HydroTherm HC-85 stopped working

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Old 01-29-18, 12:25 PM
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HydroTherm HC-85 stopped working

My furnace stopped working. Pilot light is on. Relays are coming on when thermostats call for heat. Transformer on the furnace was reading 0 VAC, so I replaced it. The furnace fired up for about two minutes and then the transformer sizzled out. What could be causing this to happen, I'm thinking there might be some kind of short farther down the low voltage line. Could the high limit controller be busted?
 
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Old 01-29-18, 04:38 PM
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Welcome to the forums.

We'd need more information than that to help you.
Do you have zone valves ? One of them could be shorted or it's wiring.
Any place wiring touches ground can cause a short.
A defective flue damper.

Manual.... HCD/HCD2-501.pdf
 
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Old 01-30-18, 05:42 AM
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There are 3 zones in the house. When the thermostat calls for heat the corresponding pump turns on and pushes the water. When heat is called, 110 is sent to the transformer that died. I measured the resistance on the 2 wires that attach to the 24v side of the transformer, and I get 9 ohms. Is that normal?
 
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Old 01-30-18, 06:37 PM
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Is that the transformer inside the aquastat ?
If yes.... I'd say 9 ohms is too low. I see a relay in the aquastat and externally.... the gas valve. Gas valves are usually better than 50 ohms.

I'm looking at diagram 1.24 (page 14) in the manual. It shows multiple relays but all supplied by installer so I'm not quit sure how your system is wired. Pictures of what you are replacing and where would be helpful.

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Old 01-31-18, 10:54 AM
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Transformer location&lt;br /&gt;<br />
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Low voltage wires go to this and the gas valve&lt;br /&gt;<br />
Is this the aquastat and should it show any kind of resistance between the screws with the wires disconnected?&lt;br /&gt;<br />
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Disconnected the valve wires from the terminals and measured 11 ohms of resistance, does that mean the valve is dead?
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Last edited by medo145; 01-31-18 at 01:54 PM.
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