On Oct 24, 10:22 am, dgk wrote:
Does the need to vent a gas water heater get factored into the
equation? Having learned a bit about water heaters in the last few
days, I see that the vent from my current heater (4") goes off to the
chimney. But, unlike the one from my furnace, this one has nothing to
stop warm air from exiting all the time. (The furnace has a shield
that opens and closes as the furnace cycles. In fact, one cold winter
day I found out that the furnace wouldn't fire because a bird had
flown into and blocked that mechanism. I soon had that cage thing
installed on the top of the chimney.)

Since the vent is not sealed to the water heater but sort of sits on
top with an opening of about an inch around it, it seems that warm
house air is free to move out and cold air is free to come in.

I'm guessing that the air movement is pretty static unless the heater
is on. The vent is at the bottom of the chimney and so is protected
from direct winds. Still, after insulating everything in the house to
hold down heating costs, a direct passage in and out is a little
disconcerting.

Sure, its a vailid factor. Of course, it depends where the WH is
located. If it's in a basement, which is more typical, then this is
less of an issue than if it's in a living space. How big of an issue
is questionable. In any house, you want some air exchange and most
rely on some leakage, as opposed to using a heat exchanger.

Along the same lines, what about the air that moves up through the
water heater even when its not burning? I would think that's one of
the major standby heat losses, unless the flue up the middle is
insulated from the tank around it?

The solution, of course is one of the new high efficiency WH that are
direct vent.







As an aside, I'm putting in a Carbon Monoxide detector. I never
bothered before because the furnace has an automatic CO shutoff and I
didn't think of the water heater as a potential source for CO; I
thought of it more as the vent from the electric dryer. That thinking
has changed. Obviously it is no where near as dangerous as the
furnace, but not to be taken lightly either.

Hmm. There is another thought. I wonder if I'd save money by
installing a gas dryer rather than an electric one? Probably not
enough to justify replacing a working dryer for over $600.

In most areas, gas is cheaper as a fuel than electric. But for a
typical family, I wouldn't replace a working AC one with gas with the
idea that it's going to pay off.