Hanging a furnace from floor joists

[John Viercinski]

Hey all,

I was wondering if anyone has a forced air furnace that is in a crawl space or attic that is suspended from floor joists or other structural members. I'll be installing one shortly and the installation instructions simply recommend angle iron, but nothing about the details. Any pictures or instructions would be very helpful.

Thanks!

John Viercinski

[Brian Backner]

A relatively simple way to hang a furnace or A/C unit is to use 3/8" threaded rod. The rod can be attached to the joists with threaded hangers or through holes drilled through angle iron that in turn is bolted to the joists. Most furnaces designed for this type of installation with either have built in connectors or be easily converted for such use. The advantage of using the threaded rod is that it is very easy to adjust the final height of the furnace and level it. When doing such an installation, consider adding vibration isolation so the running furnace doesn't turn the floor overhead into a drumhead!

Brian

[Matt Meiser]

My Hot Dawg style furnace in my shop is hung from the trusses in my shop using 3/8" threaded rod. I used a few lenghts of 2x4 positioned above the bottom chord of the truss with holes drilled through them to accept the rod. I used large washers and double-nutted everything to ensure it will stay put.

I've seen a new construction industrial facility where they used unistrut to do somethign similar. In that case it was a more conventional furnace/ac unit and they had the furnace sitting on unistrut beams which were hung from the rod.

[mike wacker]

Matt,

Good call, Unistrut is the answer to a lot of this stuff. Expensive, but alot of electrical supply houses leave there bent pieces outside for the taking. I keep an eye out, ask first of course, but a bent 10 foot piece can leave all you need for stuff like this.

A little creative cutting and bolting can turn unistrut into all kinds of brackets.

[Ben Grunow]

Use these (lags with threaded hole in head for 3/8 threaded rod)

http://www.erico.com/products/hangermate.asp

and some vibration dampers to eliminate noise. There are also rubber pads about 1.5" square available to go between the unistrut and the unit. A good hvac supply house should have all of this.

[Matt Meiser]

I've seen Unistrut at Lowes too if you can't find it for free.

[Jim Becker]

Yes, the HVAC system for our addition is suspended from the roof rafters by threaded rod holding Unistrut supports under the unit.