Linesets through the attic-proper anti vibration
dcooke570
| Posted in General Questions on
I have a 30′ length of lineset running through my attic that seems to transmit a low sounding hum through the home when the outside compresser is running. The installer used zipties and ziptied them to the rafters in the attic.
I’m thinking of using bungee cords instead of the zipties they used to cut down on some of the possible transfer of sound to the rafters which might be the low hum I seem to be hearing inside the house. Anyone have any better recommendations on how to secure the linesets going through the attic?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
I have a similar issue with line set vibration in the basement; they're screwed firmly to the floor trusses and noise carries through the house structure in strange and wonderful directions. Are your outside units mounted to the house? Are the line sets secured to the house framing where they enter the house?
This document:
https://www.daikinac.com/content/assets/LightCommercial/SplitSystems/DX11SC/TP-108A.pdf has some descriptions of mounting techniques that may be helpful.
There are also in-line isolators that are inserted into the refrigerant lines to help keep vibration-related noise from the outdoor unit from following the line set into the house; some examples are "Parker Hannifin VAB series vibration absorbers", "Goldstone HVACR Vibration Absorber", and "Packless Industries VAFS Vibration Absorber". I've also read that putting a "P" turn in the line set where it leaves the can help reduce transmitted vibration.
My outside unit is mounted to the house (Masonry block house with stucco exterior). Line sets are secured to the exterior of the house and the 3rd line set enters the attic through the soffit and is secured to various trusses as it makes its way to the furthest room.
Generally you dont want to couple something that is vibrating to solid framing. Sound isolation is generally about decoupling. I think the zip ties are actually saving you from even more noise, as long as they are hanging the the lineset rather than having them sit on the framing. As already mentioned you would want to stop the vibration in the lineset itself, and you will most likely not do that via attachment to framing.
That's the problem... they zip tied the linesets directly to the framing... not hanging from the framing
Does your system have an inverter-driven compressor?
Yes it is a Mitsubishi hyper heat unit
There are cases where the building's resonance "matches" that of the inverter frequency at a given speed. I had one first-hand experience with this on a four-story Hilton Garden Inn with a CITY MULTI VRF Heat Pump. It was resinating when the system was at the lowest speed. I've been involved with two other cases in the last fifteen years but as an advisor over the phone. I'm not saying this in your case, just offering some additional perspectives.
Vibration control can be a difficult issue to diagnose. I think you are on the right path. Isolation is key. Vibration isolation components and methods are readily available in the commercial and industrial sectors. I suspect in your case, assuming a single or tw0-stage compressor, the piping may be too close to the framing. If the wood is petrified, the issue can be exacerbated.
Isolation is key.