Repair of SIT Valve

[tmy23]

Greetings. I have a fireplace with a "coal effect" gas fired set which uses a SIT 820 valve. Noticed flame not in the burner tray. Shut it all down and after careful investigation, discovered the secondary flame is forming about a minute after the unit warms up, on the back edge of the valve between the top brass plate (Held on with a number of screws) and the valve body. I guess the plate is warping under heat (as it consistently takes about a minute once the unit cools back to room temp, but if re-ignited after being shut down, the secondary flame appears immediately. Seems likely the gasket material between the brass cover plate and the valve body has failed. Was planning to take the plate off, and determine whether it is a "formed" gasket or a "caulk" type gasket.

Has anyone else attempted to perform maintenance on a SIT 820 who might have some tips/clues?

thanks!

tmy23

 

[wooduser]

There is a burner defect called flame flashback. Flashback occurs when the gas burns in or near the burner primary air shutter, rather than on top of the burne itself. When flashback occurs the burner is usually noisy with a roaring sound. Does this sound like the problem you are describing?

Gas burns at a predictable speed. When operating normally, the gas is traveling fast enough through the primary air shutter that it wont ignite, not until the gas reaches the top of the burner, where it slows down and is then able to ignite.

Flashback occurs when the speed of the gas past the primary air shutter is too slow, allowing the burner flames to ":flash back" to the vicinity of the primary air shutter or burner orifice.

So if this is the problem you may have the primary air shutter set improperly, the gas burner not seated properly, gas pressure too low to operate normally or some other defect causing the gas to be moving too slowly.

 

[tmy23]

There is a burner defect called flame flashback. Flashback occurs when the gas burns in or near the burner primary air shutter, rather than on top of the burne itself. When flashback occurs the burner is usually noisy with a roaring sound. Does this sound like the problem you are describing?

Gas burns at a predictable speed. When operating normally, the gas is traveling fast enough through the primary air shutter that it wont ignite, not until the gas reaches the top of the burner, where it slows down and is then able to ignite.

Flashback occurs when the speed of the gas past the primary air shutter is too slow, allowing the burner flames to ":flash back" to the vicinity of the primary air shutter or burner orifice.

So if this is the problem you may have the primary air shutter set improperly, the gas burner not seated properly, gas pressure too low to operate normally or some other defect causing the gas to be moving too slowly.

 

[tmy23]

Thanks for the informative reply. So burner was untouched for years and years. I never have attempted to make any changes so the settings, so the air shutter and gas burner suggestions might not be the issue. It was running fine throughout the winter and I just happened one night watching TV lying on the floor to see past all the decorative grillwork on the front" that there was flame between the valve body top and the coal pan directly above (there is about a 1/2" gap there. I unmounted the unit from the floor of the hearth, and using swung it around so I could watch the back of the unit and as mentioned, the flame definitely seems to be located and shaped to suggest the seal between the top plate and the valve body.

 

[tmy23]

Thanks for the informative reply. So burner was untouched for years and years. I never have attempted to make any changes so the settings, so the air shutter and gas burner suggestions might not be the issue. It was running fine throughout the winter and I just happened one night watching TV lying on the floor to see past all the decorative grillwork on the front" that there was flame between the valve body top and the coal pan directly above (there is about a 1/2" gap there. I unmounted the unit from the floor of the hearth, and using swung it around so I could watch the back of the unit and as mentioned, the flame definitely seems to be located and shaped to suggest the seal between the top plate and the valve body.

As I write this it occurs to me that I could try a small bead of high temp silicon around the top plate to see if that stops it. If it does, I can take the plate off, clean it up right and do a proper job of repairing it.

 

[tmy23]

As I write this it occurs to me that I could try a small bead of high temp silicon around the top plate to see if that stops it. If it does, I can take the plate off, clean it up right and do a proper job of repairing it.

Oh sorry, I didn't answer your question, there is no unusual sound during this secondary flame.

 

[wooduser]

Thanks for the informative reply. So burner was untouched for years and years. I never have attempted to make any changes so the settings, so the air shutter and gas burner suggestions might not be the issue. It was running fine throughout the winter and I just happened one night watching TV lying on the floor to see past all the decorative grillwork on the front" that there was flame between the valve body top and the coal pan directly above (there is about a 1/2" gap there. I unmounted the unit from the floor of the hearth, and using swung it around so I could watch the back of the unit and as mentioned, the flame definitely seems to be located and shaped to suggest the seal between the top plate and the valve body.

Unfortunately, I can't identify the issue from your description.

Does my description of flame flashback describe what is happening?

Some pictures of what you are observing might help me identify a problem if it's not the flashback that your description suggested to me.

 

[Millbilly]

Just because you haven't moved the air shutter doesn't mean that's not your problem. Dust, fur, hair, emberwool, bees, spiders, etc accumulate and can be blocking the gas flow at the shutter. It's worth having it removed, cleaned, inspected,and reinstalled correctly.