[pm_sup]

Hi guys,

We have quite a large number of geothermal heat pumps on our site, the vast majority which are noisy.

We've left it to the contractor and manufacturer to sort out.

After several months of dicking around and reports, the manufacturer is blaming the contractor still.

Fact of the matter is the units are noisy.
I opened one up, because we field the complaints from the homeowners, and the problem persists.


Here's what I found;
The bottom of the machine has a compressor which vibrates like hell.
There is plenty of isolation on the lower part of the unit, so little vibration is transferred there.

Once you get into the fan chamber, the problem arises.

The lines from the pump to the heat exchanger are all hard lines. No flex couplings.

The heat exchanger is mounted to the top of the heat pump solidly. No isolation with the frame spot welded into place.

So the vibration is passed from the lines to the heat exchanger, which vibrates the top of the heat pump chassis.

I think that there should be a flex coupling, between the two, but there isn't.

The alternative is to dampen the vibration on the lines in this area, either by clamping or adding mass to the lines.

Testing with my Db meter, I was able to get a 5 Db drop in sound, just by grabbing the lines and holding them in my hand.

Disconnecting the seismic attachments, netted insignificant gains, although on some units helped reduce rattling.

I added 30# mass to the top of the heat pump. Netted me a 1 Db drop in some cases.

There is a flex coupling between the sheet metal ducting and the machine. Steel braided flex lines on all external connections to the machines

Isolation pads under the machines

Have any of you guys run into this problem and solved the issue?

 

[flashheatingand]

Don't work on too many geo thermal. Is the vibration of the heat exchanger with the chasis the problem? Or is it a compressor db. problem?

 

[beenthere]

What you describe for the refrigerant line connections to the coil are all pretty standard.

What are the refrigerant pressures while its operating and making this noise. What is the water flow rate. Is the noise only occurring in heating mode, cooling mode, or both.

What brand and model line are the geos.

 

[hdavis]

Dampen the line vibration with Sorbothane and a rigid structure. There are sorbothane grommets for this. Compressor and pump vibration isolation have the same issues for obvious reasons.

Are the units installed to manufacturer specs and do they meet man specs for noise?

 

[pm_sup]

Don't work on too many geo thermal. Is the vibration of the heat exchanger with the chasis the problem? Or is it a compressor db. problem?

The noise is generated from the transfer of the vibration of the copper compressor lines, to the solidly mounted heat exchanger. Upper chassis near the filter.

What you describe for the refrigerant line connections to the coil are all pretty standard.

What are the refrigerant pressures while its operating and making this noise. What is the water flow rate. Is the noise only occurring in heating mode, cooling mode, or both.

What brand and model line are the geos.

I cannot quote the flow rates, I don't know those numbers. Noise is both on the heating and cooling cycle. FHP

Dampen the line vibration with Sorbothane and a rigid structure. There are sorbothane grommets for this. Compressor and pump vibration isolation have the same issues for obvious reasons.

Are the units installed to manufacturer specs and do they meet man specs for noise?

Thanks for the Sorbothane suggestion. That is my feeling as well, to have a stand-off bracket and some means of isolating and dampening the compressor line vibrations prior to being transmitted to the heat exchanger assembly.

Yes they are installed per manufacturers specs. That being said there are obvious seismic attachments which are required by code as well.

There is little difference in the sound produced, if I temporarily disconnect the seismic points.

Ideally the whole heat exchanger should be mounted in some kind of dampening material.

Thanks all, for your help and suggestions.

 

[hdavis]

Good luck - there are a couple ways of approaching it using sorbothane - it's impossible to say what's going to fit in for your application. You can always use sheeting, it may be easier to retrofit.

 

[flashheatingand]

The vibration thing is hard to avoid. For discussion sake, lets assume the pressures and h20 flow is fine. Figure out how you can loosen the coil channel from the chasis, and, perhaps a little foam rubber between the joints will help.

Did the installing company abandon ship?

 

[pm_sup]

Good luck - there are a couple ways of approaching it using sorbothane - it's impossible to say what's going to fit in for your application. You can always use sheeting, it may be easier to retrofit.

Yeah, I think your suggestions are good ones.

The vibration thing is hard to avoid. For discussion sake, lets assume the pressures and h20 flow is fine. Figure out how you can loosen the coil channel from the chasis, and, perhaps a little foam rubber between the joints will help.

Did the installing company abandon ship?

Unfortunately the liquid to air heat exchanger is spot welded to the Heat Pump Chassis.

We met with the engineers, contractors and manufacturer's reps yesterday.

It was well worth while for me to have spent the time opening up the units and checking them out.

At first the manufacturer's reps are suggesting "it is what it is" and is an installation issue (of course blame it on the contractor and design of the enclosure)

So I was able to set the record straight. It is not an installation issue, except in maybe 5% of the cases where the contractor has a pipe or duct issue.

They also admitted the copper line routing for the heat exchanger(s) is done by hand. This explains the difference in copper line routing from machine to machine.

The suggestions so far from the manufacturer and engineer are;
Different sound absorption pad underneath the machine
Recheck all the copper lines (maybe add spacers)
Check the compressor mounting

One unit the contractor will change out.

A good first step and at least the manufacturer has seen we won't accept them just blaming the install. They have to take ownership of their design, and inconsistencies from unit to unit.

Thanks for the helpful posts.

Cheers