Changing Thermostat that ONLY runs of battery


  #1  
Old 09-17-13, 08:52 AM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
Changing Thermostat that ONLY runs of battery

Good afternoon!

Today I wanted to power up the heating system so its ready to go in case we get an early cold snap here in NJ.

My thermostats are 2 wired (R and W) and run ONLY off battery.

I am off out to buy a couple more thermostats as I want something more modern

I was looking at Nest but have settled on Honeywell RTH8580WF based on stuff read on here.

I would like to run mains power to the thermostat since I an changing them and want to check how to do so.

I am assuming that the thermostat runs off 12v power? Is this like wiring a doorbell? Mains to 12v transformer to thermostat?

If so, where do I connect the power wires?

Thanks in advance
 
  #2  
Old 09-17-13, 09:30 AM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,726
Received 2 Votes on 2 Posts
What type of heating system do you have? HVAC control systems are normally 24VAC.
 
  #3  
Old 09-17-13, 09:57 AM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
My heating system is baseboard hot water, gas powered with a Williamson Furnace

The transformer sending power to the heat pump and thermostat controls at the furnace says 12v/24v on it if that helps
 
  #4  
Old 09-17-13, 10:33 AM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,726
Received 2 Votes on 2 Posts
Depending on the age and model of your system there may be a C connection on the control board that you can run a wire out to the thermostat to provide constant power to it. However, if it is just a straight furnace it will probably only have two screws to connect the r and w wires. If that is the case then you could use a separate transformer to run a wire to the "C" terminal to power your new thermostat. If you provide a model number of your furnace hopefully I can find a schematic to see what components and wiring you have from the low voltage side. At the thermostat do you have any other wires available besides the r and w wires?
 
  #5  
Old 09-17-13, 10:42 AM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
Thanks...Model number is GWA-140-N-S. It is one year old.

I am confused though. Doesnt it just need a power source?

Cant I just split a 110v line close to the thermostat, run it through a transformer and connect to the stat, rather then try to run wires through my house to the furnace?

Running something from basement to first floor isnt an issue, but running to second floor is a nightmare. I was thinking for second floor I could just run 110v to a transformer in the attic then drop it down?
 
  #6  
Old 09-17-13, 10:47 AM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,726
Received 2 Votes on 2 Posts
Ok. That model number shows to be a boiler, hence my confusion as you said it was a "furnace"

Yes, you can run a separate 120V to 24V transformer to power the thermostat. You could mount the transformer very close to your thermostat location. This should be a pretty simple project.
 
  #7  
Old 09-17-13, 10:51 AM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
Thank you...where on the new Thermostat would I connect the power.

Thanks for your guidance thus far.....figuring out if I can run the downstairs to the control board would be a big help too for me...thanks!
 
  #8  
Old 09-17-13, 11:27 AM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,726
Received 2 Votes on 2 Posts
One of the wires from the transformer will go to the "C" terminal on the thermostat. The other wire from the transformer will go to the RC terminal on the thermostat. There should be a jumper between R and RC on the thermostat. Leave that in place. Of course, the wires from the furnace will go to the R and W terminals on the thermostat. Let us know how it works out.

Also, you said that the thermostat wiring was 12/24 Volts? Is there something you need to do to have it be 24V?
 
  #9  
Old 09-17-13, 11:33 AM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
Thanks.

What about the first floor...is it doable to run from my furnace control board to the thermostat on the first floor for power? If so how?

I really appreciate your time and help
 
  #10  
Old 09-17-13, 11:45 AM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,726
Received 2 Votes on 2 Posts
Without being there it is hard for me to imagine what it would take to accomplish that task. There are so many variables involved. I would suggest for the fact you said you have a 12/24V transformer on the boiler that you contact the manufacturer of ther boiler and see if it is alright to connect a 24V transformer to your system. Also, think about warranty issues if something goes wrong. I have seen people power their thermostats with the type you just plug into the wall and then snake the two wires up behind the thermostat and wire it up. If you want to spend the bucks you could look at some of the wireless thermostats on the market.
 
  #11  
Old 09-17-13, 12:29 PM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
I was looking at this one
But it says "C Wire Required"

IS C wire power?

The manual says its 24v

Ive taken off the downstairs thermostat and there are wires already ran. Ive traced them to close to the boiler so I can connect this easily to the boiler.

I of course have no idea where on teh thermostat to connect or on the boiler

Page 3 of below shows the control wiring to my boiler

http://ecomfort.com/PDF_files/Willia...e%20Manual.pdf

NOTE: I called the manufacturer and they do not deal direct with consumers!!! eff me
 

Last edited by Cantona; 09-17-13 at 12:58 PM.
  #12  
Old 09-17-13, 03:02 PM
firedawgsatx's Avatar
Member
Join Date: Jul 2013
Location: USA
Posts: 1,726
Received 2 Votes on 2 Posts
The "C" wire is the wire that provides constant 24V to the thermostat so you don't have to use batteries for power. From the linked documentation you provided it looks like the thermostat is wired to the "R" and "G" terminals on the boiler. It also appears that you could grab 24V power from the transformer "C" wire. There are two wires that come out of the 120V to 24V transformer. If you find the transformer in the schematic you will see what I mean.
 
  #13  
Old 09-17-13, 03:05 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 4 Votes on 3 Posts
IS C wire power?
Well... yes, and no... the "C" wire is a COMMON wire and serves as the 'return' for the 24VAC to the thermostat. So yes, it is a power wire of sorts.

Be VERY CAREFUL what you are doing there... adding transformers has the potential to burn out controls with too much voltage if not done EXACTLY correctly. There is no 'close enough'. Make a mistake by connecting the wrong wire to the wrong place and 'poof'... there goes a new thermostat... or the new transformer... or the boiler control...

If you look at the wiring diagram on page 3 of the boiler manual that you posted, you will see that the thermostats are connected to the R and the G terminals, and that you DO HAVE a "C" connection available to use.

HOWEVER... and this is a BIG HOWEVER! Pay close attention!

Your system is ZONED into however many zones that you have thermostats.

If you have two thermostats, you have two zones. This means that you also have ZONE VALVES most likely... unless you have multiple PUMPS, one for each zone.

This probably changes EVERYTHING about where to get the "C" wire from, and whether or not you can use additional transformers.

Before you do anything further, either describe fully how your system is zoned, or better yet, take many pictures so we can see for ourselves.

We do NOT want you to fry anything! or yourself!

I called the manufacturer and they do not deal direct with consumers!!! eff me
Yup. I knew that was coming!
 
  #14  
Old 09-17-13, 08:20 PM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
Hi

I have one pump for both zones. I have an external transformer that powers the zone valves and an internal one that seems to power the pump.

NJ Trooper...you actually guided me through wiring this up when I installed the boiler myself about a year ago! (Thanks again)

Pictures below

Name:  20130917_231251.jpg
Views: 2154
Size:  26.1 KBName:  20130917_231302.jpg
Views: 2270
Size:  45.3 KBName:  20130917_231321.jpg
Views: 2239
Size:  28.5 KBName:  20130917_231336.jpg
Views: 2054
Size:  21.4 KB
 
  #15  
Old 09-17-13, 08:24 PM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
One more of the control board

Name:  blah.jpg
Views: 2295
Size:  50.0 KB
 
  #16  
Old 09-17-13, 08:36 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 4 Votes on 3 Posts
OK... some of the pics are too dark to see anything, but I can see enough to know that you do NOT, repeat DO NOT want to use the "C" connection on the R8285 control box.

In the FIRST pic, is that the transformer that powers the zone valves?

In the SECOND pic, there are two brown wires going UP which are connected to the YELLOW wires from the zone valves... those should be the wires going to your thermostats.

The brown wire going down and to the right should be going to the external zone valve transformer.

It's kinda jumbled up with the red wires, but both sets of red wires should be connected in parallel and a wire should go back to the R8285 control box and land on terminals G and R (if I remember correctly).

Is this all correct so far?
 
  #17  
Old 09-17-13, 08:46 PM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
Yes, all 100% correct.

The system has worked like a dream since I (we) installed it, but I am assuming with nothing but battery power, a new smart wifi thermostat will probably need a battery change daily....hence my mission.
 
  #18  
Old 09-18-13, 05:42 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,539
Received 4 Votes on 3 Posts
Good...

In order to use a thermostat that requires the " C " connection, that wire would come from the wirenut that connects the 2 yellow wires with the wire back to the transformer. This appears to be the WHITE wire in the brown cable to the zone valve transformer.

The RED wire from the transformer appears to be joined with the 2 RED wires to each thermostat, and the WHITE wire from each thermostat connects to the OTHER YELLOW of each zone valve.

So, to recap, the " C " wire to each thermostat needs to come from the 2 YELLOW and 1 WHITE wirenut connection.

I don't think that the battery life is that bad, but certainly not having to change batteries at all is a plus!
 
  #19  
Old 09-18-13, 06:50 AM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
Great, thanks.

I am off out to buy a new fangled thermostat and will give it a go!
 
  #20  
Old 09-18-13, 06:58 PM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
Did it on the 1st floor today (the brown contained 4 wires so it was a case of picking one and connecting at both ends.....very simple.

Worked like a dream.....

The upstairs however does not have the wires already there to do this.

For teh 2nd floor, can I pic up a 24v transformer as another person mentioned, put it in the attic and drop a common down from that?

Anything I can do to rig it becuase wiring it from the basement to teh second floor isnt happening
 
  #21  
Old 09-18-13, 07:03 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 62,543
Received 1,598 Votes on 1,473 Posts
Yes....you can install a smaller 24vac transformer (20va) and connect it to the R/Rc and C terminals on the thermostat. That would mean you would end up with two wires on the R/Rc terminal on the t'stat.
 
  #22  
Old 09-18-13, 08:01 PM
C
Member
Thread Starter
Join Date: Jun 2008
Location: NJ
Posts: 60
Received 0 Votes on 0 Posts
Thank you everyone !

NJTrooper - If HVAC is your profession and you are in NJ, PM me your contact info....after the help you have given me on here several times, I'd like to use your service should I ever need it live.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: