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Obstructed return


rlskfoster
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hey HVAC gurus I have a couple of questions I'm hoping someone can help with.

I inspected a house yesterday with a gas heat thet was located in an upstairs hallway. The return air had a large wrapped A/C duct that took up at least half of the chase not to mention all the dirt and dust that was caked up on it. is this allowed? The unit actually sat at floor level and the return chase was boxed under it. It was pulling air from the hallway below.

Another thing i was worried about was the use of the metallic duct tape around one joint of the flue. I did not know if iy was approved for this or not.

I appreciate any thoughts.

Thanks

Buster

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Originally posted by rlskfoster

hey HVAC gurus I have a couple of questions I'm hoping someone can help with.

I inspected a house yesterday with a gas heat thet was located in an upstairs hallway. The return air had a large wrapped A/C duct that took up at least half of the chase not to mention all the dirt and dust that was caked up on it. is this allowed?

Just so I've got this right, the return air chase had an AC duct run through it? No, that's not right. Presumably, someone at one time sized that return air chase to meet the needs of the system. If there's now a duct running through it or across it or whatever, that's reduced the size of the return air path.

The unit actually sat at floor level and the return chase was boxed under it. It was pulling air from the hallway below.

Nothing wrong with that.

Another thing i was worried about was the use of the metallic duct tape around one joint of the flue. I did not know if iy was approved for this or not.

I appreciate any thoughts.

Thanks

Buster

No. As far as I know, metallic duct tape is not supposed to be used on vents or vent connectors. To be sure, you'd have to find the manufacturer's specs.

- Jim Katen, Oregon

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Thanks Jim,

I will day figure how to load a picture and it would be easier to see what i was seeing. The duct filled such a large part of the return I just had to believe it would compromise the system. I did write both the tape on vent duct and the return up and advised to consult an HVAC tech. Thanks for the help and if i figure this out today i'lll load a picture. (computer challenged person driving this keyboard!)

Buster

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  • 1 month later...
Originally posted by Jim Katen

No. As far as I know, metallic duct tape is not supposed to be used on vents or vent connectors. To be sure, you'd have to find the manufacturer's specs.

- Jim Katen, Oregon

3M Company makes a high temperature aluminum foil tape part number 2113NA specifically designed for flue vents.

What is not allowed on vent pipes and vent pipe connectors is cloth duct tape.

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Originally posted by hausdok

Hi,

ASHRAE has been trying to get contractors to use cloth duct tape for all HVAC apps since about 1997. I'm seeing less and less of it, but it's still out there.

ONE TEAM - ONE FIGHT!!!

Mike

For sealing ductwork the trend is more to using mastic with a reinforcing mesh tape.

The glue on the duct tape ages and degrades where it separates.

Check the following article at Home Energy Magazine on the test that Lawrence Berkely National Laboratory did on sealing ductwork. http://homeenergy.org/archive/hem.dis.a ... 80710.html

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Originally posted by MechAcc

3M Company makes a high temperature aluminum foil tape part number 2113NA specifically designed for flue vents.

What is not allowed on vent pipes and vent pipe connectors is cloth duct tape.

Is all foil tape approved for use on vents? If not, is there a way to tell, once it's been installed, if it's ok or not?

- Jim Katen

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Originally posted by Jim Katen

Originally posted by MechAcc

3M Company makes a high temperature aluminum foil tape part number 2113NA specifically designed for flue vents.

What is not allowed on vent pipes and vent pipe connectors is cloth duct tape.

Is all foil tape approved for use on vents? If not, is there a way to tell, once it's been installed, if it's ok or not?

- Jim Katen

There is no way of knowing for sure the 3M tape has no ink labeling on the exposed side as some metal foil tapes do. The biggest concern would be cloth duct tape and foil backed cloth tape, the type that has the visible thread fibers, as the possibility of leading to fire. True metal foil does not burn. If the tape is separating from the vent then the tape adhesive was not designed for the extreme heat of vent systems. Particularly steam systems where vent temperatures run around 500 + degrees.

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