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I have a utica hot water gas boiler that has a pilot light…

Customer Question
I have a utica...

I have a utica hot water gas boiler that has a pilot light and some new parts such as a pilot ignitor, thermocouple and now a new aquastat l8148e 1265. My issue is boiler will not fire up. It only does when i jump power 24 volts from aqua stat to gas valve

Contractor's Assistant: How long has this been going on? And how severe is the problem?

Started after install of aquastat.

Contractor's Assistant: Do you plan on doing the work yourself?

We already did. The problem seems to be the power output for the gas. It keeps moving from 12 to 24 volts

Contractor's Assistant: Anything else we should know to help you best?

If we switch to a different power supyly it fires right up.

Submitted: 4 months ago.Category: HVAC
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Answered in 1 minute by:
12/2/2017
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago
Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 23,784
Experience: 40+ yrs. experience as a licensed oil & gas technician.
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Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. First I’ll need some more info so I have a more complete picture of your situation. What's the model number of your unit?

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Customer reply replied 4 months ago
Aquastat L8148E
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

That's the aquastat relay not the boiler model. The boiler model is on the rating tag which also has the BTU input

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Customer reply replied 4 months ago
Utica Gas boiler Model MGB150HD
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

Ok, give me a few to pull the specs.

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HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

Ok, do you have 24 volts at B1 & B2 on the L8148?

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Customer reply replied 4 months ago
23 vac
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

Ok which terminals at the gas valve are you probing? Is the pilot lit. I'm assuming you have electronic ignition.

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Customer reply replied 4 months ago
I took off the plugs at the gas and metered there. Pilot is lite. If i switch to diffrent power supply it fires up.
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

You didn't answer my questions. Which terminals? elctronic ignition?

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Customer reply replied 4 months ago
TH/TR manual ignition
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

Then if you have 24 volts at B1 & B2 but not at the gas valve jump out the flame rollout switch just above the burners, it has 2 wires attached. If the unit doesn't respond then jump out the blocked vent switch which is under the draft diverter (the open box below the damper.) Either one of these devices is faulty or you have a bad connection between the gas valve and the L8148

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Customer reply replied 4 months ago
I think it a bad Aquastsat. If i remove the power output wires from the Aquastat and hook up an external 24vac power supply the unit fires up.
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

Not a bad aquastat if you have 23/24 volts at B1 & B2. You have to check what I described in my last post.

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Customer reply replied 4 months ago
The external power supply actually outputs 26 volts and this appears to make the difference to open the gas valve and fire up the boiler
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

The gas valve will open at volatges as low as 20 volts.

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Customer reply replied 4 months ago
ok i will try jumping both switches one at a time
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

No 1 at a time or you won't know which is bad if that's the problem.

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Customer reply replied 4 months ago
Bypassed switches 1 at a time and unit did not fire.
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

Then you have a bad connection between B1 & the gas valve. You can verify this by disconnecting the lead at B1 and run a line diret from B1 to the gas valve. Wiring diagram shows B1 connects to TR gas valve terminal. Double check to be sure. Those switches are in series between B1 & the valve TR

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Customer reply replied 4 months ago
Ran new wires and still same issue.
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

Check B2 rewire if necessary. The only explanation for a volatge drop between B1 & B2 and the gas valve is a bad connection.

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Customer reply replied 4 months ago
Ran new wires to both. We just tried the different power supply again and it fired up.
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

Then what you're telling me doesn't add up. 23 volts at B1 & B2 and all new direct wiring to gas valve the gas valve should open. What do you read at the gas valve end of the new B1 & B2 leads?

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Customer reply replied 4 months ago
If connected 0. Disconnect and test wire directly 23vac
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

not possible, you don't lose the voltage if you conect the leads

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Customer reply replied 4 months ago
I can only tell you what i am seeing. But that is what is happening.
HVAC Technician: Rick, HVAC Supervisor replied 4 months ago

I'm going to open this up to my colleagues so one of them can help. Please don't respond (even to acknowledge this post)until you get a response from us. If you respond first it will only delay your answer.

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