Pilot won't stay lit. Thermocouple good. What's next?

[badmajon]

Sigh. I have no idea how to move forward now. The thermocouple is good, sending out 30 mv measured with a multimeter. Pilot won't stay lit. I have a Honeywell vr8200 the same one a lot of people have used for the Brutus 10.

Also I am assuming you do not have to have power sent to the solenoid for this to work right? Unless I totally misunderstand how this works.

If anyone knows how to troubleshoot the solenoid valve itself please let me know. If I have to spend $100 on a new valve I want to make sure the one I have is bad.

 

[de3isit]

I would start b making sure the pilot has the correct pressure coming out. Too much or too little will make it go out.

 

[badmajon]

The flame looks good, I adjusted it to about an inch and a half. Are there any other things to adjust here? I know the regulator itself has some kind of adjustment screw, and there is a totally unmovable inlet valve screw on top of the vr8200.

 

[badmajon]

Also if your advice is just to replace the whole thing please say so any advice appreciated.

 

[badmajon]

Actually I think it may have something to do with pressure. The pressure is so low that even lighting it is hard to do...

 

[devils4ever]

Well, I'm not expert, but I just built a HERMS system using that Honeywell valve. If the thermocouple is putting out 30 mV, it's good. Is the pilot flame engulfing the thermocouple? And if the pressure's good, I would guess your connection to the valve is bad or the valve is bad.

 

[de3isit]

I would suggest starting out by getting a cheap pyschometer and dialing in the gas pressure before you do anything else.

 

[rhurls]

Let me start by saying that if you are not certified working with gas you should not as you can cause serious damage. That being said the trermocouple output is good at 30mv but 37mv is optimal and can be raised by adjusting the pilot flame. First you must use a manometer to check your incoming gas pressure (For Nat it should be 5"-7"wc, For LP 12"-14"wc) static and dynamic. No more and no less. Then you must check and adjust your output pressure to match what your burner manifold pressure is supposed to be. Then make sure that you have 24vac to the coils (MV & PV). If all is correct you can take a resistance check on the coils to see if one of them are shorted.Sorry but I do not have a new one to tell you what the coil resistance should be. If you can not find out the resistances and everything else is good it is most likely a shorted coil. Those valves are only meant to cycle three times every hour and burn out quick when short cycled.

To answer your other question the thermocouple output voltage is only used as a safety to hold in the pilot coil.

Attached is a link for Honeywell's cut sheet.

http://www.forwardthinking.honeywell.com/related_links/combustion/vr8300_vr8200/install/69_0234.pdf

I hope this information is helpful and please be safe while playing with gas as it is no joke and in my 25 years doing this I have seen a few people seriously injured.

 

[reynolds5520]

Also I am assuming you do not have to have power sent to the solenoid for this to work right? Unless I totally misunderstand how this works.
.

The valve does require 24V to operate.

 

[badmajon]

Let me start by saying that if you are not certified working with gas you should not

Well you obviously know your stuff, but if everyone followed your advice, I think everyone on this place would still be brewing on the stovetop with a Mr. Beer.

Anyway, yeah, the solenoid was bad. I ordered another one and it worked just fine. Don't buy used crap off amazon marketplace.