turning off power to boiler gas valve

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Old 11-19-11, 10:53 AM
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turning off power to boiler gas valve

hello. after an extended absence, i am back for some more valuable advice. i've had alot of questions in the past you have helped with. i have an evacuatated tube solar array that shares a boiler loop. i cannot have both the array and the boiler running at the same time because the boiler will then heat the solar array. so, watching these work together, i want to automate the hand off from the boiler to the solar array. i want to stop the boiler from firing,( ie now i just pull the gas valve power wire) when the array reaches 100 degrees, but let the pump run until the array reaches 134. the array starts pumping at 135. i can program this stuff to happen via a pc, but i am wondering how to turn off just the gas valve. Would i do this via a 24 v ice cube relay? i have a valant boiler, for now until either i have the cash to buy a more efficient one, or i have to buy it because of boiler problems.

you have warned me about condensation in the stack and about putting cold water into the boiler. the way this is set up right now, i have neither problem and it has been running now for 3 years. thanks for your help.
 
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Old 11-20-11, 07:54 AM
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Hello,
What about stopping the heat call to the boiler by opening the the thernmostat line with a relay there, instead of messing with the gas valve wiring.
Then if the pump needs to run, parallel wire the pump to a relay, controlled by aquastats, differential controllers, PC, etc. as you wish.



Peter
 
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Old 11-20-11, 08:48 AM
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i have to think about doing it that way. what strikes me right away is stopping the call for heat will close the zone valve. The whole idea of handing off from boiler to solar array would be to maximize the use of the heat already produced, ie from the boiler.
 
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Old 11-20-11, 11:04 AM
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Interrupting the power to the gas valve will cause the flame safeguard control to go into a lockout. This will preclude the boiler from firing automatically until the lockout is cleared.
 
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Old 11-20-11, 11:15 AM
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give me a little more information. right now, i can pull the power wire going to the gas valve, and the burner shuts off, but the pump still runs. If i want the boiler to fire, i just reattach the wire. maybe it is because this is an old boiler, and newer electronics/boilers will not allow me to do this? If that is the case, i will have to figure something else out as i want to replace this boiler. thanks.
 
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Old 11-20-11, 12:03 PM
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If you can remove power to the gas valve for more than about 45 seconds without the flame safeguard going into lockout then you have a serious problem with the flame safeguard. I would have to know much more about how your particular boiler/burner is wired to make any more comments.

UNLESS, you have an atmospheric burner and a constant pilot with only a thermocouple/pilotstat monitoring the pilot. If this IS your system it is of marginal safety.
 
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Old 11-20-11, 12:23 PM
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it has a standing pilot and is protected by a thermocouple. from what you have told me, and from what i have read, beginning next year all boilers will be required to be electronic ignition. I assume then a power interruption will cause the lockout you refer to. I'll look for another way to solve this problem. It looks like I will have to shut the boiler down based on a sunrise time rather than solar array temperature to insure I have sufficient time for boiler cooldown to avoid thermal shock to the boiler. Aube makes these switches that operate based on latitude/longitude and I already have one doing something else. This won't be the most efficient way to do things, but it will work, and i believe , should work with electronic ignition boilers too. thanks for you information.
 
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