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Removing boiler from external chimney

cgw
cgw Member Posts: 42
in THE MAIN WALL
A very common situation except that it is a commercial building (college dorm).

We are replacing boiler with a high eff. wall direct vented boiler. So the existng  atmosphereic 750MBh domestic water heater will remain on the external masonry chimney by itself. I feel I need to check the size but am not sure of the criteria.

I do not know the chimney size (I can guess at 18-24" square).

There is a 24" dia. breeching about 6' long. The water heater vent is connected to that. The total hieght is maybe 35'. The vent connector rises about 8'.

Anyone know anything to help out?

Comments

  • Charlie from wmass
    Charlie from wmass Member Posts: 4,373
    The gas code has charts

    Here in Mass the exterior chimneys need to be properly matched to the load. If the chimney is way over sized it needs lined down to the correct size.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
    https://heatinghelp.com/find-a-contractor/detail/charles-garrity-plumbing-and-heating
  • Jack
    Jack Member Posts: 1,049
    Best practice

    Is to line the chimney anyway. An exterior chimney jsut about never warms up enough to draw well. As well, the ignition and initial draw of the chimney is poor. This is especially so in the event of signficant oversizing and therefore short cycles.
  • cgw
    cgw Member Posts: 42
    Other options

    Does anyone even make a 12" liner?

    Maybe it would be better to just put in a sidewall mechanical vent and just close off the chimney?

    Probably the best bet would be to just replace the aging water heater while we are at it.
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