Pilot light goes out in the middle of the night **SOLVED!**
Have an American Standard from 1969. Oversized for 750 sq ft EDR - we have 399. four massive burners. Plenty of gas to the burners. 300kbtu in a town house!
New Honeywell (Resideo) VR8300C4506 gas valve about five Yrs old professionally installed (ASU thanks Gordo). Pilot comes on, stays on after 30 sec. - seems like flame sensor is working. Heat works - time goes by, Heat call results in no joy, inspection shows pilot out. Has happened several nights in a row but is intermittent. Cleaned pilot, replaced thermocouple, vacuumed under unit. No evidence of the boiler leaking, using water, dripping on the pilot. Figure next steps are to clean the pilot orifice (A26) , measure for 20mv at the valve end of the thermocouple, then turn the pilot screw CCW to increase pilot a bit. Could valve shut down create air disturbance to extinguish pilot? Unsure how to diagnosea failure of the valve. How hard to move to spark ignition? I have gotten great understanding of the system through the kindness of this forum, have read Dan's books!
Any other ideas? I would be very grateful. Thank you.
Comments
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Sounds like you have done your homework. Possibly a weak flame, but I doubt it. We almost never get a bad brand new thermocouple, but I cannot say never.
Any chance there is a venting issue? Clogged boiler or chimney base? Chimney cap fell off and an animal has decided to build a nest in your chimney?
Anything change on the fresh air side of the equation? New attic exhaust fan or range hood installed recently? You or someone else decide to build walls around the boiler and reduce the fresh air available to the boiler?
You mentioned oversized boiler. Any chance you recently added another gas appliance (stove, water heater, etc.) to the house and might be suffering from low gas pressure? Gas meters fail on very rare occasion, but this does not appear to be you condition.
Any chance the fifty-five year old boiler is leaking when it is firing and you have not witnessed it. Some boilers leak more when hot than when cold. No signs of rust at or near the pilot assembly?
If nothing above jumps out at you, I would start with a new thermocouple and pilot assembly. Next would be another gas valve.
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Meters don't completely fail that often but service regulators fail all the time. It is possible the pressure is dropping on a heat call or something like that. did you take the pilot assembly out and clean it?
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Are you sure it happens exactly in the middle of the night? And what time is that anyway? 12:00 midnight? I don't go to bed until 11:00 PM sometimes. If I wake up at 7:00AM would the middle of the night still be midnight, or would it be 3:00AM? So please be clear on your query!
Thank You
EdTheHeaterMan.
SERIOUSLY Though.
I have noticed that some chimney down draft conditions can blow out a pilot. I had one customer with a standing pilot in a 200 year old home where the heater vented into an old unlined chimney. Upgraded the boiler to a spark ignition system but the water heater pilot would blow out occasionally. They were too old to go outside to light the pilot and had to call their 68 year old son to come and light the pilot. Also could not afford a proper chimney liner either. Only bandaid I could see for them was a CyclePilot that would keep sparking whenever the pilot would blow out. If the pilot relit within the 30 to 60 second window before the thermocouple dropped out, then the problem was solved. Every once in a while the weather was so windy that the pilot did not relight in time. But it was easier to relight with the sparker clicking away.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Gentlemen,
Your willingness to share your skills restores my faith in humanity! Thank you all so much!
I want to address the suggestions as best I am able.
@ScottSecor Chimney is SS lined with 8" pipe, recently removed hot water heater venting into the same pipe and sealed off 3" opening. Possible the connection to the SS cap cover up top was jostled, but see no evidence.
The burners appear to be getting plenty of air and there appears to be sufficient venting. Replaced water heater with hybrid heat pump. I mention the removal of the gas water heater as we actually removed gas use from the equation. Heat pump WH moves the air around but no noticeable drafts near the boiler. Main burners seem to function properly. No walls curtailing air flow. 615 gas meter is reasonably new and pipe is 1 & 1/4 inch diameter to the boiler. Looked for evidence of leaking and see none. Gas cooktop and gas dryer work fine as again do the main burners. gas valve not that old - anyone know the warranty on a VR8300C4506 valve??
My thoughts are to next turn up the pilot a small amount, maybe run a fine wire through the pilot orifice, measure for consistent 20mv at valve end of thermocouple. After that go to supply house for a new Q327 Pilot and a new Q340A thermocouple. Thank you - sir. Oddly the pilot does seem a touch weaker than it once was even though it is the right blue color and flame is not lifting. I did find a very small leak at the gas valve on the pilot feed, and repaired that with a new 1/4" pilot tube.
@mattmia2 we have a very low pressure system here in Baltimore city and the meter is fairly new and I know it is large enough. To my limited knowledge the main burners would show signs of low pressure first as they consume more air and fuel and that I do not see. I do not think we even have a separate regulator.
@EdTheHeaterMan I appreciate the details and need for specifics, that's how we get to solutions! Last night it happened between 2am and 7:30am. Seems about the normal time. I find out in the morning around 7:30 when the boiler should fire up to go from 65 to 67 degrees in the room. Chimney is SS lined soup to nuts. I do not ever feel any downdraft or moving air. The Cycle Pilot idea looks like a great potential solution if nothing else works. Am I correct it installs on a standing pilot? looks to be a backup spark igniter.
If we get to a valve issue (again), I may ask Gordo at ASU to discuss switching to spark ignition - then again, the boiler is 55 years old. I could install the valve, but lack the equipment and skills to calibrate it.
Thank all of you for you valued input!
Kelly
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It is possible the service regulator is not opening properly when the main valve opens and the pressure drop is taking out both burners but if there is no service regulator that isn't it(sometimes it is built in to the meter, it is usually pretty obvious if it is because the meter has a diaphragm shaped part to the casting and a vent). The blocking of the vent for the water heater may be causing more draft through the boiler now. You could have Gordo look at it.
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@mattmia2 Thank you again for the input. your comments are really making me think. There is no cast diaphragm housing in the meter. I think out gas pressure is about 10"wc. I can toggle the blow down while it is running, Burners go out, pilot stays lit, then when I shut the blow down valve and the float returns to the right level, burners come right back on. I've done this several times in a row without the pilot failing. I see what you mean about sealing the hole for the gas water heater. The water heater flue had a gap between the top of the water heater and the flue pipe that no longer exists. It would make sense the draft is now higher. I was thinking first of reverse or down draft being an issue, could more draft be a factor? Is it possible the burners go off after being on for a longer time at night and the rising hot exhaust sucks the pilot out - but intermittently?
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The chimney will have more draft when it is warm especially after a long cycle but assuming it has a draft hood that is supposed to isolate the appliance's draft from the vent's draft. It does have a draft hood and not a barometric damper, right? Even with a draft hood there can be enough draft to pull through the appliance in some cases. Is the thermocouple centered in and well enveloped by the pilot flame?
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Yes, that boiler has a draft hood built-in.
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting1 -
@Steamhead Thank you for your always valued and valuable input. To all others Frank and Gordo from ASU have been great teachers. Clearly I have much to learn. I refer them to everyone in our neighborhood! Now that you mention it - I know exactly where that draft hood is - right in front.
@mattmia2 I tried last night to turn up the pilot at the gas valve. I saw no change no matter where the screw was positioned - found this perplexing - maybe the orifice is occluded?. Going to try a new pilot and thermocouple. I don't think the thermocouple is as well enveloped as it could be, but I know it is functioning most of the time because when I relight the red release comes back up and the pilot stays lit after 30sec. Seems to me if I wasn't getting enough juice from the thermocouple the pilot would go out when letting go of the red release button? As Frank pointed out - no barometric (weighted flap) damper on this.
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Did you check the supply pressure?
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@mattmia2 I have not. Do you mean the overall system pressure or the pilot circuit? I assumed since the 300kbtu burners light every time the overall pressure is not an issue. Since there is no way to adjust overall pressure ( as there is no main regulator), this took me away from thinking this could be the issue. I can run the gas dryer, the range top burners and the massive boiler main burners simultaneously without starvation of any of these, so I can't see how it would be an overall pressure issue. I don't want to monkey around with the pressure coming out of the gas valve as I do not have any combustion test equipment. I lack the tools to check the pilot pressure, but even the pilot is a good one inch non lifting blue flame through a tri-wing guide - though trying to adjust the pilot pressure lead to no observable difference.
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The supply pressure, maybe it is dipping in the middle of the night when everyone's heat is on. If the pilot flame won't get bigger either there isn't enough pressure at the supply or the orifice is partly clogged or maybe the air passages in the pilot burner are partly plugged.
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We have a couple places where this appears to be happening, though not in @Koan 's neighborhood (yet). Usually it happens in the morning when everyone's boilers come out of night setback. We usually say to change your thermostat schedule so it comes out of setback 15-30 minutes earlier, so it won't be trying to start at that point.
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting2 -
@mattmia2 Ordered a new pilot to be on the safe side. What you explained makes good sense so I'll give that a shot. Either the orifice is too restrictive or the pressure to the pilot is wonky. I am absolutely certain the burner openings are not clogged - I wire brushed all four separately and blew them out with air when I cleaned out the pilot and replaced the thermocouple. Thank you for the input!
@Steamhead Great suggestion! I noticed primarily this seems to happen coming out of setback at around 7AM. Our feed is such low pressure that I could see how something like this would happen. If it continues we could go to spark ignition or for a less expensive option try this device suggested by @EdTheHeaterMan
Please let me know if you have other thoughts. Thanks!
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the orifice and openings in the pilot burner, not the main burner, although it sounds like that pilot burner is under a decade old so unless there are chunks in your gas the orifice shouldn't be partly clogged
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you could also leave a cell phone or tablet camera recording it to see what happens when it goes out. if the pressure is dropping the relighter may not work, the thermocouple may already be cold from not a big enough flame and it closes the safety valve. the relighter won't re-open the safety valve
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Gentlemen
Ordered the parts - Arrived next day (today) Thanks Supply House
Found this on another forum (a UK site)
"I thought I would post an update for all who followed or posted on this thread. When boiler was hot wriggling both leads to overheat stat caused no problems at all. When totally stone cold a wriggle on one of the leads caused pilot to trip as signal to gas control valve was lost. This was repeatable time and time again. So it seems that expansion when warm gave a good connection but sometime during night connection was intermittently lost as spade connector cooled.
Connections now really tightened and boiler running perfectly."
I remember having to re plug the Spade connector on the gas valve. We do not have an overheat safety thermostat, but we do have a low water cut off and Vaporstat in series with the thermostat to the gas valve with some really old wiring! Will work on it this weekend and post.
@mattmia2 , @Steamhead, @EdTheHeaterMan, @ScottSecor
Thank you all for sharing your wisdom and insight!
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Two new data points:
First: Jostled the wires to the gas valve and heard it click. Removed and plugged in the lower spade connector to the gas valve that appeared to be the culprit
Second: New observation thanks to my brilliant wife.
When the pilot and only the pilot is running there is 1/2" of the top of thermocouple glowing.
When the main burners come on, it pulls the pilot flame to the left away from the thermocouple, and only 1/16" inch of the thermocouple is glowing.
New Pilot and thermocouple going in this weekend along with checking all the connections several times
Any chance a five year old VR8300C4506 gas valve is failing?
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Check your pressure. Sure sounds like the house side pressure is dropping when the main valve opens.
or have the utility do it. they should at least check it at the meter for free, may or may not check it at the appliance to see if it is a problem with the service or if the piping to the boiler is too small. Could be that the pressure is still with in their limits at the meter but lower and after the drop from the piping it is too low at the appliance.
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@mattmia2 Thank you again for the insight.
I am nearly certain the piping is not the problem. While is it 300kbtu, the pipe is 1 & 1/4 " and is under 25 feet. I have reviewed all the piping and it is all up to the correct size and then some.
I will undo the sediment drain next to the boiler to make sure there is nothing in that. Thanks again!
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If there really is no service regulator then the size and length of your service comes in to play too.
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Seems like this came down to a dirty pilot that was marginal enough to relight, but not robust enough to work under operating conditions.
Last night I could not sleep. Pilot again kept going out. Would relight each time (manually). Tested for 20+mv at valve - all good. Burners came on so I waited and watched. 4:30AM burners went off, thought thermostat was satisfied but this was not the case. Pilot went out at the same time. Relight pilot immediately but had to wait 20 sec and hold the bypass even immediately after burners went out. Got it going again by lighting pilot, waiting 20 sec, turning valve to ON. 5:00AM burners fired. Tstat satisfied burners go off and so does pilot. 3 sec later again pilot will not relight wo holding the bypass button. Relight pilot manually and wait 20 sec. I thought to myself, why was I not able to relight without holding the red button down?
It appears the manual relight gives me 20mv and I can light the pilot and it stays on. The burners then draw the weak pilot flame away from the thermocouple and I have shut down unless the burners help just enough to keep the valve open. Once the burners go out, no joy for the thermocouple. Sometimes even this is not enough and the valve shuts on safety of the thermocouple.
Long story short - replaced the pilot and thermocouple. Pilot flame far more robust and engulfs thermocouple nicely. Top 3/8 inch of thermocouple now glow orange with burners off or on. Prior to this pilot flame barely touched thermocouple with burners going, but was marginal enough to provide 20mv on pilot alone.
Thank you all - looks like this one is solved. Note to self - being able to relight the pilot is not always sufficient proof the pilot is functioning properly.
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I still wanna know how it knew it was nighttime.
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@HVACNUT I am guessing the longerburner cycles at night may have had a greater influence. That apparent pattern was a false clue - a red herring. So was the fact that I could relight the pilot every time if I held down the relight button. What really gave it away was that I could not relight the pilot immediately when the main burners went out. The thermocouple should have been hot enough to a few seconds to allow gas to flow to the pilot.
@EBEBRATT-Ed Kind sir you give me too much credit. I am a mere amateur who has developed an interest in this field. While I am handy, I rely on the generosity of the kind people here to share their vast experience and help teach me. More to your comment - I know what you mean - there can be hidden gremlins that can really have you scratching your head. Fortunately, this was not one of them. Many thanks again to all for helping me.
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Still think the pressure is dropping at night. Did you take the old pilot burner apart to see what was stuck in the orifice?
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