Mitsi Electric Wall Unit Switching Off

[marc5180]

A site that we have just taken over are having problems with a PKFYP20VBME randomly switching off. Not sure what the oudoor is but it's a heat pump VRF.

The origional installers have been back several times, connecting their laptop to the system but cannot find the problem.

There are 8 indoors on this particular system connected to a G50A controller. None of the other indoors switch off apart from this one.
I'm told that the unit can be switched on and work fine for a few hours then all of a sudden it just switches off and needs to be switched on again.

It doesn't flash an error code and even when the laptop was connected it shows as the unit hasn't switched off, when it has.

There are no Krp's or timers set on this unit and it can only be controlled by the G50a since the individual controller was removed.

There is 100% no chance anyone could be tampering with it but it has everyone stumped including mitsubishi technical.

[Yuri B.]

What about changing its pcb with another unit ?
Sorry if it sounds too simplistic.

[marc5180]

There isn't another one of these model numbers on site the rest are fancoils or 1 way blow cassettes. If we get asked to fix it then i think we would order one from Mitsubishi but it's the origional contractors decision.

[Gary]

is it just the fan motor that switches off? How do you switch it back on?

[Yuri B.]

I would not be stalled much at the fact that the models are different. Probably all use the same set and type of sensors, same type of electronic EVs. And let PCBs be not set properly in the places but just hang in air for a while of testing. Some thoughtful experimenting.

[The Viking]

OK,
I've actually seen this before.

There the installers had done some really dodgy commissioning.
The address settings on the remotes/indoor units/G50 didn't tally up.
No matter how much you look at the M-tool, it will never tell you that.

Hang on,
Just reread your post.
Have the system had a virgin restart since the remotes were removed?

Top tip:
Wait until Thermatec log on and then follow his advice...

[dawfake]

OK,
I've actually seen this before.

There the installers had done some really dodgy commissioning.
The address settings on the remotes/indoor units/G50 didn't tally up.
No matter how much you look at the M-tool, it will never tell you that.

Hang on,
Just reread your post.
Have the system had a virgin restart since the remotes were removed?

Top tip:
Wait until Thermatec log on and then follow his advice...

Swop PCB with other unit on site and see if problem moves. Also make sure unit is set for restart on power failure, perhaps power is dropping for some raeson.

[marc5180]

is it just the fan motor that switches off? How do you switch it back on? the whole indoor unit just switches off as though it has been turned off by the controller. It doesn't lose mains power though.


OK,
I've actually seen this before.

There the installers had done some really dodgy commissioning.
The address settings on the remotes/indoor units/G50 didn't tally up.
No matter how much you look at the M-tool, it will never tell you that.

Hang on,
Just reread your post.
Have the system had a virgin restart since the remotes were removed?

Top tip:
Wait until Thermatec log on and then follow his advice...
I asked them if they had done a VR since the remotes were removed and they said yes they had several times, they are 100% correct it is not mispiped or incorrectly wired.

[dawfake]

if the power supply is diconnecting even for a short period due to a loose connection, then the unit will stop, unless it has been set for auto restart. Check all electrcial connections back to the fuseboard.

[Gary]

Electronics need a good earth ground or they get crazy. And random signals can be generated by signal wiring being in proximity to line voltage wiring. Or possibly there is a loose connection or a hidden break in the wiring somewhere. I wonder if using an IR thermometer might reveal a hot spot.

Just grasping at straws here.

[marc5180]

if the power supply is diconnecting even for a short period due to a loose connection, then the unit will stop, unless it has been set for auto restart. Check all electrcial connections back to the fuseboard.
If it was losing power it would flash a 1302??? fault though surely. I will check ask if they have checked all lose connections though.

[marc5180]

Electronics need a good earth ground or they get crazy. And random signals can be generated by signal wiring being in proximity to line voltage wiring. Or possibly there is a loose connection or a hidden break in the wiring somewhere. I wonder if using an IR thermometer might reveal a hot spot.

Just grasping at straws here.
I've heard that if the signal is next to a power cable there can be interference, i've never come across it myself but you could be onto something there.

[superswill]

I've heard that if the signal is next to a power cable there can be interference, i've never come across it myself but you could be onto something there.

marc,

we had this on a large job in a shopping centre,it was put down to the comms cable running next to the 3 phase lift supply (added after) we had all sorts of funny faults and ran a few comms cables in temporarily along a different route,from memory we had to earth the screen cable at the unit end only,

may help

[Thermatech]

The fist thing is to double check that all address settings are correct at the indoor unit , local remote control & group setting / local remote controller setting at the G50.

I have had it when the G50 set up is not the same as local unit set up & then other remote controllers have also got control of your problem unit & it is just someone else turning off another unit somewhere in the building.
The VRS will not correct this if the set up at the G50 is wrong.

The next thing is 240v power to the indoor unit.
I have had poor terminal connection at the local spur cause this intermitent problem many times.

If the system is reporting 1302 then that is just the G50 & local controllers reporting the HP fault at the outdoor unit which is unrelated.

How was the local remote controller removed ?
If it is 30v dc controller then it completes an electronic hand shake with the indoor unit when system first power up.
VRS is for delete connected unit info at the outdoor unit.
to remove a local remote controller you must carry out delete procedure with the local remote controller before disconnect 30v dc cable otherwise you leave ghost controller in the system & VRS will not resolve this.

As suggested you can also set up the auto restart if you think power supply is an issue.

If the 30v dc control cable do not have screen or screen not connected to ground correctly & cables running allong side 3 phase power cables you will tend to get 6607 communication errors if magnetic interferance is a problem.
In this case use the engineer mode at the G50 & look at error history. If no communication errors in history over the period of time the indoor unit has been switching off then interferance not very likely.

[marc5180]

Thanks for your reply Paul and Thermatech.

I have been told the address settings are correct but without checking then myself then i have to take their word for it.

I don't know how they removed the remote controller but they told me they were doing a virgin restart after taking the controller out but i dont know if they also deleted the controller? How would i go about deleting it? Is it in the service manual? and the same for auto restart is this set at the indoor unit?

By having a "ghost" controller could this cause the indoor to just switch off?.

[Thermatech]

Its like this
The indoor unit did electronic hand shake with its local remote controller.
But then the remote controller was disconnected without first sending delete message to the indoor unit.
So the indoor unit still considers that it should be able to communicate with the remote controller.
But now it can no longer communicate with the remote controller so stops on a communication fault.
It cannot report comms error to RC because its no longer connected.


This should show up in the fault history at the G50 provided the indoor unit is programmed in on the G50.

To delete a ghost RC
1/ connect PAR 27 with the ghost address set on address dips.
2/ use engineers mode to electronically hand shake with indoor unit. Dial up indoor unit address & then use test button to confirm.
3/ RC confirmes indoor unit reply IC in top right of display.
4/ Delete with clock on/off button click twice.
5/ RC shows -- instead of IC.
6/ Exit engineer mode & if RC displays HO then disconnect 30v dc.
Its all in the service manual.

You can use this enginners mode to get control of any of the 50 indoor units which are connected to the G50 from any one RC.
Thats why its important to make sure no other RC also has control of the indoor unit which is switching off as the other RC could be any location in the building.

You can use any remote controller using the enginners mode to interogate the system to find out what remote controllers have control of the indoor unit.
The Mnet monitor computer service tool gives all connected unit address data & RC electronic connection to indoor units but you can get all the same data with any RC provide you know how to use the enginner mode functions.

Address setting mistake or control from wrong RC at another location in the building is the prime suspect for this indoor unit switching off.

Remember with 30v dc the remote controller can control this indoor if its connected to any outdoor unit system which is being controlled by this G50 central controller provided it has the correct address setting for this indoor unit or has been set to control this indoor unit with using enginners mode.

[marc5180]

Thanks for the detailed reply. I won't be back on site for a few weeks now unless i get a call out but i may suggest going back to have a look at the problem because the manager there wants it sorting and the installers have been back several times and not fixed it.

As soon as i go back i'll check the address settings myself and delete the ghost controller, unless it has been done already.

I'll update it as soon as i can.