High efficiency hot water heater

Then consider a Lochinvar boiler with the approved venting configuration on page 35, Figure 5-9: http://www.lochinvar.com/_linefiles/KBXII-I-O.pdf It’s a cheaper install.

Master Plvmber

in Plumbing 11 years and 7 months ago

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hawaiismurf | 11 years and 7 months ago

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I am looking at a high efficiency condensing gas-fired hot water heater, which gets a ConEd rebate. I understand that NYC code requires venting exhaust to the roof (even though the equipment has provision for sidewall exhaust) My question is, should I also draw the intake air from the roof (40′) or have the intake air come from the sidewall (10′) via a 3″ flue? I am assuming the shorter flue for intake will be more efficient (in addition to being less costly than installing a 6″ double ‘b vent’ all the way to roof)? Thanks!

Master Plvmber | 11 years and 7 months ago

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Isn’t your installer working this out? There are too many variables for someone here to tell you what your best option is. This statement confuses me: “I am assuming the shorter flue for intake will be more inefficient (in addition to being less costly than installing a 6? double ‘b vent’ all the way to roof)?” Where are you using 6″ b-Vent? Is that your chase to the roof which will contain your 3″ exhaust? If so, that’s your fresh air too if you use a boiler that allows you to pull makeup air through the chase.

hawaiismurf | 11 years and 7 months ago

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Hi Master Plvmber. Thanks and Sorry to cause confusion – I typed ‘inefficient’ rather than ‘efficient’. I have edited the original post. I guess my simplified question is – in general, is a shorter intake air path a better way to go than a longer intake air path, in terms of water heater performance? ie, if I have the option, should I draw my intake from the garden 10 feet away rather than from the roof 40 feet away?

Master Plvmber | 11 years and 7 months ago

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It won’t make a difference. The boilers’ published ratings are at the maximum venting distances. Only when those maximums are exceeded does efficiency loss begin. On that note, installers tend to think boilers won’t work if that precious venting maximum is exceeded, but the fact is that manufacturers and NYC inspectors don’t allow it because it makes their published ratings wrong. In most cases, you can adjust your combustion and exceed the maximums, just get comfortable losing some efficiency points at the highest output. But again, how are you planning to run the exhaust from the boiler to the roof? Through the old chimney? Through a b-Vent chase?

hawaiismurf | 11 years and 7 months ago

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Thanks Master, Exhaust to the roof will be through a new 3″ exhaust flue, or a 6″ B-vent w/both exhaust+intake. (that’s the decision I’m trying to make) The old chimney us not usable.