Odd problem with boiler and thermostats

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Old 12-01-12, 03:30 PM
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Odd problem with boiler and thermostats

I have a 5 year old Burnham Independence Boiler heating my tenant's apartment, and I've been having odd problems. It's a gas, single zone, steam. Pretty simple.

Several times the boiler has failed to kick in. The initial time, the pilot went out and I re-lit it. Nothing happened, so I replaced the thermocouple. Nothing happened, and then suddenly an hour or so later it began working. Problem solved, no. Several days later it goes off. I speak with my plumber who was away and after troubleshooting he suggests I replace the vent damper. No luck. I short out the thermostat wires, and it kicks in. (I had tried that earlier to no avail.) I swap thermostats with my house and it now seems to work.

He's where I'm going nuts - Another week goes by and the boiler stops working. I short the thermostat wires, it turns on. I try another thermostat, it works. Again, several days later this repeats. I now try a non-programmable thermostat. It works for several days and dies.

What could this be? I'm thinking the 24v transformer could be bad, and just on the edge of not working. Perhaps it's not delivering the right voltage and the small amount of impedance from the thermostat somehow builds up over time. The only other concern is the wiring from the thermostat, it's old wiring. But the fact that it works for a while and then stops would make no sense.

I don't want to continue swapping parts in hopes that the problem goes away.

I appreciate any insight here.

Tom
 
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Old 12-02-12, 03:57 AM
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Check your pressure-trol and the pig tail that is attached to..
 
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Old 12-02-12, 06:06 AM
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If you think it's a wiring / impedance / thermostat issue, install an isolation relay right at the boiler.
 
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Old 12-02-12, 06:11 AM
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poorplmbr, that was my first thought as I read through this but when he jumpers T-T it runs. If it was a blocked pigtail and he jumped t-t it still would not have run. On the other hand if the pressure would have bled off before he jumped t-t the thermostat should have brought it back on.

Questions for tommr;
1. Where is the thermostat located?
2. Do you do anything else before jumping t-t and the boiler runs?
3. What are your pressure settings and what model pressure control do you have?
 
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Old 12-02-12, 06:36 AM
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Have you checked ALL wiring connections,I just had a similar problem and there was a loose wire in a Taco ZVC 406,the stats would call and nothing would happen.
 
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Old 12-02-12, 07:40 AM
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Yesterday I had removed the thermostat and shorted out the wires. The boiler was working fine. To control the temperature, we simple would turn the boiler off and on from the Emergency switch on the stairs. It worked fine all day.

This AM, the boiler would not kick on again. I checked every wire and connection, opened the junction box at the transformer and double checked those connections as well. I measured the impedance from the shorted thermostat wires, from the furnace, 0 ohms.

rbeck- to answer your question the thermostat is on the first floor, probably 10 feet from the boiler. I had not done anything other than short the thermostat wires.

Now I'm guessing the pressure-trol. Poorplmbr- i didn't see a pig-tail connection there.

Thanks again for these inputs. Any further guesses now that the thermostat has been ruled out?

Tom
 
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Old 12-02-12, 09:33 AM
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Tomm, 'pigtail' is also called a 'siphon tube' and is simply a coil of pipe on top of which your pressutrol is mounted.


image courtesy wordpress.com

What are the settings on the pressurtrol? Cut-in, Cut-out (diff) ?
 
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Old 12-02-12, 09:52 AM
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Problem solved

First - thanks for all the help. I decided to bite the bullet and call a plumber. He had me troubleshoot the pressure-trol as well, by shorting out the wires. I tried that and a few things, before he agreed to come over on a Sunday AM.

He figured out what the problem was, almost accidentally. After checking everything else out, it turned out to be a problem with the low water cut-off. There seems to be problem with the board (solder joint problem) as the slightest touch of the cable/connector would cause the boiler to flip on/off. The theory is that the slightest shake of the boiler would cause the connection to loosen. All the thermostat switching, etc....was a coincidence.

Tomorrow I"ll run out and get a new board.

Thanks for the help.

Tom
 
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Old 12-02-12, 11:16 AM
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Tomorrow I"ll run out and get a new board.
Don't own a soldering iron and a magnifying glass?
 
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Old 12-02-12, 11:17 AM
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And you still have not told us what the setting on the Pressurtrol are...

Let us know this, because if they are way whacked out we can probably save you some money.

Unless you don't want that?
 
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