Heat pump external unit too loud

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#2751107 28-Jul-2021 11:12

I had a Fujitsu 8.5kW split system and the outdoor unit became noisey with a faulty fan motor which I replaced.

Here are my sound level records (results are with the system going flat out on heating):

Sound Level Fujitsu Outdoor Unit AOTR24LCC
20200529

20200529 Measured sound pressure level 63dBA at 2m
20200714 Measured sound pressure level 62dBA at 2m

AOTR24LCC Outdoor unit label shows
Sound Power level 68dBA

After fan motor replaced:

20200828 Measured sound pressure level 53dBA at 2m
Ambient noise with fan off 45dBA

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SomeoneSomewhere

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#2751111 28-Jul-2021 11:22

Given it supports demand response (the ability for an external signal/wire to command a limitation in power usage), you might be able to set it up with a timer to generate such a signal and put it into low power mode overnight. I believe it's simply a matter of closing a dry contact.

Whether putting it into 75% or 50% maximum power would actually limit the noise significantly is a question, though. They often run with a high fan power when in heating mode to reduce frost build up, and the fan power is a pretty small part of the unit power.

I'm not sure that the R32 units are that much louder. 7.1kW cooling is usually the largest of the really sound-optimised domestic-ish units. Larger units tend to be on a more commercial platform, even if they're sold as domestic.

DataCraft

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#2751668 29-Jul-2021 10:03

Here is an update I met with the installer this morning and after a bit of arm wrestling, he agreed the unit wasn’t the right one for the location considering the noise output.

I suggested it was replaced with the Mitsi which on paper is 10db+ quieter. I agreed to pay the difference in unit price to install quieter unit.

I need to do some homework first, but on paper and from the few reviews I have read the mitis looks like the more suitable unit.

I also said if that doesn’t solve the problem then I will own the issue, which I think is fair.

timmmay

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#2751677 29-Jul-2021 10:14

Great outcome :) Mitsubishi have a good reputation, and while the Daikin I have is pretty good I would give them a shot because we're having minor noise outdoor issues with the Daikin - but it's being replaced and we're paying up to $500 for the "night mode" to be installed. Our neighbor has one that looks fairly large Mitsubishi, not ducted, and I don't think we've ever heard it.

michaelmurfy

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#2751682 29-Jul-2021 10:18

I've always gotten told by multiple installers that the Mitsubishi units are better in almost every regard. I've got 2x high wall units (not ducted) and the outdoor units are nearly silent, plus the WiFi control on them is rather reliable even if it is basic and has home assistant support if you're into that.

There is something else to consider though - with a larger compressor wouldn't efficiency be hampered by having the fence right in front of the unit like that potentially making it work harder? Is there potentially another place you can put it?

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DataCraft

173 posts

Master Geek

#2751688 29-Jul-2021 10:34

michaelmurfy:

I've always gotten told by multiple installers that the Mitsubishi units are better in almost every regard. I've got 2x high wall units (not ducted) and the outdoor units are nearly silent, plus the WiFi control on them is rather reliable even if it is basic and has home assistant support if you're into that.

There is something else to consider though - with a larger compressor wouldn't efficiency be hampered by having the fence right in front of the unit like that potentially making it work harder? Is there potentially another place you can put it?

The most suitable location (for us) is where it is, potentially I will be trading some efficiency with its location. I have the Airtouch system installed over the top which is pretty good IMO.

timmmay

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#2751707 29-Jul-2021 11:11

michaelmurfy:

I've always gotten told by multiple installers that the Mitsubishi units are better in almost every regard. I've got 2x high wall units (not ducted) and the outdoor units are nearly silent, plus the WiFi control on them is rather reliable even if it is basic and has home assistant support if you're into that.

There is something else to consider though - with a larger compressor wouldn't efficiency be hampered by having the fence right in front of the unit like that potentially making it work harder? Is there potentially another place you can put it?

When Airtouch units are used you don't really use any of the native features, it does everything. The only exception with Daikin is you set night mode from the Daikin controller, which is typically installed in the roof or a cupboard.

You do need some space around the outdoor unit for airflow. 10cm behind it min, and ideally more than that in front of it.

The guy next with with a Mitsubishi is the father of someone who owns an HVAC business, so he'd have put the best in for his Dad, so I expect they are the best. They're more expensive too, but not a crazy amount more expensive.

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#2751907 29-Jul-2021 17:56

Are those of you who are mentioning Mitsubishi referring Mitsubishi Electric or Mitsubishi Heavy Industries? They are different companies, both with their own product lines.

timmmay

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#2751966 29-Jul-2021 20:42

Mitsubishi Electric is the one the neighbour has. I read about MHI a while back and they seemed pretty reputable as well.

DataCraft

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#2752442 30-Jul-2021 15:01

Hi guys,

The installer has recommend the PEAD-M125 unit. Has anyone here actually got a double stack mitsi?

I miss-read the original stats on paper the mitsi is only 3db quieter than the Panasonic, which might be a waste of time.

What would be awesome is to get some readings from a similar unit under full power with a db reader to do some comparisons.

timmmay

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#2752443 30-Jul-2021 15:05

In general I would think more / larger fans would spin slower and make less noise than a single unit. But yeah ask someone who has one.

DataCraft

173 posts

Master Geek

#2752501 30-Jul-2021 15:37

timmmay:

In general I would think more / larger fans would spin slower and make less noise than a single unit. But yeah ask someone who has one.

The unit has a massive fan on her I think that is the root of the issue it puts out a big pressure wave of sound that travels further.

Alliron

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#2772630 5-Sep-2021 23:33

DataCraft:

Here is an update I met with the installer this morning and after a bit of arm wrestling, he agreed the unit wasn’t the right one for the location considering the noise output.

I suggested it was replaced with the Mitsi which on paper is 10db+ quieter. I agreed to pay the difference in unit price to install quieter unit.

I need to do some homework first, but on paper and from the few reviews I have read the mitis looks like the more suitable unit.

I also said if that doesn’t solve the problem then I will own the issue, which I think is fair.

Don't Choose That. This is the exactly model of my neighbour heat pump, which made huge noise and stronge vibration sound when it makes heating and cooling. Im still looking for a way to solve this problem. my neighbour's heat pump's vibration sound is haunting me for a year. The Only progress is the council made them quietly at night, but they r still making vibration sound in daytime. Every morning i get woke up by their vibration. two of my rooms can not be used from 7 am to 10 pm.

gzt

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#2772747 6-Sep-2021 10:57

What is it mounted on?

Kickinbac

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#2776266 10-Sep-2021 22:27

DataCraft:
Here is an update I met with the installer this morning and after a bit of arm wrestling, he agreed the unit wasn’t the right one for the location considering the noise output.

I suggested it was replaced with the Mitsi which on paper is 10db+ quieter. I agreed to pay the difference in unit price to install quieter unit.

I need to do some homework first, but on paper and from the few reviews I have read the mitis looks like the more suitable unit.

I also said if that doesn’t solve the problem then I will own the issue, which I think is fair.

Just reading through this thread. Caution! Those sound levels are for the indoor unit not the outdoor unit.
Some things I am thinking are…
Is the system correctly sized for your house? If it is undersized it will run at higher speeds for longer periods, especially if its cold outside.

You need to be careful that you are comparing like for like in sound measurements. Also sound level increase is exponential.
An increase of 3dB doubles the sound intensity but a 10dB increase is required before a sound is perceived to be twice as loud. Therefore a small increase in decibels represents a large increase in intensity. For example - 10dB is 10 times more intense than 1dB, while 20dB is 100 times more intense than 1dB.
Unfortunately, acoustics are hard to resolve if not figured out initially. Manufacturers will give you the best sound measurement according to a standard that helps them.

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