Aquastat? Oil vs Gas?


Old 02-09-13, 05:12 PM
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Aquastat? Oil vs Gas?

It seems that some 'stats are specified for oil and others for gas. Why, what's the difference? Gas 'stats usually control 24-V devices, either directly or through relays. Not sure about oil 'stats.
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Old 02-09-13, 06:50 PM
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Oil a'stats output 120VAC on the B1 and B2 terminals while the gas models output 24VAC.

Stats made for millivolt gas valves of course output nothing, but those are 'configurable' by a jumper to be used with 24VAC valves.

One could use an oil a'stat for a gas system (and there ARE some 120VAC gas valves still around!) by connecting the burner output to the primary of a 24VAC transformer. There is at least one manufacturer who does this... can't remember which one... as I recall, the induced draft fan on those boilers was a 120VAC part and it ran directly off the B1 B2 output, then on to the transformer and to the gas valve.

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