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My boiler is short cycling, sounds only the gas valve is…

My boiler is short...

My boiler is short cycling, sounds only the gas valve is shutting down only on for 70 sec. first cycle then 5 to 8 sec. after the call comes in.

Contractor's Assistant: Have you tried power cycling the appliance -- unplugging it and leaving it off for a few hours?

Yes no change

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

Yes

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

I changes the flame sensor first but think it the gas valve now

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Customer reply replied 10 months ago
The boiler is a Weil-Mclain Model VHE Series 3
I have a Robertshaw 7100 DER-S7C gas valve and a 780-735 ignition control unit to replace the gas valve if it will work?
Answered in 11 hours by:
10/22/2017
Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 24,614
Experience: 40+ yrs. experience as a licensed oil & gas technician.
Verified

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

Your unit appears to have a mercury flame sensor. So the best fix is to retro fit it with a new ignition control, gas valve and spark pilot assembly. The Gas valve you mention shows as having no pilot outlet in the manufacturer's database.

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the ignition control is for a spark igniton pilot so it is suitable. Do you have more questions?

Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 24,614
Experience: 40+ yrs. experience as a licensed oil & gas technician.
Verified
Rick and 87 other HVAC Specialists are ready to help you
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Customer reply replied 10 months ago
The gas valve that I have came with a new spark egnition pilot assembly. What makes the old system run for 70 seconds on cold start and then cycle on and off 5 to 8 seconds to satisfy the call? If the gas valve is the problem why’s it not a consistent time?
Phone call session started

Here's the wiring diagram.

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