Noise due to vibrating water pipe of my A/C unit

[ryushimaro]

Hello,

I and my wife recently moved to a new apartment (only three years old one), and since a few days after moving in, we've been suffering from noise (low humming noise and quite loud noise) in the bedroom. The noise kicks in about every 10 to 20 minutes, and it last for about 10 to 20 minutes. It is weird that we have the noise usually at night.

Finally, we and a maintenance guy found that the source of the noise is water pipe (flexible type) that comes out of wall and goes to the A/C unit (looks like a heat exchanger). Let me explain this part in more detail. The A/C unit is installed inside kind of closet between the living room and bedroom, and the unit has in- and out- water pipe. These pipes keep vibrating, so the maintenance guy fixed them together with a plastic cable tie, then we do not have that loud noise. But we still have low humming noise. The maintenance team says that there is nothing they can do about this vibration.

Anyways, that low noise is still annoying, and it seems like the vibrating pipes vibrate the wall of the bedroom and the A/C unit. Maybe the pipe itself makes the noise. So, I am wondering if there is any way to reduce this noise. I am thinking about wrapping this pipe with some insulation stuff, but not sure whether it will work. Please give me some hint or tips. Thank you.

[jadnashua]

It sounds like your heating/cooling system in the apartment is using chilled water (and hot in the winter, have fun in the in-between seasons!). That conditioned water runs through a heat exchanger, then the thermostat controls the fan to move it into the apartment. The pumps that move the water may be the source of the noise, or it could be the fan. Some, but not all, use a valve to shut the water on/off into the heat exchanger and that could make noise if it leaks a little. It won't hurt to insulate the pipes with some foam sleeves, but there may not be much else you can do about it. If the pumps are getting old and noisey, lots of luck geting them to replace them unti they actually fail. The pipes probably feed all of the units, so travel through the apartment somehow. The noise can travel - any place the pipe is in direct contact and not isolated from the structure, it could be acting like the speaker coil and vibrating the walls/celing, etc.

I use a hydro-air heat exchanger for my heat, but I used rubber isolators to keep both the pipes and the heat exchanger isloated from the ductwork and the fan housing...it doesn't make any humming or vibrational noises.

[FloridaOrange]

I've never seen flexible hoses on a chilled water system, is that common outside of Florida?