Frozen City Multi accumulator

[PoziorPhillips]

Hi,

I had a report that ice was building up on an indoor cassette unit off a R407c Mitsubishi City Multi, this causing water leaks.

On further inspection of the outdoor condenser the bottom half of the accumulator along with the service valve area of the suction pipe was solid with ice!

My first port of call before trying anything else is to weigh out any remaining refrigerant charge as I'm thinking possible low on gas.

Would this be a good place to start and what causes the accumulator to frost over (in cooling) operations?

Many thanks.

[install monkey]

check accumulator level on dip switches- al 0 indicates prob short al 1 typically ok, al 2 possible overcharge
run indoor unit in test cool to see coil temp on indoors, download manual to find out more details or get the mitsi app to check dipswitch settings - then check gas charge

[PoziorPhillips]

Thanks Install Monkey

Two quick questions.

1 - Can you please explain to me this elusive 30% rule (I can forward exact model numbers over if helps?)
2 - Have you ever had an accumulator leak on a City Multi R407c condenser? This one on my system seems very rusty and rotten indeed!

Cheers

[install monkey]

30% -diversity- youll have a greater capacity of indoor units than the capacity of the outdoor- reason being that most of the time you wont have 100% demand all the time( small rooms will reach setpoint and thermo off) then the ammount of diversity will decrease.
as for accumulators- usually the paint flakes off around the welds- never had 1 leak though- had 14yr old tosh accumulators rot through.

[still learning]

I like. The quick. Check for charge. On. The dip switches for. The accumalator .
i get more of education on ac faults. From. This site, than i do. From my place of employment .

[PoziorPhillips]

Well all,

Believe it or not (and even Im surprised) I pulled out 30kg the correct amount of R407c charge, as per the stamped formula.

So back to square one figuring out why my accumulator was freezing up? Would anybody suggest trying anything whilst the charge is out?

Thanks.

[The Viking]

Check the indoor units EEVs, first one to check is obviously the one serving the frozen uni but would be worth making sure that all of them opens and closes as required.

[install monkey]

its common for the lev heads to pop off- but you can tell straight away by the whooshing noise and the unit still cools when you stop it on the remote controller

[Dean A/C]

Hi. I know its a little late on the matter only 3 weeks late but ive had the same problems that you where experiencing.

I left the company before the whole situation was fixed.

I found on the multi city r407c (cooling only system) that was frozen up on accumulator were the following;

1) The system had a faulty expansion valve on one of the cassettes which was stuck open and froze up the indoor coil. This unit was removed from the system and then was back up and running after left turned off to defrost.
basically the company was tight and didnt want any new parts fitted.

2) Another unit had another faulty expansion valve on a cassette which was stuck shut. tested and was faulty.
this unit never got taken out and never repaired whilst i was at the company. I presume this also had a effect on the accumulator due to the unit calling for cooling but unable to actually open and cool the room so the outdoor unit may of been backing up with liquid and iceing up.

hope this helps a little

[CraigF]

Very late to the party.... But.... I had this issue on a unit. Turned out to be a faulty probe on the outdoor unit. Changed it and 2 years later all is still good. Buggered if I can remember which one but I'm sure our good friends at Mitsi can enlighten.