Re: [GBlist] Gas-fired tankless water heaters?

["mac12" <tomthomas@uswest.net>]

A note of caution:

As we work harder to seal buildings for energy efficiency (or perhaps to 
reduce radon infiltration), we run the risk of not having a source for 
combustion air.  Picture a perfectly sealed basement with a furnace 
using room air for combustion.  You would have a bad case of negative 
pressure in the basement which would prevent combustion products from 
exhausting up the flue.  I recently spoke to one woman in New York state 
who had just this problem which manifested itself by high levels of 
carbon monoxide in the basement.  Fortunately, our detector alerted her 
to the problem.  Certainly building code or good building practice 
should have prevented this.  Yet not only was this new construction, it 
was new tract construction implying that there were many homes with the 
same condition.  Finally, her repeated complaints to the builder 
resulted in an examination of her furnace and replacement of the heat 
exchanger!  Not quite the correct remedy.

Tom Thomas
Macurco, Inc.
"Gas Detection"

snip...

> 
> The direct vent model IS sealed combustion.  It requires one wall
> penetration for both inlet and exhaust.  There is an alternative using room
> air exhausting up a flue.  Electrical water heating is a bad idea because of
> the poor power station efficiency.
> Malcolm
> 
> 
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