Burners ignite only after lighting match to flame sensor


  #1  
Old 03-13-10, 06:44 PM
O
Member
Thread Starter
Join Date: Mar 2010
Posts: 2
Received 0 Votes on 0 Posts
Burners ignite only after lighting match to flame sensor

I have a Weil-Mclain boiler, PHE-3, Series 2 (it's the wide one with several burner tubes). The system cycles OK when powered on. The blower and pump is pushing. The spark lights the pilot and the flame is lit. However, the burners will not automatically start and light up.

Here's what strange: If I burn a match on the tip of the flame sensor, the burners light up and the system runs its full cycle until the thermostat is satisfied, and turns off by itself. After the system powers up again the burners will still not light up until I light a match on the tip of the flame sensor again.

Is it a bad mercury flame sensor? Bad gas valve? Inadequate draft? What else can I check?

Thanks....
 
  #2  
Old 03-14-10, 06:26 AM
H
Member
Join Date: Nov 2002
Location: Massachusetts
Posts: 1,851
Received 1 Vote on 1 Post
sounds like to me

not getting enough pilot flame. pull out the pilot assembly remove the pilot valve orifice from under the aluminum tubing, be careful its as small as a half peanut...and hit it with a solvent like alcohol or WD40, blow it out the best you can and buff up the sensor rod with fine steel wool and the flame hood area too...(000 steel wool if you have it ). Reassemble,...and, when fired up, there should be plenty of flame to cover the sensor rod...If its still not lighting, try increase the pilot gas adjustment if there is one. Flame signal can be read by putting the meter in series with the flame sensor wire and the ignition control connection, either end. This is usually 3 to 5 microamps DC, not all meters wil read DC microamps though. the actual signal needed for your controller is printed on the controller itself...you MIGHT need a small compac mirror to see this unless its mounted straight at you...Good Luck!
 
  #3  
Old 03-14-10, 07:46 PM
O
Member
Thread Starter
Join Date: Mar 2010
Posts: 2
Received 0 Votes on 0 Posts
Problem fixed!!!

Hey hvac01453,

I took your advice and did the following:

I removed all of the parts from the pilot assembly.

I then sanded the sensor rod, flame hood area, spark electrode tip and pilot valve orifice with both a very fine sandpaper and steel wool until they all had a very metallic shine. I hit everything with WD40 and an air can.

I also inserted a small pin in the small hole of the pilot valve orifice and twisted it at an angle to make the tiny hole just a tiny bit larger.

I put everything back in place and powered on the boiler.

The system cycled as it normally does. The pilot seemed to push a bit more fire than usual. The fire sensor was definitely getting more fire. Then finally the burners fired up by themselves.

The system now turns off and on by itself without my intervention using the matches.

So thanks a lot hvac01453 for your advice. You are definitely the man!!!

Regards,
OrlandoA
 
  #4  
Old 03-26-10, 07:12 PM
H
Member
Join Date: Nov 2002
Location: Massachusetts
Posts: 1,851
Received 1 Vote on 1 Post
No problem

always great when you can fix something for a bit of labor and don't have to buy anything.
Good luck!
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: