We have moved at community.getvera.com

Author Topic: Providing 24VAC power to Z-Wave Thermostat  (Read 44865 times)

Offline drzeller

  • Full Member
  • ***
  • Posts: 103
  • Karma: +1/-0
Providing 24VAC power to Z-Wave Thermostat
« on: April 01, 2009, 04:23:12 pm »
I am putting in an RCS-TZ43 thermostat.  My existing system is a simple 2-wire setup with no 24VAC power supplied.

I know I need to get a 24VAC power supply, but am having doubts about my interpretation of the instruction manual regarding where to wire the new supply into the thermostat.

Anyone with experience in this?  I love some advice.  The link below is to the installation manual.  Page 31 is where the wiring starts up.

http://www.resconsys.com/docs/thermostats/zwave/TZ43%20INSTALLATION%20MANUAL%20141-01652-04.pdf

Thanks,
David

Offline wseverino

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 854
  • Karma: +0/-0
  • Da Man, Da Myth, Da Legend - in his own mind!
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #1 on: April 01, 2009, 05:07:31 pm »
I had to re-wire my system for my WDTC-20. It would help if we know a little more about your system.
My ZWave Network: Too friggin big to list.....

Offline drzeller

  • Full Member
  • ***
  • Posts: 103
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #2 on: April 01, 2009, 06:05:17 pm »
My heating system is a one zone, boiler-fired steam heat system.  The current thermostat is two wire, and closing the circuit turns the boiler on.  I think it is about the most basic you could have!  What else can I tell you?

Thanks for following-up.

David

Offline zmistro

  • Hero Member
  • *****
  • Posts: 966
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #3 on: April 01, 2009, 08:37:36 pm »
one thing you need to know if the old stat is works from a millivolt or 24v.

Either way you need get 24v to the stat.
If you have a millivolt  system you will need wire a relay in place of the old stat and add 24 volt transformer to power the thermostat and control the relay.
The transformer will power the relay when the thermostat calls for heat.
Parts:
1) general purpose single pole N/O  24v coil relay
2) RCS thermostat
3) 3 wire min thermostat cable from control at Boiler to Wall Thermostat.

Wire at the stat
C= 24v common ( one terminal of the Transformer common to the relay)
R= 24v Hot from transformer ( The other terminal of the 24v transformer )
W= Heat connect to one side of the 24v coil of the Gen purpose relay.

At the relay connect the other terminal to the Common side of the transformer which is the same wire used to connect to the C terminal of the stat.


If you have a 24v system but no common wire you can add this.
Or you can use an Add a wire from your local HVAC dealer These may be hard to get.


Offline drzeller

  • Full Member
  • ***
  • Posts: 103
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #4 on: April 02, 2009, 10:43:52 am »
Thanks, guys.  I may be back with more questions once I'm in the throws of things!

David

Offline drzeller

  • Full Member
  • ***
  • Posts: 103
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #5 on: April 02, 2009, 11:26:13 am »
Ok, I just did a little poking around with my multimeter.  The two wires coming to the thermostat read 28 V.  I found the documentation for the system online, and it indicates the power on those lines should be 24V.  I'm not sure how much the 4V matters.  In any case, I have just 2 lines, so I believe I am missing the common.  Does that sound correct?

As an aside, I also check the voltage at the boiler, and, too reads 28V.

D.

Offline drzeller

  • Full Member
  • ***
  • Posts: 103
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #6 on: April 02, 2009, 11:46:14 am »
I found a nice guide to Thermostat wiring.  You can find it at http://www.ritetemp-thermostats.com/images/ritetemp_Professionalreferenceguide_current.pdf

I found what I was looking for (including a Radio Shack part number!) on page 21.

It was mentioned in the Wikipedia article about thermostats. 

David

Offline zmistro

  • Hero Member
  • *****
  • Posts: 966
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #7 on: April 02, 2009, 12:26:24 pm »
Thats great . Yes your assumtion is correct you have a 24 volt system needing a Common.


What Wikki article?

Offline zmistro

  • Hero Member
  • *****
  • Posts: 966
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #8 on: April 02, 2009, 12:38:44 pm »
I looked at that radioshack product. It may not do the job. Certain thermostats cannot have two 24 power sources.

You may be able to just cut a jumper wire and add the 24 volt wall wort

I believe there is an add wire from Venstar or ?


If you add a 24 volt make sure that you don't mix the two 24v power sources together.

Offline drzeller

  • Full Member
  • ***
  • Posts: 103
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #9 on: April 02, 2009, 05:04:55 pm »
Thats great . Yes your assumtion is correct you have a 24 volt system needing a Common.


What Wikki article?

http://en.wikipedia.org/wiki/Thermostat

Offline drzeller

  • Full Member
  • ***
  • Posts: 103
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #10 on: April 02, 2009, 05:06:25 pm »
I looked at that radioshack product. It may not do the job. Certain thermostats cannot have two 24 power sources.

You may be able to just cut a jumper wire and add the 24 volt wall wort

I believe there is an add wire from Venstar or ?


If you add a 24 volt make sure that you don't mix the two 24v power sources together.

Hmmm.... I read this too late.  I have both the previous red wire and one of the two leads from the wall wort going to the RH connection and the other wall wort wire going to the 24VAC Common connection.  The original white wire goes to W.

It is working... should I change it?

D.

Offline zmistro

  • Hero Member
  • *****
  • Posts: 966
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #11 on: April 02, 2009, 07:03:52 pm »
I can't see the smoke from my office so it must be ok.  ;D

Reality if there was a issue It would have shorted one of the transformers out. or possibly over voltatge the relay. Check with a volt meter if 24v+-  then you should be good to go.
Usually I never attempt to have two power supplies conected to the same set of terminals.

Offline franklin1990

  • Newbie
  • *
  • Posts: 1
  • Karma: +0/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #12 on: April 23, 2009, 01:48:30 am »
           Well, what is the capacity of that model:Z-Wave Thermostat?

_________________
Thermostat

Offline zmistro

  • Hero Member
  • *****
  • Posts: 966
  • Karma: +1/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #13 on: April 23, 2009, 09:14:18 am »
capacity of what part?
the relay in the stat. Normaly mili-amps. enough to power the heating relay.

Offline soconnorny

  • Newbie
  • *
  • Posts: 3
  • Karma: +0/-0
Re: Providing 24VAC power to Z-Wave Thermostat
« Reply #14 on: February 24, 2010, 10:19:46 am »
I have exactly the same issue - let me ask what may  be a really silly question but if I have the 2 wires from the oil furnace going into W and RH could I add a third line from one of the two 'T' connections on the furnace relay and connect it to 24COM ? Or would it be crazy to add 2 lines from each of the 'T' terminals on the furnace and connect them with 24COM and 24RC whilst 2 other lines from those same 'T' terminals go into W and RH (whilst I cut the jumper on the Z-Wave thermostat board).

I spoke to an electrician who said that I only need to connect to RH and W and cut the jumper but I am not sure that would work.

I also explored getting a seperate 24VAC transformer from Radio Shack or elsewhere.... and got a bit confused as to which way to go ie: some were 24VAC 40va, 50va, 1000ma etc...

I checked out the radio shack part mentioned above - and that is discontinued but they sell a similar one now for 25.99.

Thanks for any help in advance.

Stephen