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Thread: Nest T stat help

  1. #1
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    Nest T stat help

    I guess they're in vouge now, and everyone with a 'smart phone' wants them in their homes around here.

    so here's their 'instructional video', from the packaging...>>

    https://www.youtube.com/watch?time_c...&v=dHKD-9uI24I

    There is no schematic , and i've a two wire 'end switch' oil burner

    I'm under the impression constant 24V needs to be @ the stat, but have no clue as to how or which terminal would require it

    Anyone else dealt with this?

    any help appreciated

    ~RJ~

  2. #2
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    Hate those d@#& things! They are made for consumers to DIY, that's why there are no wiring diagrams. They are supposed to auto configure themselves to whatever system the customer has and to whatever wiring is connected- kind of. If you have a heating/A/C system with dampers, good luck.

    I tell anybody that asks me to connect one to call an HVAC guy.

    -Hal
    Last edited by hbiss; 03-30-18 at 06:02 PM.

  3. #3
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    Yep, i'm quickly becoming an anti-fan Hal....

    ~RJ~

  4. #4
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    I think you just connect the red and white terminals. I think there is a battery in it.
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  5. #5
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    He is a vid that says what I said to do when you have a 2 wire T-stat

    https://www.youtube.com/watch?v=V2ElRkI6YF8
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  6. #6
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    Quote Originally Posted by romex jockey View Post
    I'm under the impression constant 24V needs to be @ the stat, but have no clue as to how or which terminal would require it

    Anyone else dealt with this?
    Yup.

    Nothing magical about it. It has a subbase with terminals. The are the usual R, W, G, Y, B. . .etc. and a "C" that is for the other side of the transformer. The existing two wires used by the oil burner will be R and W. You'll have to have a third wire. . .

    Yes, the unit has a battery, rechargeable. . . but it is really good (from the risk of a call-back sense) to give it steady unswitched transformer power.
    Another Al in Minnesota

  7. #7
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    Yeah, you just have a simple switching thermostat like the Honeywell Round with the mercury switch probably. See how smart that thing is, connect it and see what happens. Maybe it has a "power robbing" power option. (It puts a resistance across the white and red such that it isn't enough to pull in the control relay and runs off the voltage drop.)

    -Hal

  8. #8
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    Ok, so it has a batt that can do a 2 wire , but needs a recharge

    so a third wire from some 24V source? C-common R1+hot Rc=return to end switch?

    the unit i'm confronted with has 10 terminations, vs. the 6 in Denny's vid.....


    ~RJ~

  9. #9
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    Quote Originally Posted by romex jockey View Post
    Ok, so it has a batt that can do a 2 wire , but needs a recharge

    so a third wire from some 24V source? C-common R1+hot Rc=return to end switch?

    the unit i'm confronted with has 10 terminations, vs. the 6 in Denny's vid.....


    ~RJ~
    Rc is transformer power for the "cooling" - don't us it.

    Look. Most of your 10 terminations are not used.

    Use RH for the thermostat wire that comes from the transformer supply in the End Switch.

    You'll have to examine the "End Switch" to determine how to get ahold of both sides of the thermostat supply transformer. Hopefully its rated output voltage is within the range needed to supply the charging / operating needs of the Nest. Some of the supply transformers in oil burner controls can be rather puny.

    Use W1 to send switched power (from the transformer) to the relay, or whatever starts up the fire cycle of the oil burner.

    Add a wire from the Nest C terminal to the "other side" of the transformer that is powering the relay, or whatever starts up the fire cycle of the oil burner.
    Another Al in Minnesota

  10. #10
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    You need to bring 24 volts to the t stat if you’re using power circulators. Just bring the c terminal to the t stat. If you have a 18/2 you are screwed. Get the Honeywell version they work so much better and are comparable to all heating systems


    Sent from my iPhone using Tapatalk

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