He could be right - almost never happened before because almost never is a customer watching or checking what they are doing while having professional experience with similar designs, processes and issues. Customer does not know it all but is picking up on processes and results that are at the very least questionable.

I've asked for a plan for Tuesday (the actual trained tech. coming). They have a chance to recover some of the faith I originally had. If the trained tech. (he is also the General Manager) stays and sees that things are done methodically and properly that could be a good sign. I'm cynical, so what might happen is he comes talks to his tech. and lays out what to do and leaves to help the company owner with sales calls.

exactly. He should have said "We've been probing the depths of crappy installs for some time and making more and more money every month. I'm disappointed that someone finally figured us out" but that would require accountability for ripping people off.

My question: why are they using a different line size than specified? Is there an issue with distance and flow resistance? Or is this just what he had on the truck?

I think all the ports on the outdoor unit have the same connection sizes. However, one of the indoor units calls for a larger diameter line set, maybe because of distance. So at the outdoor unit there needs to be a reduction.

Does anyone here know someone at US Mitsubishi air conditioning group? I'm thinking someone at mid-management level or higher.

Maybe someone here has a first degree connection with an upper manager at Mitsubishi via LinkedIn. See if you can start a conversation and then forward to me if he/she will agree to talk with me.
Thanks.

In case anyone is still interested.....
Apparently there was a meeting on Monday at the AC company and then people showed up here with some new equipment. Things were better but not great.. could not easily pull below 700 microns. In the afternoon they came back with a new hose that was the vacuum type. Big improvement - pulled to 450 microns.
I pointed out that the new hose brought this morning wasn't the vacuum type. If you want to pull a good vacuum things have to be correct and in good condition. The last? problem is when turning off the ball valve to hold the vacuum - it adds 100 microns.
Anyway things are getting better.

Well.. here is another update. They tried a bunch of strange approaches including pulling with two different pumps with hoses going to the same place.
Finally went back to the setup we had yesterday but had the same issue of going from 460 to 540 when turning the valve in an attempt isolate the pump and start the decay test.
We called Mitsubishi tech support and they confirmed the pump to 500 and then hold it for one hour specification. It is commonly done in the field. The spec. would not be as it is if it was very difficult to pass.
I'm not sure what is going to happen next. I suggested a few days ago that we try a process of elimination approach but they didn't want to do that.
I guess at some point they give up and I hire someone to come find the leak and take that money out of what I owe them.

For what it's worth, I installed a two ton Mitsubishi about 2.5 years ago and was able to pull a vacuum to the specified micron levels with a middle of the line pump from Robinair and the automotive a/c hoses that came with my Robinair manifold set (I added a micron gauge to the manifold and appropriate fitting adapters to the lines). I also pressure and leak checked using nitrogen (swept the system as the manual described as well.).

It sounds like the guys working on your system are not sure of what they are doing, and/or not following best practices steps.

Good work there. You probably had no brazed joints and good quality flares. Possibly used Nylog and all the things usually recommended.
They ran the pump all night was 413 microns at 2:50AM and 408 microns at 5:30 AM.
So it is dropping very slowly. The Navac pump is good we tested it by putting the micron gauge right on the pump and got 3 microns. I called Navac this morning to ask what they think is going on. We might be pulling against a small leak - that's my concern. The decay test will be the key thing to watch.

Yes to the flares and Nylog. I had never flared copper tubing (lot of experience flaring aluminum tubing on aircraft, however), so I practiced repeatedly on scrap pieces until I was confident I was doing it correctly. This was a first project of its kind for me, but I do have many decades of tools and experience with automotive a/c, and am willing to read and follow directions, so was reasonably confident I could do the install myself, and thankfully it was successful (took me forever, though, particularly the step of routing and properly bending the copper lines through two walls, as that was definitely a first for me :)).

Hopefully you/your guys will be able to find the slow leak if that is the case.

I asked them to bring a new core tool and try again. Yesterday morning he showed up with a new core tool. So we now have new: core tool, micron gauge, pump, pump oil, and vac. hose. Pulled 413 in 15 minutes. Looking good - so we went for the final decay test (purple line).
See graph. There is no more I'm going to get from these guys so we charged the system. There is a reason it is going up. Hopefully still something not sealing in the instrumentation. I might buy a leak detector and go around seeing what I can find.



http://forums.pelicanparts.com/uploa...1696076846.jpg

Write down what the charge pressure was and check again next year. A good leak detector should find any problems, but I do not know how good the cheaper ones are. Did they braze the line set to the evaporator core onsite or was that pre attached?

They charged by weight. Done. No pressure measurement or readings of any type that I could see. They used the gauge set to get the 410A into the outdoor unit (compressor) but I didn't see any adjustment of pressures/etc. like balancing the sub cooling and super heat and all that business.

Roger that - re. a leak detector - I was thinking of getting one. Been reading about the different types.

The line sets are attached to the indoor units and outdoor unit via flares. During the pressure test of 600psi they found a bad flare and then redid the pressure test. The one thing I didn't like was brazing lines together up in the attic when I specifically asked to not have that.

I would bet that you are leak free with that deep of a micron reading.

Not many companies install them but I still like having a liquid line sight glass for the moisture indicator and the indication of a solid column of liquid to the expansion valve. Nice to have the visual.

For those interested in mini split AC. I'll continue with where I am at this point.
The system is in and "working". The performance is not quite what I was expecting but maybe I need to adjust my expectations.
We had a hot day and here's what happened. I recorded info. on the one wall unit cooling the large family room.
Here's what happened. You see the coil exit temp. going up when I think it should have held. All the heat sources (sun, attic temp. etc.) were going down.

In any case you might like my graph.http://forums.pelicanparts.com/uploa...1696898095.png

^^^

Was the compressor running, even at a very slow speed (assuming it has a variable speed compressor like mine does), at the time the evaporator temp was rising? If so, I doubt that is normal.

Currently my mini split is set on 69; room temp is 69 and the compressor is not on, so the evaporator coil is also 69 (I know that temp because I use an aftermarket controller that has a fins/evaporator coil sensor).

When I have the aftermarket controller set to a very cold temp (47-50F, which is the temp range I sleep in, year round), then the evaporator reaches temps of 45-to-near freezing while supercooling my room and then rises/levels off once those cold temps are reached.

Oh yes, the compressor pump was running I think on the high speed and the outdoor unit fan was also running. The unit is a brand new Mitsubishi 42,000 Btu 5 port Mini Split.

For those still interested - The AC contractor wanted me to do another test while recording the temp. going in (coil inlet) the wall unit. So I did that, see graphic.
Also, I called Mitsubishi again - got transferred to customer relations. The lady that answers that line knows me now. :-) Basically the only option is to continue trying to work with the contractor that installed the system. If they need help they can contact Mitsubishi or their distributor that administers the Diamond Contractor program. The distributor is supposed to have experts that advise or can come on site. The other thing she mentioned a few times.... if I don't have confidence in the original contractor get another licensed AC tech to come and take a look. Certainly not a bad idea but not happy to pay for install and fix labor coverage and then have to go to another company to get a diagnosis.
Anyway here is the last test.

http://forums.pelicanparts.com/uploa...1697036241.jpg

It makes you wonder how many installs are working but not working well. Owners don't know they just think it's a bit more expensive and less efficient than they had expected....