Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.
If our community has helped you, please consider making a contribution to support this website. Thanks!

Low power consumption wifi thermostat < 55ma

Options
pjg
pjg Member Posts: 3
in Thermostats and Controls

Hi guys new to the forum,

I see a lot of discussion on the nest , ecobee smart thermostats, and no mention of the Johnson Controls / Venstar color touch screen wifi thermostats.

I have two installed on the old style Taco SR503 switching relay control with the 15va transformer, before installing I bench tested them with a 24vac power adapter and learned they only draw about 50 milliamps so no need to upgrade the transformer to 40va.

According to Taco the SR503 is rated for 15va or .625 amps the board consumes around 100ma that leaves .525 amps to play with, I would keep things at 200 ma or less to be on the safe side.

I found and old email from Taco that shows the rating of the SR503 control - see attached.

You still need a C-wire since there are no battery's in the thermostats.

These have more feature than you should ever need, remote control with cloud, home automation , logging and remote sensors etc.

https://jcithermostats.com/colordisplay/models/

https://venstar.com/thermostats/colortouch/

100ma taco.jpg

Comments

  • pecmsg
    pecmsg Member Posts: 6,708

    Do you need all that fancy stuff that you're not going to use?

    If you're that concerned with power consumption, there are still mechanical t-stats available.

  • pjg
    pjg Member Posts: 3

    This is geared for anyone who wants a smart thermostat and not need to upgrade the 24vac transformer.

  • 109A_5
    109A_5 Member Posts: 3,316

    I suspect the Johnson Controls / Venstar are not highly marketed to the residential folks.

    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
  • SteveSan
    SteveSan Member Posts: 291

    @pjg when wiring a tstat that needs a com to these older controls, you need to wire the W from the tstat to the right T and R wired to the left T. Then take you com wire to the com side of the 24vac/com two pin connection to the left of the board. Between R-Com is always 24v on our controls. If the others are just two wires, doesn’t matter where you land them at the tstat TT connection. Hope this helps.

  • pjg
    pjg Member Posts: 3

    Thanks Steve,

    I found that out on his site before I did the install, I ended up running new thermostat wires (18/5) for each zone to connect the C-wire. Then moved the thermostat wire that was located in an unheated hall on the 2nd floor which was causing the master bedroom to overheat, even with baseboard dampers closed. The 2nd floor thermostat is now in the master bedroom and heat is much more even in each bedroom. The other nice feature of these thermostats, I can see and program them from the touch screen or web browser. The old HoneyWell T5's that were replaced were hard for me to see even with the backlight on.

    SteveSan

Categories