Crossover Duct Replacement question

[rgray58]

I plan to replace my 10" crossover flexible duct using Robert's suggested method of rigid ducting. I have a slight problem in that just using 2ea 90* ells and a section of rigid duct won't work because two piers are slightly in the way. Do you see a problem in using 4ea 90* ells to make the slight detour needed to get around the piers?

I was planning to get a checkup on my heat pump system this spring from my local HVAC guy and get an estimate from him. What is the feasibility of me buying the items I need and doing it myself? I am somewhat mechanically inclined and have no problem working under my house. The hardest thing I see is how to get the right length of rigid tube without the tools to cut properly.

[Robert]

Hi,

Usually in those cases, I use two 90* ells and run flex duct between them stretched tight as possible.

Sometimes you can also move the piers slightly to allow straight runs.


Yes, it is very much DIY.

IF you go with hard metal, use 45's instead of 90's at piers. Best to have least amount of resistance as possible.


The metal duct comes in 4 ft. sheets and can be cut with straight cut tin snips. Bend around and snap in place.


Thanks,
Robert

[tritontr]

The 90deg elbows should be adjustable to almost a strait configuration so by turning sections of the elbow you can end up with less then a 90 deg fitting. As a general rule in the hvac industry we try to use the least amount of 90 deg elbows as possible so try and adjust them as best you can to get around the piers. As far as install you will need a pair of snips to cut the duct. These are made in three styles RH cut, LH cut and strait cut you will just need a strait cut. You may also need a pair of crimper pliers when you see a piece of duct or elbow you will notice one end is crimped so it will fit into the next piece that is not crimped. just look at your job and figure how each piece will fit to see if you even need the crimp pliers. One last word of CAUTION wear heavy gloves sheet metal will cut you very badly if your not careful.

[tritontr]

Sorry Robert looks like we both were answering at the same time.

[Robert]

No problem.


Thanks,
Robert

[rgray58]

Thanks to both of you especially the advice for cutting. Bear with me, but when connecting the fittings, am I correct to plan to use sheet metal screws to hold, foil tape to completly seal the joint, and then wrap everything in duct insulation and a plastic sheet barrier?

[Robert]

Hi,

You're very welcome, happy to help. Yes, that is correct.


Thanks,
Robert