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BMS1
10-11-2008, 02:22 AM
Hello everyone Im new here to this site.I hope I can help people where I can but I have a problem that I am finding hard to solve.
I installed a new Fujitsu AOT30LMAW4 muti unit with 3 heads connected to it.2 x AST12s plus a AST24.
The problem Im having is the system runs fine on cooling but on heating Im getting a harmonic noise comming through the ceiling.There is also a vibration ploblem as well with the head units vibrating on the walls .one of the pipe runs is at a max of 25 mts and im getting vibration!Why is this happening only on heating?The units are all running mech fine.pipe lengths etc are all in there perameters.Refrigerant charge 410a is fine, power is fine.Ive put loads of these systems in but this one is nasty.Its a mono pitch roof so there is no way of getting into the ceiling to check pipework but I havnt had these issues before.It has the Fujitsu techs have no answers.I can only hope that this problem may have happened to someone else here and they found the cause

nike123
10-11-2008, 09:48 AM
On what position is connected AST24 unit?

nike123
10-11-2008, 09:56 AM
Its a mono pitch roof so there is no way of getting into the ceiling to check pipework but I havnt had these issues before.
So, that mean you did not done pipework?
After you check that AST24 is correctly conected to A connections on outdoor unit, you should check pipework for collapsed elbows or dented pipes!

DEFENDER
10-11-2008, 11:02 AM
I am also wandering whether the additonal receiver tank has been installed... you did not mention it.

Also what is the running current of the compressor in heating mode and cooling mode at full load.

I have seen similar on a systems that are overcharged... the gas pressure was higher than normal causing excessive refrigerant vibration which transfers along pipework.

What type of pipe clamps are you using?

BMS1
12-11-2008, 03:05 AM
Bottom service ports A as per installation guidelines.I know some people do get caught out and connect to the B service valves.Thanks for your imput though.

BMS1
12-11-2008, 03:26 AM
I am also wandering whether the additonal receiver tank has been installed... you did not mention it.

Also what is the running current of the compressor in heating mode and cooling mode at full load.

I have seen similar on a systems that are overcharged... the gas pressure was higher than normal causing excessive refrigerant vibration which transfers along pipework.

What type of pipe clamps are you using?

Im running 2 12s and a 24 which is the max capacity for the outdoor unit.As far as im aware the reciever tank is for use when only 2 units are fitted to the 4 head system like possibly 2 18s.
I have removed the charge and measured a new one to check that possibilty.
The pipe clamps are of a standard nylon type as used by plumbers.All pipework used was preinsulated and this has been standard practice for me in the past with none of these issues.I do think though that the problem could be along these lines though as it does appear to be worse when the outdoor unit is running at a certain speed.Still dont know why it only does it in heating though unless the load conditions are changing somehow.I even tried adding extra pipework and extending to the max runs allowed and coiling it up behind the unit to see if this would help the noise problem but hasn't made any difference.Noise transition can be such a curse.I wondered about fitting some sort of muffler to the lines to help change the hamonics.Im not to sure what would work well on a heatpump system.

BMS1
12-11-2008, 03:39 AM
So, that mean you did not done pipework?
After you check that AST24 is correctly conected to A connections on outdoor unit, you should check pipework for collapsed elbows or dented pipes!

I suppose I could pull the house apart and check this but thats not an option. I have obviously fitted my gauges and checked the operation pressures and checked the split temps on all the units to see if there could be a restriction.The units are doing loads of duty so I don't think this is the prob but then maybe theres something im overlooking.

nike123
12-11-2008, 06:54 AM
I suppose I could pull the house apart and check this but thats not an option. I have obviously fitted my gauges and checked the operation pressures and checked the split temps on all the units to see if there could be a restriction.The units are doing loads of duty so I don't think this is the prob but then maybe theres something im overlooking.

Noise is present only in heating because high pressure is present only in heating. Some restrictions could make these noise without significant pressure drop because of high speed (and pulsating) of refrigerant (like noise in water pipes of central heating when pump is set to high).
That is why you should be sure that pipe work have no restrictions.
In cases like yours, you could fit temporary (for test purpose only) piping to eliminate that option.

Is that noise present only when all 3 indoors are running or it cold be located on only one of indoors?

Did you tried to locate noise in outdoor unit with some stethoscope. I usually borrow one for that purpose (http://www.usag-tools.com/prodotti/famiglia.htm?id=899%20N) from my friend who is car mechanic. Try to borrow one from local car service shop (or buy one).

DEFENDER
12-11-2008, 09:09 AM
Not sure this is going to help but Fujitsu do recommend the fitting of the receiver tank with the selection you have installed.

Also you could try clamping the pipe with hydozorb clips and rail this can help dampen vibration transmission, ensure you clamp the pipe not the insulation of course...;)

Regards.

dai kin
16-11-2008, 12:10 PM
I had this about three years ago on the same kit!the engineer from fujitsu came out and said it was the four way valve not the comp as i thought it was,so we changed the four way valve only to find it was the comp after all.

paul_h
16-11-2008, 01:37 PM
About three years ago they were blaming all faults on 4 ways valves! I had to change a fair few for nothing :D

AS far as the OP, I've had noise in fujis in 3 different cases:
1. internal pipe welding caused noise, ie factory weld from a small pipe inserted into a large pipe was inserted to far in, restricting refrigerant.
2. Installer kinking line, very possible bending preinsulated pipes
3. Airflow problems, eg fans not running at correct speed, ie. motor or capacitor dying, making pressures too high, or other airflow restrictions.

dai kin
16-11-2008, 05:33 PM
The comp on the one i had had a small discharge muffler on it,and since the noise stopped after changing the comp we put it down to that being faulty.

graham e
21-01-2009, 02:33 AM
Hello everyone Im new here to this site.I hope I can help people where I can but I have a problem that I am finding hard to solve.
I installed a new Fujitsu AOT30LMAW4 muti unit with 3 heads connected to it.2 x AST12s plus a AST24.
The problem Im having is the system runs fine on cooling but on heating Im getting a harmonic noise comming through the ceiling.There is also a vibration ploblem as well with the head units vibrating on the walls .one of the pipe runs is at a max of 25 mts and im getting vibration!Why is this happening only on heating?The units are all running mech fine.pipe lengths etc are all in there perameters.Refrigerant charge 410a is fine, power is fine.Ive put loads of these systems in but this one is nasty.Its a mono pitch roof so there is no way of getting into the ceiling to check pipework but I havnt had these issues before.It has the Fujitsu techs have no answers.I can only hope that this problem may have happened to someone else here and they found the cause
The variable orifice expansion valve and attached external solenoid which drives it was a problem on one unit. I had one that made terrible grinding noises on heat and the variable orifice valve would get stuck when changed to cooling mode (no cooling at all) for a unit only 14 months old.

stefs_cruiser
21-01-2009, 12:35 PM
Hi,

I have seen similar issues on another brand.
You can spend weeks looking for the cause, my advise would be to replace the factory copper spun discharge mufler with a aftermarket one.
Or fit a second one space permiting.

stefs_cruiser
21-01-2009, 12:45 PM
Had some succes with these

kiwifridgie
02-09-2010, 06:41 AM
have repaired a number of these, with success. all i can suggest is that you demand a replacement outdoor unit. it should be pre-modified. there is more than one cause of the noise issues, so a simple muffler will not solve all issues.
Fujitsu IS AWARE of the noise issues related to these units but are generally reluctant to accept liabilty or accept there is a problem. (whats the lift between units? cable size, etc etc) keep on the case till they supply a unit that has been modded or is quiet enough to satisfy your customer.