Am I crazy? Chimney company says you can reduce the flu.

2x_Tom · August 17

Call came in earlier this week for a co alarm going off. Eventually the blocked vent switch tripped on him. Chimney base was partially blocked and they closed off the makeup air vents in a small well sealed boiler room (pretty sure this was the biggest issue). Told him to get the chimney cleaned and pull the covers off the vents.

He had the chimney company come out, sell him a liner and take the covers off. It happened again and he called the chimney company who came back and "fixed it".

It subsequently happened two more times before he called me back. They never opened up the makeup air vents. I checked and there's almost no draft with the doors closed. Open the outside entrance and it's okay. Fire the boiler with the outside door open and it still spills out of the draft hood but not as bad. I figured maybe there's a bird or something on the damper they didn't catch so I pull apart the flu pipe.

All looks clear BUT they've gone and reduced the 8" to 5" just after it penetrates the wall. That's about a 66% reduction in flue size. 225k net natural gas boiler, pretty sure that won't work. I shut it down and told him to get the chimney company back out. They need to get him a bigger liner or pull it out. They're insisting it's fine and something is wrong with the boiler.

Only thing I can do on my end is put in a condensing or power vent and go out the side of the house. Or throw in a baby boiler that will draft up the 5".

EBEBRATT-Ed · August 17

Chimney company is nuts. There are instances where you can reduce a liner size if the chimney is high enough to produce more draft. Usually with a tall chimney you can go down 1 size. Going from 8" to 5" is a joke.

The customer should call the local building/plumbing/heating inspector, and they should get a complete refund from the chimney company and then either have them (or preferably another company) to install the correct liner.

Jamie Hall · August 17

And in the meantime, lock out the boiler before someone dies.

EdTheHeaterMan · August 18

@2x_Tom, you mentioned that you have a "255k net". the word NET is important, because that means something in boiler sizing. Input can be as high as 350,000 input. and there is no way a boiler with that much gas input can be vented in a 5" diameter flue pipe.

There are several BTU ratings on every gas fired boiler. there is the input. That number is how you size the gas pipe and the vent system. If you look at the PFG-6 boiler above, you can see that it has a 305k input number. Now look all the way over to the Net I=B=R rating of 215k. That is the Net number you are talking about if you are using the correct terminology. That boiler is slightly smaller than the 225 NET you stated in your original post. If you look at the last column on the ratings, that heater requires an 8” vent. So unless your chimney is over 50 feet tall, that 5” liner will not be able to properly vent that heating appliance.

If you can get the manufacturer's specifications on your customer's boiler, then you can show the customer where the chimney company is mistaken. Then you can let them deal with the problem. You gave them the proper info and you deserve to be paid for that information. The chimney Company is now responsible for getting the heater to vent properly with the work that they did and probably got paid for by now. If the customer used a credit card, they may have some recourse. Otherwise that chimney company will just walk away with the failed repair and keep the money.

I stopped recommending chimney professionals and just told the customers to just look in the yellow pages for chimney repairs. (Yellow Pages must be translated into Internet for today’s customers)

2x_Tom · August 18

https://forum.heatinghelp.com/discussion/comment/1862731#Comment_1862731

You are correct I misspoke. I should have said 225k input. The chimney is about 20', I didn't measure it. If they got 6" in there and opened up the makeup air vents I'm sure they would have got away with it.

They lined the open wood-burning fireplace in the house as well with a slightly larger liner. I'm sure they're in for an issue on that as well.

Fortunately these aren't guys I recommended. You are correct, they already got paid and don't want to do anything. With what they charged him he was halfway to a good mod con or 75% of the way to a cheap one.

I don't know why but it seems like most chimney companies around here are just thieves. I have one decent one I recommend. They're the only company I've ever seen gointo a house, inspect the chimney and say everything here looks fine. Every other one wants to sell a liner, they say the existing stainless liner needs to be replaced, they want to do a fireplace insert, boiler, something. Then they whip out all kinds of scary carbon monoxide stuff to scare people into doing the work.

EdTheHeaterMan · August 18

Even a 225K boiler needs a 7" diameter x 20' high vent. So, reducing from 8" to 7" might be OK but you have the right idea. That 5" is not going to work.

I would craft a letter with the statistics of the customer’s boiler and indicate that you do not believe that the 5" liner is adequate for the 225k input boiler (enclose the rating of the boiler) and send the letter by certified mail so you know that your customer received the letter. Give your recommendations in the letter and inform them not to operate the boiler until the problem is taken care of.

It should include statements like “I have made an inspection of this Make… Model number… Serial number… Boiler at this location and have determined that the carbon monoxide problem is a direct result of insufficient combustion air and/or inadequate venting. I recommend the customer have a competent chimney professional look at the venting system including the chimney and the combustion air requirements. After the work was completed by XYZ chimney company I was requested to inspect the problem again and discovered the work performed by that company has not solved the venting and combustion air problem . The 5“ chimney liner installed by XYZ Chimney company, may have actually worsened the problem."

You can also add that you said you are not a chimney man, you are a plumber and the venting system is not up to the specification that the plumber recommends, the manufacturer recommends, or the local authority having jurisdiction would approve.

"If you have any other problems with your heating system regarding carbon monoxide, please refer them to the XYZ chimney company, the local fire department, or the local authority having jurisdiction. As you can not create the needed venting and combustion air requirements within the job description of a plumber. You can only tell the other trades what the specifications and recommendations are for the equipment.” …Or something like that.

EBEBRATT-Ed · August 18

@2x_Tom

Don't know your location but in many areas "chimney sweeps" have to be licensed or certified or something.

I wouldn't get involved and it is good that you didn't recommend them.

It's the homeowner's issue and they should contact their building dept. I would go as far as sending the building dept the information, boiler size and input, chimney height etc and let them do their thing.

Maybe your state or location has a "consumer protection agency" that can help.

That chimney guy missed that day in school.

mattmia2 · August 18

there is also a table in the code that will say something similar to the table in the boiler instructions.

Bob Harper · August 18

These guys are on top of it. I would add to spec. a smoothwall ss liner so you do not have to de-rate it 20% for corrugated. Once done, perform combustion analysis to ensure proper function. If you get it fired up to 'steady state', whatever that means, take a draft pressure reading then shut off the gas quickly. If the draft rises stronger, the liner is undersized.

Make sure they put arrows on those passive MUA grilles so the air knows which way to go. Air is dumb and will observe pressure gradients. For instance, operating an open hearth fireplace could backdraft a borderline boiler.

Most fireplaces were built with undersized flues. To reline one, you need to remove the flue tile then install the properly sized insulated liner for a 2,100F rated installation. You are not required to insulate heater flues but consider whether its a cold exterior chimney vs. warm interior one. FYI, the sizing tables in the code are for interior chimneys only.

Am I crazy? Chimney company says you can reduce the flu.

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