outdoor furnace high limit codes

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or stampings anywhere on the appliance, or in the installation manual, it would seem to me the manufacture has chosen not to have their equipment listed, tested, approved, etc.

Outdoor burners seem to thread the needle with these requirements.

If you are the installer it is your duty to see if that equipment meets the spec required by the AHJ in your area. That may be the State, or county, or township, or combination of the above.

Often times homeowners insurance companies will have a say in what they will allow and insure.

Of the various listings I have seen on wood or solid fuel burners, ASME, UL, TUV, Warnock-Hersey. Perhaps ANSI the water heater listing agency gets involved.

I'd bet NFPA 54 has a chapter on solid fuel burners also.

You could go to the UL site and search for a catagory the covers that appliance. I'd be willing to be they have a pellet stove listing, at least on the burner device if not the entire assembly.

It is a very expensive proposition for manufactures to run equipment through UL some chose not to do it. Buyer, and installer, beware, I suppose.

Why not call the manufacture of that appliance for their "take" on your question? Next the local code officials. Then the homowners insurance company.

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RadPro

Outdoor wood/corn furnaces

Are there any federal or state (PA), codes that govern high limit shutdown of these furnaces? In particular, a furnace that has a corn burning system. The system has a mode that once the target setpoint of the water is met it pulses the burner assembly at user defined intervals to keep the fire going in between calls for heat. If the unit sits for a significant period of time it will let the jacket temp build and build with no limit. I will add that the unit has a "dump" limit on it to dump heat to a user supplied load but, the limit does not kill the burner. So if the dump zone fails then what? Seems like you would want to kill the heat source also at the high limit setting otherwise the unit will keep creeeping up in temp. Any thoughts?
Regards,
Ditchdigger

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That's why most outdoor

"furnaces' are open, unpressurized systems. They just boil away until the LWC cutout power. Some, like the Hardy, has an auto refill float system to refill after a boil over.

Some of the pressurized types come with a regular water heater T7P. When it hits 210 F it pops.

A true dump zone would be a gravity flow system, so it could dump heat in the event of a power outage.

And actually the burner should not operate when it hits it's limit so the dump zone should pull the temperature down quickly.

Even with the burner, air inducer, damper door, whatever device yours has they all leak enough O2 to keep a small fire going. Or else you would be re lighting them every "off" cycle.

Solid fuel burning is not as easy as the brochure reads

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RadPro

Thanks for your response. The unit is pressurized at full temp, about 4psi, and has an expansion chamber in it. I realize that this makes it a "furnace" and not a boiler. Let me put this a different way: as I said the unit is a corn burner, with the design of the unit it has to pulse itself every 10-15 minutes to keep the fire going in the burn pot when its off of run cycle. If for some reason it gets too hot an aquastat will trip the dump circuit to dump heat. Problem is - the overtemp does not kill the pulse cycles. I would think that there is some regulation somewhere that says a burner must be de-energized should a unit reach a high limit. Seems like a simple safety feature. Basically the existing corn unit is like an oil gun pulsing at intervals whether the unit temp is below or above the high limit setpoint. I can't believe outdoor units with an electrically controlled fuel burner could slip by without having to shut the burner assembly down on overtemp.
Regards,
Ditchdigger

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I wonder that

it has any ASME, UL, or any other listings? I suspect there may not be a listing to cover a low pressure "device" like that. As I recall ASME would list the pressurized vessel but not the safety or control string.

It sure sounds like a simple relay installation could fix that "pulse" feature, while it is in high limit mode. I'd check with the manufacture before you make any field mods. It puts you in a liability position you may not want to be in

When you start to "dump zone" them it looks a lot like a dog chasing it's tail. It dumps, then calls for heat, dumps, fires, etc.

Seems all you really accomplish is overheating the "dump" zone and turning expensive pellets into smoke

I chose to buffer my wood burner with an insulated 500 gallon tank. I want those converted (chemical to thermal) BTU's to stay in my building as long as possible. I paid for them they should work for me not be squandered where they do little or no good.

Dump zones... that's Neanderthal engineering at it's finest It encourages bad operator behavior.

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RadPro

From what I gather there is not an ASME listing for a low/non-pressurized vessel. The unit is not UL listed either. This has raised some red flags in regards to the question of minimum safety standards/regulations for these units. If indeed no codes are in place for these units with an electrically controlled burner, that seems amazing to me. A dump zone is not adequate for exclusive safety control of a heating device, in my opinion. You would think that these units would have some governmental regulations in regards to safety. Sure would like to have a dead fire than scalding water emitting from the unit if the dump zone fails. Let me clarify my post by saying that most manufacturers corn units do shut down the burner assembly in the industry, but is there some sort of regulation mandating that in regards to these types of outdoor furnaces? Just curious. Ditchdigger