Direct vent side wall intake on different wall

mpage

I'm looking to have an HTP uft-80 installed. This unit will head a radiant floor in the basement and garage. The forced air furnace for the main house is vented out a north wall and the intake is on the west wall. I looked at the HTP manual and didn't see anything stating they should be on the same wall. I did see the following not about being the same height, which they would be in relation to the boiler, but not to the ground as the ground drops off towards the back (west wall) of the house. It would be easier to have the pipes run the same way as the current furnace, but should they be on the same wall?

"The exhaust vent and air intake terminals must be at the same height and their center lines must be spaced apart 1 foot minimum."

Jamie Hall

I can't think why they need to be on the same wall.

deadmansghost

I have had the experience on an installation where the sealed combustion tubing was installed on opposite walls of a small commercial building. On a day with a strong prevailing wind upon either the exhaust tubing side, or wind in the opposite direction upon the air inlet tubing interfered with pilot ignition and on a real bad day caused changes in the combustion readings also. we reconfigured the installation to manufacturers specification of the correct height and spacing on the same wall and the trouble went away. This job was 5 years ago the appliance is still operating.

SWEI

Hatterasguy said:

I can't think why they need to be at the same height.

Early mod/con boilers (Giannoni-based) required that their inlet and outlet pipes be located in the same pressure zone. High winds could make them go bonkers otherwise. I was told at the time it was driven by some sort of limitation in the capability of the blower or its controls.

SWEI

Imagine intake and exhaust located on opposite sides of a building corner. Now add a 40 MPH wind blowing parallel to one wall, towards the corner. You get fairly significant (with respect to gas pressure) positive pressure in one pipe and negative in the other.

Jamie Hall

SWEI said:

Hatterasguy said:

I can't think why they need to be at the same height.

Early mod/con boilers (Giannoni-based) required that their inlet and outlet pipes be located in the same pressure zone. High winds could make them go bonkers otherwise. I was told at the time it was driven by some sort of limitation in the capability of the blower or its controls.

Now that does make sense. Hadn't thought of that...

ced48

Lochinvar still insists that they be in the same pressure zone, must be on the same wall.

Tinman

Most Category IV units that I've installed, furnaces and boilers, require same pressure zone going all the way back to when Category IV's first came around.

Mike

Used to be the intake and exhaust had to be equal in lenght. Now, you need not have to run terminate the intake outside. But the reps keep stressing the fact of pressure fault trips. Go figure. And the pipe sizes are smaller. I would contact the manufacture rep to be sure.

Tinman

@Mike - I have no problem with disagreements but not sure how someone can disagree with the installation instructions of units that I have read, installed. I, being the operative word.

Mark Eatherton

Most of the modcon post mix blowers on the market come from the same source, EBM Pabst).

They use a "Hall pulse" detector to verify that the blower is operating at the speed the controller is asking for. If the intake and exhaust are not on the same pressure plane, and a wind is loading, you will most probably get a "Fan Speed" error code due to the blower turbine effect which can be over or under the required speed, and the boiler will lock out.

And as noted, it will mess with the combustion numbers. Avoid placing terminations in an inside corner or alcove too.

Follow the manufacturers instructions, and before you void your warranty, run the question by the manufacturer and get their response in writing for future reference. They have a lot more experience in this area than most people think...

ME