Gas and Oil Home Heating Furnaces - Misfiring Furnance

I have been experiencing a chronic problem with my LP fired Weather King 90,000 BTU furnance for the past two years. I have had 4 different heating technicians examine my situation and have spent a total of $996 on repairs and alterations to no avail as the problem continues to this day. While my problem is chronic, it is also intermittent dependent upon the factors that I will describe below.

THE PROBLEM:

When the furnace malfunctions it does so by way of the burners either mis-firing (firing and going out in rapid sucession); failing to light altogether; or flames going out prematurely during the heating cycle.

PROPER OPERATION SEQUENCE:

When the thermostat calls for heat, the furnance cycles through the following sequence of events: 1) purge cycle; 2) ignitor activation; 3) gas injection; 4) gas ignition; 5) circulating fan activation. Upon the thermostat reaching the selected tempature a) gas flow ceases; b) the burners shut off and the c) circulating fan stops.

REPAIRS AND DIAGNOSTICS CONDUCTED

I have had two ignitors installed; a new gas valve (inside the furnance) installed; new exhaust vent piping installed; flame censor cleaned; gas line pressure tested; a test (the name of which I don't know) to determine if the heat exchanger was cracked; first and second stage regulators changed on the outside of the house; second stage gas regulator adjusted on outside of house; electric heat tape applied to second stage regulator and methanol injected into the fuel at the tank. These steps have been taken over the course of the last two years yet the problem persists.

MY EDUCATED GUESS:

I believe that I have found a pattern which I believe is at the root of the problem. I have an underground LP storage tank with a steel capped dome that sits above ground level. I have an undergound fuel line that goes from the first stage regulator located in the dome to the side of the house to a second stage regulator which is exposed to the atmosphere.

The sides of the dome have rotted away allowing rain water to accumulate in the dome often staying there for several days after a storm. It should be noted that while the high water mark is near the top of the dome, it doesn't appear as though the first stage regulator has become submerged, although it's often found to be wet from condensation etc. The second stage regulator also becomes wet during rain and snow events as it is exposed to the elements.

Following a rain or snow event, usually within 24 hours or so, my furnace begins to malfunction as described. During periods of no rain or snow and apparently after the outside componet parts have air dired, the furnance begins to operate without fault.

I have come to believe that the malfunction is being caused by factors on the outside of the house in the fuel supply system and that either moisture is fouling the fuel or is causing one or both of the regulators to produce a reduced gas pressure at the furnace.

THE SOLUTION

If I'm right, one could logically conclude that all that was needed was to: 1) replace the dome making it more water tight; 2) replace and/or adjust the first and second stage regulators; 3) install a new tank; or some combination of the above.

HOWEVER, what I am contending with is that the four heating contractors who have worked on my furnace have either concluded that they could not find the fault or stated that there is nothing wrong with my furnace.

The gas company who owns the outside fuel supply system, on the other hand, has seemed to have made up their mind that the fuel supply system is not the cause of the malfunction and that they have done everyting reasonable including: 1) changing the first and second stage regulators (last year); and 2) injecting methanol in the fuel to retard the formation of ice (last year). The manager has taken the position that even if I am correct that water is filling the dome, that this IS NOT the source of my malfunction. He says confidently that "I've seen regulators completely submerged (in water) and they still work" and "we inject methanol in the fuel at each delivery to ensure that any moisture that does intrude does not freeze."

It should be noted that I requested that the gas company replace the rotted steel dome approximately a year ago and they have chosen not to do so claiming they either didn't have a replacement dome or couldn't get one from the manufacturer.

HELP ME PLEASE

As soon as I read your post, in the very beginning about LP, I went, "Ahhhhhhh. OUTSIDE problem." Bingo. Then when you said the tank is WHAT? -buried????- I went, "Double bingo. Condensation." But then you said that all these people have been involvbed and done this and that , and addressed the outside issues.

Well, yes and no. NOW they have. But what about the furnace now. What about your gas valve now. I bet if someone opened up parts to the gas system you would find that white frothy stuff due to water that has come and gone.

I am going to go back and read your post again to se all they changed out and speculate on if the problem has reocured due to re-formatiomn of this same type of froth-like in the gas valve of the furnace, for example. Also, burner slits, etc., are probably half-closed up.

I bet you need a real good cleaning.

But to pay these kind of bills on some frequent basis does not sound good.

I didn't know that they ever buried propane tanks.

Have you considered switching to oil?

THE PROBLEM:

When the furnace malfunctions it does so by way of the burners either mis-firing (firing and going out in rapid sucession); failing to light altogether; or flames going out prematurely during the heating cycle.


I can't read into this though that I know for a fact that you actually have a gas flow problem. Do you ever see the flame jumping like it is starving for gas? We need to know more about how the flame behaves, the color of it, do you see all blue or is it jumpy with yellow coming and going?

We need to help you find out if it really *IS* a gas flow problem or if the electrical is being shut down.

Do you have a flame sensor? IF the flame were jumpy in the area of the flame sensor, this could put it out on you. Or, maybe JUST the flame sensor needs cleaning, even if the flame is okay -steady and even. Once that flame sensor detect a problem? -poof, out goes the burners, just so you know.

Thank you for your ideas and suggestions, they are all very good ones. The flames are not a perfect blue with a slight amount of yellow. I'm not able to determine if the flames "jump around" more or less at any given time. The flames do, however, rapidly go on and off during malfunctions.

The gas valve is a sealed unit and shows no outward signs of discoloration.

A couple of days ago I convinced the gas supplier to come to my home to evaluate the problem. It was a dry day and it had not rained for about a week so of course the furnance was operating ok. The technician checked the gas pressure inside the furnace both on the inlet and outlet side of the gas valve and found the pressure to be with required limits. He also had me turn on the gas dryer at which time there was a negligable drop in gas pressure at the furnance, however, still within required limits.

The furnance did not malfunction while the technician was at my home.

I asked if he would install a pressure guage between the 2nd stage (outside) regulator and the furnace so that I could observe the gas pressure both when the furnance was working properly and when it wasn't. He agreed and has ordered the guage. I also requested that he replace the dome to eliminate water accumulation and he also agreed, however, it may take a while due to availability and weather.

All has been well with the furnance until last night starting at about 3:00 a.m. during a heavy snow storm. The furnance repeatedly misfired, virtually all night long.

The mystery continues....