Radiant Heat Boiler Pilot Light


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Old 09-24-02, 02:50 PM
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Radiant Heat Boiler Pilot Light

I am at my brother's house and trying to get their boiler pilot light to stay on. It is getting a bit cool here and time to get some heat. My sister-in-law removed the thermocouple, which we then discovered is actually a Powerpile Generator. I went out and bought one (for $52) and installed it. This was not the problem as the pilot light will still not stay on. Any suggestions about how to test the powerpile generator using a multi-tester? Ohms, and/or volt readings? How about some suggestions as to what might be wrong?

Thanks, Bob
 
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Old 09-24-02, 02:58 PM
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Last edited by jonathanisaac; 08-03-06 at 07:23 PM.
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Old 09-24-02, 03:05 PM
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I turned the pilot control to "pilot", then pushed the button in and light the pilot light with a match. I then held the aforementioned button in for about 3 mins, light went out. I then relit the pilot light and held the button in for probably at least 10 minutes, it still went out when I released the button.
 
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Old 09-24-02, 03:32 PM
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Not sure of the type of thermocouple you are referring to, but on a regular thermocouple, make sure orifice tube is clean and flame is burning directly on thermocouple bulb. IF it is, then you could have a defective pilot safety device. On a regular thermocouple, undo tc(thermocouple) from valve. Light the pilot, with volt meter, touch the end of the tc with 1 lead and the tc lead line with the other. The reading should be between 25 and 35 mV. If not reverse the tester leads. If still no reading tc is bad. You can test the pilot safety device with ohm meter. Remove tc from gas valve. Insert one lead where the tc goes into the valve and the other lead on the side of the valve. If no ohm reading, then the pilot safety device is bad.
 
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Old 09-25-02, 08:35 AM
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Powerpile generators come in 3 voltage ranges. 250 millivolt 500mv and 750 mv. The most common is 750mv. So, the first thing to do is make sure the replacement is the right one. Next, look at the pilot flame. Nice fat blue flame with maybe a small yellow tip? The flame wants to engulf the last 3/8" to 1/2" of the end of the thermocouple. If the flame isn't so good, you may have to take the pilot burner out and clean it. The airflow orifices often get clogged wtih lint. Some gas valves are polarity sensitive. Try reversing the Powerpile leads at the gas valve. Also, make sure you're on the right terminals. They should be marked PP. If you have a meter that will measure millivolts, take a voltage reading at the leads while you keep the pilot flame lit. If the voltage is up to snuff, replace the the gas valve.
 
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Old 09-25-02, 02:32 PM
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I have a dmm that reads about 1 mv when the pp is in the pilot flame. Should it read 750 mv when disconnected from the valve, but heated up? It is a 750 mv unit. I am going to put the new powerpile and the old powerpile in a torch flame and see if there is a difference in readings.

Thanks, Bob



***EDIT***

OK, I just went and put both the old and the new Powerpile in the flame of a torch. They both do the same thing. I put the black lead from the DMM to the white lead on the powerpile and the red lead from the DMM to the red lead from the powerpile. When I do this the DMM rapidly counts down from about 20 mv to 1 or .9 mv, getting slower as it gets closer to 1 mv. It does this whether the end of the powerpile is in the flame or not. Does this mean the new powerpile is bad, or that I am not doing this right? Does this mean I need a new gas valve here?

Thanks for the input,

Bob

***EDIT***
 

Last edited by BobMachus; 09-25-02 at 02:59 PM.
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Old 09-25-02, 03:14 PM
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Hi Bob:

Are you sure you have the meter set to read DC millivolts? You want to heat the end farthest away from the leads. That's the hot junction and the other end is the cold junction. The voltage is generated by the temperature difference between the hot and cold junctions.
 
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Old 09-25-02, 03:32 PM
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Oh yeah, .......DC, duh.

Since when in a torch flame the the leads count pretty rapidly up to and beyond 750mv DC, I suppose that means it is time for a new Gas Valve. Do I need to get a whole new valve, or is the magnetic pilot valve available as a part?

Thanks, Bob
 
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Old 09-25-02, 04:37 PM
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Ok- have you put the thermopile back on the the furnace and taken a voltage reading with the pilot lit? Still getting a good voltage or does the pilot need cleaning? Arevsure the wires are on the right terminals? Will the pilot burner now stay lit or does it still go out? If it still goes out and the voltage is good, try reversing the leads before condeming the valve. If it does turn out that the valve is bad, you'll probably have to buy the whole valve. The problem is usually the burner/thermopile so be sure to check it thoroughly before condeming the valve because it won't be cheap.
 
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Old 09-26-02, 09:59 AM
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Update....

I put each of the PowerPiles in the boiler and ran the pilot using the start button. With a DMM on the leads the old powerpile went to 670 mv and the new one went to 590mv. I am assuming this means the flame is not hot enough since when in a torch flame the powerpiles each produce over 750 mv pretty quickly. I am going to return the new powerpile since the original seems to work. I am going to remove the pilot assembly and make sure it is clean. I am also going to adjust it's aim a bit to put more of it on the powerpile. Thanks for help, keep those tips comin' if ya got 'em.

Bob
 
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Old 09-26-02, 02:31 PM
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What happens if you light the pilot but heat the thermopile with the torch? Does the valve pull in and keep the pilot lit or does it still drop out? If it still drops out, reverse the leads and try it again. If it still drops out and you've got good voltage, then you'll probably have to replace the valve. I looked up the specs for a Honeywell Powerpile and they indicate that 540mv is the minimum, so the 590 reading you're getting is borderline. I would think that the valve would stay in at 670mv. I looked around my archives and found a tipsheet from Robertshaw that says you can go all the way down to 325mv on their valves. Try taking an ohm reading on the two terminals that the powerpile connects to and see if you have continuity. [with the powerpile disconnected that is]
 
 

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