HVAC Help Please

I have been inspecting numerous new homes that have the air handlers located in the attic space. The AHU are suspended from the roof trusses with metal straps at each corner. The straps are installed behind the AHU casing. I cant see how far down the straps are connected because they go into the casing/shell.

The code says strapping shall be at points within the upper and lower one-third of the AHU vertical dimensions.

I am not sure if I understand the code properly where it says the upper and lower one-third.

Any explanations would be appreciated, thanks in advance

Strange strokes for different folks???

Your question is fairly cut and dried must have four straps and can be located within the first 1/3 of the unit as measured from each end. Stay out of the middle section or you will have a Teeter Totter.

What has got me scratching my head is where you state the straps go into the casing/shell. I don’t follow.

This method of hanging a furnace or are we just talking AHU; no furnace is alien to me always in this area we mount on a platform

How about some pic’s


Thanks for your reply.

I’m doing these inspection as QA inspections for a builder. He said the AHU “ONLY” have the upper third supported and not the lower third.

The AHU are suspended from the trusses with metal factory straps at all four corners connected to the units.

I’m not sure what he means when he says they do not have lower third support. What would be the lower third support he is refering to?

As far as the straps going into the casing, I mean the straps hang from the trusses and run down to the interior side of the unit, not along the exterior. I cannot see where the straps actually attach to the unit. They penetrate into the shell of the unit.

I really cant think of a way to describe it. I wish I had a pic to download.

Hope this explains it any better

Thanks again

I am drawing a blank being you are in Fl. are we describing just a Ahu or a furnace/ahu there is a big difference.

If the unit what ever it is has straps installed on all four corners I do not see the problem.

It’s a split system with the air handler unit in the attic.

They appear ok to me. The builder said the units only have upper third support and not lower third support as required.

Matt I am having communication problems here.

Does this split system have electric heat, gas heat or is there no heat and just a fan section (AHU)

I could see where this unit might need 3 sets of straps to hold a complete system two on the heating section/blower section and one on the A-coil section. Other than that I am striking out.


The system is electric with 10 KW heat strips.

I apalogize for not making myself more clear.

The builder said the system lacks the bottom one-third support and only has the upper one-third support.

Thanks again for trying to help me out.