Gas and Oil Home Heating Furnaces - LP furnace startup problem

Hello all-

My problem involves my Heil model NULK125DK03/ 867.779442 LP furnace. It has five burners and HSI type ignition. The furnace has recently, (this winter) taken to starting with an occassional flare-up from the fifth burner to be lit (extreme left side ). In other words, four burners light instantly, while the fifth and last one is slow to light and when it does, it lights with more available gas resulting in a flareup and not as gently as the other four. I had a service man come in and clean the burners and cross pipe thinking it was cob webs or rust obstruction. After cleaning, and naturally only while he was there, all lit ok and furnace was declared by him to be fixed. Approximately five fireups later, back to same problem.

I have two ventless LP heaters in the house also. After the last delivery of LP, I immediately saw that their flame pilots were burning mostly yellow, not like mostly blue prior to delivery. I have no idea if there is any relationship between this and the start up/flare up problem with the furnace.

Any ideas, advice, or suggestions of how to fix this problem, would be appreciated. Thank you.

After cleaning, and naturally only while he was there, all lit ok and furnace was declared by him to be fixed. Approximately five fireups later, back to same problem.
Dirt is inside the pipe and gets up against the orifice - poking it back in provides a temporary fix?


What happens if you rap on the back of the burner either while it is firing, or when it is not?
Does that temporarily clear the problem again?





I have two ventless LP heaters in the house also. After the last delivery of LP, I immediately saw that their flame pilots were burning mostly yellow, not like mostly blue prior to delivery.
Whoa!
Could be methanol added to suck water out of your system.
But sounds like a good way to get CO poisoning.



I have no idea if there is any relationship between this and the start up/flare up problem with the furnace.
I don't know either, but I doubt it.

No yellow flames in the house! Shut them off!

When the serviceman was here, he blew out the burners and cross piece after removing them from the furnace and disassembling them. He switched burner #5 for burner #4 when reassembling them. (#5 is still giving the problem). He tapped on the burners while lit, and they sparkled a little, he adjusted the air flow to #5, retried lighting after blowing out residual gas, all was well for several starts while he was here, then later back to the same problem.

I had 12 psi pressure at downstream of gas valve, he adjusted it to 11 psi.

I have had no water problems.

I have CO2 monitors around the house at the heaters and at the furnace.

(#5 is still giving the problem).
The problem is the orifice.
Moving the burners around does not change the orifice.




I had 12 psi pressure at downstream of gas valve, he adjusted it to 11 psi.
Not PSI, rather inches of water column.



I have had no water problems.
I wouldn't expect any if they are putting methanol in your tanks!
Anyway, the color does suggest an impurity, and it could be water or something harmless. But I wouldn't consider it to be normal.
Were you sweeping in the room? How long did the yellow persist?

If the burners are blue, the pilots might have lint or dust in them.



I have CO2 monitors around the house at the heaters and at the furnace.I hope at least one has a digital readout.

Did your service guy check the heat exchanger for cracks? If there is a crack, that flue will not draw the gas into itself thus giving you delayed ignition and/or a lazy burning, slightly rising flame.

No, he did not check the heat exchanger. I will have him do that soon. It could be a problem as you say.

Yes. one of the monitors has a digital re-out.

We switched the burners around to try a process of elimination. By the problem remaining in the fifth position, that suggested an orifice or some other problem. The orifice as the problem is questionable to me since almost immediately, but still after the rest of the burners, it lights and with the suggestion that gas is present before ignition.

Any further help is appreciated. Thanks.

the problem remaining in the fifth position, that suggested an orifice or some other problem. The orifice as the problem is questionable to me since almost immediately, but still after the rest of the burners, it lights and with the suggestion that gas is present before ignition.
Correct. The problem is that the pilot chaseway the spreads the fire from one burner to the next is obstructed or misaligned.
Swapping the burners should have moved the problem assuming that the chaseway is integral to the burners.

An obstructed orifice would yield a burner that has a smaller flame than the others.

At this point, other than getting the heat exchanger checked, what can I do? The cross pipe and the burners come apart and reassembly doesn't seem to suggest an exactness to alignment, in other words, they slide together and that's it. We didn't change anything from what it was to now except switching the burners.

Additional on the pilot lights on the ventless heaters...I am now noticing that at times the pilot light burns with a good blue,small yellow tip flame and at other times, with the mostly yellow flame. Something is screwy with the fuel delivery I think. Any thoughts?