Originally Posted by Peter_1
If the installation is new and was done by the official importer of Mitsubishi, all should be done under warranty of the techs who installed these units, so why worry before.
Same for the pipe sizes, that's their problem. You may not doubt their competence because you have a problem with a new unit.
They have to solve it til lit works fine and on the parts is a warranty of 3 or 5 years.
Even a new unit can fail , even it's a Mitsubishi.
We have a client who installed in November last year a PUHY200 from Mitsubishi with 4 indoor units. he had nothing but troubles with one of the indoor units (in a server room of a hospital hear nearby) since the start-up. This cassette still decreases in cooling capacity and on some days - not every day- when the client arrives in the morning, the server room is at more then 33°C. Since more then 3 months now, 3 movable splits are installed in this room together with the cassette, regulated at 28°C, in case of.
Mitsubishi Belgium came now already 3 times to the site. They always bring with them their 'very handy portable computer' with their very specialized 'maintenance software tool' They connect it to the system and log for some days all the values.
Manifolds??? They don't need it anymore, all with the computer. The modern techs of these days!!! :cool:
First conclusion: there were electrical interferences, noises on the lines, caused by the fact that no shielded wires where used for the control wires.
They also cutted away some wired bridges on the PCB.
OK, rewired everything with shielded wires. Was a big job for my client.
OK, connected the computer again and logged again for a week. In the meantime, indoor unit decreased slowly in capacity some times during this logged week.
They saw this time that the R407c was even not fractioned. Wow, they can even see each component of the gas, without a spectrometer. What are these Japanese engineers such a smart guys. :rolleyes:
But what they saw was that there was a gas in the system which didn't belonged in there: nitrogen or air.
But, LP and HP were normal, alle the logged temperatures were within the specs.
Again, I felt stupid I'm that old fashioned guy who does everything with the manifold, temperature meter and a sliding ruler of Danfoss.
OK, evacuated all the R407c, vacuumed till 2 Torr for almost 2 days and refilled it with new gas. They even can calculate with a computer how many gas there gas to be filled in a system.
17.6 kg, wow,...17.6,.. not 17.8 or 17.4 no 17.6 . Again,...wow, what a smart Japanese engineers. They even don't need a sight glass and they even don't need a liquid receiver. Both should of course be very handy but who am I to doubt their competence.
And the wonder happened, the system cooled.
For 2 days.
Computer is now connected again on the system. I wonder what the magical software now will say.
I also asked also the engineer the following because the system was running at 18 bar in cooling mode for an ambient temperature that day of +/-15°C. "Why not lower the HP to increase capacity, increase COP and decrease power consumption?" They use EEV's, so this is perfect possible.
The answer was predictable: "Well, the software" again the magical software "determines the right HP and we can't change this. But it can't harm the system if it runs at that pressure"
I stopped asking questions.
It can't harm indeed the system but it should harm less our environment if it should run with a lower HP.
There was also no satisfying answer why there was a swing of +/- 0.75 bar on the LP while measuring. If we install a pack, the PLC holds the LP on 4.25 bar, not 4.30 and not 4.20,...4.25 bar.
Why can't they just do this simple regulation?
I told you this story just to say:
1. it's not because something happens that we made a fault.
2. it's not because there are a lot of electronics in the units that these units are de facto better units.
3. It's not because you can connect a computer to a system that these systems can serviced better, faster and more accurate.
4. It's not because you call a specialised engineer that they can pinpoint the problem. Replacing PCB's, well my youngest son of 13 can co this.
5. If you can't apply the thermodynamic basics to a systems , even if the space the PCB's and the contollers takes is larger then then condenser, even if you can connect 15 computers to the system, you will not solve the problem.
These conclusions can also be made for EEV's in a refrigeration system.
They better had replaced the whole indoor unit like we asked the first time.
Coming back to your questions: 33 bar =55°C condensing and 10 bar = 11°C evaporating.
Seems both very, very high. Air in the system perhaps?
They better should restart completely
