Hot water boiler burner shutting off/pilot stays on.


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Old 04-04-13, 12:05 AM
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Question Hot water boiler burner shutting off/pilot stays on.

Hi,

I am a new member who joined because of the help and knowledge given by the Moderator, "lawrosa". As an ex-service technician for the State/A.O. Smith HWH company, I hope you like a challenge.

A Google search found your suggestions to a question on this site last year, in reply to the thread, "Pilot light will not stay lit when water is hot". My problem is almost the same, and I'm stumped -- and so are 3 plumbers PLUS the techs at A.O. Smith!

My problem: my pilot light stays lit for hours, but once the burner is turned on, both the burner AND the pilot go out in 15 minutes, every time. If I wait 5 minutes for the boiler to cool off, I can relight the pilot and the burner. Then they both go out again after 15 minutes.

The HWH is in a vented garage, it's 18" off the ground and I assume it worked fine before I started renting the house 6 months ago. There is a gas furnace 12" away from the boiler, but there doesn't seem to be any connection between the two. Nor is there a connection between outdoor wind, temperature, day vs. night, etc. So I think the combustion chamber is overheating. It happened when I moved in, it cleared up (after one plumber vacuumed the bottom), then started again a few weeks ago. So it seems to be related to the air supply.

I built a 1/2" copper pipe-vacuum attachment for my Shop-Vac, as lawrosa described. I vacuumed the inside of the air intake area and the bottom of the fire arrestor disk. It's a yellowish, 4" round thing, like this:

http://cdn.stripersonline.com/c/cb/c...tach431340.jpg

This photo also shows the type of gas valve I have.

I also scrubbed the arrestor with a plastic brush (the kind made to clean refrigerator coils), but neither helped this time.

I also replaced the thermocouple/TCO (temperature cut-off) assembly, as suggested by the A.O. Smith tech support guy -- he was "98%" sure that would fix the problem. Well, I must have the "2% problem". No dice, and I'm out $70. It's this type:

Fun plumbing pictures

The original pilot was rated at 200*C, and the new one I installed is 180* -- the tech support guy said that should NOT be the problem. Can I trust him?

Before I reinstalled the burner with the new pilot assembly, I vacuumed out the combustion chamber: there as a little bit of rust in there, as well as on the burner head and on the top of the flame arrestor. I got all the rust off, vacuumed the inside of the CC and gently vacuumed off all of the rust that I could reach on the arrestor.

Replacing the pilot assembly was a breeze, except for trying to get the burner/pilot assembly to sit in its support bracket, centered under the flue. I could not get it to sit there if the gas tube was attached to the gas valve; I left it suspended in the chamber, just to the side of the bracket. It works, and the tech said that being off-center is NOT unsafe. Should I trust him on that?

I withdrew the 4-foot flue baffle: it was lightly rusted (no loose flakes falling off) but was solid.

I did the flue vent smoke test using a piece of incense, and there IS a slight draft after it warms up for 5 minutes. But is the updraft strong enough? How can I tell? I am willing to blow air out through the vent to the garage roof next. (Maybe a squirrel got stuck up there?)

The pilot flame is entirely blue, and the burner is blue with a red/orange at the top. I think these are normal. The burner flame does not wander or mushroom, which could trip the TCO switch.

Long story short (well, shorter): I did everything that the AO Smith people suggested and followed all of the instructions they e-mailed me.

My question (which lawrosa touched on last year): if the chamber IS overheating, how can I determine whether it's not getting enough air through the arrestor at the bottom, or if the hot gases are not venting out fast enough at the top?

Would it be hazardous to crack open the chamber door for 30 minutes to see if it still overheats? I'd sit right there with a fire extinguisher -- and a beer -- to feel safe. ;o)

I've vacuumed and scrubbed the arrestor enough times that it SHOULD be clear -- but how small are those holes? A.O. Smith said there are 3,000 holes! If they're as narrow as a needle, how could a scrub brush ever clean them out?

For personal reasons, I can't have any more plumbers look at it. And "Moe, Larry and Curly" only want to sell me a new $1,000+ boiler.

Here are the HWH specs:

"State Select" brand, 50 gallon water heater
Model number GS650YOCT
Serial number: EQ4322424
Dated: Feb. 19, 2004


Any help, advice, speculation or wild guesses are welcome at this point.


Thanks in advance,


RH
4/3/13
 
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Old 04-05-13, 06:52 PM
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Partially open the garage door for the 15 minutes. See if it still happens.
 
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Old 04-06-13, 06:41 AM
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The original pilot was rated at 200*C, and the new one I installed is 180* -- the tech support guy said that should NOT be the problem. Can I trust him?
They all should be replaced with 200 C models.....period. New units came with 180 C... Then AO smith went to 190 C then finally 200 C....


I could not get it to sit there if the gas tube was attached to the gas valve; I left it suspended in the chamber, just to the side of the bracket. It works, and the tech said that being off-center is NOT unsafe. Should I trust him on that?
There is no reason not to slide the burner in the support slot. You need a bright flashlight and shine it through the window when installing the burner...Its a no brainer... Do it right. IMO there is no off to the side. Thats plain laziness.


My question (which lawrosa touched on last year): if the chamber IS overheating, how can I determine whether it's not getting enough air through the arrestor at the bottom, or if the hot gases are not venting out fast enough at the top?
Slide the rubber grommet that seals the burner tube through the chamber door.up toward the gas valve. Move the insulation so the air could get in around the burner tube. I use a screw driver to do this.

Its for test purpose only and should not be left like that. Watch and see if it functions normally. Let us know.

Its hazard is that you are bypassing the sealed chamber and flammable protection. If gas was spilled in the garage a explosion can occur...

If the corderite disk got wet for any reason this would be the issue. The disk material expands and seals the holes from what I was told from AO smith.

Do you need a 50 gallon? Anyway you could by a new AO smith from your local Furguson for around $400, and install yourself if your handy. IMO I would probably get rid of that thing. It was a bad design and was only made for a few years with the corderite disk.

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Old 05-12-13, 04:04 PM
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Thanks for feedback

Hi,


Thanks to you all for replying so quickly: I haven't checked in b/c I didn't expect the fast replies.

Pulpo: I did open the door and it had no affect.

lawrosa:

I spent over $70 for the TCO/thermocouple and my re$ources are limited: I will have to trust AOSmith that the 180*C TCO is not the problem.

The burner could not physically sit on its support AND reach the gas valve outside the chamber: the burner tube is not the flexible type. I think one of the Stooges I hired might not have screwed in the gas valve/thermostat enough when he replaced it -- if it were 1/4" closer to the boiler, it would all align. Again, I have to trust AOS on this not being a problem. Or a danger.

I did wedge a screwdriver into the burner tube grommet, but I don't think I got last the insulator: I placed a burning piece of incense near the grommet opening, and the smoke was not drawn into the opening. I will try again with a 1/4" copper tube, which is hollow.

Since I first posted in April, I've gotten other suggestions from AOS, and they think that I don't have enough updraft from the draft hood to the vent pipe.

I asked if they had a video to show me HOW FAST the smoke from a match or incense should be drawn into the hood, but they didn't have one. Neither did YouTube.

If anyone can find one, or post one here, I'd appreciate it.

If it turns out that the cordite disk/flame arrestor is the problem, I'll replace the boiler with a more dependable brand (I hear that Rheem is good). But I have to thoroughly test all the possibilities.

Money is tight.


Thanks again,


RH in CA.
 
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Old 05-12-13, 05:18 PM
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I think one of the Stooges I hired might not have screwed in the gas valve/thermostat enough when he replaced it

One of the stooges put the wrong gas valve in. They have all different shank lengths for different models. There are 5 different shank lenths from what I remeber...

Thats just bad workmanship on the stooges part... Guess some are ignorant and arrogant. They dont know and they dont care....

I would call them back asap. The burner needs to sit under the flue baffle. Possibly part of the overheat issue. That could be a safety issue.

Since I first posted in April, I've gotten other suggestions from AOS, and they think that I don't have enough updraft from the draft hood to the vent pipe.

Additionally the baffle should be removed to check the integity. I have seen then break, drop, bend, twist...ect and block the flue gases. That may be your issue.

If you did not have good draft the H/C blue and red grommets around the in/out pipe would be melted. Ignore the foam, but you get the idea.





Again AO smith dont make the disk model anymore. AO smith is the best IMO.
 
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Old 05-21-13, 12:47 PM
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I looked over a photo I took a few weeks ago, looking down the flue at the burner and I can see that it WAS centered under the flue. So I am going to wrestle it back into position, where "Curly" had it.

I will need adhesive to keep the chamber door insulation from moving around (it's very fragile material, maybe fiberglass?). Here's the part; what type of heat-resistant adhesive would you recommend?

9003531005 - AO Smith 9003531005 - FV Pilot Assembly, 180 - High Altitude

The baffles themselves look OK: no pitting, just what I'd expect to see on a long piece of metal sitting in a flame for years. I can post some photos soon.

There doesn't seem to be any back-pressure from the draft hood: the H&C grommets are not melted; and the incense smoke I used to test it does NOT blow outward.

I would still like to see a video of how fast the smoke SHOULD be sucked into the vent. AOS doesn't have any available.

I'm hoping my overheating problem is a combination of the burner being off-center, and the old TCO being defective. I could use a hot bath.

Thanks.

RH
 
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Old 05-21-13, 01:54 PM
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NG right?

You want the 200 C model and not the 180 C temp range.

Plus they come with a new gasket.

Also the one you linked to is High altitude. Are you That high?????

9003521005 - AO Smith 9003521005 - FV Pilot Assembly, 200 - Natural
 
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Old 05-21-13, 06:43 PM
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Wrong TCO version?

Yes, it's natural gas.

I'm just north of San Francisco in a valley, so I don't think that the Parts person at AO Smith should have given me the Part No. for a High Altitude version.

Thanks for catching that. I was told the 180*C version should work fine, just like they told me that the burner being off-center would be just fine. I'm starting to think there's a lot of idiots over there at AOS. Nice, well-meaning idiots... Maybe they're all at High Altitudes.

So, if I buy the 200*C part from Pex Supply or my local dealer, I'll get a new gasket with it: would you suggest glueing it into position so it doesn't tear apart from over-handling? The previous gasket did appear to have adhesive on it, and it held in position when I first replaced the thermocouple.

I'm going to fix this problem one step at a time.

Thanks again,

RH/CA
 
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Old 05-26-13, 09:14 PM
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Update

Hi all,

I was told by the Parts Dept. that they suggested the "High Altitude/180*C" TCO because that's what was listed as the replacement part. I asked what the "High Altitude" refers to, but I'm still waiting for them to answer.

Does anyone know what it refers to, and why would the TCO trip off the burner at a 20*C lower temperature?

I'm guessing that the water in the WH boils at a lower temperature at high altitudes, probably because of the lower air pressure.

I'll probably replace the TCO with a 200*C version like the original had, and I'd like to know what type of adhesive I should ask for to keep the fiberglass chamber cover gasket in place?


RH
 
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Old 05-28-13, 01:55 PM
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Exhaust vent photos

Hi,


While I'm waiting to hear back from any of you, or AOSmith, about what "High Altitude" refers to, I posted a few photos to see if anyone thinks the 3" exhaust venting looks suspicious.

(I hope the photos appear in this order):

> the flue baffle seems OK, but I'm not an expert. No parts are burned through.

> draft hood and Hot and Cold plastic grommets look OK, no signs of back-pressure.

> the 3" single-wall exhaust vent pipes were pieced together and look like something from a Dr. Seuss cartoon; could this be the reason why there is a very weak updraft when I do the smoke test? Should there be at least a foot (or more) of straight pipe coming off the draft hood?

> the boiler's vent merges with the 6" gas furnace pipe, which then lead out through the garage roof. The top of the exhaust pipe does sit above the peak of the garage. There is little-to-no wind to cause back-pressure.

> I suspect the exhaust pipes were changed by a previous tenant, since there was a 4-foot piece of *straight* pipe left beside the boiler when I rented the house. I don't know why it would have been changed.

Any wild speculations are welcome.

RH
 
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Old 05-28-13, 02:32 PM
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Did the disk get wet?

I was told by the Parts Dept. that they suggested the "High Altitude/180*C" TCO because that's what was listed as the replacement part.
I referenced and seems like thats the right part. Possibly a typo with the high altitude....???

I guess you need to verify the thermal switch is the culprit. Possibly the disk is fine...

It all may be fine and the gas valve is at fault. If the t stat does not work and the water temp gets too high the same issue will happen with pilot out.

If the water extremely hot after this happens?

Even if not the valve can be bad.

Ill say it again...Dont through money at it. Cut your losses. A new 40 gallon at the link I posted run about $350. You have flexible lines and can install yourself.







I would ask the
 
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Old 05-28-13, 02:37 PM
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Old 06-01-13, 12:31 PM
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Hi,


Thanks for the link: AOSmith never sent me this and I will look it over this weekend.

So, is a "High Altitude" TCO used for homes that are at high altitudes? Sounds like a dumb question, but I'm a layman. Then the 200*C TCo you linked to would seem to be a 'more exact' replacement.

I assume that you don't have any concerns with the exhaust vents and the relatively slow updraft of smoke at the draft hood.

I will take your advice about replacing the entire unit to heart. You said that AOS makes good boilers, so I will look for a similar model by them (since I am not the home owner).

Any other recommendations for natural gas, 50-gallon HWH is appreciated.


Thanks again,


RH
 
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Old 11-07-13, 03:15 AM
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Confirming the SKU

Hi all,

I did correct the exhaust ducting over the draft hood and it didn't help.

So, I'm ready to bite the bullet and buy another (the CORRECT) $75 thermocouple/TCO. But since I can't get the right part number from AO Smith/State, nor Pex (an online supplier), I'd like to ask if any of you pros can tell me if these markings on my old TC/TCO can tell me the right SKU?

LawRosa thinks it's this SKU/part, and I just want a second opinion. Not that I don't trust or appreciate all his help, but b/c I'm pretty broke and can't afford to buy another incorrect part.

I agree with LawRosa that I think it's this part:

9003521005 - AO Smith 9003521005 - FV Pilot Assembly, 200 - Natural

(BTW: I called Pex directly for the part number, but they gave me one that was WAY off. Even ~I~ knew it was wrong.)


Thanks for all your help.

RH
 
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Old 11-07-13, 07:08 AM
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That 200c part in your pic is correct... AO smith uses 900 #'s now to identify their parts...

IMO I would not waste money at all... I did not re read this thread but if you have the corderite disk in there cut your losses and change the heater....

Spend the money there....

My opinion....
 
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Old 01-06-14, 12:37 PM
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Will buy a new boiler

Hi,


Happy New Year everyone!

I am going to replace the boiler with a new one this spring -- I can't afford to right now since I overspent on Xmas gifts.

Until then, I'm going to take Lawrosa's advice and move the grommet that seals the combustion chamber around the main gas line up and away from the chamber door for a short time to see if the increased flow of air around the gas line makes the burner stay lit for more than 15 minutes.

If it does, I might leave it that way until I can afford a new boiler: there are no flammable liquids, chlorine bleach, paint, etc. in the garage, so I don't think I have to worry about an explosion.

Thanks again for all your advice; I'll let you know what happens, in case anyone else has the same problem.


RH
1/6/14
 
 

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