How to install a High Efficiency Furnace

[letterman]

I'm replacing an old oil furnace due to a basement flood. I'm putting in a gas furnace instead and looking for a used one because I can not afford a new one. I was offerred a used high efficiency furnace that was removed from a building being demolished. It's complete with the sheet metal.

I have installed several of the older standard gas furnaces, but have never even touched a high efficiency one. Aside from running the pvc inlet and exhaust pipes outside rather than using a chimney, is there any differences or special concerns about installing a high eff. type?

Thanks

[Stormin Mormon]

Condensate drain.

Some come with a specialized thermost. The Rheem Contours I've installed, they need their own stat, and five conductor thermostat wire.

[Big Bob]

That's because the have a special transformer and run on 87.6 volt line voltage.

[Colbyt]

The only two things you need be concerned about is the exhaust venting and condensate.

Even with the fan forcing the air there are limits on the number of els and elbows. Of course the path should always be up as with a regular vent.

You will also need a place to drain the backflowing condensate (slightly acidic water). This may require the installation of a pump if you do not have a floor drain and the unit is in the basement or crawl.

Colbyt

[Bill]

Get an installation manual from the manufacturer. They also have service manuals. Usually all the owner gets is an "owner's manual", so no one knows these other manuals exist!

[ilbebauck]

In addition to the other tips....once the system is up and running, set the blower speed to be within the temperature rise range listed on the furnace sticker . When you install the exhaust and intake PVC Piping pitch it at least a 1/2" per 10' length toward the furnace so the condensate will run back to the furnace mounted condensate trap, make sure the condensate from the furnace and Piping is trapped with water before starting up, and when youre running the PVC pipes....rough-up all pipe ends and fittings and use PVC Cleaner before applying the PVC Cement ; this is important so you get the strongest leakfree joint possible since youre dealing with CO . At the termination point outside (for the Pipes), dont allow the exhaust gas to go into the intake pipe --- seperate them by at least 15" pointing in opposite directions. Also be at least 15" above the ground if you live in a snowy area and be 4' away from any windows and doors with your Pipe terminations. Seal around the pipes that come thru the outside wall.