Mutsubishi Multi

[r.bartlett]

gents we have a 2 pipe PURY? with 6 PEFY 63 ducted units. We have only just got this building and noted that 2 of the indoor units have very clean filters compared to the rest(they all draw retrun air from the same void) . Further investigation shows these 2 don't run. :confused:

The system doesn't fault and continues as if nothing has happened. We saw some signs of burning in the indoor control box but access was limited and we hadn't got the go-ahead to investigate further.

Should the system just keep running like that without 2 of the 6 indoor units running??

Why no fault code - could someone have done a restart and deleted the 2 units rather than fix them?

[stufus]

It's always a possibility someone else has discovered this previously and deleted the affected units from the m-net,therefore the system will carry on regardless.
Another thing to check if the units are all of one controller is the model number of the controller ,i had one a few days ago on a 2 year old system where a par 21maa was used to control 5 units via the 12v connection .Nobody noticed 1 of the units hadn't run since it was installed ,as a par 21 will only do 4 units...
Cheers
Stu

[Thermatech]

It could be that those 2 indoor units have no 240v connected. In this case the units are still on the Mnet but cannot operate due to no power supply but in this case the units do not send a fault message to any remote controller because this is not a fault. City Multi systems are made so that you can turn off 240v power to any indoor unit & it does not cause a fault & shut down the complete system as with other types of VRV / VRF.
So MCB for those units off, or fuse removed at the local spur something like that.

The last ac contractor could have disconnected the Mnet at the 2 indoor units & then carried out a virgin restart at the outdoor unit. In this case the system re initializes & then only communicates with the indoor units still left connected.
In this case test the Mnet connection terminals at the 2 indoor units for 30v dc & make sure its plugged in onto the circuit board.
Connect a PAR21 or PAR27 remote controller to each unit & see if they operate or trip on a fault.

When you get access & instruction it should be straight forward to identify the cause as the units may have been left off for a reason.

[r.bartlett]

I had a look in one of the control boxes. Signs of burning but there was 240v onto the unit. however as I didn't have a tall pair of steps and we were not appointed as official contractor (which we now have been given the verbal ok) I didn't want to go too far.

I will be going back on Wed to investigate further. However I don't have a Mitsi controller afaik

Richard

[stufus]

Was the scorching in the top right hand corner of the electronics section .I recently surveyed a site and came across a couple of unit's with scorching there.
On inspection found a component blown clean of the boards don't know what it's called though .it's a green disc at right angles to the board and forms part of the fan circuit as far as i could make out.
Like yourself didn't get to deep into it ,However the fans were running.Going back tomorrow will let you know what I find might be useful .
Cheers
Stu

[Thermatech]

The green disk is often the zener diode which protects the circuit board from excessive high or low power supply voltage.
Typically it will blow if you have a poor N connection or disconnected N.
I am not an electronics engineer so i have not got a detailed explanation about this but I tend to view this component like a fuse so if it has failed then investigate the 240v power supply to locate the cause.
My understanding is that if the circuit board did not have this protection then there would be the potential for the circuit board to overheat & catch fire if exposed to incorrect power supply voltage.

[stufus]

10 OUT OF 10 for Thermatech
Went back today and found a loose neutral on the ring main serving that bank of indoors.
But strange enough all units are still operating ,changed mode on all units, no problem ,did notice thermo off wasn't working on heating,didn't adjust fan speed or switch them off,Can't afford to have them down while waiting for new parts.
I'll fully test them when i have replacement boards in my hands
Cheers
Stu

[Gingerair]

Sure there's many members that have seen this before, but a loose neutral in a dist board can cause a lot of damage, especially if the indoor units are fed off different phases.
If you lose the neutral then you can get 440v right through the single phase supply of the indoors, it'll fry everything, boards, fan motors, condensate pumps..

They may not fail straight away, but it won't be too long before things start going toes-up..

Ginge :)

[r.bartlett]

645764566455

I went back today and checked further both units were the same. fried PCBs at the same point.

I have concerns that this was done very early on in their life as the filters and fans show no signs of dust and they are over 5 years old...

So we need 2 boards but my other concern is what caused this to happen in the first place??

Richard

[stufus]

That's the very same as what i found.Check all neutral connections.
Did it for me.
Sparks probably meggered with spur on way back when ,or repaired a bad neutral and stayed quite about it .
Cheers
Stu

[Thermatech]

Hi Richard

The damage is consistant with a power supply problem like poor N connection.
The red & blue cable on the red plug is 240v L&N coming direct from the L&N 240v power supply terminals.
The first components in the 240v circuit on the board is the fuse & ZNR.
After these safety devices there are the 240v load components connected like the transformer & fan control circuit.
The blown ZNR zener diode has done its job & saved the circuit board from going up in flames.
If there was a ground fault at the unit then the fuse only would have blown.
So suggest look at the 240v power supply ring main & fuse spurs to make absolutely sure the power supply is ok before you power up the new circuit boards.

[r.bartlett]

I wonder if this was done during installation as the units certainly do not look like they have ever run..Not bad since they have been maintained every 3 months since being installed.The last one AFTER I first reported them as not working..:-)

However I studiously checked for 230v on L+N and can confirm this was sound..

I am awaiting confirmation of costs before proceeding but if I was the end user I would be considering a legal case against the incumbent maintenance contractor

Richard

[stufus]

The problem is far to many contractors consider cleaning the filters as a full maintenance visit ,and usually send a first year or G.O. to do it who in fairness are generally paid from the neck down.I have come across this more times than i can remember .
There are two problems here .
1- The contractor not providing the proper service
2- The client representative signing off on each visit and failing to notice there was a problem.
As you said, it's high time people were held accountable for this type of crap !!
Cheers
Stu

[r.bartlett]

Yes indeed. I am led to believe we can interrogate the outdoor unit to see if these two units have ever been working as we suspect they failed at some point during installation and due to the rather inflated cost of the replacement boards (eye watering!) they probably just thought they could get away with it..and have done for many years

However whilst that goes on in the background can someone ID these two items? 64616462

[stufus]

I haven't seen either of them in a few years,
But from memory and it's not very reliable at the best of times ,you're set up is for simultaneous change over operation,usually used for open plan areas the controller sets the zone temperature and the remote sensor in the second picture detects the zone temperature .All connected units operate together ie. all heat or cool together.
As i said it's been a while since I last time i came across this setup.(i think that's what it was for)
I'm sure Thermatec will be along shortly to tell me I'm totally wrong:D
Cheers
Stu

[Thermatech]

The Procon YACO is an auto changeover thermostat.
So you have a Y series heat pump City Multi system which can only heat or cool & needs to be told which mode to work in.
The YACO ( Y Auto Change Over ) has a set point temp & adjustable dead band.
Below the set point & dead band the outdoor unit runs in heat mode then above the set point & dead band the outdoor unit runs in cooling.
The temperature sensor location is critical as this impacts when the system runs in heating or cooling.
The enduser can set any set point temperature at the local remote controllers but the YACO dictates the operating mode heat or cool depending on its setings.

If you look on MEUK web site you should be able down load the YACO manual.

[r.bartlett]

Gents

We have been given the go-ahead to repair the units. Seems they do not want to use the original contractor and/or maintenance company although personally I would have thought they'd have a strong case.... However I personally would like to interrogate the system to see if we can assertain when these two failed or if they have ever been working.

Can someone please confirm the proceedure to check this
Would somone popping down to do a reset wipe out this data in any case??

Going to site on Friday with PCB's to get them running

Richard

[Thermatech]

Richard

I dont think the outdoor unit memory will tell you how many hrs each indoor unit has been operational
It will record the total compressor run hrs & number of compressor starts.

[r.bartlett]

Richard

I dont think the outdoor unit memory will tell you how many hrs each indoor unit has been operational
It will record the total compressor run hrs & number of compressor starts.

I have had this from a Mitsi tech:



Let me have model number of Outdoor Unit and I will show you how to prove it via the Outdoor Unit pcb (if it is new enough).

The late 407c and the current 410a keep running time/error history/addresses in the pcb.

[stufus]

I have had this from a Mitsi tech:



That's all well and good but a lot of people don't bother or don't know how to initialize the date stamp to begin with..so even if you get in it will probably be way off.
And if your going back to YMFC stuff it wasn't available in the early systems.
Plus it's very easily erased .
I was at a 2006 unit the other day that thought it was still 2008..
Cheers
Stu

[r.bartlett]

I believe it's only 5 years or so. If you know the method then I would apreciate it. The mitsi tech hasn't got back to me.

[install monkey]

if it was comissioned by mitsi then the laptop connected on the m net will give a snapshot of valve positions,coil temp and return air values but to check this would be hard.check the drip tray for tide marks and any signs of corrosion on the steel end plates of the evap coil,or dust on the fan scrolls-filters could have been maintained but who cleans fan scrolls and casings

[soleowner]

as a par 21 will only do 4 units...
Cheers
Stu

In the US market, all wall mounted remote controllers (PAR-21, PAR-30, PAR-27, MHK-1) can control up to 16 IDU's in a group. The number of RC's per group is 0~2.

[soleowner]

I believe it's only 5 years or so. If you know the method then I would apreciate it. The mitsi tech hasn't got back to me.

Did you find out how to check run time on IDU's?

[soleowner]

However whilst that goes on in the background can someone ID these two items? 64616462

This control scheme seems redundant. The system can cycle system change-over via OAT, schedule, master, or weighted average. This assume you have a central controller with web browser licenses. I am looking into the YACO device. If no CC, then a master controller (Lowest addresses IDU) can be set or a PAR-27 or system group controller. Surely a System Group Controller is less expensive than the set up they have now.