Like great "Out of Business!" sales and old tires, a direct-vent furnace is supposed to BLOW OUT!
You know, blow-out sale, a tire blow out and furnace venting. Blow out.
But what happens when, with a direct-vent furnace - it's not a blog out, but a blow in?
Observing that bell-shaped thing a home inspectors knows that it is the furnace vent. The first things I do when I enter a house is turn on the dishwasher, and crank the HVAC up or down.
This house has a high-efficiency, condensing-gas furnace. They are wonderfully efficient, in their fifth generation or so (the bugs have been worked out), and while expensive they are popular.
Most furnaces, like mine, send a huge portion of their heat up through a metal flue that exits the roof. They take their oxygen to burn from inside the house. By comparison to the condensing units they are not very efficient.
These condensing furnaces are set up to draw in fresh air from outdoors, so they aren't taking so much oxygen from the house for combustion. Then they burn the exhaust more than once, so what blows out is cool enough you could blow-dry your hair with it. You might not want to as the exhaust is full of CO, don'tcha know.
The associated tubing is PVC, which is not able to take much heat, so you know what blows out is pretty cool, about 105F.
The exhaust is supposed to blow away from the house, out through that round hole at the end of the bell (or Mercury space capsule, depending on your generation). Because of that set up these vents are allowed closer than 4' to a window.
The intake air is supposed to be drawn in from the base of the bell, near the siding.
But look at this photo! The siding is wet with condensation! When I felt it I could feel the heat blowing against the siding. And the end of the bell was drawing air in!
IT'S SET UP BACKWARDS!
The house is heating, so my initial fear that it was plumbed incorrectly at the unit was quelled somewhat. But I thought to check with a couple of other home inspectors to get their takes! They are two that are familiar with this system, and both said it was probably arranged backwards near the exterior of the house.
That is where the Y-shaped connection would be located, combining intake and exhaust for proper in and out.
Covered with drywall I could not see it.
- How the "HVAC professional" got that connection backwards is beyond me!
- Why they didn't notice this when the "HVAC professional" installed and "tested the system" is beyond me!
- Why this was never noticed before by a home inspector is beyond me! (Maybe the house was only inspected in the summer?)
So, I did the only thing I could do - suggested that the buyers have another "HVAC professional" look at it! Only this time, get a real one!
My recommendation: sometimes when a home inspector sees something he's not seen before it is easily diagnosed. Sometimes a circumspect home inspector checks with others. Doing this can be a Best Practice! Either way, a home inspection is to test everything and see if it's operating correctly! This system is not. And was so identified.
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560