Boiler heater not being controlled by thermostats

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Old 03-08-15, 06:47 AM
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Boiler heater not being controlled by thermostats

I've got a hot water/boiler/radiator heating system with 3 zones controlled by 3 different thermostats. The heater lights up about every 5 minutes regardless of whether the thermostats are calling for heat. I've even disconnected all 3 and it's still lighting every 5 minutes. House seems to always be at 75F.

I think the Honeywell Aquastat Relay (type L18148J) is not controlling and maybe there's some low temperature limit that makes it keep firing? Anyways, do you think this is the problem? Should I just replace the whole unit? Should I call a professional?
 
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Old 03-08-15, 07:14 AM
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Replace the 'whole unit', meaning the boiler? or just the aquastat?

What is the make and model of the boiler?

Do you own and know how to use a multimeter?
 
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Old 03-08-15, 07:15 AM
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You disconnected the thermostats, is that what you mean?

Are your zones controlled by electric zone valves?

What make/model are the zone valves?
 
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Old 03-08-15, 07:26 AM
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Has anyone 'messed with' the aquastat lately?

Is the AUTO / MANUAL switch inside the aquastat been switched over to MANUAL for some reason?
 
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Old 03-08-15, 08:23 AM
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I checked the auto/maunual switch and it's in auto.

I meant replace the Aquastat unit. The boiler is 20+ years old but seems to be working fine. Made by Vaillant Model # GA92080 E1. I did just replace the intermittent pilot light unit - it was stuck open continuously firing the pilot.

Yes, I disconnected the thermostats.

Zone valves are electric - Honeywell 8043E1012

I have and can basically operate (touch probes to contact areas and read the needle) a multimeter.
 
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Old 03-08-15, 08:58 AM
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OK, the next thing to do is to disconnecting one of the wires from the zone valves to the T or TV terminals on the aquastat.

By disconnecting the thermostats, you've only ruled those out themselves, there could still be a problem with the zone valves or the wiring from the zone valves to the boiler.

If the boiler stops firing on it's own after disconnecting either the T or TV wire (either one, doesn't matter which)

OR, you could set your multimeter to measure AC VOLTS and touch the two probes to the " T and TV " terminals.

If you measure ZERO (no needle movement), then the zone valves are calling for heat and further troubleshooting in that direction is required.

If you measure 24VAC, then the zone valves are NOT calling for heat and the problem can be traced to the aquastat.

Do you know if you have a "millivolt" gas valve?

You can tell by which of the "B" terminals have wires on them.

If you have millivolt system, the wires to the burner will be on B1 and B2 and NO wire on B3. Also, there will be NO JUMPER from the TP terminal to the Z terminal.

If you have a 24V gas valve, the B1 and B3 terminals will wire to the valve and there WILL BE a jumper from TP to Z.
 
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Old 03-08-15, 09:13 AM
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I don't measure any voltage with my multi meter set to 50V total deflection placing a probe on each of the T and TV connections. Just an FYI - all of the thermostats are set so they should not be calling for heat (50F).

It looks to be 24V - B1 and B3 are connected
 
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Old 03-08-15, 09:16 AM
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You're sure the meter is working, correct?

Test by touching the TV and the Z terminals. You should always see 24VAC there.

If meter is working, and no voltage at T and TV, then disconnect one of those wires.

Boiler should stop firing up...

Is your circulator pump also running continuously?
 
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Old 03-08-15, 09:23 AM
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Meter's working correctly with the TV and Z test (also tested in an outlet initially).

Disconnected TV and it stopped firing.

Circulator pump is not running now either.
 
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Old 03-08-15, 09:42 AM
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Circulator pump is not running now either.
But it was before you disconnected the wire, correct?

OK, nothing wrong with the boiler... problem is upstream, at one (or more) of the zone valves.

There is a lever on the side of the zone valve.

If the valve is stuck open that lever will move freely with no resistance.

If closed, you will feel resistance and when you move it will hear the gears 'whirring' inside.

Check to see if any of the valves are stuck open.
 
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Old 03-08-15, 09:55 AM
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One is stuck open (basement). When I reconnected the TV wire the pump seemed to be running (if I put a hand on it I can feel it vibrate). I'll have to check it for a while to see if it turns off. Fairly quite, can't hear it turn on and off.
 
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Old 03-08-15, 10:28 AM
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One is stuck open (basement).
OK, so now, remove one of the RED wires (either one) coming from that valve to where they all tie together and retest for 24VAC at T and TV and the boiler no longer firing continuously.

Were you able to free up the stuck valve?
 
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Old 03-08-15, 11:15 AM
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When I was trying to disconnect the wire the gears started turning and closed the valve. I then went to the thermostat and turned it so that it was calling for heat and the valve opened. Then I turned off the heat and the valve closed. Boiler turned off and on with the opening and closing of the valves. Must've been a loose connection. Do you have a good way to figure out which might be the loose connection in that bundle of wires were all three zones come together?

Also thank you so much for your help today. You're fantastic!
 
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Old 03-08-15, 11:25 AM
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Do you have a good way to figure out which might be the loose connection in that bundle of wires were all three zones come together?
No, other than a very close visual inspection...

I'm leaning more toward a valve head that's starting to wear.

If you are sure that you had all the t'stats turned all the way down and the valve hung open, it's probably a mechanical issue rather than electrical.

A LOOSE connection would not hang the valve open, but a SHORT CIRCUIT could.

So make sure that none of the wire ends are exposed and touching another wire...

It COULD REMOTELY POSSIBLY also be the thermostat itself.

Thanks for the kudos! You're welcome!
 
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Old 03-08-15, 11:30 AM
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About those valve heads... in case it comes to having to change one.

There are OLD and NEW style power heads.

The NEW style has TWO screws and TWO 'locating pins' securing the head to the body.

The OLD style has FOUR SCREWS.

The NEW style head can be changed in about ten minutes because you do NOT have to drain the system to change the head.

The OLD style requires draining the system to change the head, and installing an adapter kit ($13) that completely rebuilds the old valve body and allows using the new style head.

Replacement head:

40003916-026 - Honeywell 40003916-026 - Replacement Head for V8043E Zone Valves

If you have OLD style, the adapter kit:

40003918-006 - Honeywell 40003918-006 - 2 Way Powerhead Conversion Kit (Water)
 
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Old 03-08-15, 11:34 AM
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If it were the thermostat - how could it still be sending a signal when I disconnected it?
 
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Old 03-08-15, 11:38 AM
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Looks like a new one. Should I just replace?
 
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Old 03-08-15, 02:30 PM
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If it were the thermostat - how could it still be sending a signal when I disconnected it?
Good point! It can't! Unless there is a short in the wiring to the thermostat, but after it got un-stuck, you said it was working... so probably not that either.

Looks like a new one. Should I just replace?
That's up to you! You should first identify whether it's old or new style before deciding to do it now, or after the heating season is over. You do NOT want to drain the system now !
 
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Old 03-08-15, 05:05 PM
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Thanks again for all your help.
 
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