T stat

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  #1  
Old 11-14-13, 04:16 AM
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T stat

Oil fired boiler 3 zones 1HW and 2 heat.

Could a Tstat cause a boiler to cut out for a second when firing then re fire. Firing fine cuts out for 1 second and then continues. It only happens on 1 zone only that I have noticed other zones work as should with no cut outs.
It is a very cheap t stat too plastic slide one. I will replace it tonight anyway.
 
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Old 11-14-13, 06:35 AM
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If there's a zone valve between the t'stat and the boiler, I would suspect the ENDSWITCH in the zone valve first.

Can you tell if when the burner cuts out the PUMP also cuts out?

If the zone valve or t'stat is at fault, it would.

Do you have a voltmeter and know how to use it?
 
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Old 11-14-13, 06:44 AM
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really cannot tell if the pump is cutting off. It is a power vent and that keeps going. I also hear an audible click from down near the burner controls (same click I hear when it shuts down regularly)
Trouble is that it only cuts out for a about a second and that's it. I do have a volt meter and know how to use it so can trouble shoot if needed. I need a new stat for another room so I thought trying that would be a no brainer.
 
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Old 11-14-13, 06:51 AM
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I think there is a zone valve between. Here is a link of some pics of the system I am at work so it's all I got for now
http://www.doityourself.com/forum/bo...-overflow.html
 
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Old 11-14-13, 07:07 AM
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I remember your system now...

Yes, Taco zone valves.

Is the 'cutout' predictable enough that you won't have to get a chair and a cooler of beer and 'babysit' the boiler until it happens?

If so, set your meter up for AC volts (24) and connect to the wires that come from 2 and 3 on the zone valves to the T T on the boiler aquastat.

When any zone calls for heat, this voltage will (should) be zero. If you see the meter jump when the burner cuts out, that would indicate that the endswitch is momentarily 'letting go'. This would be MUCH easier to see with an analog meter.

If when the questionable zone calls for heat you see the voltage 'floating' a few volts above zero, but the other zones go all the way to zero, that would also indicate a problem with the endswitch in that zone valve.
 
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Old 11-14-13, 07:59 AM
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I will have to babysit it, but I will see what is going on tonight. Usually does it every cycle so not to bad.
Worse case will it hurt anything to let it go a bit if I cannot duplicate it right off.

Still gonna get the new stat cause I need one anyway for the upstairs room.
 
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Old 11-14-13, 09:19 AM
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So would they be under the cover?? Again I am not home and it my be crystal clear when I get there, but I want to have my ducks in a row when I get there. Should it read T T at the connections and should I have 24 volts when no call for heat.
 
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Old 11-14-13, 09:27 AM
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So would they be under the cover?
Would what be under what cover?

T T connections are fine...

Yes, when there is NO heat call, you will read 24VAC nominal.

Heat call from any valve should be ZERO volts.
 
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Old 11-14-13, 10:11 AM
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Under the cover of the Aquastat.
 
  #10  
Old 11-14-13, 03:28 PM
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Have 28 volts at the TT. how hard to change the end switch. We do not use 1 zone and could rob peter to pay paul from a valve
 
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Old 11-14-13, 03:58 PM
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how hard to change the end switch
Don't know in Taco... IF you could find the proper switch.

I do know that it's 'do-able' with the Honeywell...

But swap out the whole power head if you want to try that route at troubleshooting, makes sense, and it's easy.
 
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Old 11-14-13, 04:42 PM
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Well I got it to do it twice on the first fire up and of course the fist time was before the meter was hooked up and the second time It did it and I looked over and the lead had fell off. Cycled it many times after that and nada zip zilch. Here is what I noticed though. When I cycled it on the other Zone the contacts in the Aquastat came of and on crisply. When it was the questionable zone there was some creaking when closing ie took a fraction longer to open and close. When it did mis fire the contacts opened and then closed. The last few cycles the contacts sounded crisp like the other zone.
This zone has only ran 1 or 2 times since last year due to having a woodstove could that endzone switch had a bit of crud on it and it is now worked off ?
What is the procedure for changing the power head do I have to drain?
Did not get a new t stat as I was too late to the store. I may switch them around and see if the problem moves zones i the problem comes back.
 
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Old 11-14-13, 04:55 PM
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Well I just ran it again and I had a few small blips (contacts clicked) that were for a fraction of a second. Just enough to barely be noticeable on the firing and to make the meter got to OL (overload) or a fraction and then back 0 (actually .011) I think they were too fast for the gauge to catch
 

Last edited by Stelmashuck; 11-14-13 at 06:37 PM.
  #14  
Old 11-14-13, 06:35 PM
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Well I switched out the powerhead with an upstairs head I do not use (man that was easy just twist clockwise) and the contacts click nice and crisp and there are no blips, creaks or small clicks like when it ran like before. Looks like time or a new powerhead for the upstairs zone. Really hope that's what it was. New one looks to be under $100
 
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