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Thermostat Wiring

  1. #1
    is not wearing pants Point37's Avatar
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    Thermostat Wiring


    so 1 of my upstairs thermostats stopped working about a week ago...my house has 3 heat zones...2 upstairs, 1 downstairs...for cooling i have 2 zones...1 up and 1 down...all 3 of my thermostats are robertshaw programmable 9700i that run on 4 AA batteries...i don't think i have 24VAC hooked up at my thermostats cause when i pull the batteries the screen shuts down...i have a taco sr503 switching relay box in the basement...in that box i know i have 24VAC on all 3 zones cause i tested the connections...from that box the thermostat wires go up the wall to a junction box that looks like a shitshow...from that junction box the wires go all over the place...all of the wiring in the house is weird cause it's a modular house...so my wiring from the second floor goes up to the attic and over to an outside wall and down that wall into the basement...all the wiring from the first floor goes up into the space between the first and second floors and over to the same outside wall and down that wall into the basement...i plan to buy an electrical tone generator and try to figure out what the hell i'm dealing with this weekend hopefully...and maybe i will be able to hook up the 24VAC so the thermostats have power instead of needing batteries...i may replace the broken thermostat with a smart thermostat (looking at nest or ecobee at the moment) or i may just replace in kind or with a cheaper programmable thermostat...the only time i would really like to be able to change a thermostat remotely is during the summer when it's an in-between day where i can just turn the ac temp up to 80 so it won't kick on and open the windows...if anyone has any tips i'm all ears...heating system is a Heat Transfer Products wall hung boiler and indirect fired superstor tank

    bought this
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    sr503 switching relay


    junction box from hell


    upstairs thermostat 1 (1 heat 1 cool)


    downstairs thermostat (1 heat 1 cool)


    upstairs thermostat 2 (1 heat)







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  2. #2
    Super Adventurer SRTie4k's Avatar
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    Re: Thermostat Wiring

    It sounds to me like trying to run new cable is going to be way more hassle than doing some basic troubleshooting.

    Ensure continuity from the t-stats to the connections at the control. That box doesn't look all that bad to me, I've seen much worse, it shouldn't be too hard figuring out which wire goes where.

    If all wires have continuity, I'd probably remove all the t-stats and selectively swap them out in a known good location, and toggle them all on to verify they each kick the circulators on.

    Doing that should tell you whether it's a bad wire, a bad t-stat or a bad input on the control.

    Oh and it might be a good idea to check continuity at the fuses in the control.

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  3. #3
    Lifer ZX-12R's Avatar
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    Re: Thermostat Wiring

    The manual to your thermostats says it operates on battery only so unless you upgrade, there is no reason to run wiring for 24VAC power. If you upgrade to a smart thermostat, it may be possible to harvest power from the Rh and W terminals but that isn't always the case.

    Is it your heat/cool thermostat acting up or the heat only one? What are your symptoms? Since it's winter and you're having problems I'm guessing it's the heat circuit you're having problems with. When the suspect thermostat calls for heat, is your burner kicking in but the circulator isn't working? Is the circulator working but not the burner? Is nothing happening at all? Any other pertinent information?

    I own the same cable toner you are looking at and it works very well. It is sensitive to the switching electronics in some fluorescent bulbs, LED bulbs, and dimmers but you can usually make out the tone over the noise. If not, you have to secure power to those nearby circuits.

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  4. #4
    is not wearing pants Point37's Avatar
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    Re: Thermostat Wiring

    Quote Originally Posted by SRTie4k View Post
    It sounds to me like trying to run new cable is going to be way more hassle than doing some basic troubleshooting.

    Ensure continuity from the t-stats to the connections at the control. That box doesn't look all that bad to me, I've seen much worse, it shouldn't be too hard figuring out which wire goes where.

    If all wires have continuity, I'd probably remove all the t-stats and selectively swap them out in a known good location, and toggle them all on to verify they each kick the circulators on.

    Doing that should tell you whether it's a bad wire, a bad t-stat or a bad input on the control.

    Oh and it might be a good idea to check continuity at the fuses in the control.
    Thanks...yea new wire would be more of a pain in the ass...I swapped the front from one of the other working thermostats on to the broken one and that didnít help...I also put the front from the broken one onto one of the other working backs and that did work...I plan to swap the rears out to confirm that the back of the thermostat is the issue after checking wire continuity...the fuses in the box looked good but I will check those as well

    Quote Originally Posted by ZX-12R View Post
    The manual to your thermostats says it operates on battery only so unless you upgrade, there is no reason to run wiring for 24VAC power. If you upgrade to a smart thermostat, it may be possible to harvest power from the Rh and W terminals but that isn't always the case.

    Is it your heat/cool thermostat acting up or the heat only one? What are your symptoms? Since it's winter and you're having problems I'm guessing it's the heat circuit you're having problems with. When the suspect thermostat calls for heat, is your burner kicking in but the circulator isn't working? Is the circulator working but not the burner? Is nothing happening at all? Any other pertinent information?

    I own the same cable toner you are looking at and it works very well. It is sensitive to the switching electronics in some fluorescent bulbs, LED bulbs, and dimmers but you can usually make out the tone over the noise. If not, you have to secure power to those nearby circuits.
    Thanks...the upstairs heat/cool thermostat is broken (nothing on the screen, batteries have been tested and are brand new and fine) so Iíd like to upgrade to a model that doesnít need to run on batteries thatís why I want to get the 24VAC to all 3 thermostats...the one thatís broken has 2 cables going to it while the other 2 thermostats only have 1 cable...so I should have plenty of wires to get the power up there I would think


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  5. #5
    is not wearing pants Point37's Avatar
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    Thermostat Wiring

    Pulled all the thermostats apart traced all my wiring...I have 24v to all 3 thermostats...my dumbass was on the wrong multimeter setting...now I am trying to figure out which smart thermostat to buy...I do have a google mini speaker on the first floor which has nothing tied into it at the moment

    Mass save has both nest and Ecobee for $150 each...

    https://www.poweredbyefi.org/masssav...ermostats.html

    Started comparing them...at first nest seemed like the best choice due to the learning function, the geofencing for 2 phones vs just 1 for Ecobee and the lack of need for a common wire that the Ecobee requires...the one thing that the link below doesnít cover is that the nest doesnít have a variable differential...itís set at 1 degree and canít be changed...Iím running a 1.5 degree differential now so itís funny that nest doesnít have this capability...I run it this way for wear and tear on the equipment...so I think Iím going with the Ecobee...reading up on having to run a common wire doesnít sound too hard

    https://thesmartcave.com/ecobee-vs-nest/

    Differential settings...

    https://support.ecobee.com/hc/en-us/...ee-thermostats

    Each thermostat location has at least 1 extra unused wire in the bundle I just have to run a common wire from my boiler to that shitshow of a junction box which is maybe 5 feet away and then wire nut that wire to 3 wires, one from each thermostat bundle then install the Ecobee...if I like it I plan to replace the other 2 thermostats...I may install the Ecobee downstairs and move the downstairs thermostat upstairs so itís more accessible to play with

    https://support.ecobee.com/hc/en-us/...-installations









    Anyone see anything wrong with my plan?...Iím no electrician


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  6. #6
    Lifer Kurlon's Avatar
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    Re: Thermostat Wiring

    Even though the Nest can in theory run in vampire mode without a common, it's MUCH happier and easier on your equipment if you just give it one.

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  7. #7
    is not wearing pants Point37's Avatar
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    Re: Thermostat Wiring

    Quote Originally Posted by Kurlon View Post
    Even though the Nest can in theory run in vampire mode without a common, it's MUCH happier and easier on your equipment if you just give it one.
    Yea my issue with the nest is the non-adjustable differential


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    Lifer Kurlon's Avatar
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    Re: Thermostat Wiring

    I wouldn't sweat the differential, it's not fixed. On and off points adjust based on the inertia of the system in the house it's in. The whole point of the Nest is maintaining an even temp without short cycling. Unless your setup is radically oversized for the house it shouldn't be an issue.

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  9. #9
    is not wearing pants Point37's Avatar
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    Re: Thermostat Wiring

    Quote Originally Posted by Kurlon View Post
    I wouldn't sweat the differential, it's not fixed. On and off points adjust based on the inertia of the system in the house it's in. The whole point of the Nest is maintaining an even temp without short cycling. Unless your setup is radically oversized for the house it shouldn't be an issue.
    i just like having the extra control...i ordered the ecobee...it should come in this week so i can install it this weekend...i plan to run a common wire from the boiler to the junction box and connect to 1 spare wire from each thermostat bundle...then i am going to remove each thermostat and test the ecobee at each location to make sure it will power up...if it powers up i will move the downstairs thermostat upstairs so i can play with the ecobee...if all works out i will buy 2 more and not have to deal with swapping batteries every once in a while...MassSave limits you to buying 3 thermostats per year at the discounted price

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  10. #10
    Soul Rider Paul_E_D's Avatar
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    Re: Thermostat Wiring

    We run the Ecobee on our new system. Like it a lot. I think my hvac installer set the differential to .5 That surprised me, but it doesn't short cycle. Not sure if it's the placement of the tstat, or the nature of forced hot air, or if it's just smart enough to not do that, but I'll leave it that way since it works. I can't remember why but the hvac installer preferred the ecobee.

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  11. #11
    is not wearing pants Point37's Avatar
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    Re: Thermostat Wiring

    Quote Originally Posted by Paul_E_D View Post
    We run the Ecobee on our new system. Like it a lot. I think my hvac installer set the differential to .5 That surprised me, but it doesn't short cycle. Not sure if it's the placement of the tstat, or the nature of forced hot air, or if it's just smart enough to not do that, but I'll leave it that way since it works. I can't remember why but the hvac installer preferred the ecobee.
    other than the differential adjustment info this is where i found the rest of the info about the differences between the two...
    https://thesmartcave.com/ecobee-vs-nest/

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    is not wearing pants Point37's Avatar
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    Thermostat Wiring

    Tried to install the thermostat today...would not power up...donít think I connected the common wire to the right terminal on the boiler...I have to make an appointment with my boiler guy for a cleaning anyway so Iíll talk to him I guess

    May have to get the common from the air handler

    https://support.ecobee.com/hc/en-us/...mpatible-with-





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  13. #13
    Lifer Kurlon's Avatar
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    Re: Thermostat Wiring

    You may have to flip your two normal wires to the tstat.

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  14. #14
    Soul Rider Paul_E_D's Avatar
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    Re: Thermostat Wiring

    Now that the ecobee has been running for over a month, I can start to look at the data. Here is the runtime of the heatpump(orange) vs oil(red) with the average daily temps shown on the black line. I have the crossover temp set at 35 degrees. It's been somewhat mild, but not unusually so. Looks like I'm using oil less than half the time. My first electric bill running the heat pump increased by about 50-60 dollars. Need more time running to really determine my heating costs, but it looks like a 150/month average oil/electric combined. Not bad as our place does not have modern levels of insulation.
    Attached Thumbnails Attached Thumbnails Thermostat Wiring-ecobeedatafeb20-jpg  

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  15. #15
    Lifer Kurlon's Avatar
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    Re: Thermostat Wiring

    Can you control the switchover based on outside humidity level rather than temp? Based on the two systems I get to play with that seems to be the bigger factor in weather or not the heatpump setup is happy or not.

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  16. #16
    Soul Rider Paul_E_D's Avatar
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    Re: Thermostat Wiring

    I haven't heard that. My understanding is that heatpump efficiency drops off at around 32 degrees. Now, that will often mean a lower humidity... but i don't think the controller would use humidity. What is your reason?

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  17. #17
    Lifer Kurlon's Avatar
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    Re: Thermostat Wiring

    Cooler temps plus higher humidity outside mean it's much more likely the outside unit will ice up, even if the temps are well above freezing. Coworker got a new heatpump setup as part of a home rehab purchase last year, cold temps don't bother it but cool + high humidity basically shuts it down.

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  18. #18
    Soul Rider Paul_E_D's Avatar
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    Re: Thermostat Wiring

    So, that's another benefit of this system. It's not using humidity, but if the heatpump is struggling to satisfy the thermostat for a certain time frame, it will switch over. Funny you should mention that cool/high humidity scenario as that is exactly what we had yesterday. We did notice at one point that the heatpump was struggling to maintain set point and cool air was being pushed out. We actually were wondering if something was wrong, but by the next rune cycle we had toasty air again. It either defrosted, or it switched over.

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