How often to clean a gas boiler chimney flue?

bipbap

We've never had the chimney flue cleaned in the decade we've owned the building.
We have a gas-fired steam boiler and a terra-cotta lined flue in a brick chimney.
It's a multifamily building, 3-story brick.
How often should it be cleaned?
I've heard some people say yearly but I'm not sure.
Any thoughts? Thanks in advance!

Jamie Hall

It should be inspected yearly, when you have the yearly inspection and cleaning and adjustment of the boiler (you do do that, don't you?). If the boiler is burning clean, it may not need to be cleaned more than once every few years.

bipbap

To be honest, no we don't do a yearly inspection/cleaning/adjustment of the boiler. A guy from the insurance company comes out once a year to do an inspection but it's like a 5-minute long look.
Is there any way I can tell if it's burning clean?
I'm happy to have a pro in, but I wish I knew what to look out for or how to know what that visit should look like so I know I'm not getting ripped off by a guy who fiddles with a few things and then gives me a $400 bill (which I think we had happen to us once before in a previous home).

STEVEusaPA

What @Jamie Hall said.
A reputable hvac company will do a full system/safety check, and check combustion with an analyzer.
Check chimney at that time, but it probably never needs to be cleaned.

Jamie Hall

Where are you located? We probably know someone reliable...

The boiler should be cleaned once a year, even with gas, and the burners should be adjusted for best efficiency and combustion; that takes special measuring instruments. Since you mention that this is steam, they should check the low water cutoff(s) and pressure control(s). All this takes time -- and knowledge. We don't talk price here, but the work doesn't come free; that I can assure you.

The insurance company is probably only looking at the pressure relief valve and for obvious signs that the burner is way out of whack. They are interested -- and you can't blame them -- in being reasonably sure that you don't blow up or burn down.

bipbap

Sure I'm open to suggestions of local guys who know their stuff.
We're in Brooklyn NY

mikeg2015

I don't see why. It's never been done on the coal or gas fired boilers at the industrial plant I worked at, or the community college after that.

Cars don't need theirs cleaned either. Although they are much less efficient at combustion, and exhaust temps are much higher.

EBEBRATT-Ed

I would suggest calling a chimney sweep to check the chimney and an HVAC contractor to check "find a contractor" on the home page

Jamie Hall

Try @JohnNY or @EzzyT ... and there's at least two or three others who are good. Under "find an contractor"

On @mikeg2015 's comment... well, just because it hasn't been done doesn't mean at least an inspection shouldn't be done. And I might add that a car's exhaust is a totally different thing -- much higher gas velocities under pressure. Not comparable at all.

mikeg2015

Let me clarify...

Should you check for blockages? Sure. But you should have a flue cap with screen to prevent such issues. A visual check isn't a bad idea. but that wasn't the question. Do you need it cleaned? No. There's no significant byproducts of combustion in a gas fired system that could build up in the pipe.

It was never done at those facilities, because it's a non issue. If it was blocked, the pressure sensors would catch that.

All that being said, should a chimney or liner be inspected periodically? Yes. Good idea. Especially if aluminum liner or clay tile lined masonry chimney. Less critical on a stainless steel flue or liner.

KolinFarel

I have a home from 1885 with a very large, unlined chimney (at least 18″ square) that currently serves my oil furnace and gas water heater. I would like to put in a wood stove and was hoping to use some of the space in this oversized chimney for a flexi-steel liner. I have seen conflicting statements about whether I could just add one liner for the stove only, leaving the other two appliances as they are, or whether I need to get a separate liner for each one.

Obviously, I’d like to pay for only one liner, but I don’t want to do it if it’s unsafe. I can’t, however, figure out why I would need three liners.

Any thoughts?

STEVEusaPA

You should start a new thread, maybe Erin can move it to a new thread.
You can't fire oil and gas into an unlined chimney by code, so don't even think of adding the wood stove.
If you can drop one liner you can probably drop 3, properly sized, but I don't know if that is legal off the top of my head.

mikeg2015

I don't see why dropping 3 liners would be an issue at all. But leaving one unlined could cause problems. Make sure you seal the top of the chimney too. All that trapped heat will radiate a surprising amount back into the house, and keeping the liners warm will reduce condensation.

Bob Harper

Per NFPA 211, all chimneys should be inspected annually. If it needs sweeping or repairs the inspection will reveal this.
No, each woodstove must vent into its own separate flue and liners are not tested nor listed for use ganged in an unlined flue.
Being multi-family increases your liability and makes it a commercial application. Check with your state to see if they require a state boiler inspection. The presence of some terra cotta tile in a chimney does not make it "lined". The chimney must be suitable for the class of service. While gas fired appliances typically do not require sweeping, they do very often rot the inside of the flue requiring relining. Chimneys are also often relined for sizing purposes. Here pros will disagree but the bottom line is the chimney must work. To prove that requires a combustion analyzer and proper draft gauge operated by someone certified to use them.
Install Unlisted low level CO monitors in each apartment regardless if you have code required UL listed CO alarms, which are junk.