Radiance 2600 with Robertshaw valve -pilot is weak

[GlenTheMachine]

I had a low voltage on my old thermopile (200 mV) so I replaced it. But the new one isn't much better (about 230 mV). I think the issue now is that my standing pilot light is too weak. It is mostly yellow and doesn't encompass the body of the thermopile — the flame isn't big enough. It also gutters quite a bit.

I believe there is supposed to be a way to adjust the strength of the pilot light on these systems, but turning any of the screws on the valve doesn't seem to make any difference. Can anyone give me a pointer?

 

[DAKSY]

Can you post a pic of the front of the valve? The older Robt. Shaw valves have a "PILOT" marking
on the lower left & there is a slotted SS screw adjacent to that marking. That screw needs to be removed & the pilot
adjustment screw is located behind the one you removed. You'll need a tiny slotted screwdriver to adjust the pilot screw.
Once you've satisfactorily adjusted the pilot, replace the original screw & snug it.

 

[GlenTheMachine]

Can you post a pic of the front of the valve? The older Robt. Shaw valves have a "PILOT" marking
on the lower left & there is a slotted SS screw adjacent to that marking. That screw needs to be removed & the pilot
adjustment screw is located behind the one you removed. You'll need a tiny slotted screwdriver to adjust the pilot screw.
Once you've satisfactorily adjusted the pilot, replace the original screw & snug it.

...found it. Thanks!

Unfortunately it doesn't seem to help. I can make the pilot go out, but I can't make it any bigger. Which means it has to be the orifice, right?

 

[DAKSY]

Could be. Have you verified the gas pressure at the valve?
Are all shut-offs between the incoming gas supply & the unit WIDE open?

 

[GlenTheMachine]

Could be. Have you verified the gas pressure at the valve?
Are all shut-offs between the incoming gas supply & the unit WIDE open?

I haven't checked. By I can get the stove to light if I put a AAA cell across the thermopile leads. And once it's lit, it burns great. Which seems to me to indicate that it's the voltage the thermopile is producing, and not the gas supply.

 

[DAKSY]

The millivolts produces by the TP is a result of the engulfment in the pilot flame.
The flame should engage the top 3/8" of the TP in order to generate adequately.
What mV are generated by the TP when the unit is burning? 200 is plenty.
On the PILOT you SHOULD have from 450 - 550mV...

 

[GlenTheMachine]

The millivolts produces by the TP is a result of the engulfment in the pilot flame.
The flame should engage the top 3/8" of the TP in order to generate adequately.
What mV are generated by the TP when the unit is burning? 200 is plenty.
On the PILOT you SHOULD have from 450 - 550mV...

When the burners are on (and, obviously the on/off switch is on), the thermopile reads 190 mV.

Much of the time the pilot doesn't engulf the thermopile fully at all. It maybe engulfs half the diameter of the thermopile. Sometimes not even that, it just kind of licks one half of the thermopile. With the thermopile installed but not hooked up to the valve, I get maybe 300 mV. With it hooked up to the valve but the on/off switch off it's below 200 mV. Oscillates between maybe 150 and 180.

 

[GlenTheMachine]

When the burners are on (and, obviously the on/off switch is on), the thermopile reads 190 mV.

Much of the time the pilot doesn't engulf the thermopile fully at all. It maybe engulfs half the diameter of the thermopile. Sometimes not even that, it just kind of licks one half of the thermopile. With the thermopile installed but not hooked up to the valve, I get maybe 300 mV. With it hooked up to the valve but the on/off switch off it's below 200 mV. Oscillates between maybe 150 and 180.

And *immediately* after I turn the stove off, I get 330 mV off the thermopile. With the thermopile still hot I can turn the stove back on and it lights right up.

 

[DAKSY]

Can you post a pic of the pilot burning?

 

[GlenTheMachine]

Can you post a pic of the pilot burning?

Hard to photograph, but here you go...

 

[GlenTheMachine]

 

[DAKSY]

Hard to see what's going on there...Can you 'tweak' the pilot hood with a pair of needlenose to get more flame on the TP?

 

[GlenTheMachine]

Hard to see what's going on there...Can you 'tweak' the pilot hood with a pair of needlenose to get more flame on the TP?

Doubtful. The flame just doesn't extend far enough from the orifice, so I don't think fiddling with the hood would buy me much... and both the pilot tube and the thermopile are screwed into a bracket, which I can't really bend.

I suspect the pilot hood itself is pretty far gone as well.

 

[DAKSY]

OK. I'm thinking you need to verify the incoming pressure at the port on the front of the valve.
If it's adequate for the fuel you are burning then I'd start looking at the pilot tube (kink?) or pilot orifice.

 

[GlenTheMachine]

OK. I'm thinking you need to verify the incoming pressure at the port on the front of the valve.
If it's adequate for the fuel you are burning then I'd start looking at the pilot tube (kink?) or pilot orifice.

How do I verify the pressure? Just check to make sure the valve is fully open?

It's LP by the way.

 

[DAKSY]

You will need a manometer. On the front of the Robt. Shaw valve there are two ports, labelled "IN" & "OUT."
You want to check the "IN" side. It should be at 10" - 11" of water column (WC)...

 

[Millbilly]

I'm going with a bad pilot tube, orifice, hood. Basically soot or bug partially blocking your gas flow from the valve to pilot flame. If your burner looks good im thinking pressure ok.