Old floor furnace pilot goes out after 1/2 hour ( & so does the heat ! )

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  #1  
Old 12-03-12, 12:42 PM
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Old floor furnace pilot goes out after 1/2 hour ( & so does the heat ! )

Hello all:

Old bungalo in California with an old floor furnace. Seems to have worked well for years. I put in a new millivolt generator & it idles at a nice 500mA. ( devilish job in that crawl space I might add. )

When the heat has been on about 1/2 an hour the furnace goes off & the pilot goes out too.

I thought it might have been the heat limiting switches, but I noticed if you disconnect them the pilot will stay on so they only control the main gas valve.

Thoughts ?

When the furnace goes off does it blow out the pilot ? I've got a real healthy flame at the pilot & clean connections to the control valve. Does the electromagnet in the control valve lose strength with time ? Maybe when warm the resistance goes up & the magnet lets go ?

Dunno. Asking for advice..
Thanks !

Jaan
 
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  #2  
Old 12-03-12, 03:35 PM
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The usual cause of pilot outages is a pilot orifice and pilot burner that need to be disassembled and cleaned.

The pilot flame should look like a small blowtorch. When the pilot burner and pilot orifice need to be cleaned, the pilot flame has yellow tips or is a soft flame that is easily blown around like a candle flame.
 
  #3  
Old 12-03-12, 07:12 PM
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Thanks for the observation. It's a very strong flame, but I'll go disassemble & clean & see what happens. I'll leave an update...
 
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Old 12-04-12, 03:17 AM
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Usually there's a brass nut at the end of the pilot tubing to hold the pilot tubing into the pilot burner. You need to loosen that nut until it's free, and you'll find the pilot orifice at the very end of the pilot tubing, forming a jet of gas for the pilot burner.

Some orifices can be cleaned with the wire from a wire brush. On other the hole is too small and you need to blow out any dust and dirt with air.
 
  #5  
Old 12-09-12, 08:28 PM
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Well let's see. Cleaned out the little pilot orofice with a watchmakers reamer. I get a beautiful blue flame ( Photo enclosed ). Darn it, it goes out again. Here is an email from the lady living there:
Once the pilot light is on, it stays on until I try to turn on the heat. To ignite any of the burners I have to turn the heat up to around 70. They ignite and stay on for about 20 minutes then everything goes out and not even the pilot light will come on again.

Any chance the control valve loses magnetism when warm & shuts itself off.? The new thermo idles at a good solid 500 milivolts with pilot on.

Thanks for any opinions 1

Jaan
 
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Old 12-10-12, 03:25 PM
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Could be a worn out gas valve, but you probably need someone with an experienced eye to see what's going on. The pilot can be blown out when the burner shuts off, as your tenants describes.
 
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Old 12-10-12, 04:23 PM
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If that's a PG9 pilot generator, it should be 750 MV

Okay, so when the burners come on, does the pilot flame shrink?
 
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