HVAC Mini Split Question

[David2011]

One downside of the multizone mini split is sometimes my daughter wants heat in her downstairs bedroom while I want cooling in my upstairs bedroom. This can't be done. All units are heating or all units are cooling... it can't be some of each.

Mitsubishi has a line that will heat one zone and cool another. My AC guy was telling me about them when he installed a conventional 3 zone system in my shop and all seasons room.

 

[Scra99tch]

I'll do both not tempted to pressurize to the rated capacity of the compressor which I believe is around 600PSI for mitsubishi hyper heat. But will probably bring it closer to 450-500 psi with nitrogen and do the bubble check around the flared joints.

This is in the manual for the operation of the high pressure switch.

High pressure switch(HPS) Pressure Normal
HPS
537 ± 22 PSIG Close
696 +7-15 PSIG Open

 

[RaisedByWolves]

I had a hell of a time with my Mitsubishi 3 zone. I finally realized that the electrical connections on the compressor were:
1 - 2 - 3
but the line ports were
3
2
1
So I had wires for 3 crossed with the lines for 1 and vice versa. That is when I learned I could use the compressor to pump the freon out of the line set back into the compressor coils. There is a solenoid for every port on the compressor manifold which syncs with which interior unit is on... and getting freon.

I vacuumed the lines then pressurized them with Nitrogen and let them sit for a day. Of course after that I vacuumed again and released the refrigerant. I forget the nitrogen pressure I used for testing... but, yeah, it was up there. There is some "nyloc" or something sealant that I used on the flares... just the flared surfaces, not the flare nuts and not the outside of the flare that touches the nut.

The quality/expensive yellow jacket flaring tool was worth every penny!

I just used a quality set of Yellow Jacket gauges. I didn't buy the expensive electronic micron vacuum gauge. I think I ran the vacuum pump for a couple of hours just to be sure.

We make evap coils where I work and our dip tanks (tank of water to show leak and contain possible explosive decompression) feed lines are 500psi.

We have only had a few coils rupture, but it is impressive when it happens. This is only for rework.

For leak detection they go into the “Halo box” and are charged with helium, which is in turn detected by a mass spec detector.

 

[Scra99tch]

We make evap coils where I work and our dip tanks (tank of water to show leak and contain possible explosive decompression) feed lines are 500psi.

We have only had a few coils rupture, but it is impressive when it happens. This is only for rework.

For leak detection they go into the “Halo box” and are charged with helium, which is in turn detected by a mass spec detector.

Okay maybe I'll just do 499 PSI

 

[DAM 79]

Hi I had a quick question about a multi zone heat pump install. When you pull a vacuum on several installed heads is the whole plumbing liquid and gas line under vacuum? Or should you pull vacuum on each service port? Reason I ask is I've seen pictures of the interior and the all the gas lines are all plumbed together. But the individual zones liquid lines are all actuated through valves so can't be under vacuum?? If I have this correct.

I'd like to put these under pressure with nitrogen to check for leaks for <3 hours. Then pull vacuum for possibly even much longer say overnight but can't be there for 2-3 days to do both zones.

I just saw this post and I will give my 2-cents to all the DIY guys out that Don’t !!!
If you have a multi zone ductless system and you need to definitely put the system under pressure to test for leaks !!! You should soap bubble every flare fitting!!!!! Bubbles don’t lie!!!!
Next when pulling a Vacum you should do a triple Vacuum!!! I believe that is what Mitsubishi recommends and it is in there literature that’s where you put the system in Vacuum and pump down checking your Micron gage it should be well below 400 microns !!!! Then you break the vacuum with dry nitrogen and then pull another vacuum and repeat the process for a total of three times
You want that system dry and free of any moisture!! That is what kills the compressor over time !!!
You should also install a surge protector on the condenser disconnect also very important because without one you will have problems with any warranty claims those unit are very sensitive to voltage spikes and lightning strikes !!!!
And yes all your indoor units Will run in heating or cooling you can not have one indoor head running in cooling and the other in heating Unless you installed a branch box or went with a different outdoor unit !!!! I’ve been in the trade since the mid 90s and run the install department at the company I work for !!!
Again Just My 2-Cents

 

[Scra99tch]

I just saw this post and I will give my 2-cents to all the DIY guys out that Don’t !!!
If you have a multi zone ductless system and you need to definitely put the system under pressure to test for leaks !!! You should soap bubble every flare fitting!!!!! Bubbles don’t lie!!!!
Next when pulling a Vacum you should do a triple Vacuum!!! I believe that is what Mitsubishi recommends and it is in there literature that’s where you put the system in Vacuum and pump down checking your Micron gage it should be well below 400 microns !!!! Then you break the vacuum with dry nitrogen and then pull another vacuum and repeat the process for a total of three times
You want that system dry and free of any moisture!! That is what kills the compressor over time !!!
You should also install a surge protector on the condenser disconnect also very important because without one you will have problems with any warranty claims those unit are very sensitive to voltage spikes and lightning strikes !!!!
And yes all your indoor units Will run in heating or cooling you can not have one indoor head running in cooling and the other in heating Unless you installed a branch box or went with a different outdoor unit !!!! I’ve been in the trade since the mid 90s and run the install department at the company I work for !!!
Again Just My 2-Cents

Thanks for the reply.

I am tempted to hire out the install but I always feel bad asking for just the hookup as I really don’t want to pay someone for the rest of the grunt work.

Plus I have a feeling I’m not going to get a competent installer for a one off like this although I have not made any calls.

I’ll be doing essentially what you said with pressure and vacuum.

I’ll be using a yellow jacket flare tool that give a bit deeper flare. Measuring as I go for the correct dimensions and torquing down correctly.

I am going to practice several times on deburring with a Vargus tool and proper flaring on some scrap tube.

Using rectorseal blue soap to check for leaks then applying nylog to the flare cup to make sure I don’t gall any of the copper.

 

[David2011]

I just saw this post and I will give my 2-cents to all the DIY guys out that Don’t !!!
If you have a multi zone ductless system and you need to definitely put the system under pressure to test for leaks !!! You should soap bubble every flare fitting!!!!! Bubbles don’t lie!!!!
Next when pulling a Vacum you should do a triple Vacuum!!! I believe that is what Mitsubishi recommends and it is in there literature that’s where you put the system in Vacuum and pump down checking your Micron gage it should be well below 400 microns !!!! Then you break the vacuum with dry nitrogen and then pull another vacuum and repeat the process for a total of three times
You want that system dry and free of any moisture!! That is what kills the compressor over time !!!
You should also install a surge protector on the condenser disconnect also very important because without one you will have problems with any warranty claims those unit are very sensitive to voltage spikes and lightning strikes !!!!
And yes all your indoor units Will run in heating or cooling you can not have one indoor head running in cooling and the other in heating Unless you installed a branch box or went with a different outdoor unit !!!! I’ve been in the trade since the mid 90s and run the install department at the company I work for !!!
Again Just My 2-Cents

Mitsubishi definitely has a line of mini splits that are cap of heating in one zone and cooling in another at the same time. From the des on their website: “Enter VRF zoning systems offering either heat pump (heat or cool) or heat recovery (simultaneous heat and cool) options.”