gas fireplace main burner will not light

[HayZee518]

millivolts and milliamps are two related but two different values. milli means divide by one thousand. a value of 3 millivolts means .003 volts, 5 milliamps means .005 amps. 750 millivolts means .750 volts etc.
www dot allelectronics dot com have direct reading analog meters but they are limited to about 50 millivolts or 50 milliamperes.
a thing called a shunt is needed to measure voltage or amps above the rated capacity of a meter. a 200 to 1 shunt will drop 200 volts down to one volt through the shunt. the meter is connected across the shunt to read volts directly.

[paul52446m]

Paul, what do you think if a user wants to check a millivolt generator to go to radio shack or this ste: www dot allectronics dot com and purchases an analog meter? what is the current in Ma through a typical gas valve? if a millivolt meter can't be obtained, a milliamp meter could be wired in series to the valve to measure current.

Hi Paul here. You being a electrician would know more about this than i would.
to test milliamp s down to 1 milliamp like i have to on boiler controls and do it actuarially i have one tester for milliamp s and another for testing millivolts, and they both have several scales on them I do not know how to convert millivolts
to milliamp s. When i test a RA890 boiler control i have to do a pilot turn down test to see where the control will drop out on safety, which is around 3/4 of one
milliamp. These testers i have old so i don't have any idea whit they cost now days. It would be nice if they made a cheap tester that did both, but i don't know if they do. Later Paul

[HayZee518]

Paul, what do you think if a user wants to check a millivolt generator to go to radio shack or this ste: www dot allectronics dot com and purchases an analog meter? what is the current in Ma through a typical gas valve? if a millivolt meter can't be obtained, a milliamp meter could be wired in series to the valve to measure current.

[paul52446m]

Thanks for your help, I think i am going to try new wire and all, i removed the marrets that link the thermostat to the stove, and jumpped them, and everytime it fired, tried turning it on via thermostat and nothing, left teh stat on, went over and jumpped the 2 wires and it fired, removed jumper and it died, replaced teh jumper and for about 15 seconds and it stayed lit, for about 2 minutes then shut off with the stat set at 90,

With out a tester on it we are playing a guessing game. You always lose a lot of power going out the wire and through the thermostat. If you do change the wire, i would go to a 16 gage wire and never more than 25' of wire.. Make sure all wire ends are clean and tight. If you find someone with a tester, take off the wire on the TH post of gas valve. With pilot going, test between PP & PP. This will tell you what the thermopile is putting out for power. then with thermostat calling for heat, test from THPP to the Th wire that you took off.
This reading should be at least 40 over what the gas valve needs to open it.
When a gas valve get a little age to it, the grease in the moving parts get a little dry and it takes more power to open the valve. later paul

[jeph]

Thanks for your help, I think i am going to try new wire and all, i removed the marrets that link the thermostat to the stove, and jumpped them, and everytime it fired, tried turning it on via thermostat and nothing, left teh stat on, went over and jumpped the 2 wires and it fired, removed jumper and it died, replaced teh jumper and for about 15 seconds and it stayed lit, for about 2 minutes then shut off with the stat set at 90,

[paul52446m]

Jummped the terminals and it fired everytime, themostat is about 15 feet from the fireplace, and the wire is a low voltage wire about 20 gauge or so. The reason I believe it is the thermopile or gas valve is this unit gets used maybe once a week and has run perefctly for the last five years, just not this year.... Also, are all thermopiles pretty much the same? are tehy interchangeable?

the thermopile's will all be about the same, the difference in power is the pilot
burner that they are in. The power can be from 250 to 700 millivolts. You would have to have it tested to see what you are getting for power. they put the size of the pilots in a burner to produce the power they need for the different gas
valves. Small gas valves will open with 85 millivolts and some of the larger gas valves need 240 to open them.. Make sure your pilot is clean and some gas valves have a pilot adjustment to turn them up a little. later paul

[HayZee518]

check this source for thermopiles
Thermopile - Home & Garden - Compare Prices, Reviews and Buy at NexTag - Price - Review

[jeph]

Jummped the terminals and it fired everytime, themostat is about 15 feet from the fireplace, and the wire is a low voltage wire about 20 gauge or so. The reason I believe it is the thermopile or gas valve is this unit gets used maybe once a week and has run perefctly for the last five years, just not this year.... Also, are all thermopiles pretty much the same? are tehy interchangeable?

[paul52446m]

Well, the stat that I took out was a 24v unit, I replaced it with a millivolt stat as per the tech's instructions, still ng, has a standing pilot and will not light all the time, sometimes if I press the ignighter button next to the gas valve it lights, strange, thermopile itself looks discolored and was really dirty till I cleaned it up

sounds like you are losing too much power in the circuit. Take off the wires that
are on the th and th. leave the two thermopile wires on the pp and pp post.
lite pilot let it heat up and then take a jumper wire and jump the th and th post.
Do not touch the post or wire ends with your finger, that will short it out.
If it fires up every time then the problem is not in the thermopile or gas valve..
Make sure all wires are clean and tight. Make sure screws are tight in the thermostat. Are you running low volt wire to your thermostat. If so what gage
is it and how far is it from your gas valve to your thermostat? Later Paul

[jeph]

Well, the stat that I took out was a 24v unit, I replaced it with a millivolt stat as per the tech's instructions, still ng, has a standing pilot and will not light all the time, sometimes if I press the ignighter button next to the gas valve it lights, strange, thermopile itself looks discolored and was really dirty till I cleaned it up

[paul52446m]

I just recently had a repairman in to look at my ng stove and said it was the thermostat, but a new one did nothing, I came to the conclusion that it is the thermopile after testing but am looking for a good and cheap place to get one. OEM Heat N Glo wants 100$, does anyone know of an aftermarket for these parts? i checked the website from the previous post and it was mainly honeywell piles.. nobody round these parts <my home location> seems to know anything.... its like a secret society or something..... thanks in advance.... JePh

I am a dealer and i buy thermocouples and thermopile's in a box of ten. I think
Honeywell is as good as any and in a box of ten i might through away or turn back in at least two of them. When you changed thermostat's did you use one made for millivolt, you can not use a standard stat on millivolt. Later Paul

[jeph]

Replacement Thermopiles....

I just recently had a repairman in to look at my ng stove and said it was the thermostat, but a new one did nothing, I came to the conclusion that it is the thermopile after testing but am looking for a good and cheap place to get one. OEM Heat N Glo wants 100$, does anyone know of an aftermarket for these parts? i checked the website from the previous post and it was mainly honeywell piles.. nobody round these parts <my home location> seems to know anything.... its like a secret society or something..... thanks in advance.... JePh

[HayZee518]

check out this NEXTAG site for thermopiles.
Thermopile - Home & Garden - Compare Prices, Reviews and Buy at NexTag - Price - Review

[sunmtnforge]

I must be buying the wrong thermopile, I have the third one that I have bought installed. This one only lasted a few months. They have come from two different stores. I will look for a bigger supplier. Thank you for your help.

[HayZee518]

the other guy changed out the thermopile and this fixed his problem. if you know anything about thermopiles, they are made up of dissimilar metal wires for instance iron constantan and copper form what is called a j-k thermocouple. joined at one end one metal gives up electrons when it's heated forming a dc current. these are connected in series adding up their voltages to something usable.