Honeywell L8124A Aquastat


Old 05-12-11, 09:27 PM
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Honeywell L8124A Aquastat

I have an oil hot water furnace with a "summer/winter" hookup, meaning it also provides domestic hot water. The Aquastat controller is getting 120 volts in, but there is no power coming out for the burner motor or the circulator when the thermostat is set to demand heat. My guess is the thermostat transformer is burnt out. What is the replacement information for the thermostat transformer?
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Old 05-14-11, 12:54 PM
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The transformer is not field replaceable & likely not the problem. Disconnect the thermostat wires from the aquastat & check for 24 volts AC between the terminals. If you have 24 VAC, the transformer is good. Install a jumper across the T-T terminals & see what happens. If the relay(s) pull in & the circulator & burner run, the problem is either in the thermostat or it's wiring.
Old 05-15-11, 09:54 AM
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When you say 'thermostat transformer', then perhaps you have a separate transformer with electric zone valves? If you have zone valves, it's more likely a problem with one of those. Need more info...

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