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Old 02-03-2010, 11:54 PM   #1
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2 boilers thermostat wire installation...

hi, recently I installed 2 oil boilers "burnham", these each one has limit switch with transformers, one for each, now the old ones use to be connected to a relay box with 120 vtls and transformer goin to the thermostat, but once you ask for heat both boilers work at the same time, the owner wants to control each boiler separate by using one thermostat; I got one honeywell wireless 2 stage thermostat (since i only have 2 wires coming from the house) but this set only make to run one boiler and the other not even a power on the w2. some one can tell me what other choices do I got? or do you know any other thermostat that will make work this 2 boilers separate? I can run a 5 wires thermostat cable and does not have to be wireless... thanks.


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Old 02-04-2010, 12:50 AM   #2
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The best way is with an outdoor reset control that can control 2 boilers.
The Wiel McLain BCP-3 is one that works real well for this type of application. And saves the owner money one his heating bill. By controlling the heating water temp.
It will only bring in the second boiler if the first one is not bringing the water temp up quick enough. And you tell it how long it should take the other boiler to come up to temp.
It also does automatic lead lag boiler switching so they get even wear and tear.

The other way. is to install a simple 24 volt relay system for the stat to control the relays, and the relays bring on the boilers. How ever that doesn't give you the lead lag control. Nor does it save money on the heating bill like a outdoor reset control does.


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