Mitsubishi HI KX4 140 problem

[gwilliamson]

Hi Chaps
I have a MHI KX4 140 system running 3 x FDTCA45 indoor compact cassettes which is having a few problems.
Firstly it tripped out on a E36 error which is high discharge which after checking the thermistor was reading correctly i believed it was a refrigeration shortage. However after recovering the charge, performally a vac and weighing back in the correct 7.5kg charge i still have the same problem albeit less often as the outdoor ambient temp has now dropped!

I have noticed the indoor unit when set to cool to 18 has a return air of about 23 and goes into cooling quite happily for about 10 minutes, then goes off for 4 minutes and then back on, and so it goes on.
When the indoor unit stops asking for cooling the coil thermister is at >0 degrees so i am thinking it is going into a frost protection.
However this constant cycling on and off doesnt reach the desired set temperature any where near quick enough. All the coil thermisters are recording the temperatures correctly so i do not suspect errors there.

I am beginning to wonder if the indoor EEV could be faulty or blocked causing freezing at the indoor coil and the high discharge temp at the outdoor unit???.
The other 2 indoor units on the system seem to be ok but are very rarley used.

Does anyone have any words of wisdom on this subject?

Many thanks

Gareth

[The Viking]

To start at the end...

What type of room is the (running) indoor unit serving and what is the humidity in that room?

[gwilliamson]

The room is a small office 5 x 5, 2 people and a couple of computers. The system ran fine for the first 2 months only developed this fault in the last few months. Its only 3 months old.
Regards

[TLA]

gday, there is a pcmente4 programme for computer it plugs into your outdoor board and records all system operations including eev pulses, etc,
also check your interconnect wiring.
cheers

[gwilliamson]

Ok , still having problems and have some more info.

The outdoor unit (kX4140) is coupled to 3 indoor unit all FTCVA45 ie 4.5 compact cassettes.

When all 3 indoors are cooling then it all runs fine but when only 1 is running (doesn't matter which one) then the low pressure drops to around .10mpa or 1 bar , the TD rises from about 50 to 90 degrees and the coil stat at the indoor unit drops from about 4 to 0 degrees causing the indoor unit to go into frost protection and stop asking for cooling.

Once the indoor coil rises to about 10 degrees then it will all come on again for about 5 minutes until it drops again to 0 and so on.

I have recovered the charge twice now and weighed back in the required 7.5kg one lot being virgin 410a

I've spoken with Mitsui Heavy a few times and even they are mistified.

So basically it all runs fine when all indoor units are cooling but when only 1 indoor unit is on then it either goes into a frost protection on the indoor cassette or trips out on low pressure!!

Model numbers;
FDCA140HKXEN4R OUTDOOR
3 X FDTC45KXE6 INDOORS

( i know the indoor units are from the new KX6 range and the outdoor units are from the older KX4 range but i have been assured they are compatable! Starting to wonder though?)

Any ideas guys?

Thanks

Gareth

[rakkk]

Hi, I' d like to ask you something for nthe Mitsubishi KX4 that probably you know.
Are both compresser inverter or are fixed speed that are controlled by an external controller??

[gwilliamson]

Only 1 compressor outdoors and its an inverter

Regards

[nike123]

Is it possible that one indoor unit is to small capacity for that one inverter compressor?
From what I know, Inverter compressor could not work below 30% capacity!

[gwilliamson]

Had a guy from MHI on site for a day trying to work out the problem and he is just as mystified.

There are other systems there working with just one cassette on at a time and no problems at all so its not a over capacity issue.

Any other words of wisdom as i am completely stumped with an unhappy client?

Thanks

[stefan_cool]

Hi Gareth,

do you have still the problem? I think that i have a solution for you.

BR

Stefan

[nike123]

Hi Gareth,

do you have still the problem? I think that i have a solution for you.

BR

Stefan

Why don't you share your solution with rest of us?

[nike123]

From this diagram, I suppose (as I said earlier), that it cannot work below 30% of total indoor capacity.
http://farm4.static.flickr.com/3273/3098290369_08080db7b7_o_d.jpg

[gwilliamson]

Thanks Guys.

There is 3 x 4.5kw cassettes connected to the outdoor unit so when only one is running this would equate to approx 32% when only 1 is running.

There are similar systems in the same building that sometimes only run with 1 indoor unit that do not suffer from this problem.

I am meeting another guy from MHI next week onsite and hopefully he can shed some light on the subject.

Must admit i am getting totally fed up continually going back to site and not finding a solution - Client is a bit peeved too! Understandibly especially as the kit is only 5months old.

I am still not convinced the KXE6 indoor cassette is compatible with the FDC140KX4 outdoor unit!! But have been assured they are.

Any ideas?

[Thermatech]

It would be interesting to see what temperatures & pressures the other systems have when running with only one indoor unit cooling as a comparison.

The low indoor coil temp , coil frost prevention & low suction pressure would indicate poor refrigerant flow through the indoor units but strange that its affects all 3 which ever one is cooling ?

1/ I wonder if the low ambient control on the outdoor unit is working correctly in the cold weather we are having ?
Overcondensing = low discharge pressure & liquid flashing off in liquid line before arrival at indoor unit = poor refrigerant flow through LEV valve & indoor coil = low suction pressure.

2/ Perhaps the liquid line has a restriction ?
Can you measure liquid line pipe temp at intervals along the pipe from the outdoor to the indoor units.
If there is a restriction then you will find the refrigerant flashing off at the restriction & frosted pipe / much lower liquid temp.

3/ Perhaps all 3 indoor units have a blocked capillary tube from the LEV valve distributor to the coil.
Can you open up the indoor unit & measure temp of all the capillary tubes.

I have seen all of these problems over the years on split / multi split & VRF systems.

It could be as simple as too much rod into a 3/8 or 1/4 brazed joint which is partially blocking refrigerant flow or a kink in the tube at a bend.

Somthing is restricting the refrigerant flow & you just need to find it.

[nike123]

Thanks Guys.

There is 3 x 4.5kw cassettes connected to the outdoor unit so when only one is running this would equate to approx 32% when only 1 is running.

There are similar systems in the same building that sometimes only run with 1 indoor unit that do not suffer from this problem.

I am meeting another guy from MHI next week onsite and hopefully he can shed some light on the subject.

Must admit i am getting totally fed up continually going back to site and not finding a solution - Client is a bit peeved too! Understandibly especially as the kit is only 5months old.

I am still not convinced the KXE6 indoor cassette is compatible with the FDC140KX4 outdoor unit!! But have been assured they are.

Any ideas?

Similar and identical are big difference!;)
For compatibility check this table:

http://farm4.static.flickr.com/3143/3103557226_a42c4ef28c_b_d.jpg

[nike123]

Before this gooes further with unnecesary asumptions I give you some tehnical detals:

http://farm4.static.flickr.com/3069/3103621538_b76988a3b9_o_d.jpg

If your only one operating indoor unit demands less than 100 % capacity, that is very close to minimum capacity of outdoor unit of 31% and that is enough for activation of protection functions. That is exactly what your symptoms points to!
I think that is time to stop search for problem where there is not exist.

[Thermatech]

With a room temp of 23 & set temp of 18 we would normally expect the LEV valve to open up to allow more liquid into the coil & produce max cooling.
If the unit stops with this on coil 23 deg C with coil frost prevention when would have to suspect refrigerant flow problem.

Would still like confirmation of room RH or WB temp.
If the WB is below about 15 then the unit is going to be running in coil frost prevention anyway & the indoor circuit board could be ramping down the LEV valve because it can see low coil temp. Then stop on cfp.
The suction pressure will be low & comp discharge temp too high.

I have done so many site visits when the contractor is assuming that the problem is with the equipment but have found that cause is a simple installation or application mistake.

Then the contractor looks like a plonker infront of his customer & the manufacturer.

I am sure Gareth will want to be absolutely sure that there is not a problem with the installation first & then put pressure on the manufacturer to resolve this problem.

[nike123]

With a room temp of 23 & set temp of 18 we would normally expect the LEV valve to open up to allow more liquid into the coil & produce max cooling.
If the unit stops with this on coil 23 deg C with coil frost prevention when would have to suspect refrigerant flow problem.

Would still like confirmation of room RH or WB temp.
If the WB is below about 15 then the unit is going to be running in coil frost prevention anyway & the indoor circuit board could be ramping down the LEV valve because it can see low coil temp. Then stop on cfp.
The suction pressure will be low & comp discharge temp too high.

I have done so many site visits when the contractor is assuming that the problem is with the equipment but have found that cause is a simple installation or application mistake.

Then the contractor looks like a plonker infront of his customer & the manufacturer.

I am sure Gareth will want to be absolutely sure that there is not a problem with the installation first & then put pressure on the manufacturer to resolve this problem.

As young gentleman here said, if something is wrong with instalation, it could be easily found with MentePC software which every distributor have to give to their service engineers.
If it is unavailable for gwillamson, I will give him software!


gday, there is a pcmente4 programme for computer it plugs into your outdoor board and records all system operations including eev pulses, etc,
also check your interconnect wiring.
cheers

But I doubt, because, as I understood, everything works fine when all indoor units are in function, and error could not be connected with one specific indoor unit. If there is some restriction on common pipes then that restriction would be more visible when all units are in operation then when only one is in operation!

Of course, everything I said is based only at what information we got here!

[gwilliamson]

Ok, Firstly many thanks for all your replies.

Nike123, I would very much like a copy of the Mente software if you have it available. I spent a day last month with an MHI engineer on site using this software and asked him for a copy and was told its not really for Engineers!!

When all 3 indoor units are running in Cooling then all is fine. EV at the indoor unit is about 80 pulses and a coil temp of 4C - Air on 22, Air Off about 7. Also about 5bar & 20bar respectively.

When only one is running then the EV is still about 80P, coil temp equal to or less then 0 which in turn operates the indoor unit to go into frost protection and consequently turns off the outdoor. Pressures are about 1bar or less suction.

Have had this problem when the outdoor temp is 5 or 25. Doesnt make any difference what the ambient is.

Last time we were there we disconected the EV on the indoor unit PCB and electronically wound it open some more. From the Mente software we could see the coil temps rising to about 4 and the pressures also climbing to realistic figures. However didnt keep this open too long as liquid was starting flood back.

By the way in Heating Mode all works fine.

I understand thats its close to the minimum operating levels whilst only one indoor unit is running but its a good 30 metre piperun and there are not any other problems elsewhere in the building where 8 more outdoor units run a combination of 34 more indoors.

It doesnt make any differnce which one of the 3 indoor units are running on their own, they all have the same symptoms.

I am very much starting to think its a compatibilty issue between the KX4 outdoor unit and the KX6 indoor 4.5kw compact cassette. The rest of the building is done in KX4 cassettes as at the time of installation (June08) MHI where just starting to introduce the new KX6 range and the 4.5kw models were all the new KX6 guise. All other models are KX4.
According to the charts it confirms to me that they are not compatible but i spoke to MHI at the time of ordering and they confirmed they would all work together and ignor what was written in the compatabilty charts!

Starting to wonder if i have found an error?

[gwilliamson]

Also, the first signs of a problem with this system was back in August when the outdoor ambient temp was 27 ish and the unit had tripped on an E36 error which is high discharge. Checked the normal, thermisters etc, recovered 410a as suspected a shortage but all was fine and weighed it all back in.

Since then it just stops working on the indoor frost protection as above although i have managed to get it to trip on LP whilst working on the system. Discharge temp i still quite high though at about 90 - 100 degrees but these units do not trip until 130.

I suspect once the ambient temps rise again next year then i could start to see high discharge temps again.

Got to get it sorted before then!!!!

[nike123]

Ok, Firstly many thanks for all your replies.

Nike123, I would very much like a copy of the Mente software if you have it available. I spent a day last month with an MHI engineer on site using this software and asked him for a copy and was told its not really for Engineers!!



If that software is not for service engineers, I don't know what is more suitable than that. :eek:
It is simple data gathering software and you could not do anything with him except monitor operation!

That guy want to look like some guru with PC in front of "simple" refrigeration engineer.:rolleyes:

I will sent you software in few minutes!
Read thoroughly instructions for setting PC for correct interpretation of CSV data format.

[gwilliamson]

Many thanks Nike

I will send you a PM with my email address.

Regards Gareth

[gwilliamson]

Nike, tried to do that but you cant recieve Pm's

If you Click on my V card you will find my email address

Regards

Gareth

[nike123]

I already sent you file! Check your e-mail!

[nike123]

Nike, tried to do that but you cant recieve Pm's


My setings for PM system are OK and it is enabled for more than year.;)

[gwilliamson]

Sorry nothing recieved but i have just checked my email address and realised its an old one so i have changed it to a working one. Would you be good enough to send it again. My apologies.

[nike123]

Sorry nothing recieved but i have just checked my email address and realised its an old one so i have changed it to a working one. Would you be good enough to send it again. My apologies.

Done........

[gwilliamson]

Nike123, Many thanks all recieved, will have a look tomorrow and put it on my laptop.
Regards
Gareth

[Greengrocer]

What remote controllers are you using on the cassettes?
The FDCA KX4 140 system uses the 3 wire RC-E-1 controller. The new KX6 system & FCU's use the RC-E3 which is a 2 wire controller. I dentical to look at except for the wiring. Not sure if this is an issue or not but might be worth checking.
Some one also mentioned about a pipe-restriction earlier in this thread. Did you install pipe-work & did you use factory supplied ref-nets? If so I presume you cut back the ref-net to match the main run pipe size. I mention this because we has a case a while ago where someone had brazed up a ref-net without cutting off the smaller dia step down stubs - thereby causing a restriction in the main pipe run. Just a thought.
Keep the feed back coming. Would like to hear the solution (if there is one) to your problem. We too use a fair bit of MHI kit & have installed a few 140KX4 systems with no problems.

[gwilliamson]

Hi All

Just an update. Spent the morning on site last week with an engineer from MHI. Plugged in the software and watched the system behaviour for a while.

When going into cooling the pressures drop significantly, on a couple of occasions enough to trip on LP. During this cycle the indoor LEV temp points drop below freezing and switch off the indoor unit under frost protection.

Whilst the KX6 indoor units arent on the list for connection to the older KX4 140 outdoor units MHI believe this is now allowed with the updating of the outdoor PCB software version which was promptly done.

Its like the LEV does not open quick enough or wide enough at startup hence the massize LP drop, however if the unit can avoid tripping on LP then the pressures come back up and stabalise very well and all is good.

Since updating the software we did not get the LP trip and all seemed to be running ok. However it was about 1 degree on the roof that day and we found it very difficult to cool the rooms for any length of time as they were reaching set temperature of 18 within minutes and the occupants were moaning!!!

The only other possibilty which has been mentioned already would be a restriction on the liquid line but the pressures do come back up to a sensible level after about 2 minutes so i am not too sure?

I will go back next year on a warmer day and check the system over and keep you updated but for now its fingers crossed!!!

[nike123]

It is always nice to see update on problem we discuss here.
Thanks!