Fujitsu multi systems. noises

Hi all.
I've got a couple of fujitsu multi systems (Aot30lmaw4) with 4 heads on each system.
These systems are bringing complaints of loud noises from the indoor units.
The systems have been installed for 2-3 years now and i have been called back every winter since.
They only seem to cause a problem on heat mode.
Fujitsu keep asking for pipe run lengths and cable sizes (Kind of like they are denying any issue- or its an install problem)
I have seen the noises only once, (they seem to ocuur worst at night) and the indoor units were vibrating and causing panels to rattle.
Customers still reckon they get worse than what i've seen/heard
Can anyone offer advice to what i do next????
I have spent many hours on these units with no pay, and Fujitsu don't want to know about it.
Any help would be much appreciated.

So, what are the lenghts of pipes?
Is outdoor unit and indoor units clean?
Did you recovered and weighed amount of refrigerant?
Does all indoor units make noise?

system 1. has 4 ast12 hi walls.
Shortest pipe run 7m longest 12m. pipes run up .5m from id unit, level through ceiling space, and down 2.5m to od unit.
Yes i have spent many hours doubting my work and have all welded id unit connections and reweighed gas charge.(3.3kg) no need for addition as pipes are within length.
This unit is the worst for noises.
System2 has 3ast09 and one ast18 hiwall indoors.
All id units have pipes running straight down behind id unit(approx 2.5m)
from there pipes run horizontal(underfloor of house) to od unit. some rise(.25m) to make od unit connections.
Pipe runs are within spec and additional gas charge added (3 times now to be sure)
All units are correctly installed and install process correct,(evac, wiring, etc etc)
all units make noise.
units are noisy even when switched off (yes, i am aware eev still feeds some gas through at all times)
Some units are especially noisy when one unit is turned down or off (eg bedrooms get loud when lounge rm is turned off at bedtime)
Faults occur even when system is just on during the day. but not all the time

What is construction of walls where indoor units are installed?
So you are saying that you have two independent systems and indoor units of both systems are noisy only in heating mode?
Is that correct?

i have two separate systems, in two different houses. nothing unusual at all with the installs.
Noise, (the only time i have really seen it myself), is actually from the indoor coil vibrating and groaning.
It lasted 30 sec at the time. and was apparently quiet compared to usual.
Every time units run on heat, they get noisy

The whole situation is weird. i have never seen anything like this before, but my customers are describing almost the same thing and they do not know each other.

Siystem 1 outdoor unit capacity is low for 4 indoor unit of 12000BTU capacity. That sum to 48000BTU and outdoor unit is only 30000BTU.
I think your problem lies there.
Try to remove one indoor unit from system and see if noise is gone. If yes, you found your problem.
They probably need to use only certain number of in door units in same time which matches outdoor unit capacity.

System 2 is also mismatched for case when all indoor units runs at same time. 3x9000 and 1x18000 gives 45000Btu.

That is something i had not considered.
According to fujitsu install manual, i can connect up to 49000btu total for the system.
They even provide a chart/ manual (on the sales brochures) for adjusted id capacity when more than 2 units are connected.
Will pump system down and shut off one of the 12 id units and see if a difference / improvement can be seen(heard)

Sure you can connect but you cannot get more than 130% of nominal capacity of outdoor unit and that could not be more than half hour. I suppose that, in that moment of compressor overload, some noise could be generated from compressor and/or EEV.
You could connect 4x12000BTU but you cannot use full capacity of all units in same time all the time.
System electronic should take care of that but, that connection combination is at the end of applicable combinations table and I presume that there is the where problem lies.
Why is system dimensioned like that?

surely a situation where the connected indoor units are larger than the capacity of the compressor would result in a low high side pressure, like an oversized condenser.
as a result i would expect the system would fail to perform adequately and that would be my issue.
From all my tests i still get 550psi @15.5a on heat before comp is forced to slow down by operation of hp sw#1
From there system will run quite happily cycling somewhere between 475-525. (all units max heat & fan).
Both systems perform similarly.

Will Keep this forum posted if i have any luck with altering connected system capacity anyway.
Thank you for your input Nike123

My LG Multi units when on heat mode make vibration noises... even on some of the units that are turned off or thermostat off. It was found to be the compressor running at full tilt causing transmission of the vibrations along the pipework. We fitted rubber pads behind the mountings of each indoor unit to dampen any noise and vibrations and it seems much better now.

Quote:

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Originally Posted by nike123

Is outdoor unit and indoor units clean?

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Sorry, but you did not answer one question, the one above.
In heat mode, as you know, the cooling of the refrigerant is made by indoor unit.
I know that are sensor that feel the rise of temp, but the delay between time of happening and the response could be the gap of 30 seconds of noise.
If there is no heat exchange in the indoor coil, the refrigerant is overheated and the pressurre rises,... result: indoor coil is making noises and is vibrating. If the indoor coil is dirthy, this could be the answer.
Second, the dip-switches of the system,... Did you modify something ?