Mitsubishi HI SRC50ZD-S

[savica]

Hi all, I have same question like Mack issued long ago, thread closed
Copying:
http://www.refrigeration-engineer.co...SRC50ZD-S-R410

I see at that time Install Monkey send some advice.
Anybody there that can help? Thanks Savica.

[install monkey]

https://drive.google.com/file/d/0Bz6...ew?usp=sharing
link for manual, whats the problem with it?

[savica]

Thank you!
Regardresly this is for other series I believe principles are much the same. You know, makers often spread platform solution across meny models I'll try to figure out what can be wrong. It just suddenly stopped to heat. In HI POWER mode it delivers enough heat, but then when enters normal operating efficiency is pure. Although compressor and fan works in sync pipe is bearly heated to 24 degrees. Then device stops and often doesn't start again so I need to switch power off even taking fuse to enable device start from the scratch. I'm thinking of clogged capilar, bad cold start capacitor or discharging pipe temperature sensor... Working for 15 years in automatisation and embedded firmware development I'm new to this area but I hope workflow experience in solving problems will be enough to start.
Regards,Savica.

[install monkey]

pull out the gas to comfirm correct charge

[savica]

Done already, system vacuum tested and proper amount of gas returned back. I checked indoor exchanger temp sensor because manual says that this is one monitored for high pressure protection and it's OK. I believe also that discharge pipe sensor in outdoor unit after compressor must be checked. On cold start discharging pipe is getting hot, I manually controlled indoor sensor (keeping cold) till getting almost 60 deg. on pipe and than release blowing. Temp on pipe start to fall and never returns although I hear compressor is on max speed. I'm afraid that compressor/inverter is too week, hardly saying it's burned or damaged
Any advice more before cutting the patient ?

[install monkey]

typically indoor coil sensor should reach 30 deg before increasing fan speed, in hi/boost mode all that does is override the thermostat setting and run the indoor fan at a higher fan speed tapping, maybe run the diagnostic mode on page 19 of that manual might give an indication of any alarms, or thermister issue

[savica]

diagnostic mode don't show any error, or stop code. all sensors and inverter inspected. compressor resistance OK. compressor is shut down by high pressure protection. one thing is bothering me. there is some thermostatic valve before evaporator. what if this doesn't open! maybe this part is broken. have you heard on any replacement of this?

[install monkey]

when you power up the outdoor you should hear the outdoor lev chattering as it reaches the closed position check the lev head is positioned correctly - little dimple on the head to align it, you can check the resistance acrross the lev plug- about usually 4 coils, should be in the manual for how to test

[savica]

tested, showing correct resistance. this is stepper motor if I can notice, known technology from many years in industrial aut. if it has needle on rotor then only some particle can cause this to stack. i'm asking again did anybody replaced this valve and found reason why not working? also i'm confused with control pcb layout. there is mounted header connector receptacle signed with OFF but there is nothing connected to it.
on the end i putt all together and tested while working. sensor acquisition ok, actuators as expected by manual, also reactions related with declared temperature states and then after 3 successful cycles it came to defrost. after it, compressor was working in highest speed and producing strange noise like its empty can! then gas line leading to compressor started to ice from some small reservoir up to compressor AND THERE WAS NO NORMAL FUNCTIONING. only thing helping is cycling power after 10 min. delay...

[savica]

strainer??? one day of testing. working and quick going to defrost. after that doesn't start heating. compressor sounds like empty. frosted pipe from strainer to compressor. i will replace strainer first to see if start to work, next is electronic expansion valve...

[savica]

strainers replaced, problem NOT solved. when nitrogen inserted into the system from liquid side it doesn't come out on service valve (gas)!!! pipe catted after evaporator doesn't release it also. is it possible that evaporator can be clogged?

[savica]

electronic expansion valve replaced also. register still freezing although outside temp is around 10deg. C! I'm asking if anybody has experience with capillary tubes. found that many use cut-and-try methodology to find the right length. those I presume regulates same compression in them and compressor and mass flow but I'm not familiar on which temp and pressures in heating mode I need to experiment? is it enough to short capillaries until I don't freezing register? it seams to me that mass flow in my unit is somehow imbalanced. seems that capillaries are to long, speeding gas flow, giving it higher velocity than needed and pressure drop on register entry cause to fast gas evaporation in first phase of register so it quickly gets frozen. maybe I don't need them at all. why they use EEV and capillaries in same application I'm not clear. by my understanding it's enough to have or EEV or capillaries anybody that can help???