# Issues with C-Wire (no power)



## dalumberjack (Jan 7, 2012)

Hi everyone.

I am trying to run a C-Wire for my thermostat as it seems only two wires were ran before since it was an old mercury switch. Here are the pictures of my situation.

As of right now, I have the red wire connected to the C-Wire on both the furnace board and the Tstat (I know I should of used a different color). I how ever am not getting any power from it for some reason. I am a little lost when it comes to this old furnace so any help is greatly appreciated.

My furnace is an old Old GE Day and Night furnace.

Click To Enlarge!

Tstat


Furnace Board


----------



## Doc Holliday (Mar 12, 2011)

R terminal from furnace is your 24 volts, should be connected to R terminal at stat.


----------



## dalumberjack (Jan 7, 2012)

Doc Holliday said:


> R terminal from furnace is your 24 volts, should be connected to R terminal at stat.


So could i bridge the R and C terminals on my furnace board so my C-Wire is powered or should I just bridge the RH and C terminal on my Tstat? In all the videos shows how to wire this 3M50 Filtrete Tstat it shows them using a C-Wire coming off of the C terminal on the board. Maybe they just bridged the R and C terminals on the board for power?


----------



## Doc Holliday (Mar 12, 2011)

Neither. At the furnace check voltage across the r and the c terminal. You should show 24-ish volts. Un-wire stat first. 

You do not need C connected from furnace to stat unless you have a digital stat that is being powered by 24 volts. 

What other wires do you have from furnace to stat? Original wires, only two?


----------



## Doc Holliday (Mar 12, 2011)

Heat only? RH and RC are the only terminals that should be jumped IF you have heating and cooling on one transformer. If only heat than no jumper, just RH.


----------



## dalumberjack (Jan 7, 2012)

Sorry to be confusing!

Is heat only. I am running a third wire (C-Wire) as my Tstat needs it for wireless capabilities. All the videos I saw from filtrete just showed them connecting the C-wire from the furnace board. But mine does not show any power. When i check from the C terminal to the R terminal I get 28 volts.

There was a second option of running power from a transformer plugged into a wall socket but I thought running the Tstat was easier. Ohh Murphy's law and noobies like myself.


----------



## gregzoll (Dec 25, 2006)

dalumberjack, R from the furnace to rh or rc on the thermostat, with a jumper between the two on the thermostat. W on furnace to W on the thermostat, C from furnace to C on thermostat. Nothing hard about it. Oh, btw be prepared for the wifi plug-in to go tits up after three months or so. I ended up swapping my wifi card to one from OurHomeSpaces on my 3m-50 and have not had a lick of problems with it since I have done that.


----------



## dalumberjack (Jan 7, 2012)

gregzoll said:


> dalumberjack, R from the furnace to rh or rc on the thermostat, with a jumper between the two on the thermostat. W on furnace to W on the thermostat, C from furnace to C on thermostat. Nothing hard about it. Oh, btw be prepared for the wifi plug-in to go tits up after three months or so. I ended up swapping my wifi card to one from OurHomeSpaces on my 3m-50 and have not had a lick of problems with it since I have done that.


I have it wired like you explained. Must be something weird going on that im not getting power from the C terminal.


----------



## gregzoll (Dec 25, 2006)

Or the fact that you have not set the thermostat up properly, by making sure that it is "Off", and changing to Mode 1. As for testing for 24vac from C to R, you need a voltmeter or multi-meter. More info on this over at the radiothermostat forums, but you are better sticking in here, since you will get better help.

BTW, when you hooked up the thermostat, did you shut down the furnace before disconnecting the old, and hooking up the new thermostat?


----------



## dalumberjack (Jan 7, 2012)

gregzoll said:


> Or the fact that you have not set the thermostat up properly, by making sure that it is "Off", and changing to Mode 1. As for testing for 24vac from C to R, you need a voltmeter or multi-meter. More info on this over at the radiothermostat forums, but you are better sticking in here, since you will get better help.
> 
> BTW, when you hooked up the thermostat, did you shut down the furnace before disconnecting the old, and hooking up the new thermostat?


Yes i shut everythind down before connecting the c wire. I will try shutting everything down again and restart to see if that changes anything. I have a volt meter and the reading between C and R is 28 volts.


----------



## gregzoll (Dec 25, 2006)

Then it should be working. What mode is the thermostat stating, when you press the upper right button on the side, until it states off, then press "Menu", "Hvac"? It should state "1" in a very large number to the right.

Now you may have to press the reset button to reset the unit, but it should be working. Now one way to find out if you did not blow anything on the furnace, is to touch the R & W together to see if the furnace starts up.


----------



## dalumberjack (Jan 7, 2012)

gregzoll said:


> Then it should be working. What mode is the thermostat stating, when you press the upper right button on the side, until it states off, then press "Menu", "Hvac"? It should state "1" in a very large number to the right.
> 
> Now you may have to press the reset button to reset the unit, but it should be working. Now one way to find out if you did not blow anything on the furnace, is to touch the R & W together to see if the furnace starts up.


Furnace works. Under menu and hvac settings it set to 1. I also reset everything as well. Maybe i will have to call someone. This furnacebhasnt been serviced (electrical wise) since 1991. Maybe there is something wrong with the C Terminal on the furnace board. Just weird that when i connect C with R on the board with my volt meter I get 28 volts. But if i test the C Wire by itself its dead.

What would happen if i hooked it up to the R terminal? I assume bad idea.


----------



## gregzoll (Dec 25, 2006)

Easier, get some rest, head to RadioShack or Lowe's, etc in the morning if you have one, and pick up a 12VAC to or 18VAC adapter and connect one adapter wire to the R wire at the furnace or at the thermostat, and the other adapter wire just to the thermostat's C. That puts 2 wires on the RH, the furnace power wire and the adapters wire; this is not a problem.

http://forums.radiothermostat.com/viewtopic.php?f=12&t=5850


----------



## dalumberjack (Jan 7, 2012)

gregzoll said:


> Easier, get some rest, head to RadioShack or Lowe's, etc in the morning if you have one, and pick up a 12VAC to or 18VAC adapter and connect one adapter wire to the R wire at the furnace or at the thermostat, and the other adapter wire just to the thermostat's C. That puts 2 wires on the RH, the furnace power wire and the adapters wire; this is not a problem.
> 
> http://forums.radiothermostat.com/viewtopic.php?f=12&t=5850


Thank you for all your help. You have been kind and helpful.


----------



## beenthere (Oct 11, 2008)

The C terminal is NOT a powered terminal. It is called common(hence the C). The power terminal is the R terminal. C is the return path for the 24 volts. Similar to neutral on a 120 volt circuit.


----------



## dalumberjack (Jan 7, 2012)

So I rechecked all the wiring around my furnace and I found the R terminal wire was a little torn up in the attic. I re-ran that wire and now I get power. Maybe it was causing some fluctuations in the voltage or something. 

But now it seems the wifi module does not work. It will flash yellow but I can't find it when I scan for networks. After a while it will flash red then just stop flashing all together.

I do now get constant 28 volts across the RH and C terminals on my thermostat. So at least I now know thats not an issue. 

Thanks for all the patience and help guys.


----------



## gregzoll (Dec 25, 2006)

Shut down durnace, pull batteries, then reverse process. When the thermostat reboots, press menu then press on the radio tower icon on the left to mate the radio with the thermostat.

Now a key here, is that the radio needs to be in the right side slot, and your router must be set for wpa/wpa2.

This is why I spent the money on the OurhomeSpaces radio, due to the problems with the rtcoa radio. rtcoa sent me another, when the first went bad, but I have never used it, so it is sitting as backup.


----------



## harleyrider (Feb 20, 2007)

dalumberjack said:


> I have it wired like you explained. Must be something weird going on that im not getting power from the C terminal.


the C is common, you dont get power from that terminal, the R is your 24 vac hot terminal. Putting the leads on your volt meter between R and C you should see 24 vac.


----------



## hvac5646 (May 1, 2011)

POOOF......sssssssst...:laughing: j/k


----------



## dalumberjack (Jan 7, 2012)

gregzoll said:


> Shut down durnace, pull batteries, then reverse process. When the thermostat reboots, press menu then press on the radio tower icon on the left to mate the radio with the thermostat.
> 
> Now a key here, is that the radio needs to be in the right side slot, and your router must be set for wpa/wpa2.
> 
> This is why I spent the money on the OurhomeSpaces, due to the problems with the rtcoa radio. rtcoa sent me another, when the first went bad, but I have never used it, so it is setting as backup.


I tried to look up that company to see what their module looked like. All I got on their homepage was info about what they do.

Care to point me in the direction of where you got their wifi module. 

I might return to home depot for another to see if its a tstat issue. Waiting on reply from Filtrete to see what they say. Won't hold my breath though.


----------



## gregzoll (Dec 25, 2006)

It is the same style module, and is actually a Wireless-B radio, not Wireless-G like the RTCOA. That is probably why I have had better luck with it. Here is the radio http://store.ourhomespaces.com/products/OHS-USNAP-module-for-Radio-Thermostats.html









You can actually contact Radio Thermostat and they will send you a new radio. Otherwise, you may do like I did and go for the other one. I have actually had the guy that runs Our home spaces call me personally and work on a problem that we had with my thermostat not working properly with the website, when he did a upgrade. Very good service that I have had compared to RTCOA. Definitely a difference between the two, plus a lot better solution in my opinion compared to the one that RTCOA went with.


----------



## More Power! (Aug 2, 2011)

I played with one of those Filtrete wireless thermostats. Lousy product, IMO. Even once I persuaded it to work: The thermostat, their web page and the Android app all disagreed with the thermostat's status. That was _definitely_ disquieting. Plus, understand this: The wireless operation of that thermostat is _only_ via their "cloud" services. Personally: I'm not comfortable having control of my HVAC system via some "cloud" servers. _Especially_ services that can't seem to get three displays in sync. "It's 72F and the fan is on." "No, it's 70F and the fan is off." "No, it's 54F, and the thermostat is in 'away on vacation' mode."

Yanked the wireless module right away, then yanked the thermostat and replaced it with a Honeywell non-wireless model. Much, much happier.

From my research: If you want wireless HVAC conrtol, Z-Wave is the best way to go. Honeywell makes nice Z-Wave programmable thermostats. That's the way _I'd_ go, if I wanted to go wireless.

I wouldn't touch a Radio Thermostat Company of America (that's who makes the Filtrete wireless thermostat) product again for all the tea in China.

Jim


----------



## gregzoll (Dec 25, 2006)

Jim, problem is with the honeywell, you are stuck with one type of program or site to control, vs, the Filtrete/rtcoa with the radio I posted, you can control through there with the iPhone app. BTW, the android app for the rtcoa has issues, just like the iphone, and some of the other programs. The thermostat is good, just the module that comes with it is bad. My first radio went out in less than two months after I installed, is why I went with the OHS radio, which is a lot better radio module, and a whole lot easier to control. Plus I can monitor the TED5000, and they also have a light module, and some more features through other modules.

I hated the RTCOA website and the whole having to run a third party software on a computer that had to be up 24/7, if I wanted to watch usage. OHS, the site does the monitoring, and I can adjust schedules also on there.


----------

