works until the burner goes on and then the voltage drops and the circulator turns off. When the burner shuts off I hear a small buzz from the controller (probably one of the relays); if I tap the controller box slightly, the 120v goes back to the circular and the buzzing stops.

Do I have to replace the entire controller box or can a part be replaced, like a defective relay? I have a background in electrical engineering, so replacing a part is not all that difficult. The controller box is made by Honeywell, but there is no part number to be found anywhere.

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Old 11-26-05, 10:32 AM
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the numbers

if not on the inside of the cover try removing the controller and look on the backside .
 
  #6  
Old 11-27-05, 06:03 AM
handyinnh
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Talking Controller

No model number under the controller box. Part of the underside of the controller box is attached to a square junction box; the number may be there. Does the controller box have to be an exact match or can any Honeywell controller do the trick, as long it's for a FHW (Forced Hot Water) system

I'm going to experiment with cleaning the relay contacts, prior to replacing anything, to see if it corrects the problem.

Thanks for the help!
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