Seeing as everyone is rushing to offer an opinion on this one, perhaps IÂll offer mine too.

If your house is 2 floors, not including the basement, why in G-dÂs name did they install the GSHP on the 2nd floor? If it HAD to be on the 2nd floor, perhaps it should have been suspended from the ceiling with proper isolation.

I would like to hear more about how the decision on this was arrived at.

Your compressor is NOT in ÂoverdriveÂ.

BTW, is your compressor a scroll or reciprocating? What about the blower motor, fan belt PSC, or directly coupled ECM?

SR

The house design dictated where the units were located. It is a 2 story plus basement with open floor plan on the mian level. The second floor area is located directly above the main open living space in the house - so there really was no place to put in the main duct for a basement unit. I think the builder would have put the unit in the basement if he could have - and he knew vibration was going to be an issue. They did take precautions for both acoustic and vibration noise reduction. The acosutic measures are working on the second floor (can barely hear the fan and compressor in the surrounding spaces) - the vibratrion measures into the floor are not working.

The compressor is a "compliant scroll mounted on vibration isolators" and the blower motor is a "variable speed DC motor directly coupled to the fan wheel". In the Econar GeoSource 2000 verical unit, the compressor is at the bottom of the unit - fan is on top.

The fan speeds range from 1200 to 1500 rpm at the low speed, 1300 to 1700 at the med speed, and 1500 to 1900 at the high speed.

I was searching around on line and found out about vibration isloators. They make floor mount versions and suspension versions. Obviously - the floor mount would be an easier fix - do you think floor types would work? If not - we could suspend the unit from the ceiling. The space above the unit is still open into the attic and we would put beams across the top of the hvac closet for 4 hangers. That also sounds like a good option to consider - I would rather have vibration transfered into the attic structure than down below.

From what I have read - the rubber floor mats that were put down do not provide any deflection and are actually helping to transfer vibration into the floor. Since the surface area of the mat is covering the entire base of the unit - it's like a giant amplifier into the lower structure and ceiling below. Is that correct?

If we went with floor isolators - one on each corner of the unit - would that be a better approach?

The unit weighs between 200 and 300 pounds but I do not know the corner weights of the unit. The isolators (floor or suspended) are rated for 35, 120, 250 lbs ... what size would I need and how much deflection would be required - there are a lot of options.

Thanks for any help you can provide.

You will have to discuss all options with your installer and perhaps experiment. Go to the suspended option if you have to. It may turn out to be the better option to alleviating the noise problem downstairs but may present a different set of challenges. Whatever you do may turn out to be a compromise as opposed to a perfect solution.

Your GHP sound like a good unit; your specific questions will have to be posed to your installer, as he is the man on site.

Good luck & please keep us posted on your progress and final result.

Steve

what other challenges can you think of with a suspended option?

The hvac closet already has 2x4 wall structure around it. i would think these walls could carry a 200 to 300 pound suspended load. I would think a few 4x4 beams running across the top could support the metal rods holding up a metal platform or straps. The 4x4's could be isolated from the wall structure with rubber vibration isolator mounts. The rods could be isolated with isolator spings. Am I mssing something?

I will post the resolution. We were up at the house today in the AM and heard the upstairs unit kick in from below - it sounds like someone turned on a whirlpoool bath tab - the sound the pump makes if you are standing right next to it. This has got to get fixed.

Thanks

Curious, but when our heatpump was installed the installers initially failed to remove the rear brackets with which the unit was shipped. When the unit was wired in and fired up it seemed on the loud side, and the tech immediately shut it down and looked for those brackets. Evidently he'd seen it before.

Here's the quote from the manual: "NOTICE! Failure to remove shipping brackets from spring-mounted compressors will cause excessive noise and could cause component failure due to added vibration."

Just a possibility, and probably not what's going on with your unit, but you never know. (We bought from a different company than you.)

Good luck,

M

Don't overlook noise transmission via the piping. A bellows/flex coupling is often used to isolate the unit vibrations from the piping.

thanks - very good sugegstions. I never thought about shipping brackets but that makes a lot of sense. My units are supposed to have vibration isolators on them - but they would have to be secured down when shipping. I have passed that info to the builder.

I have done a lot of searching on the net - and happy to see that there are a lot of vibration control products readily available. If it turns out to not be a simple thing like pipes or brackets - then I believe the best solution will be to suspend the unit form the ceiling. I will keep you posted on my progress.

Thanks

a long winded description follows. Here is a summary:

We have both low frequency (20 to 33 cycles per second ) and high frequency (50 to 60 cycles per second) vibrations. The mats cut down the higher frequencies (although they still let enough through to create noise) , but do nothing to block the lower frequency vibrations.

The loudness of the noise is created by the rubber mat underneath my hvac unit which is covering the entire surface area of the bottom of the HVAC unit and the floor below - thus amplifying the vibration. The insulation we put in the walls and the ceiling below is working - but it is cutting down the acoustic noise (noise created by compressing air) - but batt or blown insulation does nothing to block or dampen noise caused by structure vibration.

The problem can be solved by removing the rubber mats and replacing them with 4 vibration isolators - which are essentailly leg supports with springs - under the 4 corners of the unit.

There was a recommendation to suspend the HVAC unit from above. This could be done but is probably not necessary.
I will keep you posted on the progress.

*************************detail

In my quest to understand the physics of what is happening with the my hvac vibration on the second floor of my home under construction, I stumbled data sheet that has some interesting info in it.

See http://www.b-line.com/product/PDFLibrary/pipehangers/index.htm.

Click on Vibra-Trol and then the Introduction. Download the PDF data sheet.

The table on the second page shows the amount of vibration reduction as a function of the deflection of the vibration cancellation device used.

If you look at the left most column in the table - the 1/16th inch deflection corresponds to what you get with a rubber mat or neoprene pad. The N/R means not recommended. The HVAC unit we have on the second floor operates in the 1200 to 2000 RPM range (or 20 to 33 cycles per second). If you look at the table you can see that the vibration reduction by a mat/pad in that RPM range is not very good.

The Econar units also have a Compliant Scroll compressor. I checked their specs and the unit runs in the 50 to 60 cycles per second range (or 3000 to 3600 RPM). You can see in the table that mats or pads are OK for these higher RPM rates - but not the best. They would still allow 10 to 12% of the vibration through the mats at these higher frequnecies. You also have to consider harmonics - which are additional frequencies generated at +/- 1/2, 1/3,1/4, 1/5 etc of the center frequency of the compressor. If the amplitude of the vibration of the center frequency is high, harmonics at lower frequencies will also be high. That means the harmonics at lower frequencies can also pass through the rubber mats.

If you look on the right hand side of the table - you can see what the noise reduction is for spring mounts (you can see an example of one of these on the cover of the attachment - left hand side of the picture with yellow spring and bolt sticking up). A spring device with a 1" deflection provides 97 to 99 percent reduction in vibration for the lower RPM ranges of the fan, the higher RPM range for the compressor, and the harmonics at low frequency created by the compressor.

At the bottom of the data sheet - they provide a calculation on how to size the springs based on the weight of the equipment. The corner load is 1.25 times the unit load divided by 4.

The spring mounts are not terribly expensive, maybe 10 to 20 dollars each. The springs themselves (depending on the brand) are about 3.5 to 4.5 inches tall with no load, and about 2.5 to 3.5 inches tall when compressed with a load - assuming a 1 inch deflection - which should be adequate for our problem.

It would be pretty easy to suspend this unit from the ceiling. Install the ceiling mounted hardware while blocking up the unit at its present height. Then remove the 3" rubber block supplied by Econar. Then turn it on and try again. Make sure that the shipping brackets and any screws that hold the fan in place have been removed. Also make sure that the duct work is isolated and flex hoses are used for the final connections per manufacturer's instructions. Call Econar's 800 number and get all the help you need.

Have you verified that all shipping lockdown brackets have been removed; that was an excellent suggestion.

I dont understand what youre saying about harmonics. Correct me if Im wrong but harmonics are MULTIPLES of the fundamental frequency not FRACTIONS!

SR

I thought about suspending the unit. The challenge is that the only available structure to support the unit are the closet walls that surround the unit - and one of these these walls (the closet entry) would need to be beefed up if I wanted to suspend the entire 400 pound load.

I decided that I would try the spring isolator feet first which I know will reduce the vibration noise significantly. If I want to get further reductions - I cand then use hanger isolators attached from the ceiling or walls to the bottom of the unit to channel some vibrations upward. These hangers would not have support the entire 400 load, just provide enough support to allow vibrations to channeled up and then dampened.

The hvac contractor has agreed to put the vibration isolators in - so I am very happy about that. I specified a spring mount with a 2 inch deflection and that should cut down vibrations between 97 and 99 percent in the freqnecy range I am dealing with. COmpare that to the rubber mats I have in there right now which provide about 1/16th of an inch deflection.

Harmonics are multiples and they occur at fractions of the fundamental frequency wavelength (1/2, 1/3, 1/4 , 1/5 etc.). So a 20Hz fundimental will have hamonics at 40, 60, 80, and 100 hertz and so on. The 20 hetz fundimental - which is the lower speed of my hvac blower fan and the first harmonic are both at a low enough frequency that the rubber mats now in place will not dampen them (rubber mats and neoprene feet dampen frequencies at 45 hertz and above).

Re Harmonics:

So by definition we are in agreement. Youre talking about 2nd, 3rd, 4th etc. order harmonics that are still MULTIPLES of the fundamental frequency. There is no such thing as a 1/3 harmonic! Regarding wavelength, the point is moot, as we arent discussing speaker or antenna theory.

SR

SR

sound waves are waves - similar in theory to light waves. they both have wavelenths, and the frequnecy is proportional to 1/wavelength. the only difference is that sound and light travel at different speeds.

You are wasting my time and not helping - and that is what this thread is about. The bottom lines is that I have vibrations - caused by both the fundimental frequnecies of the motor and compressor as well as the harmonics they produce - and that is what I need help eliminating.

thankfully there are other posters who care enough to help - not pick at words. and when I post the solutions hopefully that will help others that encounter the same type of problem.

Well I wont waste anymore of my time either.

Good luck!

SR

Update - vibration isolation springs installed and the vibration noise is gone.

The source we used for the parts is www.acousticalsurfaces.com. There is a lot of good information about vibration isolation on that site.