Pilot safety switch tripping – intermitent


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Old 01-07-15, 04:31 PM
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Pilot safety switch tripping – intermitent

UPDATE: We’ve now had some consistent weather in the low 20’s and teens the last few days (and are getting to single digits tonight) and wanted to post a follow up:

PSI have remained below 21 (verified on our improvised gauge), so clearly all the great help we got here in improvising a way to service our expansion tank without a serviceable isolation valve was invaluably genius in getting our pressures back in normal range. Higher temps that we observed previously correspondingly dropped. Thank you for that.

We are posting the following in a separate thread; but also post it here for context:

Naturally, we have another quirk however, as our boiler is intent on educating us fully this winter.

The episodic tripping of our pilot safety that we reported earlier has returned with the cold weather. Here are our observations so far.

1. on none of these occasions have we found the pilot light out (ours is always on; old boiler design).

2. on the majority of instances, it occurs after the burner has been running with steady call from the thermostat for significant period of time; then approximately 1 minute after thermostat call is finally met and burner is off, the pilot safety trips.

3. on all of these occasions (that we can recall anyway) it is when outside temps are below 20

4. thermocouple voltage tested fine when we encountered this in our earlier post; but we changed it anyway at that time.

5. pilot appears blue, not yellow

6. However, we do seem to be having some difficulty setting the placement of the thermocouple in the pilot properly (we’ve reviewed some good instructions on placement); both in height and side distance from the pilot to achieve proper contact with pilot Currently we are as almost as low as the assembly adjustment will permit and there is no lateral distance adjustment (do we have the right thermocouple?; it is identical height from the fitting as the one we replaced several months ago.)

7. we have an urban gas supply.

We’re contemplating replacing the pilot/thermocouple assembly, since perhaps this is related to a cruddy or deteriorated pilot tube? But we don’t know if this a) makes sense, b) is something we can do ourselves, and, if both are true c) what kind of assembly we need to get. We haven’t tried ‘cleaning’ the pilot tube/pilot tube orifice; does that sound like a reasonable next step and if so a few pointers would be much appreciated.

High limit set at 180; Limit at 140 for circulating pump.

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  #2  
Old 01-07-15, 04:52 PM
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That does appear to be a rather wimpy pilot flame. The end of the thermocouple should be glowing a dull red and if it isn't then the pilot is too small. The orifice is located between the brass fitting and the pilot burner proper. Check also that the cap on the pilot burner isn't maladjusted, it should have one jet of flame directly on the thermocouple.
 
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Old 01-07-15, 05:08 PM
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That pilot flame doesn't look big enough to me either... So when it's really cold out, and you've got a rip-roaring draft in the chimney after the burner shuts down, it might be possible that the draft is enough to pull the flame away from the TC and even blow it out.

I don't think there is a way to adjust the pilot flame. Cleaning the orifice would likely help.

Something I think you should know about the L62AA control...

In Non-100% shutoff models L61LL and L62AA
applications, if the pilot flame is extinguished, the
switch will interrupt gas flow to the main burner only,
shutting down the appliance. Pilot gas will continue
to flow until the pilot gas is manually shut off.
The small amount of gas that is released with a pilot outage will or SHOULD get pulled up the chimney, but it's a good thing to know that this control does NOT cut off the pilot gas, only the main burner gas.

They do have a model that DOES cut off the pilot gas ... L62GB-3C ...

L62GB-3C - Baso Gas Products L62GB-3C - SPST Manual Reset Pilot Switch w/ 100% Shutoff & Universal Mounting Plate

But to install this would require re-piping the pilot gas tubing to the control, and then to the pilot assembly.

And something looks a bit caddy wompus with the burners. Is that one on the left tilted, or is it the camera angle parallax? This wouldn't have anything to do with the pilot outage, but just looks weird to me. Maybe it's not 'seated' correctly?
 

Last edited by NJT; 01-07-15 at 06:03 PM.
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Old 01-07-15, 05:16 PM
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You can buy the 1/4" tubing and fittings in various lengths:

PEX - Radiant Heat - Radiant Heating - Plumbing Supplies - SupplyHouse.com

There's hundreds of different pilot burners available:

Pilot Burner , Honeywell Pilot Burner , Pilot Burners , Honeywell Controls - SupplyHouse.com

Just info you might need... not suggesting you jump on this right away.
 
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Old 01-07-15, 05:31 PM
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I don't think there is a way to adjust the pilot flame.
I haven't read the entire thread but many (not all) combination gas valves do have either a limiter screw or a separate pressure regulator for the pilot. The adjustment, if it exists, is under a screw in the body of the valve assembly.
 
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Old 01-07-15, 05:47 PM
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combination gas valves
It's not a combination valve.

That's the problem.



That aluminum tubing right off the regulator is the pilot tubing.

I don't think that old regulator has an adjustment for the pilot size.
 
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Old 01-07-15, 05:47 PM
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Thanks Furd and Trooper. The "draft theory" for pulling the pilot away from the thermocouple makes sense.

A question about cleaning the pilot burner. It appears to have some small holes with slits to the top and (no surprise) appears to be steel / iron. What is the recommended way to clean these holes and slits? Brass feeler gauge? Emery cloth? Something else? Should we try and disassemble this to clean it or should we be cautious on disassembly out of concern for creating a gas leak with the pilot in the process?

And thanks for mentioning the burner orientation. They are in fact level and is an artifact of my picture taking ability.
 
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Old 01-07-15, 05:50 PM
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Those holes aren't the orifices. Soft brush would clean those up.

The orifice is down inside as Furd mentioned... and would require some disassembly to get to it.
 
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Old 01-07-15, 06:09 PM
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Nope, that's not a combination gas valve but neither is that aluminum tubing coming off the top of the pressure regulator the pilot gas supply. That tubing from the top of the regulator is a vent and the end of that tubing enters the combustion chamber to burn off any escaping gas that may result from a ruptured diaphragm.

The pilot supply comes from a small valve, called a B valve, immediately downstream of the main manual gas valve, often tapped into the main valve. (Note the 1/8 inch plug on the inlet to the burner manual valve.) I see what appears to be two different tubes along with an electrical cable taped to the main gas piping. Unfortunately I don't see where they are eventually going.
 
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Old 01-07-15, 06:14 PM
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I should probably bring the other gas train photos from the other thread over also.

I see what appears to be two different tubes along with an electrical cable taped to the main gas piping. Unfortunately I don't see where they are eventually going.
I thought that stuff was going into the BASO switch... the copper is the TC and that goes to the bottom of the Baso pilot switch. The power for the main valve should be coming from there also. I presumed that the other wires were 24VAC feed and thermostat... sound likely?

Howz, can you get some better angles on all that stuff?
 
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Old 01-07-15, 06:17 PM
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I think I see the B valve you talk about Furd... in this pic, branching off the main ahead of the regulator, yes?

 
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Old 01-07-15, 06:23 PM
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Very impressive Furd, here's a better look. We just took a few pictures to show the 1/4 turn thumb screw valve that comes off the main gas valve (the B valve) and it is what we use to turn off the pilot.

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Old 01-07-15, 06:29 PM
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Would it be any good / harm to clean it up tomorrow with some emery cloth and brass feeler gauge (when cool) followed by a few spritzes of "air in a can" from the computer parts store?

Also, if the orientation of the slots is off, how do we reorient them?
 
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Old 01-07-15, 08:01 PM
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I don't think you'll hurt it...

One hole should point right at the TC, and then one each right and left... I don't see how it could be crooked.
 
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Old 01-07-15, 09:27 PM
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If that is a copper tube going to the pilot burner it really should be changed for aluminum. Under the influence of the heat from the main burner copper can oxidize and flake off internally and that will often cause clogging of the orifice. Also make sure the B valve handle is in perfect alignment when open as it is a low pressure and even partially closed as it appears to be in that picture can limit the gas flow.

Sometimes the "cap" on the pilot burner can be rotated to align the flames, sometimes not. In your case it is probably rusted solid but IF you clean the orifice you may alleviate the problem.
 
 

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