Urgent - Pilot light won't say lit

[mike gratton]

Okay here's the low down . . . Pilot light sayed lit all summer. First cool day we fired her up and all was good . . . or so we thought. Pilot light out . After several relights we called a tech out. he changed the thermocoupler(sp?) and tried it. seemed okay.I asked him to cycle it a few times because we found that it was going out when the burner shuts down. So after a few more tries, the pilot goes out again. He then trries to clean out the pilot line. Same result. After checking the burner he concludes, "it must be the gas valve". Installs - checks - gets $400.00 all told - leaves - all good. . . get home from work this morning and the house is at 60F. I have a call out for him to come back, however in the mean time I have a few Questions.

Is it normal to not use any meters or other equipment to test valves or thermocouplers? He said there is no way to test them. Have you ever seen this before? What else could the problem be? Doesn't this mean the gas valve was NOT faulty and I should get (at least) the cost of the part back? The specs on my boiler are as follows:

Viessmann Atola Model GLN-25 Installed in 1983

TIA

Mike

[C.J.]

A thermocouple generate about 300 millivolts (0.3 volts) of DC current. You can test them with a good multimeter. They're inexpensive and can go bad overnight. A new one every three or four years is not a bad idea.

Yes.

Pilot burner and/or pilot orafice. If there is insufficient gas going to the pilot burner, the vacuum (draft) created when the main burners shut down could suck-out the pilot. If this has never happened before, you'll probably be OK with replacing the pilot burner assembly, which includes the orafice. I have taken them apart and reamed out the orafice with a piece of

22 or 24-guage copper wire. This reults in a pilot orafice hole much larger than it's supposed to be, but it allows for a wide range of adjustment. If you aren't comfy playing with it, don't. Pilot burner assenblies are fairly generic and shouldn't be too expensive. (under $50.00) If you want some added insurance against pilot outages, have a relight kit installed. Generic, very easy and fairly cheap. And they work.

Probably, but I wouldn't go second-guessing until the whole problem is worked out. Good luck.

[CBHvac]

Bull. My cheapie meter that I use as a backup can test them...(Cheap, meaning under $190)

Yes.

A bad connection at the techs interface...find a new one.

Nope. No one here can tell you, and the valve, could indeed have been bad, and thus, the new thermocouple he installed prior can now be toast. Replace the thermocouple and have someone that knows what he is doing test the new one...or the existing one.

[Tony Hwang]

[mike gratton]

Thanks guy for you help. Here's where we are now.

Well apparently there was a recall on the unit in the late 80's. For one reason or another whoever owned this house at the time got missed and the manufacturer is no longer paying for the retro. I guess they had a lot of pilot light issues with the unit and decided to retro them with an electronic ignition. The tech said he could do it a lot cheaper with a relight kit which someone also mentioned here. How reliable/safe is this option. I am told the other route is quite costly, and i'd rather not be downthere 2-3 times a day to light it. BTW, I did get the check back and only paid for the service call so far. I will have to pay for a relight kit later when it come in. How much do these things run installed?

TIA

Mike

[C.J.]

I mentioned a relight kit. It's under $100.00 over-the-counter, and takes less than an hour to install. Here is the deal:

An electronic ignition lights the pilot (or main burner) on each call for heat. When the furnace is off, there is no standing pilot. This is the norm on modern day equipment. There is a significant amount of retrofitting to install one on a machine without it.

A relight kit is just that... it "relights" the pilot in the event the pilot goes out. It "piggybacks" right onto the older equipment, and wires into the system transformer. Whenever a standing pilot is extinguished, it takes the thermocouple some time (30-60 seconds) to sense the flame outage and stop producing the 300 MV of electricity required to keep the hold-coil in the gas valve open. When the thermocouple cools, the valve closes and that's that... you have to manually relight the pilot. The relight kit uses and electronic sensor (probe in the flame) to determine the instant the pilot goes out. It then "sparks" through the same probe and relights the pilot. If it doesn't do so within the cooling period of the thermocouple, the gas valve will close as usual. Perfectly safe.

If your unit is over 10 years old, don't bother with the big electronic conversion. You already have a new gas valve. Go with a relight kit and relax.