New multi-split air conditioner doesn't seem up to performance.

EvilMegaDroid · 2025-09-27T17:37:28-0400

Hey guys, I had an 8.3kw outdoor unit installed with 3 heads (2x9000, 1x18000). Mitsubishi unit with ln series heads.

The issue is that when testing for 1 hour, all 3 heads active the unit cannot bring the temperature below 20c for the full house. Is that weird? Problematic.

Asking because its an new unit so I want it to perform as best as possible and I don't think its normal for in the mild spetember temperature to only drop 3-4c.

Output temperature on the head seems to be around 14c, and the head seems to chill out even when I have it put to 16c on setpoint.

The apartament is around 82m2 without doors.

Indicated the heads with red in the house picture. Its an new apartament with no paint at the walls (so maybe that affects). Windows are closed.

pecmsg · 2025-09-27T20:36:09-0400

What does the installing contractor say?

rundawg · 2025-09-27T20:42:04-0400

Moved your thread to the AOP Residential HVAC forum.

please take note of this new location.

EvilMegaDroid · 2025-09-27T20:56:26-0400

I have not raised the concern with them yet plan to do at Monday. Hopefully they don't return with something like 20c is comfortable for living conditions.

Also, am I overblowing this discoloration on supposed NEW indoor units. When asked they told me its
normal and manufactured diffects.

BBeerme · 2025-09-27T22:27:31-0400

Where are you looking to see the discoloration?

VTP99 · 2025-09-27T23:36:36-0400

TyHanska · 2025-09-28T10:14:44-0400

We appreciate your input, but I had to delete your post because the forum rules state only "Pro Members*” can comment in the AOP forums.

Forum Rules

You are in the Trade, so please take the time to apply for Pro Status. It is free and easy to join.

Apply here.

We look forward to your questions and contributions going forward.

Thanks for your understanding.

Admin

pecmsg · 2025-09-28T11:09:43-0400

The discoloration is from manufacturing the coils. Its normal.

EvilMegaDroid · 2025-09-28T18:31:08-0400

Checked today, all 3 heads have that in the same location and as you guys are pointed out its for sure something normal.

Mostly was worried since the indoor units were old stock at 2023 production.

The coils other than the age look clean and no discoloration etc.

I did some tests today.

All 3 heads at total of 8.3kw output for 82m2 house.

Starting temperature: 25c
Setpoint 16c (lowest allowed).
Reached 20-20.5c in 1 hour, was not trying to go lower (I think, AC was not pushing that cold air).

Starting temperature: 23c
Setpoint 31c (highest allowed).
Reached 28-28.5c in 3 hour, was still working at full power, althrough sometimes one of the heads stops pushing out warn air.

The house has probably around 65-70m2 in open air circulation since there are no doors.

I was thinking of asking the installer to check the pipes for leak and for low refrigerant.

pecmsg · 2025-09-29T06:59:23-0400

EvilMegaDroid said:
I was thinking of asking the installer to check the pipes for leak and for low refrigerant.

So your willing to pay for a leak check?

New multi-split air conditioner doesn't seem up to performance.

Top Contributors this Month

Recommended Communities