boiler fan shuts off but the gas stays on

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Old 11-03-12, 06:29 PM
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boiler fan shuts off but the gas stays on

When my boiler reaches high water temp it shuts the fan off but not the gas causing flames to back up? I'm missing something. Any ideas?
 

Last edited by fixmyown; 11-03-12 at 06:49 PM.
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Old 11-03-12, 07:14 PM
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Sure are! How about posting the manufacturer and model number of your boiler for starts.
 
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Old 11-03-12, 07:45 PM
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Weil Mclain model he-5 on natural gas
 
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Old 11-03-12, 07:57 PM
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Residential boilers are a little outside my area of expertise. We have both some highly talented amateurs and some professionals that volunteer their time on this forum. Unfortunately the topic moderator has not been heard from since the storms hit the east coast. You may need to wait a few days to get a good response.
 
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Old 11-03-12, 08:29 PM
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ok. Thanks for your time.
 
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Old 11-07-12, 03:44 PM
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When the thermostat calls for heat the exhaust fan comes on. After about twenty seconds the hot service igniter comes on and stays on for about thirty seconds. The gas valve opens and it ignites fine. After running for about twenty minutes the water reaches 170 degrees. At that time the flue exhaust fan shuts off but the gas valves stays on and at that time some flame comes out from underneath the unit fir about three seconds then the gas valve closes. Soon the hot surface igniter comes on, glows for about thirty seconds and shuts off. it tries it again two more times. I shut the unit down and once the water temp lowers all works fine until the high temp switch is again activated. When the unit is running before failure i pulled the pressure tube off at the pressure switch and it shut the gas valve immediatly. Replace the hose and it cycles and starts up and continues heating the water. help would be appreciated, Thanks.
 
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Old 11-09-12, 07:45 PM
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At that time the flue exhaust fan shuts off but the gas valves stays on and at that time some flame comes out from underneath the unit fir about three seconds then the gas valve closes.
The best advice you can be given at this point is to shut the system off and do not use it until this problem is fixed. This sounds like a fire hazard to me... either that or CO poisoning issue.

You've either got a defective control (sticking relay, bad pressure switch), or a defective gas valve.

Weil Mclain model he-5 on natural gas
Not enough...

What's the FULL information from the data plate on the boiler?

Do you have the manual for your boiler?
 
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Old 11-11-12, 03:49 PM
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The fact that the inducer shuts off before the gas valve closes sounds scary. Call your boiler expert...he can take some meter readings while it's running and get to the bottom of it in a hurry.
 
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Old 11-12-12, 05:26 PM
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I do kinda wish that fixmy would come back and let us know he's still alive.

He hasn't checked in since his last post.

Posts like this and I don't sleep well at night (or even at my desk during the day!)
 
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Old 11-12-12, 07:00 PM
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Your problem probably lies in the gas valve. Its probably sticking and needs to be replaced.
 
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