Steel chimney liner req'd for water heater only?

Jen_3

Hi everyone -

This forum has really been helpful in helping me figure out what to do about my boiler. I've talked to a number of plumbers and heating contractors and am now convinced that I need a new boiler. I've received 5 estimates and am getting the last one tomorrow. One reason for differences in price is that some are replacing everything - all pumps, valves, etc and some are only replacing the boiler. The other difference is how the boiler's exhaust is handled (if I'm understanding correctly). Some contractors want to vent the boiler with power combustion make-up air, which one guy called "fan in a can," and some want to go through the chimney. The boiler is in an unfinished basement that has a large 40' by 25' footprint, but has a very uneven floor and is low in places (around 5'). The current 25yo Weil McLain is vented through the chimney. The contractors that want to go through the chimney want me to install a steel liner. However, one contractor wants to both install power combustion for make-up air and also put in a chimney liner - does this make sense? If this is the "right" way to do it to prevent CO poisoning then I want it done, but I would save quite a bit to go with the contractors that don't think I need both. The contractors that don't want to put in a steel liner are venting the new boiler through the side of the house - in my understanding (correct me if I'm wrong!) this means that the boiler is no longer vented through the chimney in any way. In either situation the hot water heater will stay in place and be vented through the chimney. I have a brick chimney - the top is finished with beautiful masonry work but no liner is visible above it. One heating contractor told me after pulling out the metal pipes connecting the water heater and old boiler to the chimney that inside is just brick, with no visible liner.

My bottom line question: If I use a contractor that will not add a chimney liner, am I risking CO poisoning or any other bad outcome by continuing to vent the water heater through the chimney if it is not lined? The water heater runs on natural gas, as will the new boiler. I'm moving in 4 years, so I'm trying to minimize costs.

Thank you very much for your advice!

Al Letellier

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Jen, it depends on a lot of things and where you live, and what the codes are. Here in Maine, it is illegal to vent an oil fired appliance into an unlined chimney. Also, if two appliances are vented into the same flue, the total square inch area of the flue must equal the SUM of the areas of both connections....so we have to watch chimney size as well as liner.
Power venting is venting out through the side wall of the house and may be your only option if the flue is not large enough for both the boiler and the water heater.
The "fan in the can" is a means of bringing in enough air to support the combustion process. It is not the only way of doing it. Getting as many quotes as you did is only confusing the issue for you. Pick 4, throw out the low price and carefully consider the high, if he's a reputable contractor. Highest price may be the best, but too high may not be the right way to go. Consider hiring an independent consultant or check with your local inspector about what is required before assuming that you are getting the right information. Good luck.

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Jen_3

Boston

Hi - Thanks for the advice! I'm just north of Boston, if that helps anyone advise me about the local code. The hot water heater and natural gas boiler were both vented through the chimney when we bought the house (and passed our home inspector). Jen

don_52

yes Jen..

and that would be fine as long as it's an atmospheric
boiler and water heater, with a stainless steel liner.

to confuse things further you've got two power venting
choices, one that addresses the water heater and one
that "sorta" does.

however with all these different option's before you
i'd get a "second set of eyes".( per above )

go to "find a professional" on the left sidebar, type
in your zip, find one of the "wall guys" offer to pay
him his service call rate to come out and help you sort
this out.

they can explain what can and can't be done, if it is
found that none of the above "is best for your place"
they'll trash em', potentially unsafe or marginal
installs really irk these guys, if they can help it
they won't let it happen.

be safe, don

don_52

yes Jen..

and that would be fine as long as it's an atmospheric
boiler and water heater, with a stainless steel liner.

to confuse things further you've got two power venting
choices, one that addresses the water heater and one
that "sorta" does.

however with all these different option's before you
i'd get a "second set of eyes".( per above )

go to "find a professional" on the left sidebar, type
in your zip, find one of the "wall guys" offer to pay
him his service call rate to come out and help you sort
this out.

they can explain what can and can't be done, if it is
found that none of the above "is best for your place"
they'll trash em', potentially unsafe or marginal
installs really irk these guys, if they can help it
they won't let it happen.

be safe, don

Bill_39

Make sure they get permits

If they get permits and it is in Malden the inspector will def make them install a fan in a can and a chimney liner

John Mills_3

Brick chimney?

With no clay tile liner, certainly line it. Should be lined regardless of what you vent into it. Today's equipment will risk serious condensation damage if you don't. Power vent equipment with no diluation air or boilers with dampers that let the chimney cool in the off cycle are the worst.

With a good tile liner, the 7 times rule of the National Fuel Gas Code comes into play.

The flow area of the chimney cannot be more than 7 times the area of the draft hood outlet. Most home water heaters have a 3" draft hood outlet, even if vented in 4". That's about 7 sq inches. Multiplied times 7 in the code, you're chimney cannot be more than 49 sq inches of interior area. Around here, most tile liners are 6.5 x 10" and a smaller liner is needed.