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C wires, Nests, and Gremlins

Jamie HallJamie Hall Member Posts: 13,419
A sort of plaintive comment here. And yes, I've tried to get helpful information from Nest. Good luck with that.

Does anyone have access to how a Nest is actually wired up? Inside? I've been following the "Help C Wire" thread pretty carefully, and folks have come up with answers -- the relay, particularly -- which really ought to have worked. There are other problems with that install.

But. What does actually happen to the helpfully designated terminals inside that contraption? Is C actually a common ground to everything? What powers the nitwits computer and battery? Rc? Rh? Either? Both? What happens on a call for heat? No relays, I suppose... is Rc isolated from Rh unless there is an external jumper? What about the other terminals?

And so on.

I regard the thing as a first class, if very clever, kludge. But they seem to sell a lot of them, and it would be helpful to us who feel impelled to help the victims to know what really happens inside...
Br. Jamie, osb

Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
mattmia2SuperTech

Comments

  • pecmsgpecmsg Member Posts: 1,510
    R and back feed from Y or W not sure.

    The problem developed with computer boards. Enough current to HOLD a triac closed in turn keeping the relay, contactor closed!
  • hot_rodhot_rod Member Posts: 13,855

    A sort of plaintive comment here. And yes, I've tried to get helpful information from Nest. Good luck with that.

    Does anyone have access to how a Nest is actually wired up? Inside? I've been following the "Help C Wire" thread pretty carefully, and folks have come up with answers -- the relay, particularly -- which really ought to have worked. There are other problems with that install.

    But. What does actually happen to the helpfully designated terminals inside that contraption? Is C actually a common ground to everything? What powers the nitwits computer and battery? Rc? Rh? Either? Both? What happens on a call for heat? No relays, I suppose... is Rc isolated from Rh unless there is an external jumper? What about the other terminals?

    And so on.

    I regard the thing as a first class, if very clever, kludge. But they seem to sell a lot of them, and it would be helpful to us who feel impelled to help the victims to know what really happens inside...

    Jamie, we are analog men living in a digital world :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
    Zman
  • STEVEusaPASTEVEusaPA Member Posts: 4,420
    hot_rod said:


    Jamie, we are analog men living in a digital world :)

    Sounds like you need to make a new t-shirt...
    steve
    Alan (California Radiant) Forbes
  • hot_rodhot_rod Member Posts: 13,855

    hot_rod said:


    Jamie, we are analog men living in a digital world :)

    Sounds like you need to make a new t-shirt...
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
    STEVEusaPA
  • Jamie HallJamie Hall Member Posts: 13,419
    Yeah... !
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • JUGHNEJUGHNE Member Posts: 7,203
    Exactly where I'm at.....but all the helpful kids aren't home anymore.
    Do you think there was any vacuum tube equipment on stage?
    Anyone hear any "fuzzy distortion"?

    I liked to watch tubes as you could see the audio fluctuate within the glass. Sight and sound show.
  • ratioratio Member Posts: 2,563
    The most subtle gotcha with triacs/SCRs/etc. is that they aren't open/closed like a switch or contactor, they are really-high-resistance/really-low-resistance. The implications aren't intuitive to someone who isn't familiar with electronics, but thinking of a silicon device as on/off will bite you in the hiney, sooner or later.

    A bigger, but less common, gotcha is that they are occasionally switching the low side (looking at you, Trane). I don't know enough to know if this is a requirement of the particular device or merely a design choice, but couple that with the first gotcha and confusion reigns!

  • Jamie HallJamie Hall Member Posts: 13,419
    I have picked up enough of the modern digital age to know that switching the low side at least for automotive work is actually the normal way to do it, but there since it is DC they are working with power transistors. This can really mess with your head since it can be remarkably difficult to figure out whether the fact that your ride doesn't run is due to a bad ground -- or a bad ECM or what have you.

    Does make it harder to hot-wire the beast, though... there is that.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • mattmia2mattmia2 Member Posts: 1,880
    Most microcontrollers can sink far more current than they can source.
  • EdTheHeaterManEdTheHeaterMan Member Posts: 802
    I want to order the T shirt
  • hot_rodhot_rod Member Posts: 13,855
    ratio said:

    The most subtle gotcha with triacs/SCRs/etc. is that they aren't open/closed like a switch or contactor, they are really-high-resistance/really-low-resistance. The implications aren't intuitive to someone who isn't familiar with electronics, but thinking of a silicon device as on/off will bite you in the hiney, sooner or later.

    A bigger, but less common, gotcha is that they are occasionally switching the low side (looking at you, Trane). I don't know enough to know if this is a requirement of the particular device or merely a design choice, but couple that with the first gotcha and confusion reigns!

    Also a true RMS meter is important to own for troubleshooting these days, reading those weird sawtooth and triangular wave forms.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
    ratio
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,316
    I wanna go back to a T87 and a relay
  • Jamie HallJamie Hall Member Posts: 13,419

    I wanna go back to a T87 and a relay

    Mine seem to be working just fine...
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • ChrisJChrisJ Member Posts: 11,261
    We can start> @EBEBRATT-Ed said:
    > I wanna go back to a T87 and a relay

    I kind of get it, but at the same time this is similar to saying you want to go back to the Ford model T.

    Yes, it was cheaper to build and far easier to troubleshoot but it doesn't even have heat.......

    If you look at most of the Nest threads on here including this one you'll notice the computer it self isn't the issue. The lack of a common wire is and the Nest is the only one I know of that tries to cheat at this.

    Honeywell got it right with the EIM. It uses only two wires and only powers the thermostat with them. Everything else is done back at the equipment by the EIM and the thermostat communicates with the EIM wirelessly. It works and it always works.

    It also won't die if the system needs to run continuously.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • ratioratio Member Posts: 2,563
    ChrisJ said:

    Honeywell got it right with the EIM. It uses only two wires and only powers the thermostat with them. Everything else is done back at the equipment by the EIM and the thermostat communicates with the EIM wirelessly. It works and it always works.

    I'd say nearly right. It actually is a wireless connection from the stat to the EIM (you can power the stat from an independent power supply, there's even a 5000 [IIRC] series that will run on batteries), but it suffers from the usual wireless issues of interference, etc.; and I have experienced those kind of issues, albeit infrequently.

    Carrier has their 'Edge Pro' thermostats that can be mounted in a two-piece configuration, with only two wires connecting the face of the stat to the base. They get that part right—the two wires are power and communication—but they are hard to program if you're not familiar with them, and it's quite difficult to find a manual on-line for them. It's to the point that I just email our vendor if I need a manual.

  • Jamie HallJamie Hall Member Posts: 13,419
    The thing about the Nest -- and some other wi-fi enabled thermostats -- is that they really do work well, if used in their intended application (forced air heat) in a reasonably modern house, which will have the C wire at least present, if not connected. And, perhaps, it is not really a fault of the unit, so much as the chances are very good it never even occurred to the designers, secure in their Silicon Valley bubble, that there could be anything else.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • ChrisJChrisJ Member Posts: 11,261
    ratio said:

    ChrisJ said:

    Honeywell got it right with the EIM. It uses only two wires and only powers the thermostat with them. Everything else is done back at the equipment by the EIM and the thermostat communicates with the EIM wirelessly. It works and it always works.

    I'd say nearly right. It actually is a wireless connection from the stat to the EIM (you can power the stat from an independent power supply, there's even a 5000 [IIRC] series that will run on batteries), but it suffers from the usual wireless issues of interference, etc.; and I have experienced those kind of issues, albeit infrequently.

    Carrier has their 'Edge Pro' thermostats that can be mounted in a two-piece configuration, with only two wires connecting the face of the stat to the base. They get that part right—the two wires are power and communication—but they are hard to program if you're not familiar with them, and it's quite difficult to find a manual on-line for them. It's to the point that I just email our vendor if I need a manual.

    Ratio,
    I'm confused how you can say they suffer from the usual wireless issues but then also say it's infrequent. I just don't want someone reading this thread and then assuming they will have headaches if they try to use a Redlink setup.

    I'd have to say the chances of someone having issues with a Redlink setup seem to be much slimmer than issues with a power stealing Nest. No?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • ratioratio Member Posts: 2,563
    ChrisJ said:

    Ratio,
    I'm confused how you can say they suffer from the usual wireless issues but then also say it's infrequent. I just don't want someone reading this thread and then assuming they will have headaches if they try to use a Redlink setup.

    I'd have to say the chances of someone having issues with a Redlink setup seem to be much slimmer than issues with a power stealing Nest. No?

    Wireless is subject to more disturbances than wired, that's all. The RedLINK connection is quite robust, but not as reliable as a wired connection. In some cases, it won't be enough for successful operation. I would like to see the EIM able to communicate with the thermostat over the power wires, that would make them just about perfect.

    That said, I've recommended Honeywell over Nest every time, & will continue to do so.

    SuperTech
  • EdTheHeaterManEdTheHeaterMan Member Posts: 802
    edited June 30
    ChrisJ said:

    We can start> @EBEBRATT-Ed said:

    > I wanna go back to a T87 and a relay



    I kind of get it, but at the same time this is similar to saying you want to go back to the Ford model T.



    Yes, it was cheaper to build and far easier to troubleshoot but it doesn't even have heat.......





    Correct... No heat at the last Christmas Parade
    it was very cold!

    PS, I have 2 Nest Thermostats and 2 Nest cameras

  • ChrisJChrisJ Member Posts: 11,261

    ChrisJ said:

    We can start> @EBEBRATT-Ed said:

    > I wanna go back to a T87 and a relay



    I kind of get it, but at the same time this is similar to saying you want to go back to the Ford model T.



    Yes, it was cheaper to build and far easier to troubleshoot but it doesn't even have heat.......





    Correct... No heat at the last Christmas Parade
    it was very cold!

    PS, I have 2 Nest Thermostats and 2 Nest cameras

    You only forget to retard the timing before cranking once....... :)
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • EdTheHeaterManEdTheHeaterMan Member Posts: 802
    edited July 3
    Don't I know it!











    not really me
  • HVACNUTHVACNUT Member Posts: 3,517
    And if I'm elected president, I will make it mandatory that every American will have to physically stand in front of the thermostat to operate it.
    Convictions punishable up to 10 years loss of cell phone. And a do not serve order at every Starbucks. We're too spoiled.

    I get a lot of service call with these things so I guess it's good for me, but...
    EdTheHeaterMan
  • ChrisJChrisJ Member Posts: 11,261
    > @HVACNUT said:
    > And if I'm elected president, I will make it mandatory that every American will have to physically stand in front of the thermostat to operate it.
    > Convictions punishable up to 10 years loss of cell phone. And a do not serve order at every Starbucks. We're too spoiled.
    >
    > I get a lot of service call with these things so I guess it's good for me, but...

    You lost my vote.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    HVACNUT
  • ratioratio Member Posts: 2,563
    But you gained two or three of mine.
  • Jamie HallJamie Hall Member Posts: 13,419
    and mine
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • Erin Holohan HaskellErin Holohan Haskell Member, Moderator, Administrator Posts: 1,418

    hot_rod said:


    Jamie, we are analog men living in a digital world :)

    Sounds like you need to make a new t-shirt...
    We made this for all the analog guys feeling nostalgic:



    Available here: https://teespring.com/analog-guy-in-a-digital-world

    President
    HeatingHelp.com
    CanuckerSTEVEusaPAHVACNUT
  • STEVEusaPASTEVEusaPA Member Posts: 4,420
    What is that one set at? LOL
    steve
    Erin Holohan HaskellEdTheHeaterMan
  • ratioratio Member Posts: 2,563
    Maybe it comes with a sharpie to set it yourself.
    EdTheHeaterManErin Holohan Haskell
  • EdTheHeaterManEdTheHeaterMan Member Posts: 802
    It depends on whether you are standing on level ground.

    I just ordered mine. I hope I don't get mercury poisoning
    Erin Holohan Haskell
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