Mitsubishi City Multi

[Jase]

1) Outdoor : PURY - EP300YHM-A
2) BC Controller : CMB -P108V-GA
3) 7 x fan coils
4) AG 150 Centralised controller

Been having problems with commissioning the above system.
Experiencing voltage drops on the M-Net transmission.
Reading 29.4 Vdc @ the M-Net board on outdoor unit but upon testing voltage inside at fan coils the reading drops to around 25 Vdc.
It's not a long cable run. Have even replaced the cable but not much joy. Prior to changing out the cable there was 2 fan coils with no LED's showing on the PCB's. Also no LED at the BC box. Checked power supplies and found all to be satisfactory. Power being supplied from transformers to PCB's too!
Once the cable was replaced the LED's for the fan coils came on but still no LED on the BC box.
The AG 150 is not showing much too. It shows the address settings of the fan coils and local remote controllers and is in alarm condition. Fault is '6607'.

The control for this system is being used on the M-Net set up. The remote controllers are wired in on the M-Net transmission.

There are only 4 x remote controllers being used and all system is addressed.

Address:

unit 1 - 001 no remote controller
unit 2 - 002 remote controller - 102
unit 3 - 003 remote controller - 103
unit 4 - 004 no remote controller
unit 5 - 005 (master) - remote controller - 105
unit 6- 006 (slave) - no remote controller
unit 7 - 007 remote controller - 107

Can anyone shed any light on the BC box control?
Should the LED be on upon powering up or does the LED only come on upon system transmitting correctly?

This is a very strange phenomenon and don't know if the system will require a software re-boot.
Look forward to any advice.


Regards
Jase

[stufus]

Hey Jase
6607 is communication error in the case of the AG150 this can be caused by powering down the outdoor.
In the case of the voltage drop can you remove and reconnect the indoor units one by one.
In theory it should make no difference which way you run the m-net cable,but for troubleshooting later it helps to run it as follows, OC-BC-IC-IC-RC-RC etc etc
It's possible you have a duff board some where pulling down the voltage.
Check the factory wiring at the transmission line terminal blocks in all units as sometimes these can be mixed up .Between 30v and 12v.
What type and size is your transmission cable and where is it grounded
M-net led's should be on when power at outdoor as outdoor generates 30v for control loop
Regards

Stu

[Thermatech]

When the Mnet DC voltage drops below about 27vdc then you will start to get 6607 faults due to poor comms.
Normally with a small system such as this you will have full 29 - 30 v dc at all indoor units & remote controllers.
When there are 16 or more indoor units & lots of remote controllers & perhaps very long Mnet cable lenghts then perhaps the Mnet voltage will drop just enough to need an Mnet Boster pack.

But in this case there must be a problem in the Mnet loop which is causing the voltage drop.
Its going to be a problem with the cable or cable connection at the unit terminal blocks or a problem with one or more circuit boards.

All the time you have 30v dc at the BC box the red LED will be on. So if that was not on then that indicates to me that there was low Mnet voltage at the box. But as there was full voltage at the outdoor unit there must have been a problem with the cable between the outdoor unit & the box.

So 1st I would suggest double double check all Mnet cable connections at outdoor unit + BC + indoor units + RC.

Then I would suggest scoot round 6 of the indoor units & pull the Mnet connection plug from the circuit board.
Disconnect the AG150.
This makes the system 1 outdoor + 1BC + 1 indoor unit
+ 1 remote controller.
Do a virgin restart on the outdoor unit to force it to accept this new system configuration.
If it works without 6607 then add 1 more indoor unit + vergin restart. Repeat the procedure untill you find the problem.
If it goes 6607 straight away & you have low Mnet voltage then you know the problem is with the outdoor or BC or that 1 indoor unit + RC or a problem with the wiring between those 4 items.

The problem is with the voltage drop you just need to locate what the cause is.

[Jase]

Thanks for replies!

The system wiring has been checked and all appears normal, however have found 2 fan coils with faulty pcb's. These have been replaced and have even replaced the transmission cables just to be sure.
The voltage on the M-Net is reading 29.4Vdc between the outdoor and BC box. No red LED showing on the BC.
Voltage drops recorded at the fan coils.
Disconnected the BC and the system picked up the first 2 fan coils on the line. Upon connecting the third fan coil the voltage dropped. Upon re connecting the BC box the transmission failed. System was virgin restarted upon any configuration changes too. Have also found 2 remote controllers at fault.

Could the BC box be at fault too??


Thanks
Jase

[stufus]

Hey Jase
I think it may be time to start checking the electricians work.
It's be a while since i did any major work on mitsi systems but two IC boards and two RC's faulty straight out of the blocks although not beyond the realms of possibility sounds a bit suspect. Is there any chance someone meggered the transmission line or power supply circuit with some of the spurs on.
A blown BC board sounds like a distinct possibility now.

Cheers
Stu