Honeywell VS8421D Pilot Adjustment

[bkaul]

My ventless fireplace pilot is turbulent/noisy, and I think adjusting the pilot pressure down a bit should help. The valve is a Honeywell VS8241D, and there's a cap screw on the corner of the valve near a label "PILOT ADJ" - I assume there's an adjusting valve down in this hole, though I can't get light/camera positioned to see anything, but that leads to my question. What kind of screw head is on it? I can get a small flathead to sort-of catch on something, in what feels like the way a screwdriver can sometimes drop into an Allen head screw, but it won't turn it. None of the Allen head sizes I've tried have grabbed (nor Torx for that matter), but I might just not have stumbled on the right size yet. The manual on Honeywell's site shows the cap screw in one picture, but it doesn't specify an adjusting procedure. Has anyone had success determining what kind of tool to stick down that hole (shown top left with cap screw removed)?

 

[DAKSY]

On MOST gas valves, the Pilot Adjustment screw is slotted. Try a larger flat head screwdriver.

 

[bkaul]

Thanks. The largest flat-head screwdriver that fits in the hole catches on nothing. The next size down kind of drops in at ~ three positions, making me think it's trying to engage a hex head. But none of my Allen wrenches catch on anything either. I wonder if it could be a drilled/security Allen or Torx bit?

 

[bkaul]

Found this in the manual on Honeywell's website:

Pilot Gas Connection, Flow and Adjustment:
Connection Size: 7/16-24 UNS.
Flow: 1700 Btuh at 4.0 in. wc pressure drop.
Pilot is not adjustable.

Maybe it is a tamper-proof arrangement on these, despite the Pilot Adj cap screw. If anyone has managed to adjust it, I'll be curious to hear how. Mine's definitely gone turbulent:

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[Lennox65]

Found this in the manual on Honeywell's website:

Pilot Gas Connection, Flow and Adjustment:
Connection Size: 7/16-24 UNS.
Flow: 1700 Btuh at 4.0 in. wc pressure drop.
Pilot is not adjustable.

Maybe it is a tamper-proof arrangement on these, despite the Pilot Adj cap screw. If anyone has managed to adjust it, I'll be curious to hear how. Mine's definitely gone turbulent:

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Have you tried cleaning the pilot assembly?
The vent free pilots are definitely louder than a typical standing pilot, but yours sounds like there is some resistance in the tube that is causing that sound.

 

[bkaul]

Have you tried cleaning the pilot assembly?
The vent free pilots are definitely louder than a typical standing pilot, but yours sounds like there is some resistance in the tube that is causing that sound.

I haven't, but I'll give it a try. Thanks.

I am thinking high pressure rather than deposits in the line as a root cause of the turbulence because it's blowing so hard horizontally rather than maintaining a vertical flame (with no external airflow driving that motion). The noise is definitely related to the high flow; when I first light it, before the thermopile is warm enough to keep the solenoid valve pulled in, the flame is quiet, laminar, and vertical. Once it's hot, the horizontal velocity picks up and I get turbulent flow out of the pilot nozzle (hence the noise).

 

[Lennox65]

I haven't, but I'll give it a try. Thanks.

I am thinking high pressure rather than deposits in the line as a root cause of the turbulence because it's blowing so hard horizontally rather than maintaining a vertical flame (with no external airflow driving that motion). The noise is definitely related to the high flow; when I first light it, before the thermopile is warm enough to keep the solenoid valve pulled in, the flame is quiet, laminar, and vertical. Once it's hot, the horizontal velocity picks up and I get turbulent flow out of the pilot nozzle (hence the noise).

The reason that vent free pilots are not adjustable is because they are a critical component of a system that has no vent.

This is an answer to a similar question on another forum:
"How did you determine the pilot flame was too long? I've never seen a standard stating flame length. I do know most ODS pilots consume 1200-1600 BTU/hr normally.

ODS pilots are precision engineered components and not for the DIY because of precisely what you did. Nobody, including veteran service techs, should ever tamper with an ODS pilot. The reason there was no pilot adjusting screw is because this is a critical factor in the proper operation of an ODS. If every homeowner or service tech fiddled with these screws, you'd have a lot of people not waking up in the morning. There is also a separate pressure regulator on the pilot tube.

This is one of the biggest dangers with ventfree--tampering.

You may have voided the warranty and listing on your logset, which you documented here in public. Just say no."

 

[bkaul]

I know it's an old thread, but wanted to update with what I determined in case others dig it up in a search. As Lennox65 noted above, these vent-free units are nonadjustable: while it says "Pilot Adj" near that hole, that's just a matter of using the same casting for different valve configurations. There's just a plug in there, not an adjusting screw. The regulator on the pilot tube is the actual control mechanism. These regulators are a poppet-valve style with a rubber seat. They're sealed/nonserviceable (for good reason), and I haven't bothered to drill out the rivets to disassemble the old unit, but I'm guessing the reason it was no longer effectively controlling the pilot pressure is that the rubber seat had degraded (seems more likely than a spring failure). Either way, this was the issue.