hydrotherm fire chamber door, melting/Burning

lwal

I recently decided to have my carbon monoxide tested in my gas burners flue. It came in at 104 PPM. My plumber removed the jacket and flue pipe, brushed the inside of the boiler to remove the carbon buildup and used a compressor and vac to clean everything up. This lowered the carbon monoxide to 14 PPM. MY plumber also suggested I change the Gas Valve (24 Volts) which I intend to have him do next pay check. The reason for my question is: Would the Gas valve or the carbon buildup be the cause for the little door on the boiler near the fire chamber to be melting? He was not really shure what the cause was and suggested I just leave the little door off. What do you thinK. Thanks for any sound advice.

Al Letellier

melting door

Never alter the way a boiler is built. The "melting" door is probably the result of excessive back pressure in the chamber as a result of the partially plugged boiler flue passages, and that also contributed to the high CO readings. But remember, you have to make high CO before you find it, so make sure he checks the firing rate, and properly adjusts the flame. I'm not sure why he wants to replace the gas valve. He may have found something you didn't describe, but we don't have that info.

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J.C.A._3

Al,

Usually what I find is the wires to the gas valve and plastic blocks for the terminals have been compromised by the time the door has melted. I think the guy is providing cheap insurance at this point.

You're right on the money for the reason, and that the firing rate should be checked and verified, especially after the gas valve replacement.Been there done that and think he's making a smart choice. Chris

Steamhead

Also check the chimney

to see that it's not plugged or restricted. I've seen this cause sooting in gas boilers.

There are several schools of thought on this, but IMHO if the boiler's in otherwise good shape and not already so equipped, it might pay to upgrade to spark-to-pilot ignition using a Honeywell or similar kit which includes a new gas valve. In areas where gas pressure gets low on the coldest days of the year, this will eliminate the pilot going out from the lowered pressure. And you can plug a stack damper cable right into the spark module.

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jim murtaugh

combustion air

all previous tips are good checkk firing rate and chimney clean all flue passes but also check boiler room for proper combustion air thanks jim murtaugh

Darin Cook_3

LWAL

It sounds like you have a HC series Hydrotherm. I have seen that problem numerous times on that boiler, also on the MR series (modular multi-boilers). You had your boiler cleaned and obtained a reading of 14ppm of co in the flue. That is a great reading.

Two years ago I had a contract to do the boiler servicing on the local National Guard base. All were the MR series ( nat gas). Every unit had that little door melted/burned off. I tested all the units before I serviced them with my Bacharach 120, they were all in the 50 - 90 ppm of CO range. Gas pressure at the manifold was 3.5 " WC. The chimneys above the draft hoods were drafting at -.08 ". Below the draft hoods they were -.04 WC. This was in warm weather. It appeared that a curtain effect was going on. After cleaning they were in the 15 - 25 ppm of CO range. They were not "dirty looking" to the eye. I replaced all the doors. I recommended we change the drafthoods over to barometric draft regulators. No money in budget for repairs. Two years later I am asked to do the boiler servicing again. Guess What? All the doors are "melted" again. The draft numbers were in the same range again (warm weather).

I would venture that your issue is related to venting also. This boiler model seems esp prone to this. The boiler passageways do not seem restrictive to the eye. In this case the drafthoods are doing exactly what they are supposed to, separating the appliance from the chimney. Break out a draft guage and start checking your draft above and below the drafthood. Please do not start randomly changing parts on your boiler. There is a fix for your boiler but you need to get out the testing equipment and play heating detective. Good Luck.








Darin

Steamhead

Darin, were these boilers

connected to older chimneys designed to provide enough draft to pull air thru a coal-fired boiler?

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Darin Cook_3

Jim

Please bear in mind that if there was a lack of combustion air the CO numbers from the equipment would be terribly high not the 14 ppm of CO he was reading.






Darin

Darin Cook_3

Steam Head

No these were 10" B vent chimneys believe it or not. The maint guy was convinced that there was not enough draft. The powered combustion air grills were also stuck in the open position since some of the motors had failed. I forget the total connected BTU load somewhere around 400,000 btu's.







Darin

Mark Eatherton1

I think...

it has to do with the design of the fire box. The doors are in the direct visual path of the radiant energy coming off the burner bed. Granted, that part of the zone SHOULD receive some cooling effect from secondary air passing through the zone, but remember that radiant energy does not affect air temperature directly. I think the doors need to be beefed up to a cast iron door instead of a medium gage metal with mica looking glass...

ME

Steamhead

Interesting

Around here we have a lot of old coal-designed chimneys and they always have a lot more draft than needed for current model boilers. This amount of draft can pull the flame off an oil burner's retention head which would make the boiler soot up (ask me how I know that). And especially on an atmospheric gas boiler with no stack damper, it can suck much of the heat out of the boiler on the off-cycle even though there's a draft hood installed.

If your B-vent chimneys were several stories tall, you might have been duplicating the old coal designs.



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joe j

hydrotherm hc boilers

this boilerhas a metal baffle plate on top of boiler betweenthe sections that cuts down the draft.put two 1/2nipples on top of sections to raise the baffle.that will give better draft no more burntwires or melted sight or tridicators