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1-zone no heat

Hilly
Hilly Member Posts: 417
System is a classic loop system with 5 zone valve.
Problem Zone:
1. 28V at Thermostat
2. remove thermostat and jumper - zone valve stays closed, no heat
3. at boiler remove thermostat wiring and jump - zone valve opens, yes to heat

So to me this confirms that the zone valve functions properly.
Is it possible to have a short somewhere in the thermostat wiring and still get 28V?
They recently did a kitchen reno and this room is on the 2nd level above the kitchen so damage is certainly possible. If the wire is damaged is there a viable wireless solution for this?

Comments

  • So, you say the zone valve opens, correct? Does the pump turn on? Does the boiler come on? Can you feel a temperature difference with one hand on the supply pipe and one on the return pipe?
    What are the heat emitters (radiators, baseboard, radiant)?
    Often wrong, never in doubt.
  • Hilly
    Hilly Member Posts: 417
    edited August 2017
    Yes if i jumper in the boiler room.
    1. Motor turns
    2. End switch clicks
    3. Boiler fires
    4. Pipe gets hot
  • Then you should have a

    5. Room starts to warm

    If not, something is keeping the hot water away from the heat emitter, whatever kind of heat emitter you have. OK, I'll ask again:

    Radiators, baseboard or radiant? Or is there a fan coil upstairs?
    Often wrong, never in doubt.
  • Hilly
    Hilly Member Posts: 417
    If manually jumped then yes the room will start to warm. It is a series loop.
  • HVACNUT
    HVACNUT Member Posts: 4,194
    When you say you have 28v at the stat, are you measuring across R,W, or is the stat 24v powered (R,C,W) and measuring across R,C?
    And you're jumping R and W and you don't get 24v to the ZV motor.
    How many conductors in the wire? Any extras?
    If the circuit is open, you shouldn't get 28v across R,W, unless it's picking up a ground somewhere.
    Here's a pdf for a Honeywell wireless thermostat, but maybe we can all solve it with some more info.
  • Hilly
    Hilly Member Posts: 417
    Yeah i am getting 24v on r/w ... 2 wire only.
  • You've got a bad thermostat.
    Often wrong, never in doubt.
  • Hilly
    Hilly Member Posts: 417
    Im hoping. This was a "while You're here job" i told him i would come back and try a new thermostat and trace/test/clean-up the wires. This type of work is why i love zone controls and relay panels.
  • HVACNUT
    HVACNUT Member Posts: 4,194
    edited August 2017
    If everything is OK with the wiring, you will read 24v at the thermostat sub base terminals because it's getting the common through the transformer coil. Once the thermostat contact closes, the wires are just different sides of the same circuit.
    If you're able to test across a working thermostat with the contact closed, voltage should be 0.
    Are you able to do a continuity test?

    Also, in point 3 of your first post, if you removed the thermostat wires, what were you jumping out? Did you hardwire from the transformer to the ZV motor?
  • Jamie Hall
    Jamie Hall Member Posts: 17,060
    Um... maybe a bad thermostat; as likely as anything. But... there is another possibility. There may be a bad connection. You may be getting 24 volts -- when the thermostat is open. But there might be enough resistance in the rest of the circuit somewhere -- as I say, bad connection or possibly damaged wire -- that the voltage drops low enough at the zone valve that it won't operate. When the thermostat is calling, do you have 24 volts on both the thermostat connections on the zone valve?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JUGHNE
    JUGHNE Member Posts: 8,943
    Does that tstat/zone have it's own transformer.
    Some will show the 24 VAC but when loaded will fall on it's face and not deliver.
  • GW
    GW Member Posts: 4,303
    "While you were here" ...love it! There are two types of customer- one is quick to blame, two is open to a coincidence.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • Hilly
    Hilly Member Posts: 417
    No no. I was looking at a basin. He text and said while you're there can you look at my sons room, we don't get heat. He was great about it.
  • Hilly
    Hilly Member Posts: 417
    edited August 2017
    28ohms is what i get across the 18awg wire.

    These is a Honeywell 8043 zone valve
    At the motor of a working valve i get 28v.
    This one i am only getting 14V
    Is this a valve issue or a small sort somewhere?
  • Hilly
    Hilly Member Posts: 417
    I completely removed the thermostat wiring and used a spool as a "temp thermostat" line and determined. 1.Existing thermostat was shot. 2. The wiring in the walls has to be damaged.

    It wont nice but theres two closest stack upon each other above the boiler room so i will be able to run wire through there, to the attic and then down to the new thermostat.
  • Paul48
    Paul48 Member Posts: 4,470
    Before you condemn the wires, twist them together at the thermostat , and check resistance in the boiler room. It's just proving your theory, and it only takes a couple minutes.
  • Hilly
    Hilly Member Posts: 417
    edited August 2017
    I did that @Paul48 and got 28ohms... Some online calculators tell me I'm up near 4300' of wire for that reading.
  • Paul48
    Paul48 Member Posts: 4,470
    That's a done deal then.......As you said, somebody put a screw or nail through a wire.
  • HVACNUT
    HVACNUT Member Posts: 4,194
    > @Paul48 said:
    > That's a done deal then.......As you said, somebody put a screw or nail through a wire.
    >
    >
    >> Yup. And R was being used to switch the thermostat, not C, so the screw, nail, Sawzall blade also shorted and smoked the thermostat
  • JUGHNE
    JUGHNE Member Posts: 8,943
    Just came from AC call. The Y was directly shorted to ground somewhere. Took out two transformers, I did the third one but added a 3 amp fuse. Blew immediately.
    Temp revamped the W wire for cooling.
    New cable when it is cooler in the attic and will add common to avoid battery changing.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 10,276
    If you remove the wiring at both ends (stat & basement) twist the wires together at the stat and check the resistance if it's high (or open) the wires are damaged. You should read 24 volts across R & Y only when the stat is open. No volts across R & Y when closed
    Hilly
  • Paul48
    Paul48 Member Posts: 4,470
    HVACNUT said:

    > @Paul48 said:

    > That's a done deal then.......As you said, somebody put a screw or nail through a wire.

    >

    >

    >> Yup. And R was being used to switch the thermostat, not C, so the screw, nail, Sawzall blade also shorted and smoked the thermostat

    I thought he said it was a 2-wire stat?
  • Hilly
    Hilly Member Posts: 417
    @Paul48 it is indeed a 2 wire stat.
  • HVACNUT
    HVACNUT Member Posts: 4,194
    > @Paul48 said:
    >
    > I thought he said it was a 2-wire stat?
    >
    > Yes, meaning the 24v side of the transformer was going through the thermostat, not the common. And the wire was cut, pinched, or whatever, and shorted to ground.
  • Paul48
    Paul48 Member Posts: 4,470
    I must be mistaken....I thought that 2-wire stats were not powered by a transformer, and they only use a set of contacts to pass voltage. I'm not an electrician.
  • HVACNUT
    HVACNUT Member Posts: 4,194
    You're not mistaken. I'm not explaining it right. At the boiler, on the transformer, (in this case) the common goes right to the ZV motors.
    Power (R) from the transformer goes through the thermostat, then to the ZV motor.
    The OP said the thermostat was bad also, so whatever cut the thermostat wire must have caused a direct short to ground as well, otherwise the thermostat would have come out of this unharmed. And it happened quick because it didn't blow the transformer.