Omnistat RC1000

[maxeym]

RC1000 stopped controlling system...only hear relays clicking but Ac does not come on. Placed conventional thermostat on system and all was well. I then placed a different RC1000 on sys but same clicking relays witHout sys firing up.

 

[pete_c]

The RC1000 might be doing that power stealing thing. 
 
I only saw it with the RC80 and never removed anything in place for the Omnistat2.
 
It is called an HAI Thermostat Isolation Module part number:  29A00-1.
 
Its been years now and I have not seen that issue.
 
Thermostat Isolation Module
 
I tested the same way you did a few years back.  It was low on the WAF when it occurred.

 

[ano]

The RC1000 can have the same power problem that the RC80 had, but the symptom is the backlight will go off and the display will flicker. The best solution is to add the power supply wires from the HVAC unit, but long time ago, they only ran a few wires (4). If your house is newer, chances are you have enough wires, but they are not always connected. (I think it is the red wire).

 

[maxeym]

Thanks for the info.
 
 I checked the voltage and it is 27V from hot to each other leg, ie heat, AC and Fan.  It has worked fine for years and suddenly it stopped.  

 

[Mr Spock]

Just because the relay is clicking does not necessarily mean its still working.  The clicking comes from the coil pulling in the contact forms.  The contacts themselves can still be bad.  Use your multimeter to confirm what is happening with the AC and fan wires when the relay clicks.  You may need to run a set of wires out of the back side of the stat so you can read the voltages when you reinstall the faceplate.

 

[maxeym]

Sorry to be so long coming back, I broke my right ring finger and I'm right handed so I could not use it effectively 
 
So I am measuring with my meter with one lead on a wire hooked to red terminal and the other on a wire hooked to the yellow terminal and I read 26 volts when the therm is not calling for AC. I expected to see zero volts and 26 volts when the therm called for AC. Do i have to find a ground to hook the meter lead that is now hooked to the red terminal to get an accurate reading?

 

[Del91574]

You are effectively bridging the relay when you place your meter between the yellow and red. Electricity goes the path of least resistance even if it's just your meter.

 

[maxeym]

I connected a wire from the common terminal on the HVAC unit to the Omnistat and it all works now.
 
Thanks for everyone's help.

 

[maxeym]

I connected a wire from the common terminal on the HVAC unit to the Omnistat and it all works now.
 
Thanks for everyone's help.

 

[pete_c]

Good news maxeym!