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smcmurrey 07-23-2008 10:09 PM

Ductwork install questions
I'm doing some ductwork and have a few questions about when to use mastic, aluminum backed tape, and just the silver backed duck tape. Here are a few questions
  1. When joining two lengths of flex pipe should there be a metal piece or can they just be taped together?
  2. What is the proper way to attach a flexduct to a register? (tie wrap, silver duct tape, mastic, ...)
  3. On the register box coming off the unit, mine has steel attachments with adjustable flow flappers that the flex duct attaches to. Should mastic be painted around them where they attach to the register box or just taped or both?
  4. My system has return air filters downstairs at the register grills and there is a 1" filter directly on the unit upstairs. Should I run filters on both or just one? If both how often would the upstairs filter need replaced?

amakarevic 07-24-2008 09:26 AM

all i can say is that, if you are using aluminum flex duct, you should NOT be joining pieces directly one to the other but use hard elbows, which can be straightened or 45 or 90 deg, and use clamps to affix duct to the elbow. that, in my opinion, is the safest way. the special clamps can be found at lowes right next to flex ducting.

smcmurrey 07-24-2008 03:05 PM

Thanks, I'll stop by the hvac supply on the way home and pickup the flexduct couplers. Will anyone else comment on the correct way to install flexduct to a register?

Termite 07-24-2008 04:09 PM

Are you using aluminum flex duct, or insulated flexible duct?

First of all duct tape has no place in duct installation. Use it for other things around the house, but not on ducts. Use foil tape if you're going to tape anything.

Insulated flex ducts should be attached to the floor/ceiling boots using zip ties. Where you're butting two pieces together you definately need a metal sleeve in there

Filters won't hurt anything. Use them on both systems to keep the A-coil cleaner if nothing else. How often they get changed depends on how much dust and dirt is in your house. Don't let them get too dirty. I change mine monthly, but my house is dusty.

smcmurrey 07-24-2008 05:36 PM

I'm using insulated flex duct. I know regular duct tape isn't used, I've got two different tapes from the hvac supply. One is a aluminum backed, the other is more flexable and silver backed. Thanks for the responses.

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