Mitsubishi Heatpumps average?

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Glazza

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#251088 8-Jun-2019 00:15

We had two Mitsubishi units installed last year - one in our lounge in April, and one in our bedroom in October.

The lounge unit had minimal use last year (as the house was getting renovated). However when using it this winter, we notice that it makes a “gurgling” noise quite frequently.. it’s loud enough be be annoying, and sounds very odd... but it’s not overly loud at the same tome.

However, this is better than the bedroom unit - this is a GL42 unit, this unit seems to really struggle with outside temperatures below 5 degrees - where it seems to stop, makes a sounds like a small trucks “air brakes”, then appears to cool for a couple of minutes, then resumes heating again.

What I’m trying to work out is, we had 10 year old Fujitsu units in the same locations. These were only replaced because we were renovating, and couldn’t handle the thought of putting the old unit back up to have it fail, and need to be replaced. The Fujitsu units where basically the same sized units, 5.8kw in the lounge and 4.2 Kw for the bedroom. However, although been 10 years old, and if I am to believe the installer (that I don’t anymore) Fujitsu are poor performers next to a Mitsubishi unit.

Interested in other thoughts... normal?

Cheers

Batman

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#2254136 8-Jun-2019 00:49

i have had Mitsubishi Fujitsu Toshiba Daikin, they all make good heat, no issues.

Aredwood

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#2254138 8-Jun-2019 01:35

The gurgling noise will be the liquid refrigerant flowing through the unit. Is that noise coming from the indoor or outdoor unit?

The stopping and restarting will be the unit doing defrost cycles. Does ice appear on the outdoor unit?

How long are the pipes between the indoor and outdoor units?

Does the outdoor unit get plenty of airflow, and is not installed somewhere that would cause it to create it's own microclimate? (air coming from fan on outdoor unit getting recirculated through outdoor unit)

How large is your bedroom? As I have an approx 10 year old Mitsubishi Heavy Industries heatpump in my bedroom. Although I bought it secondhand and installed it last spring. It Is the 2.5KW model, and so far it has way more heating capacity than what my bedroom needs. Despite no insulation in my house. So far this winter, still haven't had a night where is has been cold enough to make it run continuously. It has to keep switching on and off to stop the room getting too hot. (as the lowest operating speed of the compressor still provides more heating than needed)

How cold has it been getting outside? As between 0 - 2deg or so is the worst for any heatpump. As ice will form on the outdoor unit. Often, the heating capacity at negative outdoor temperatures is actually higher than at the 0 - 2deg range. As less problems with ice forming, as no humidity in such cold air.

Glazza

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#2254144 8-Jun-2019 07:44

Hi, thanks for the detailed reply. Responses below.

Aredwood: The gurgling noise will be the liquid refrigerant flowing through the unit. Is that noise coming from the indoor or outdoor unit?

The noise is from the indoor unit.

The stopping and restarting will be the unit doing defrost cycles. Does ice appear on the outdoor unit?

I’m not sure to be honest. I’ll try and check when it next does it.

How long are the pipes between the indoor and outdoor units?

I’m guessing there, lounge would be 3.5m and bedroom would be 5m

Does the outdoor unit get plenty of airflow, and is not installed somewhere that would cause it to create it's own microclimate?

Should be ok I think. Both in open areas, with the back of the unit 150-200mm away from the house.

How large is your bedroom? As I have an approx 10 year old Mitsubishi Heavy Industries heatpump in my bedroom. Although I bought it secondhand and installed it last spring. It Is the 2.5KW model, and so far it has way more heating capacity than what my bedroom needs. Despite no insulation in my house. So far this winter, still haven't had a night where is has been cold enough to make it run continuously. It has to keep switching on and off to stop the room getting too hot. (as the lowest operating speed of the compressor still provides more heating than needed)

It’s not big... 3x4m, hallway door is open however.

How cold has it been getting outside? As between 0 - 2deg or so is the worst for any heatpump. As ice will form on the outdoor unit. Often, the heating capacity at negative outdoor temperatures is actually higher than at the 0 - 2deg range. As less problems with ice forming, as no humidity in such cold air.

The issue with the bedroom one starting to sound like a truck with air brakes then blowing cold air was occurring last night. Probably happened 3 times. Overnight low was 6 degrees.

Aredwood

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#2254170 8-Jun-2019 09:48

Are you sure that the reason that it was blowing cold air. Wasn't simply because the room is heated up to the set temperature? As most heatpumps have to switch to fan only mode at a slow speed. So that their internal temp sensors can accurately measure the room temperature.

What was the reason given for installing such a large heatpump in a small room? As the GL42 has a rated heating capacity of 5.4KW Can a plug in electric heater keep that room warm, even on the coldest nights? If it can, then that heatpump is definitely stupidly oversized for that room. Only exception would be if daytime air conditioning is a design requirement. As the heatpump would have to fight against the sun.

My bedroom heatpump would sometimes run at low fan speed, stop for a little bit, run the fan a max speed for approx 1 second, then start heating again. It hasn't done it recently. And when it was doing it, outside air temp was 15deg or so and set temp was on 18deg. Guessing that this is the “truck air brake” noise that you are referring to.

My theory is that the unit was struggling to manage the room temperature. (they have a form of fussy logic control) And the burst of high fan speed might be some form of subroutine reset in its control code, or a diagnostic test of a possible failed fan or blocked filters.

Due to the unit operating in conditions where it is way oversized for the room.

Batman

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#2254178 8-Jun-2019 09:55

When it makes gurgling noises it is defrosting the outside unit.

Glazza

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#2254218 8-Jun-2019 10:56

Are you sure that the reason that it was blowing cold air. Wasn't simply because the room is heated up to the set temperature? As most heatpumps have to switch to fan only mode at a slow speed. So that their internal temp sensors can accurately measure the room temperature.

Maybe, I’ll try and measure the off air temp when it next does it. It typically seems to do it when the room is cold, and it should be warmer than it is... but hey, this is typically at like 4am, so I’m not overly alert either.

What was the reason given for installing such a large heatpump in a small room? As the GL42 has a rated heating capacity of 5.4KW Can a plug in electric heater keep that room warm, even on the coldest nights? If it can, then that heatpump is definitely stupidly oversized for that room. Only exception would be if daytime air conditioning is a design requirement. As the heatpump would have to fight against the sun.

Yup design is for cooling as well... I really left them too size and install. A couple of different places quoted basically the same sized stuff, so maybe stupidly I just assumed it was right?

Guessing that this is the “truck air brake” noise that you are referring to.

It sounds like gas releasing... I understand it isn’t, but yea. I don’t think it is the fan ramping up briefly, maybe it is... annoying if that is it.

Due to the unit operating in conditions where it is way oversized for the room.

Hmmm fun time ahead I guess..

Aredwood

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#2254265 8-Jun-2019 13:23

Try setting the Louvre to point straight down. When it is blowing cold air, see if the Louvre remains pointing down or if it changes to horizontal by itself. As my bedroom heatpump switches to horizontal by itself, when it goes into no heating fan only temp sensing mode. This will be a way for you to see if that is what your one is doing.

What is the compressor in the outdoor unit doing when the indoor unit is blowing cold air?

Also, my unit (when you first turn it on) goes to horizontal Louvre, fan blowing cold air. As it is waiting for the compressor to speed up and deliver heat to the indoor unit. It then changes to vertical Louvre once it senses that the indoor unit heat exchanger has warmed up and can now deliver hot air.

Was daytime air conditioning something that you need? As my little unit still has plenty of air conditioning capacity for night time summer cooling. And it still cycled on and off, as hardly any cooling is needed once the humidity has been removed from the summer night air.

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Jase2985

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#2254296 8-Jun-2019 13:40

maybe have it serviced, it could be out of gas?

Kickinbac

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#2254471 8-Jun-2019 18:18

Maybe get the installers back to check them over and they will still be under warranty. They could be short on refrigerant. You could call also Mitsubishi (BDT) directly and talk to their technical support. There shouldn’t be any noticeable gurgling of the refrigerant but it sounds like it’s defrosting which is the unit reversing and heating the outdoor coil to melt the ice. Usually the indoor fan motor will stop while this is happening. Frequent defrosting can also be a sign of low refrigerant.

bfginger

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#2254687 9-Jun-2019 09:18

Although Mitsubishis have a reputation for being reliable it is a mistake to associate build quality with specifications quality. The specifications of most high wall heat pumps on the market are poor.

The 5.4kw GL42 has a minimum working capacity of 1.4kw heating while the equivalent for similar sized Daikin Cora and Panasonic Aero VKR is 1kw and 0.9kw. The GL42's outdoor unit is 34kg versus 51kg and 43kg for the Cora and VKR. The GL42's outside unit is a maximum 3 and 5db louder than the equivalent Cora and VKR.

While there could be a fault or installation problem the GL42's outdoors inverter unit is underengineered and is always going to have to turn off and on more often than better equivalent units. The equivalent Mitsubishi Ecocore AP may be better than the GL but not much better.

The minimum working capacity is important because the lower it is the less often the unit has to turn off and on and the more consistent the indoors temperature. A high minimum working capacity means the unit has to turn off and on like an old non inverter heat pump when under light demands and may cause more noise disturbance while operating.

If you have a small 12m2 bedroom the 5.4kw GL42 may be oversized for it. Does this room have large sun facing windows or no insulation? 3m ceilings? Very cold house? If it's under standard conditions I don't see how they could think putting a living room sized heat pump in a modest bedroom was the right option.

The likely appropriately sized for a 12m2 bedroom Panasonic Z20VKR can operate down to 0.85kw. To get similar minimum working capacity performance from a Mitsubishi you'd needed to have got a Diamond LN25 or LN35 which can go down to 1kw. The Diamond LN25/35 has their HyperCore technology so shouldn't have too many problems with cold weather and may have been a more appropriate choice for your bedroom.