I wonder if there is some form of warpage going on. Is the damper right above the unit. Perhaps move the damper further away from the unit if possible? Thats all I can think of, is it gets very hot and then you stop using it and it cools down and warps badly. And when you run it consistently it just stays hot and doesnt get a chance to cool down and warp badly.

I would consider this, but I just replaced the damper 4 weeks ago. It's barely had to work, as winter is almost over. And same symptoms were happening on the old one, which turned out to be fine as we can see by my previous sentence. There were no problems for the first 6+ years and nothing physically has changed.

There has to be some other reason than defective parts because you have replaced them multiple times and still have the problem.

Some other info.

https://www.nachi.org/spill-switch-inspection.htm

https://www.youtube.com/watch?v=eByvj2l1E7E

spill-switch would get stuck, causing the Vent Damper to stop working

From what I read there tells me you misunderstand how it is operating. Spill switch is meant to cut operation of the appliance if it is not venting correctly. Has nothing to do with activating a damper. So if you have a powered damper that gets a signal to open and close, there may be a timing issue there which is tripping the spill switch. I first read the problem as the damper not opening, is this correct or is the damper operating fine and the spill switch keeps activating? If the damper isnt working then the spill switch would be doing its job correctly.

What type of damper are we dealing with (non spring butterfly, spring loaded butterfly, powered) and how is it orientated (horizontal or vertical)? Is there anything that high heat would adversely affect inside the damper (like weather stripping for a tight seal)?

Is it possible for high winds to often push venting combustion material backwards due where the termination exits the house? This could close the damper and make the spill switch activate. I realize that is the point of the backdraft damper, to stop drafts coming back, but it could be making the spill switch activate if the damper gets closed during operation.

My first thought on all the above is that there should be a powered damper that opens during operation and closes when off, one that is not affected by high heat (does not have weather stripping inside). That would remove the wind possiblity or other damper problems that could occur due to type and orientation, and how much draft is made by the unit. If the unit doesnt make enough push to open the damper then it would trip the spill switch.

You may want to have your chimney inspected and cleaned. You want to make sure there are no exhaust problems.

I guess I will then have the chimney checked as your answer sounds logical.

Is there anything special that the chimney guys should use or do to verify what maybe wrong with it? Do they use cameras like the for sewers? Any ideas what this might cost (the inspection).

I just want to make sure I don't do more than I need or have them do a solution which will have them coming back very year trying to "re-fix it" so that they can charge me more and more... on purpose

Much thanks for any additional the input!

I think they should use a camera and do a thorough inspection. If this is an old chimney perhaps a clay tile may be falling off and partially blocking the flue. Maybe the cap is too restrictive.

No estimate what it costs. But this is a safety issue and you want peace of mind there is no problem. Once it is inspected and deemed safe then there should be no need to spend more money on the chimney itself.

When was the last the time the boiler was serviced? If it has been a long time then consider hiring a professional to assess the situation.

What is the function of the spill switch? To shut off or prevent firing of the burner(s) if there is a draft issue. What is the problem here? The spill switch is shutting down the burner. Conclusion - (since parts have been replaced) either 1) there's been a run of defective parts or 2) there's a draft problem. Seems like for the amount of money you've spent on guessing what the problem "might" be would cover at least part of the cost of having a real professional check it out.

Draft problems are what sometimes end up killing people due to CO leaking into the house.

I want to thank again for all of the inputs to my situation. Yesterday, I finally had the time to take a peek at my chimney with a buddy of mine. As one can see by the photos attached, it looks pretty good when we opened it. Just a few very small rocks (which we since removed with a commercial vacuum), and there is nothing that is really blocking the clay chamber. I also stuck my hand inside (as far as I could), and I could easily feel a small draft, which in my opinion shows that the air is flowing. I am also including a photo of how the chimney top looks like from the outside.

https://chimney2017.imgbb.com/

I realize that there might be a crack or two in the clay lining somewhere inside the flue, but if there was a piece or whole section missing, I would most likely find broken clay pieces laying at the bottom. There were none.

Sure, I can still hire a professional to put in mirrors (camera) and do a more extensive inspection, but from my own investigation, I am not sure I need to do anything else seeing what I saw.

Any other input / comments?

Looking into that hole isnt inspecting the whole chimney. It may have some form of blockage on the vertical part. You can get an extendable inspection mirror for not that much and look up the chimney during the day to look for a blockage.

What about the hole that the duct goes into? Is that clear? Gas venting requires natural rising to vent correctly. Where does the upper vent hole go? Does it have to go down to what you show in the picture to get to the chimney?

My questions about the damper were not answered so that isnt ruled out yet either.

You can post pictures here in the future, dont need the third party site to show pics.

Hi Vith. Thanks for your numerous replies. I have added 2 more photos inside the link that I used above, so you can see the duct from two angles. It has the right pitches (I think).

As far as the vent damper (sorry for not seeing it earlier), this is what I have. It has a 15 seconds open/close mechanism.

Ooop, forgot to show the link for the vent damper: http://www.supplyhouse.com/sh/control/product/~product_id=46491600

A draft hood and spill switch is supposed to be before the damper. I dont see a draft hood and the accompanying spill switch as shown on this schematic.

Also of note, the spill switch activates by heat, so it should be installed on a draft hood. In the case of a backdraft, the heat comes out of the hood and activates the spill switch. If this spill switch is installed in the flue it would probably activate often due to the heat.

I was thinking of this some more this morning that maybe the draft hood is part of the unit, so I pulled up the manual and sure enough it is. So you wouldnt see the draft hood on the flue. Ref page 34 and 35.

The control supplement manual has instructions for the damper. It says it must be fully open before the main burners light. Page 20 and 21 for procedural check.

Hi again... Thanks for further input. I have just added ANOTHER photo under the same link, which clearly shows the spill-switch location (circled in blue), which is the default location for this unit. And yes, that's exactly what happens: When the vent doesn't open, the heater (boiler) doesn't start up until someone has to PRESS on the spill switch to re-attempt it and it then works 100% after that until the next time it "stops".

https://chimney2017.imgbb.com/

Sounds like it is narrowed down to an intermittent damper activation. Either the motor is having trouble moving the damper or there is a wiring issue, perhaps the wiring harness has a loose connection maybe in the 4 pin connector or at the control board.

Everyone,

Once again thank you for all your very helpful comments that
you gave me this past May. As "heating" season is going to start soon here in
the Northeast, I will be again relying on my gas boiler again.

Since the last posting here, I had a professional come out here to clean
& inspect the boiler, double check the chimney (he stuck a mirror into it
and we both saw daylight) and he proclaimed the unit in perfect working
condition. The Pro did advise me on two things that I wish to run by you all for
further opinion, lf you don't mind.

1) The Pro advised (he has over 30
years of experience) that I should get a "better quality" spill switch than the
one that I currently am using. The one I have (and already changed 2 times) is
the one that is made specifically for this unit (rated at 210F):

http://www.supplyhouse.com/Weil-McLain-510-300-013-Spill-Switch-w-Reset-210-F

He
said I should get a better quality one made by Field Controls, something
like:

http://www.supplyhouse.com/Field-Controls-GSK-4-200-Gas-Spillage-Sensing-Switch-w-Manual-Reset

or
even

http://www.supplyhouse.com/Field-Controls-FTS-6-180-Safety-Switch-w-Manual-Reset-120-240V

Now,
my question is this: Since my Weil-McLain EG-45 SPDN unit is rated at 210F, and
I will put a spill switch that is 200F or even 180F rated, is that okay? The Pro
did confirm that my existing spill-switch location is in the right spot and that
I do not need two of them for my type of a unit.

2) As far as the
Vent-Damper (to remind, I installed a brand new one last winter, made by Field
Controls). The Pro said that he would just leave it in MANUAL mode. When I asked
him about the danger of having "bad gasses" leakage into the house, he stated
that the boiler will shut itself off as there are other protection sensors there
and that this AUTO function is now included into the Vent-Dampers more for
better efficiency of the unit than for safety. Is he right?

I should
also add:

a) I do have a 4" clean-air going into the boiler room directly
from the street (boiler room being a closed-off section with 2 doors, with two
return 20 inches x 8 inches ventilation grille's that have the air escape into
the rest of the basement). The actual room measures 6 feet long x 7 feet wide x
8 feet high and only contains the gas hot water heater and the gas
boiler.

b) On the advice of the Pro, I tried turning on the heat (via my
Thermostat) a number of times during the summer's hot & humid days (it was
like 80F in the room, so I had to set the Thermostat manually to 82F). The unit
started-up every time without problems and I let it work for 5 mins or so before
turning it off. The Pro said that during the very humid days that the heavy air
that gets trapped in the chimney could force the Vent-Damp to trigger the spill
switch. It never did.

I await your comments. Thank you again in advance
for your time and knowledge.

I go back to an original thought above, and feel there might be a flaw in the mfg design with the damper that close to the unit. There is literally no space for buffer and if the damper doesnt open at exactly the right time the spill switch gets triggered. Perhaps leave the original damper open and install a different powered damper a bit further away.

Vith: I wish I could agree with you, but then why did I have ZERO problems for about 5 years with the same exact setup and only then the problem started to appear at intervals of 2 twice during winter-timer, then next year 3-4 times and up to last year, which was like 10 times. I think my next step then is to change the damper to MANUAL and see how all of this reacts. Thank you again!

I wanted to let everyone know that it seems like my
problem has been finally solved. I
thought it is important to post this solution in case someone else has these same
issues and could perhaps find this helpful.

After putting the vent-damper into the MANUAL mode
(always open), it did not take more than 2 days for the spill switch to trigger
again. So, I decided to order the
Fields Controls GSK-4 switch:

http://www.supplyhouse.com/Field-Controls-GSK-4-200-Gas-Spillage-Sensing-Switch-w-Manual-Reset

Upon its installation, I am happy to report that for one
week, everything was working perfectly in MANUAL mode and now for the past 3
days, the vent-damper is set back to AUTO mode and still working properly. During these 10 days, we’ve had a variant
of rainy, damp, dry and cold weather outside.

So it turns out that I do not have a chimney or negative
boiler room pressure problem (as I always thought), and it all was due to the
spill switch behaving badly. May I
remind you, this was my 3rd spill switch (the official one sold by
Weil-McLain) that I was trying out.
What is interesting, is that the “official” spill-switch (model # 510-300-013),
that is made by Weil-McLain and used by me has to be actually attached to the
metal of the vent hood for operation:

But the Field Controls GSK-4 specifically tells you that
“The switch should not contact the metal. They should be mounted at least 1
inch below the hood opening”

https://s3.amazonaws.com/s3.supplyhouse.com/manuals/1261234685280/20730_PROD_FILE.pdf

QUESTION:

---------------

I always thought that the spill switch MUST have physical
contact with the draft hood in order to monitor “for temperature reading &
monitoring of combusted gasses/fumes that are coming out the vent” but as it seems,
I guess the boiler that has the actual sensor to trigger the spill switch? Can someone please clarify this?

In any case, thank you EVERYONE for trying to help me
with this issue. I am happy that I got
my boiler cleaned and checked out by the pro, and his advice to get the GSK-4
turned out to be right.

So then the question: Why are there temperature rating system (200F or 210F or 250F) for different types of spill switches? Is it because when the heat & fumes start to backdraft, the temperature rises higher & higher in the draft hood (or the Weil-McLain unit itself)?

Possibly because larger burners inherently put off more heat, so higher temps would be required. Not sure that is a factor here. The one you removed says 210 and the one you installed says 200 so, pretty similar, just installed slightly different and the 200 isn't giving you false positives now.