Bradford White Combustion

Skip

Our company installed a BW Combi-cor 75,00 btu unit 2 months ago for a client in NC. Unit seems to have been running fine up until a few days ago. Client called me on Super Bowl Sunday and said she smelled a bad odor in the mech. room which smelled like exhaust. I checked the unit and there was some flame from the burner actually coming out from the burn chamber and going into the air intake and turning the insulation at the bottom of the tank black. There was black soot all over the burner and at the exhaust pipe termination.
I called Tech support and they said the unit was not getting enough air for proper combustion. The mech. room is ~ 4'x8' with two 6" horizontal ducts thru the outside wall. One is 12" from floor, other is 12" from ceiling. Checked LP gas pressure (12" wc). After removing burner and
cleaning it I fired it up, unit ran better but flame appears to be larger than normal and is "dancing around" in burn chamber instead of a nice even straight up pattern and is shutting off every 5 minutes and then relighting. Air shutter is open all the way. Even with the window open (more air) unit is still doing this.
I think the gas valve is putting too much gas into the chamber.
Has anyone else had a problem similar to this?
Radiant heating contractor in NC

I was also reading the posts about the Combi-cor HE problems from hot rod and others from a few days ago. Guess I won't be using these units anymore for the lower end jobs.

Bob Harper

Is that gas pressure your inlet or manifold? If inlet, is that a static reading, with the unit firing, or full load with everybody firing?
Please describe the venting and if it's clear, height, materials, etc.
What other depressurization sources in this mech. room? Clothes dryer? Other atmospherically vented appliances?
What kind of CO numbers did you read?

I'd shut this down until resolved.

hr

Check draft

and you may need to clean the entire flue if it, too, sooted up. Are you sure it has the correct orfice/burner/ pilot for gas or lp, it could have the wrong one for the fuel you are using?

hot rod

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Dale

Check the fine print

Make sure you are taking the gas pressure per manufact. instructions, leaving vacuum connections on while taking gas pressure tests will give you much more gas than design.

Skip

BW combustion issues

Hey everyone,
Thanks for all the input.
More info on venting and such: BW unit is only gas appliance in mech. room with weatherstripped door to rest of house.
Venting is with 3" schedule 40 PVC (well casing-not foam core) pipe with total of three elbows and total length of 14' out thru wall with elbow pointed down with wire screen at end.
Gas pressure test was done at 1/2" back iron tee drip before going into gas valve marked for propane. Reading was 12"wc with unit not firing and it dropped to 11"wc when unit fired up along with gas clothes dryer and gas kit. stove also running located in seperate locations.

We went up today to ck. & clean WH and noticed someone had installed window screening (fine mesh) on the outside of the two 6" combustion air ducts leading to the outside wall. (the homeowner to keep out bugs). We had installed 1/4" hardware cloth over openings per NC code. The window screening had a lot of fine dirt on them so that probably was constricting air flow.

Anyway, we cleaned the PVC vent, pulled off the blower, pulled out the baffle (lots of black soot) and wire brushed and vacuumed the flue inside the unit. Recleaned the burner, replaced the gas valve, put it all back together and fired up the unit. It appears to be running as good as when we first installed it. The burner flame seems to be a little too yellow at the tips but it was not cutting off as before and I was not getting any CO readings inside the mech. room as when I first got there. So we'll see. Exhaust CO readings at outside vent were around 40ppm. Will check on it in a few days.