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Boiler not responding to thermostat, must be manually turned off

Hi! Actually, I think I know enough to know I don't know enough to fix

this myself, so I'm just trying to make sure I know what's likely

malfunctioning so that I'm not taken advantage of by the repair people.

Here's the problem. I have a 12-year-old (approximately) Weil McClain

natural gas boiler, (not connected to my separate water heater), model

EG 55 SPDN, that suddenly, today, remained on well beyond the thermostat

setting. (It does go off when the water temperature goes above a

certain setting, though.) Clearly, it's not responding to the

thermostat--I turned the thermostat setting way down and the boiler

continued to operate. I have had to turn the boiler off manually, using

the on/off switch on the boiler.

So is the problem likely a)the thermostat itself, b)some other part of

the electrical system (located, I assume, on the boiler itself), or

c)something else?<span style="color:#000000">

Read more: <span style="color:#003399"><a href="http://www.doityourself.com/forum/thermostatic-controls/485893-boiler-not-responding-thermostat-must-turned-off-manually.html#ixzz2HL7m3OAz">http://www.doityourself.com/forum/thermostatic-controls/485893-boiler-not-responding-thermostat-must-turned-off-manually.html#ixzz2HL7m3OAz[/color]



  • JStar
    JStar Member Posts: 2,752

    My guess is that a control circuit is shorted together, bypassing the thermostat.
  • Paul48
    Paul48 Member Posts: 4,469

    disconnecting one of the thermostat wires at the boiler and see if that shuts the boiler down. Let us know.
  • graviton
    graviton Member Posts: 4

    JStar and Paul, thanks very, very much for responding.

    Paul, actually, I'm afraid to tamper with things as they are, since I'm at least getting heat, although I have to manually turn it on and off.

    JStar, I assume from your answer that the thermostat itself is fine, and the electrical unit on the boiler  needs a new control circuit.  Is that correct?  Or does the entire electrical unit need to be replaced?
  • JStar
    JStar Member Posts: 2,752

    I think that it could any number of things. The control circuit has several points where your symptoms could be caused. A good boiler guy should have no problem figuring it out.

    Have you had anybody look at it? Where are you located?
  • graviton
    graviton Member Posts: 4
    A little follow-up

    Joe, I haven't had a chance to call the guy I've used in the past.  I'm going to call him tomorrow.  I live way at the northern end of NYC, pretty far from Metuchen.

    I just put the thermostat down to its lowest setting, about 40 degrees, and the boiler still went on as soon as I turned the manual switch on the boiler to ON.

    So, if the problem is not with the thermostat but  with the electrical unit on the boiler (the control circuit shorting out), does this never, sometimes,usually or always mean the whole unit must be replaced or just the control circuit?

    And how big a job is this repair?
  • JStar
    JStar Member Posts: 2,752

    I usually don't go into NYC, but the city is full of good boiler guys that post here.

    It could be as simple as a quick change of wire, or could be a bad control. It's hard to say without doing any tests. More than likely, it can be fixed without changing the whole system.
  • graviton
    graviton Member Posts: 4
    Genuinely appreciative, Joe!

    Joe, thanks a million for your input!  I feel I'm an informed consumer now, so when I speak to my repair guy tomorrow I won't be unprepared to discuss the situation.  And you saved me from running out and getting a new thermostat!!
  • Paul48
    Paul48 Member Posts: 4,469

    It could be as simple as a mouse biting your thermostat wire.Cross your fingers, it's something stupid like that.
This discussion has been closed.