Boiler not operating when call for heat


Old 07-26-17, 08:22 PM
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Boiler not operating when call for heat

I have a Utica Boiler that feeds 5 zones. The boiler does not fire with a call for heat for the hot water tank. The solenoid operates, but system does not run. I manually operated each of the remaining 4 zones to see if maybe I have a bad HW solenoid, but had the same result..... no circ pump, no fuel pump and no burner action.

I removed the cover to the Honeywell L8148A Aquastat box. I manually moved the contactor relay and immediately the circ pump starts, then after about 5-7 secs the fuel oil pump starts and then burners start. I release the relay, everything shuts down.

I jumpered the TT points and the system started.

I have verified 120v at circ and boiler connectors and 26VAC at the TT points, both in the Aquastat.

System pressure is 30#, so this is not a low water pressure issue.

It his highly unlikely that all 5 solenoids would fail (4 that have not been used since April). So I do not believe it has anything to do with the 24 VAC side.

I am apt to replace the Aquastat, but when I jumper out the TT, all is fine.


Thank you!
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Old 07-26-17, 09:00 PM
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Welcome to the forums.

but when I jumper out the TT, all is fine.
Ok.... so it's not the aquastat.

Do you have a zone control system or just five zone valves with a spaghetti mess of wiring ?

I'm guessing no zone controller which means a lot of wiring.
My first thought is a second defective 24vac transformer. This transformer runs the valves. A quick confirmation is..... is the HW zone valve open ?

My second thought is a broken wire between the zone valves and TT.
My third thought is there a safety sensor open in the TT line.

For a tech this would be an easy repair. For us it will be hard to tell you what to check.
Do you have a voltmeter ?

Can you take a few pics of the wiring and post them here.

System pressure at 30psi on a cold boiler is way to high. It should be closer to 12-15psi. You may need to check into the expansion tank pressure. There is a sticky at the top of the forum that describes the testing. This isn't your current problem but will need to be looked into.
Old 08-02-17, 04:57 PM
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When the zone valve opens fully, it closes an end switch which signals the aquastat to turn things on. On Honeywell zone valves, the 2 red wires go to the end switch. The end switch is not replaceable, but the end switch, motor, and mounting plate are available as a unit, so you don't have to replace the whole zone valve (no messing with the piping). is one place to get parts. Agree with PJ that pressure is too high, but that's another problem. Good luck, Steve
Old 08-02-17, 09:05 PM
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Thanks for the additional info Steve. Since he tried each zone valve manually... a defective end switch is probably not the problem here.

We were waiting to hear back from the OP. He seems to have forgotten he posted here.
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