I have an all-in-one GSHP unit (CM tranquility 20) in my basement using the "old" duct work of the house (sized appropriately). The ducting send and return was fitting by my contractor to the plenum of the unit. They did a nice job, however I underestimated the compressor and fan noise. While I did not expect whisper quiet I'd get with another type of furnace (gas, etc) I did have an expectation of a bit less vibration and compressor run noise.

That said, it will be difficult and costly to fully decouple the duct work from the floor joists it's attached to. I do have plans though to add external dampening material (rubbery mastic tape) to deal with high/mid frequency vibrations of the duct itself from the units vibration.

However, this won't deal with all of it of course. Since low frequency vibration is an issue too, I was thinking of fully disconnecting/decoupling the send/return from the unit and instead place a "gasket" or flexible/insulated duct work of some type between (think cutting a 4 inch slice out of the ducting and replacing with something soft and flexible that won't transmit the vibration.

Is there anything out there which is suitable for this? I can probably just use the same insulation material used inside ducts, but unsure.

Also, what kind of insulation/foam/etc might I put IN the ducting send/returns to cut noise down but not interfere with air movement or have a problem with moisture (reduce sweating)?

Your ideas are welcome, thanks

Colin

I am not a professional and I'm sure you'll get more complete responses from others, but my geothermal ductwork has a very thick rubber piece that connects the geo system to the ductwork going to the house. It appears that this material was made for this specifically. So, I believe what you are looking for is out there.

And thank you for posting the question. I had wondered why they used that small piece of material between the geo system and the ductwork. You probably answered my question by asking yours.

Ona is right. It's very easy to make a flex duct connector. It typically has a 2-3 inch rubber separation and will most likely solve your problem. Honestly, your installer REALLY should have done this in the first place.

Thanks for the replies, I am still in the "warranty" period for their work, so will likely call them out to resolve on their dime. They're local to me and overall good folks, so don't see it being an issue. Worst case, I do it. This is one of those gray areas with install retrofits that I do understand can be fuzzy about how far they need to go as far as the scope of their install.

Knowing there's material out there used, I'm certain I can find it at a local HVAC supply house if I need it. So it's good to know there's some possible solution being done by others.

Anyone know what the make/model/type of isolation material used it? (i.e. a brand or such)

Thanks

Colin

We usually use Durodyne junior flex.

Check to see if the contractor took the shipping brackets out from under the compressor. The unit will be noisy if they were left in place.

Yup, that was it. I pulled the cabinet walls off the compressor housing and sure enough the shipping brackets were still in place. I pulled and what a difference. I'm going to let my installer know so they can note it for the future, by the sounds of it, it's a typical oversight.

So now that took a HUGE percentage of the noise out of the system (yah! I might finally stop hearing about it from my wife and kids ;-). I still need to deal with the vibration noise (which is now less than before) and I believe decoupling the ducting from the furnace should do the trick. However, I'm going to let this sit for a while and see if I can avoid that step. Might try some mastic isolation tape on the exposed main duct work to dampen it some.

Thanks for the tips!

Colin

Roger that!

I guess this is too late, but here are some photos of my connection material.

sorry about the size - next time I'll do a test post in the "test post"