FURNACE FLUE CODES ON 90%

[robertdelamater]

HOW FAR AWAY FROM A WINDOW SHOULD A 90% FURNACE BE, FLUE COME OUT RIM JOIST

[Jerry Peck - Codeman]

Hi Robert,

Do you have the manufacturer's name?

Those all come with very specific instructions and each, while similar in many ways, can vary in some other ways.

I'm sending a note out to a person who may be able to provide a more detailed answer, but it will come down to what the manufacturer states in their installation instructions.

The other person will, hopefully, have time to respond within a day or two, sometimes he is very busy.

[Hearthman]

As with ALL appliances, your best answer lies with the manufacturer's listed instructions. You cross-check this against the applicable codes in your area then apply the more restrictive elements. For instance, the IRC would require such a vent be 4' away from mechanical air intakes and 12" above grade. However, in Mass., you would also need to terminate at least 4ft. above grade OR higher if that side of the building is prone to snow drifts.
The listing will deterimine the maximum vent run, number of offsets, pitch, etc. Especially important is the termination. Some leave it rather simple while others are rather explicit in their requirements. When you have a mfr. stating very specific requirements, follow them to the letter. This is because:
a) he spent a LOT of time and money testing this configuration
b) it is probably in response to one or more incidents where this was found to present a problem

These systems have to be balanced to work properly. Failure to abide by the listing could result in anything from diminished performance to outright failure of the unit. For example: you modify the venting outside the mfr.s listed instructions. The unit can no longer breathe as designed. The unit runs hotter than designed yet cool enough not to trip the high temp. limit. You burn out the heat exchanger prematurely, which could lead to loss of performance and even carbon monoxide exposure.

I'm sorry but there is no one general answer other than refer back to the listing and codes.
HTH,
Hearthman

[Jerry Peck - Codeman]

Hi Hearthman,

Thank you for taking the time to respond so quickly.

Your information is much appreciated. Hopefully the information will be of help, however, Robert will still need the manufacturer's name, model number, and their installation instructions as you said.

Robert,

Once you have the manufacturer's name and the model number, the installation instructions should be available online, with that additional information we can provide additional clarification to answer to your questions of how far from the window (clearance to openings in the building) and how far from the rim joist (clearance from combustible material).

Looking forward to the manufacturer's name and model number.

Thank you,

Jerry