New Mitsubishi installation error fix

[maher]

Hello Everyone,

I just created an account because we installed a A/C system last weekend in 3 of our upstairs bedrooms and we are experiencing some (strange) issues.

First off our installation contains the following:
- Mitsubishi SCM50ZS-S outside unit, which came charged for 45M of tubing according to the supplier
- 3 Mitsubishi SRK 20ZS-W inside units
- room A has 10 meters of tubing (so 10 for discharge and 10 for suction pipe)
- room B has 6 meters of tubing (so 6 for discharge and 6 for suction pipe)
- Room C has 2.5 meters of tubing (so 2.5 for discharge and 2.5 for suction pipe)

Everything seems to be wired up correctly and we have vacuumed all 3 of the lines beforehand and left them all for about 20 to 30 minutes afterwards to check the pressure of each line if it would drop or not (to check for leaks). Everything seemed fine and we opened up the lines.

We then tested all the systems by turning them on all 3 at the same time and let them run for about an hour. Again everything seemed fine at this point they all cooled and everything was working as expected. This was last Saturday (18th of Juli). Then on Sunday we turned 2 of the 3 rooms on at night and again everything was working perfectly fine.

Then come this week we turned on one of the rooms and it didn't seem to cool really while it ran for a good couple of hours. Because of this I started testing yesterday and turned them on all 3 at the same time again. Only this time I got an error code:

- Timer light on
- Power light blinking 7 times

According to the manual this meant "Refrigerant is insufficient Closed service valve" which seems strange to me since we vacuumed all the lines and it seemed all fine. Also I'm pretty sure that we opened up all the lines.

Then we took the power off today and plugged it back in to give it a hard reset, now we have a completely new error. When we turn on the unit in one of the rooms we it starts running and then after about 10 seconds it shuts off again and displays the following error:

- Timer ligt blinking 4 times
- Power light blinking constantly

Again we checked the manual and this seemed to mean the following: "Broken discharge pipe sensor wire, poor connector connection".

Now I'm not sure what this means or could be since this is a completely new system.
I really was hoping someone here could point me in the right direction on what could be going on. All help would be highly appreciated.


FYI I am in the Netherlands

[martinw58]

if you run all 3 units together and its ok then you need to check units are wired and piped correctly if you have crossed the inter connecting wiring or pipes you will only notice if you run one unit at a time

[maher]

@martinw58 I understand the message I posted is pretty long so just to give a recap.

it worked fine in the beginning
then yesterday it showed an error saying "Refrigerant is insufficient Closed service valve"
then I took the power of it today and it gave me a new error afterwards saying "Broken discharge pipe sensor wire, poor connector connection"

[hyperion]

It would appear that you did not carry out a full OFN pressure test of the pipework, before you vacuumed the lines out. It is quite possible that you have a small leak which has allowed some of the refrigerant to escape. There may also be a minimum pipe length recommended for each unit, as 2.5 metres is pretty short.
For calculating the overall length of the pipe runs, you normally only need the length and size of the smaller, liquid line.
As mentioned above, carefully check that you have not crossed any of the pipework or wiring. Once you have done that, you may have to resort to calling in an air conditioning service engineer who is familiar with the Mitsubishi Heavy Industries equipment.

[maher]

It would appear that you did not carry out a full OFN pressure test of the pipework, before you vacuumed the lines out. It is quite possible that you have a small leak which has allowed some of thge refirgerant to escape. There may also be a minimum pipe length recommended for each unit, as 2.5 metres is pretty short.
For calculating the overall length of the piperuns, you normally only need the length and size of the smaller, liquid line.
As mentioned above, carefully check that you have not crossed any of the pipework or wiring. Once you have done that, you may have to resort to calling in an air conditioning service engineer who is familiar with the Mitsubishi Heavy Industries equipment.

Thanks for the response. I agree that it's most likely a small leak then, however I do find it a bit odd because of the fact that we vacuumed it with a micron gauge and after vacuuming left the gauge on for 30 min to check if there was any change and there wasn't.

I did check the wiring and pipework multiple times actually but that all seems on the up and up.

Also something very interesting happened. I did another hard reset because the new error striked me as odd. Now the second error I had (about the discharge pipe) is gone. I'm currently running all 3 of them again to see if they will automatically turn off again.

Even if they don't it still doesn't really seem to cool that well so I would say there is an issue somewhere for sure (probably small leak them I'm afraid)

[Brian_UK]

A vacuum test is a test of the dryness of the system.

Also the vacuum test only places a pressure of one atmosphere, 1 bar, on the test area.

To comply with regulations there should have been a strength test followed by a pressure test. The pressures involved could have been up to 45 bar or thereabouts.

[maher]

Thanks for the answer Brian, that actually makes a lot more sense to me then, guess best bet now is letting someone come over to actually do the pressure test and fix the most likely leaks that are present and fill it up again.

[frank]

You can use a water/soap solution to test around your pipe flare connections to look for a leak