Air handler support

[peterk2]

New construction has the air handler set on styrofoam blocks in a drain pan that sits on plywood that is set on the bottom chord of the truss. No attachment to anything. I can move the handler if I push enough. No walkway or platform. Unit has a drain pan and a water level switch. Builder is telling me all is OK. Installer says all is OK. What gives?

PeterK

Argyle Home Inspections

Download Attachment: IM000134.JPG

539.37 KB

[mgbinspect]

That's a pretty typical installation here except for the lack of access part. It really can't go anywhere unless someone pushes it and the ductwork serves to keep it in place to some degree as well. I can't imagine that weight would require a load bearing bottom truss cord, but I could be wrong. I certainly wouldn't loose any sleep over it.

We always suspended our air handlers to minimize interior noise and vibration.

[Chad Fabry]

It's wrong. It shouldn't be on stryo foam and more tha likely it should be hung from the truss, not resting on the bottom chord.

[mgbinspect]

"When installed in attics, they are normally suspended by cradles that are attached to the rafters of the structure itself" - Residential Construction Academy - HVAC - In partnership with the Home Boulders Institute.

I do see air handlers on very dense Styrofoam about the size of modular bricks. They appear to be made for the purpose, but I don't know. It seems they'd offer a bit of sound dampening.

It is curious, though, that no one ever says anything about an air handler or furnace standing up on metal ductwork in an attic directly on the floor framing. What's the difference? I don't get it?

We each must choose our battles. I typically leave that one to the HVAC installer and the county. But, that's just me. With new home construction I tend to stick to the rediculous stuff like: Waste lines draining up hill; gaping holes in air handlers and ductwork; missing GFCI protection; top wall plates not lapped at corners; missing nail plates in framing; or that front porch I posted about a month ago, etc. Things that are dangerous, terribly inefficient or aren't going to function as intended. I don't try to re-design the house.

To my way of thinking, a good New Construction Inspection even serves the builder. It's really an exercise in making sure that even he got what he paid for out of his subs! In example: The plumber reduces the flexible central return duct volume by 30% to accomodate his waste line and doesn't inform anyone that he had to do such a thing. (Now, there's a real case for the value of Design/Build construction. When you have your roofer and mechanical subs at the table with you during the design and pricing phases, a lot of that kind of silliness is avoided!)

I suppose I'm in the minority on the subject of new home construction inspections, but I feel pretty strongly about it. When I begin, I make it clear to my client that cosmetics and preferential stuff belong on their punch list. I'm going to make certain that the construction and installations are acceptable. And, for what it's worth, in probably 800 or so new construction inspections I've NEVER received a single complaint. Is it possible that we are sometimes too hard (picky) on builders?

I have always liked suspending them in attics and eaves and that's what we did in our homes for sound purposes. And, for the same reason, we DIDN'T suspend them from the floor system. But we were doing Custom Design/Build homes and you paid dearly for just about everything we did throughout the house. (We even back primed all of our exterior trim and mitered and scrolled every trim joint throughout the house. Our floor joists were always on 12" centers and often a size up from what was required. You NEVER see that stuff anymore and the fact is building that way IS EXPENSIVE! When one of our homes was re-sold the listing agent was always sure to mention that it one of ours.)

It's pretty hard to make a tract home Builder on a tract home budget make a primo custom quality home. Homes these days seem expensive, but it's all relative. If a tract home is going for $375K a Primo Custom home's going to cost $425K+ for the same square footage and what we're talking about right now is one of the reasons. These big "expensive" tract homes are simply glorified VW buses! They are a far cry from the Cadillac.

I suppose it would be nice and helpful to recommend it be suspended for sound and vibration purposes.

(Whew! I'm thankful not to be in the home building industry today. I'd probably be running a lot of home inspectors off the property with a shotgun.)

[Jim Katen]

Originally posted by peterk2

New construction has the air handler set on styrofoam blocks in a drain pan that sits on plywood that is set on the bottom chord of the truss. No attachment to anything. I can move the handler if I push enough. No walkway or platform. Unit has a drain pan and a water level switch. Builder is telling me all is OK. Installer says all is OK. What gives?

PeterK

Argyle Home Inspections

It needs a work platform in front of it and a walkway to get to it.

It doesn't need to be secured particularly well. It looks like there's a hanger strap supporting the plenum at the lower left corner of the picture.

The foam blocks are a good idea. The AHU should be suspended up off the bottom of the pan with something that doesn't rot. PT wood blocks, rubber blocks or dense foam are all fine.

The weight of the unit isn't going to hurt the trusses.

- Jim Katen, Oregon

[peterk2]

Thanks all for your help and insights. I hope that I can return the favor in the future.

[hausdok]

Hi Peter,

Good to see you here. Someday, someone is going to have a question about hot water or steam heating systems and you're going to be right there to help them get smarter. That's why TIJ is here. Just a family of like-minded folks talking and helping each other work things out.

ONE TEAM - ONE FIGHT!!!

Mike

[Bill Kibbel]

I would question whether the two trusses were specifically designed to support a furnace on the bottom chord. I don't see as many trusses as most HIs, but I know if the bottom chord is a 2x4, it probably wasn't intended to carry any more load than drywall. Ask the builder to provide the truss design drawings, which are required to include the design load of the bottom chord.

[Bill Kibbel]

R802.10.4 Alterations to trusses.

... "Alterations resulting in the addition of load (e.g., HVAC equipment, water heater) that exceeds the design load for the truss shall not be permitted without verification that the truss is capable of supporting such additional loading."