Replies

1. 
   Shacko | Nov 17, 2009 10:50pm | #1

   Without knowing the exact type of boiler you have the first thing to check is the thermocoupling, thats the little tube that the end of sits in the flame of the pilot light, they do go bad.

    

   "If all else fails, read the directions"
1. 
   TommH | Nov 18, 2009 01:12am | #2

   Exactamundo to quote the Fonz, although the gas company guy called it a "generator" because it apparently generates a micro-current that goes back to the gas valve and somehow is involved in opening the valve when the thermostat calls for heat. Finally got some benefit from that gas company service plan I've been paying for all these years...Dug up the packaging...Honeywell Powerpile Generator. Looks like a metal cigarette with a wire attached.

1. 
   ErnieK | Nov 18, 2009 01:18am | #4

   Exactly...they have different types and different names. And they have to "prove" the flame before the main gas valve will open.

1. 
   TommH | Nov 18, 2009 01:19am | #5

   Makes sense...a good safety feature.

2. 
   Shacko | Nov 18, 2009 01:25am | #6

   Generator is correct, but the most common term is thermocouple, glad you got it fixed.

    "If all else fails, read the directions"

1. 
   TommH | Nov 18, 2009 01:28am | #7

   Thanks; it's always good to gain knowledge.

1. 
   TommH | Nov 18, 2009 02:12am | #8

   I think I misquoted the Fonz...I think it's "correctomundo"

2. 
   DanH | Nov 18, 2009 04:38pm | #12

   "Thermocouple" is only technically valid for the units with a single junction. "Thermopile" is a "stack" of thermocouples that generates more juice. A given furnace/boiler may have either or both (or none at all, if no standing pilot).The thermopile is especially common in unpowered units where the additional juice is needed to run the thermostat.
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

3. 
   Dave45 | Nov 18, 2009 02:54am | #9

   The pilot light heats the thermocouple which generates a small current that acts as a permissive to allow the main gas valve to open when the furnace comes on. If the pilot out is out, the gas valve won't open and flood the space with gas and possibly make things go BOOM!! - lol

1. 
   TommH | Nov 18, 2009 03:10am | #10

   Yeah, especially if there is a water heater nearby with a standing pilot...nice source of ignition. Query, when my thermocouple crapped out and didn't provide the micro- current (thus preventing the gas valve from opening to start the furnace), the pilot also did not stay lit. I started it up, but it didn't stay lit. Does the thermocouple also "turn off" the gas to the pilot when it's not working?  another safety feature?

   Edited 11/17/2009 7:13 pm ET by TommH

1. 
   dude | Nov 18, 2009 11:44am | #11

   sometimes if you unscrew the thermocouple from the gas valve & scrape the contact on the end with a jacknife it will then work when reattached

   we also used to clean the pilot orfice if it went out too often

   the above info is from a former service tech but i dont know your abilities & a call to a tech might be best if you need to touch the pilot light itself as they are somewhat fragile on the fittings ( aluminum pipe )

2. 
   DanH | Nov 18, 2009 04:42pm | #13

   The thermocouple operates an electromagnet that in turn operates a small lever inside the gas valve assembly that holds the pilot valve open (after you release the button), and also enables/disables the main valve.I'm sure there are several different designs.
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

3. 
   TommH | Nov 18, 2009 06:31pm | #15

   So that's why the knob for starting the pilot requires you to push down on it for 60 seconds. Presumably this mechanically opens the valve to send gas to the pilot. By holding it for 60 seconds, the pilot stays lit until the heat energizes the "generator",creating the current which will activate the mechanism that will keep the valve feeding the pilot open. I always wondered why it was necessary to push down on that knob for a minute

4. 
   DanH | Nov 19, 2009 04:40am | #16

   Right, holding down the button activates the same lever that the thermocouple activates. Once the thermocouple has warmed up, you can release the button and the thermocouple electromagnet does the job.
   A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter

2. 
   ErnieK | Nov 18, 2009 01:15am | #3

   If it is a standing pilot (always on), the first thing to check is the thermocouple, like mentioned previously. Make sure the flame surrounds the thermocouple and is not pushed away by some type of air movement.

   They are generally not too expensive, but sometimes changing them can be a pain.

3. 
   BigBill | Nov 18, 2009 04:51pm | #14

   All the above are correct for a standing pilot.  Should anyone have an electrionic ignition type (they may make a clicking sound from a small sparkplug like igniter or no noise from the glow plug type) the first thing to check is the flame sensor.  It performs much like the thermocouple.  Your furnace will try to light but fails to go because the flame sensor isn't telling the gas valve to stay on.