Spill switch

347

Hello All,
I have a customer how had a Burnham Independence steam boiler installed three years ago. Last year the spill switch tripped and shut the boiler off. Homeowner reset it and worked fine. Tripped again toward the end of the heating season. I went by to reset it and checked the chimney for blockage and draft, all seemed good at the time. Well it tripped again this year and was reset. The room seems to have ample air for combustion, but left a boiler room window open to see if that was the problem, it tripped again a few weeks later. I does not trip all the time just once in a while.
Anything to look for? Should I change the spill switch? It's located in the back of (close to boiler) the built in draft hood.
Thanks in advance.

JUGHNE

Could the boiler be over fired?

347

Maybe. Check the firing rate with the gas meter?

JUGHNE

That would be a good start.
Is the pressure set pretty high on the control that it may never cycle and get a chance to cool down?

Or the limit button could be wimpy and popping early, can't be much money to change that.

EBEBRATT-Ed

Any trees around the chimney?? Is it an outside chimney? Could be a downdraft and if so it might spill momentareley until the chimney starts to draw.

I would check the firing rate maybe you can reduce it slightly less input needs less draft

Danny Scully

Is the chimney sized right? Just so you know, that boiler has to be spilling for 3-3.5 minutes straight for the spill switch to trip, so getting to the bottom of this is important (as I know you already know).

347

No trees aroundy, yes outside chinmey . I'm assume the chimney is sized right, the installing company had a chimney guy in to do the work.I'll get back there ths week to check gas pressure.

Danny, thanks for that tid bit, I was wondering how long before the spill switch trips.

Thanks again everyone. I'll keep you posted.

EBEBRATT-Ed

Possibly the chimney needs a liner. I am sure you know when it's spilling it's spilling Co so stay on top of this, don't wan't anyone getting hurt.

347

I was told it was lined when boiler was instaled, it has a label on the wall. I'm going stop by this week and keep trying to figure it out, just looking for some ideas. Thx

Fred

Is it possible the damper door doesn't open fully, on ocassion?

347

The damper seems to open.

ChrisJ

The damper has a safety that will not allow the burner to light unless it's fully open.

Inspect the chimney, make sure it's sized properly and lined.

Any huge kitchen exhaust hoods without a proper makeup air damper that could be causing a down draft? What about fire places? Whole house fan someone had running with the heat?

Something is starving the mechanical room (basement?) of air, or the chimney isn't drafting, randomly. Sounds like a switched fan somewhere to me.


The good news is because of how a drafthood works, if the appliance is spilling in theory it shouldn't be spilling any more CO than when connected to a proper flue. This is typically very low, 0-50ppm? Many do not realize a draft hood appliance doesn't require any outside draft to burn properly. But you're still venting a huge fuel burning appliance into a home. The real dangerous side comes when the appliance runs out of O2 and starts spewing CO because of it.

The bad news is I still wouldn't want it in my house very little CO or not.

j a_2

Did not read all the answers so sorry if I am repeating.....Clearly insure the chimney is sized correctly, over is as bad as under sizing....Insure make up air is sufficient, per manf and local codes, as well as gas codes....check to be sure spill is installed in proper location.....again did not read previous answers so appoligizes for repeat answers

captainco

No one can look at a flue and determine if it is too small. Little or restricted yes.. A draft test is the best way to verify a flue is properly sized. Insert draft gauge in flue above drafthood and observe draft for 5 minutes. Then manually turn off the gas valve. If the draft goes up and stays up for more than 15-20 seconds the flue is undersized or restricted. If it stays where it is there is no problem. Problem would be negative building pressure.

Tim McElwain

The fact that this is not happening every day or frequently during the day tells me there may be some behavior that takes place from time to time that creates a negative condition in the building. The information from captain co is correct so use it. I have also found that the boiler we are talking about does from time to time have a spillage issue when the boiler goes from a cold start. Have a professional come in and move the spill switch just a slight bit and try it and see what happens. Do a combustion test from cold start up to the point were you are making steam. Make sure there is a CO detector in the building.

347

Here's an update.
Went to the job today and met with chimney person. Flue is 6" and about 25' tall (Outside) and all clear. Hooked up a draft gauge and the draft was 0.01(above the built in draft hood and vent damper) and would not rise. Turned on the water heater that is connected to the same flue and still no rise. Chimney guy and the roof felt a very good draft while I got nothing at the base of the vent. When the burner turned off (water heater is already off) the draft gauge did not move up or down. While the burner was off and the damper closed the chimney guy disconnected the W/H flue and put his hand over the 4" and the draft gauge went up almost 0.05". I have clue why that would happen.

I also clocked the gas meter and found it over firing about 15,000 BTU's (boiler is 140,000 input). I adjusted the gas valve and got it down to the firing rate.

I hooked up my combustion meter and the numbers were way out of wack.I pulled the burner cover off and found part of the flame retardant material missing behind the burners (left side only) and what looked like soot on a couple of burner tubes. I pulled two burners out and they were a covered a little and had some soot in them.

I will go back and remove the draft hood and check out the sections and will clean if necessary.

Any suggestions would be appreciated.

captainco

Were you measuring the draft of just the boiler or the flue after they connect? Did you put the draft gauge in the water heater flue? Seems odd that the water heater was stealing all the draft but anything is possible.

347

I took my measurement just above the boiler vent damper, before the 6" wye and the water heater also had little draft.

Mark Eatherton

I've seen this happen before. The water heater vent branch is acting as the draft relief for the main vent stack, thereby shorting the lower large vent connection of negative draft.

Best solution is to install barometric vent dampers on both appliances. Alternative would be to install a restrictive orifice on the draft hood of the water heater to restrict the amount of relief it can provide to the main stack. Tricky proposition when the vent connector is only 3" to begin with.

In any case, if you do install barometric dampers, you will need to install a roll out spill switch that is interfaced with the thermocouple of the water heater to avoid long term spillage from the barometric damper.

ME

ChrisJ

Mark Eatherton said:

I've seen this happen before. The water heater vent branch is acting as the draft relief for the main vent stack, thereby shorting the lower large vent connection of negative draft.

Best solution is to install barometric vent dampers on both appliances. Alternative would be to install a restrictive orifice on the draft hood of the water heater to restrict the amount of relief it can provide to the main stack. Tricky proposition when the vent connector is only 3" to begin with.

In any case, if you do install barometric dampers, you will need to install a roll out spill switch that is interfaced with the thermocouple of the water heater to avoid long term spillage from the barometric damper.

ME

If the problem is the water heater is acting as a draft relief, and this is causing problems, how would adding more "draft reliefs" aka barometric dampers fix the issue?

A roll out switch and spill switch are two different devices. A double swing barometric needs a spill switch installed as per the manufacturer's instructions. Two spill switches, one mounted on top and one mounted at the bottom of the barometric is even better but most consider one good enough.

347

Thanks for the reply Mark and Chris.
I don't get what your saying about a relief vent at the water heater. The water heater flue is 4" and about 18" long before it hit the 6" wye coming out of the chimney.
The boiler has a built in draft hood so I don't think I can install a barometric damper on it.
I'm just trying to get to the bottom of the problem that just started in the last 18 months. Everything seemed to be fine the 4 previous years.
Nothing has changed in the house.

ChrisJ

347 said:

Thanks for the reply Mark and Chris.
I don't get what your saying about a relief vent at the water heater. The water heater flue is 4" and about 18" long before it hit the 6" wye coming out of the chimney.
The boiler has a built in draft hood so I don't think I can install a barometric damper on it.
I'm just trying to get to the bottom of the problem that just started in the last 18 months. Everything seemed to be fine the 4 previous years.
Nothing has changed in the house.

I have a barometric damper installed with my drafthood on my boiler. It was part of an experiment, but ended up being left there just to help reduce the draft my 30' b-vent produces at times. It's really not needed, but since it was already there I left it.

However, barometrics reduce draft, they can never increase draft which is why I'm a bit baffled by the recommendation.

Perhaps @captainco or @Tim McElwain have a recommendation.

Charlie from wmass

I think you're onto something by clocking the meter. Has anybody sent a camera down the liner?

347

No camera, but the chimney guy looked down and it was free and clear. I looked into the base and it was free and clear. I leaning toward semi clogged sections. Gotta start somewhere.

ChrisJ

347 said:

No camera, but the chimney guy looked down and it was free and clear. I looked into the base and it was free and clear. I leaning toward semi clogged sections. Gotta start somewhere.

My original chimney was small, had a 4x7 opening and someone had jammed 4 separate sections of 6" liner in it. It didn't draft good, and was very clogged in spots and absolutely impossible to clear.

You couldn't look straight down mine though as there was an offset in the attic.

EBEBRATT-Ed

make sure flue pipe is not pushed to deep into the chimney. check venting chart to see if the water heater vent can be reduced in size.

When the flue come up from the draft hood how far does it rise up before it turns toward the chimney??

347

Ed, The chimney liner has a capped tee in the chimney. It has about 30" (including the 6" wye) of 6" coming out of the tee. There's about 10" of 6" smoke pipe off the vent damper then goes right into a 90 and into the 6" wye.

Mark Eatherton

Chris, I should have used the term "Draft REGULATOR" and the term SPILL switch. My bad. The draft regulator, when the appliance is in the OFF condition, AND it is properly adjusted (weights) will regulate the draft conditions in the chimney (metal or otherwise). To the OP, you will have to block off and or eliminate the existing relief vents on both the boiler and the WH when you install the draft regulators.

A word of caution, and I am sure that Jim and Tim will concur. If you choose to do ANY of these recommendations, you are modifying the appliance outside of its approved application, and you therefore are responsible for and assume all liability for any dangerous situations that might occur.

Quite honestly, if you are not certified and qualified to do this work, then don't. Find a person who IS properly trained to handle it for you. Qualified people can be found at https://www.nationalcomfortinstitute.com/pro/index.cfm?pid=1072

Sorry to be so blunt, and I have been through the certification process, but I can't tell whether you are a licensed professional who is qualified to do this type of work, or not.

ME

347

Mark, thanks for being so blunt. I'm a licensed professional. I do not have a lot of experience with matters of this nature, but always tying to learn. I will look into that Web site.
Thanks

Mark Eatherton

Glad to hear it, and glad you are here to learn. As the name implies, we are here to help. Just don't want to get anyone into trouble, and when dealing with things that can and do kill people, caution becomes even more important.

Safe travels and never stop learning. If you get a chance to attend one of Jim Davis (Cap'n CO) classes, or Tim McElwains classes, by all means do so. Money well spent in either case.

ME

captainco

As Mark was saying barometrics need to be added in place of the drafthoods and the drafthoods need to be eliminated.

Drafthoods are designed to prevent appliances from venting and totally eliminate the control of combustion air to the burners.

Barometric connect the flue to the equipment and control venting and combustion air under all variable conditions. Barometrics when set up correctly do not allow dilution air into the flue until all the flue gases go out first. A drafthood does just the opposite which is stupid. Barometrics minimize dilution air whereas drafthoods maximize it.

Spill switches needed to be added to the barometrics which will shut the equipment off if the flue gets restricted or there is severe negative pressure.

As Mark said, it really requires someone who has the training and knowledge to do this or at least consults with us that do. I personally started eliminated drafthoods from appliances back in 1979, not necessarily for this type problem initially but this ugly problem showed its face very soon.

Flue restrictors are only recommended when used with barometrics and then only if draft is always in excess of -.05" or higher 12 months a year.

Charlie from wmass

@347 if it worked for 4 years what lchanged. I know it has always had a draft hood so that's not the issue. Clean the boiler, but clogged section would cause the roll out switch to trip not the spill switch. Over firing can cause your issue. Is it the same water heater?

Charlie from wmass

If that is the problem. I have not heard it said that the boiler room was very hot go back and read the other posts.edit the Spill switch tripped even with a window open to the boiler room

ChrisJ

@347
Would it be possible to have some pictures of the chimney and the connected appliances along with their flue piping?

347

Charlie, water heater is the same. I realized that cleaning will not solve the draft problem.

Hatt, did not think of the knock out plug. Will look into that when I go back.

Chris, I will take pictures when I go back just don't how to upload them onto the site.

Boiler room really never gets hot. The roon is roughly 13' x 28' with a open doorway and 4'x4' opening into the other side of the basement (same size).

Thx again to all

ChrisJ

347 said:

Charlie, water heater is the same. I realized that cleaning will not solve the draft problem.

Hatt, did not think of the knock out plug. Will look into that when I go back.

Chris, I will take pictures when I go back just don't how to upload them onto the site.

Boiler room really never gets hot. The roon is roughly 13' x 28' with a open doorway and 4'x4' opening into the other side of the basement (same size).

Thx again to all

Just drag the file into this window if you're on a PC. It'll upload it into the message.

Not sure how to do it on a phone.

347

I have a tablet, not sure either.

347

Hello All,
Here is an update.
When back to the job and took some combustion reading while on the phone with David from NCI (thanks for the recommendation ME) and all the numbers were in normal range. The draft for the boiler were -0.02 while running and jumped a little when shut-off. Spoke to Burnham about the spill switch and got a little lesson the inner workings of it along with the temperature its designed to shut off at. Used my meter to check the ambient temperature near the spill switch and it started at 98 while the boiler was running and went up to 168 when the damper shut-off, which is all below the 200 or so its designed to shut-off at. All seemed fine until I heard the auto feed come on and did some investigation. Was a little surprised to find the boiler has a hole in it.
Not sure if that could have something to do with spill switch but who knows it might.
Need to replace the 7 year old boiler.
I'll keep you posted.

Charlie from wmass

Yes the products of combustion plus steam would overpower the chimney and you found your culprit

347

Charlie, I hope that is the cause. I never would have thought about a leak in steam boiler causing that kinda of problem. Let's hope that's it.

j a_2

@347. Good find on the leak...Prior to that Iwas going to suggest relocating the spill switch..on the boiler..Depending on the water heater model you have there They are protected by a TRD...Is the venting configuration correct......smaller over the larger...I would never ever suggest modifications on the venting, unless approved by manufacture, liability far out weighs gratification....