Depends on the manufacturer.
There are settings that can quiet the noise. Might be a dipswitch, could be some buttons you have to push or might be a programming change.
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Hello - we have installed some VRF heat pump systems and ever since heating season starts, there have been complaints of gurgling noises that can be very loud and disturbing while in heating mode, when the evap is off. This of course only happens when the condensing unit is on (so at least another evap is on in the same network) and the noise starts during defrost and continues for about 20-30 minutes afterwards, happening pretty frequently. This is happening on all 6 condensing units that were installed there, same problem everywhere.
We emptied one of the units of refrigerant completely and there is no leak, so we refilled and added an extra 20% surplus of refrigerant but the noise remained. We are not sure what to do.
Depends on the manufacturer.
There are settings that can quiet the noise. Might be a dipswitch, could be some buttons you have to push or might be a programming change.
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Is the gurgling like pipe movement? Or something coming from the coil thats off?
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make sure the EXV's shut off 100%when the unit is off. like was said, prolly a setting.
bigger question is why did you add "20% more refrigerant"?
With VRF systems, the expansion valve of the indoor units always stays open in heating mode, so even though the unit is off, during and after defrost cycle, there is always a noise. Manufacturer says that valve does not close 100% in the indoor units so that refrigerant is not get "trapped" inside and this is the same everywhere.
Mitsubishi is stating that they don't have this issue anywhere else, however we are getting the same issue on all 6 condensing units.
We added refrigerant as we figured perhaps we were missing some, but it has not helped the noise issue.
Refrigerant charge is NOT added as a guesstimate repair.
Blind charging should expect to cause problems and abnormal operation. Charging should only be done via the calculated charge amount from the manufacturer, while noting important readings of operation like discharge temperature and delta, among others.
It should be noted that certain parts of certain manufacturers VRF systems have disclaimers that the equipment should not be placed in certain noise sensitive places due to concerns over equipment making sounds that would affect the surrounding environment.
EEV operation is based on oil return to the outdoor units.
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Absolutely - the manufacturer is guiding us here when we add or take away, since we did follow their formulas with regards to condensing unit, piping length etc. We are adding and taking away small quantities.
Also, these units are approved for installation in noise-sensitive areas. Manufacturer claims they have no issues elsewhere, and really this is a quite loud and abnormal noise. It is the sound of water running but extremely loud
Is Mitsubishi willing to help you with some onsite tech support, since this is 'not happening anywhere else?'
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2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
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Yes, they have been helping us on-site but they too are stumped and are not sure what to do. They have asked Japan for their advice, and waiting to hear back.
What is strange is that the same issue is happening on many indoor units here (all wall-mounted) on all 6 condensers. It is not specific to one of the 6 VRF systems..
Well..that makes is a Tokyo-level mystery...one where some department might suffer some dishonor, and even as a Gaijin, I can see this as a problem they will be willing to work on until it is solved.
Please keep us up to date on their progress.
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2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
Member, IAEI
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By the way, here is a link to see a 5-second clip of the noise. This is happening in heating mode but with thermostat on OFF.
https://drive.google.com/drive/folde...0e?usp=sharing
Sounds like unrestricted refrigerant flow.
I wonder if you can set the EXVs at 2-5% during the off cycle. It would slow the flow, but not allow refrigerant to get trapped. Honestly though, I don’t see why trapping would be an issue. You would need to have an extremely high temp. Event to reach burst pressure.
Hey is this Mitsubishi City Multi? We take care of a couple of those systems. A few are water source and one building that's air source. The bc boxes in those definitely produce some noise as well as the piping makes some noise when it's running hard. I dont think we have ever had to take the decibel meter to it but there's a couple that make what one customer (has a BC box in a hallway adjacent to his office, full framing and a fire wall)says its enough noise to have people ask him what's going when hes on the phone. (I think hes exaggerating a lot but I can hear it well standing directly under it in the hallway) this particular system has about 20 foot elevation drop and maybe 85 feet of piping between outdoor air source unit and BC box. Let me know if there's any other info you could use. Cheers
Paul
EXV on indoor units in FAN and Thermo Off mode is always open to ensure oil recovery.
Thanks for sending the info. We understand that the valve must stay open the problem is every couple of hours it is such a loud noise, and then the gurgling noise remains for about 30 minutes after defrost, and the supplier says that on all other installs there are no complaints and it is hardly noticeable, whereas here it is loud and disturbing, and nobody knows why.
how is all the piping secured? the best way to eliminate noise (vibration) transfer from one surface to another is to create an air gap. if all the piping is rigidly connected to the structure, or just touching in the right spots, it will transfer noise. could also have something to do with the building construction, resonant frequencies, etc.
Hi guys,
Did you actually solve this problem?
I have a similar gurgling noise.
Once any of the indoor units is on, it starts right after the first minute for 15 minutes then it stops for 15 ok and keeps the pattern indefinitely. It does it in both cooling and heating mode. The system is consisted of 3 indoor units (they are really close to each other) but the external unit must have at least 15-20 meters in distance and 4 meters elevation. The gurgling noice is mostly noticeable on the big indoor unit (24000btu).
PS. I’m a homeowner, never dealt with HVAC before, but desperately trying to get help, can’t sleep with it (too noisy) neither without it (too hot).
PS2. It did this from the first power on, so either a config or an installation issue must be the issue
Any advise would be greatly appreciated
Mate
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