Originally Posted by
David Samloff
David, there is no additional outside air in the system, other than what will be infiltrated into the home. The negative is a potential problem that we proposed to the buyer.
As far as combustion testing, this is a little beyond our scope and may only become evident after an extended period of heating, several hours possibly.
The cheapest solution for these homeowners David is a fresh air duct to the return plenum with a weighted damper setup on the duct then adjusted to bring the main building envelope to a slight positive or neutral pressure depending on location.
A one pipe system done this way will actually work more efficient & safer than a two pipe system.
The combustion testing would more than likely reveal the problem withing 15 minutes if the one taking the readings knows how to interpret them.
Good luck.