On Jul 4, 10:51 pm, "Edwin Pawlowski" wrote:
wrote in message

A week ago I installed a big attic fan to draw the hot air out and
cool the house and I have observed the fan interfering with the
updraft of the water heater by performing the following test.
Any thoughts, comments, suggestions, or discussion would be great.

Yep, it is a real concern. CO poisoning is not because the gasses are
quickly drawn up and out of the house, but you still don't want the flue to
be reversed.

Before turning the fan on, be sure there are plenty of other openings to
draw air through. Open the windows and a screen door so that a minimum is
the same size as the fan opening. If possible, close off the area with the
water heater so it cannot suck air from there. You can always add another
vent so the heater can get a supply of outside air for combustion.

We left our teenaged children at home on evening and my daughter almost set
the kitchen on fire with a smoking overheated pan. They got that out so my
son figured he'd ventilate the kitchen with the whole house fan. The oil
burner was running and it was then smoking up the house as the fan drew
through the flue, the only opening in the house. By the time we got home,
the fire trucks were gone and everything was back to normal.

Wow. That sounds like an experience. Since it was winter the house
was sealed and you must have gotten a lot of backdraft.