Ductless Mini Split Install

[DavidGT650R]

Hi guys, my name is David. I've been lurking around for a while but this is my first post. My wife and I are in the process of buying our first home. We are pretty young and we are both still in college so things are really tight right now. But the house we plan on buying has no central heat or air. Its got a little junk wall furnace that is supposed to heat the whole house. There is no ducting in the house at all, but who needs ducts right?
So I plan on buying a 2 zone(possibly 3 zone) ductless mini split. I've done quite a bit of research and it seems like something I can tackle. I feel comfortable working with electricity. I drew up a wiring diagram earlier today that I would like to share with everyone to double check my work. I feel like I can do the vacuuming and charging of the system but I would really prefer to leave that part to the professionals as I've read that the pressure has to be dialed in pretty on point. I charge car a/c units all the time. But this might not be as easy as it looks.
Guys, thanks for any future information I'm hoping to get![URL=http://s761.photobucket.com/user/davidmazdarx7/media/DMS%20Wiring%20diagram.jpg.html] [/URL]

 

[justinjoyal]

Unless I missed something, your diagram is correct.

If you really wanna do this by yourself, make sure to:

- buy the correct size system
- choose proper locations for indoor and outdoor unit.

Also, unless you buy one of those cheap, poor quality pre-packaged kits, you will need copper tubing for the gas lines, and you'll need to flair or solder the ends to connect them together.

Units usually come precharged with the right amount of gas (for standard/common installations.) A good vacuum is important.

 

[Fatboyslim]

Your drawing is correct

 

[Fatboyslim]

You will probably need 10 gauge wire if using a 30 amp breaker

 

[DavidGT650R]

Slim, thanks for the double check. Im not sure yet whether or not ill be using 20 or 30 amp breakers or 10 or 12 gauge wire. Im not sure what system im going with yet. But i really want 3 interrior units. Possibly will do 2. If i have to do a long run i may use 10 g. Have you guys had problems having a tech fill refridgerant?

 

[DavidGT650R]

Unless I missed something, your diagram is correct.

If you really wanna do this by yourself, make sure to:

- buy the correct size system
- choose proper locations for indoor and outdoor unit.

Also, unless you buy one of those cheap, poor quality pre-packaged kits, you will need copper tubing for the gas lines, and you'll need to flair or solder the ends to connect them together.

Units usually come precharged with the right amount of gas (for standard/common installations.) A good vacuum is important.

I replied to you earlier but i guess it didnt post. Thanks for the input, do you think the factory line set is junk? I could still get it, cut the factory ends off and flare it myself if i had to do so. I plan on installing everything. Then i wanted to hire an a/c tech to come out and vac test the lines and then charge the line(or bleed it). But i dont know what a going price would be on that. I read somewhere that for a CHEAP vac pump, gauge set, and micrometer, someone had paid about $200. I just want to do this all right the first time, but funds are limited for now.

 

[fastjohnny]

Don't know your location or heating needs, but the Mitsubishi or Fujitsu units will provide heat to much lower temps, Mitsubishi to -13F. I considered a 3 zone, but elected to go with 3 separate units (SEER 30 vs SEER 19)

 

[MushCreek]

Depending upon the size of the unit, you won't need a 30A breaker. My Mits are on 15A 240V breakers. The manufacturer will give you a minimum and maximum breaker size. It only required 14 ga. wire from the outdoor unit to the indoor unit. Some jurisdictions may require a disconnect between the outdoor unit and the indoor unit.

 

[walrus]

His drawing is not correct per NEC, he needs a disconnect for the indoor unit. Maybe its in the unit but its not in the common units I've seen. Daikon, Fujitsu, Mitsubishi . In Maine they aren't enforcing the indoor disconnect but other areas may be.

Remember these things are supplemental heat, in cold areas the amount of heat they produce goes down as temps go down.

I'm in Maine and love my 12,000 Fujitsu but I shut mine down when it gets really cold. Maybe you are in area that isn't an issue.?

If you are going to install it, make sure you nitrogen test, these things don't like leaks as there is only 2 to 3 lbs of R410a in these units. Also evacuation is critical also.

 

[MushCreek]

There's been some discussion about the indoor disconnect. Technically, my Mits don't need one because the indoor unit is less than 1/8 hp., but good luck arguing that with an inspector.

 

[justinjoyal]

I don't know about an indoor disconnect where you're at. None needed here in QC.

No need to nitrogen test... It never hurts, but it's definitely not needed.

OP, in what kind of temperatures will you be using your units?

 

[Jackfre]

His drawing is not correct per NEC, he needs a disconnect for the indoor unit. Maybe its in the unit but its not in the common units I've seen. Daikon, Fujitsu, Mitsubishi . In Maine they aren't enforcing the indoor disconnect but other areas may be.

Remember these things are supplemental heat, in cold areas the amount of heat they produce goes down as temps go down.

I'm in Maine and love my 12,000 Fujitsu but I shut mine down when it gets really cold. Maybe you are in area that isn't an issue.?

If you are going to install it, make sure you nitrogen test, these things don't like leaks as there is only 2 to 3 lbs of R410a in these units. Also evacuation is critical also.

You are correct as to the NEC requirements. When I was in MA the inspector called me on it and I told him I flatly refused to put the interior disconnect in as I didn't want to look at it. I showed him the outside disconnect.
To the OP, everything looks good. Make sure that on the eve wiring 1 goes to 1 2-2, 3-3. 1&2 are legs of 220. 3 is a communication wire.

 

[LS6 Tommy]

I don't know about an indoor disconnect where you're at. None needed here in QC.

No need to nitrogen test... It never hurts, but it's definitely not needed.

OP, in what kind of temperatures will you be using your units?

You ALWAYS nitrogen leak check. If someone taught you to leak check by checking vacuum after you evacuate, they were 100% wrong.

Tommy

 

[DavidGT650R]

I don't know about an indoor disconnect where you're at. None needed here in QC.

No need to nitrogen test... It never hurts, but it's definitely not needed.

OP, in what kind of temperatures will you be using your units?

Well I live in Amarillo, Tx our weather is really random. We've had summers up to like 110 at max usually. Winters usually the max cold temp would be -15 with the windchill. but the wind blows hard here. We can have like 60MPH gusts some days.

 

[DavidGT650R]

Thanks for all the information guys. I dont think Ill bother with an interior disconnect unless I absolutely have to do so. Im excited to get going on this, but I still have to actually buy the house. This is such a slow process, but itll be worth it. The wife has been harassing about buying a house for years! haha

 

[justinjoyal]

You ALWAYS nitrogen leak check. If someone taught you to leak check by checking vacuum after you evacuate, they were 100% wrong.



Tommy

Guess we've been doing it wrong for 20+ years. Say that to hundreds (thousands?) of satisfied customers with trouble-free units. ;-)

Nitrogen will be used in some cases but definitely not all the time.

 

[Jackfre]

Guess we've been doing it wrong for 20+ years. Say that to hundreds (thousands?) of satisfied customers with trouble-free units. ;-)

Nitrogen will be used in some cases but definitely not all the time.

Why not all the time? What determines nitrogen check or not?

 

[DavidGT650R]

Is nitrogen easier to detect a leak with? Im not questioning the use of it, I am just curious why. Does one need a license to buy nitrogen? And where would I get it from if I do plan on trying it myself? If I do have to vac/charge the system, I want to do it right the first time.

 

[justinjoyal]

I dont know about laws regarding nitrogen in your area..

We'll nitrogen check on bigger systems with several possible leaking points or places that would be hard to get to for a future fix.

Standard Ductless piping usually have very few connections and vacuum check has been working fine for years.

Of course It's never a bad thing to push nitrogen in there but we found it to be unnecessary for regular, out of the box ductless installs.

 

[LS6 Tommy]

Guess we've been doing it wrong for 20+ years. Say that to hundreds (thousands?) of satisfied customers with trouble-free units. ;-)

Nitrogen will be used in some cases but definitely not all the time.

Why not all the time? What determines nitrogen check or not?

Is nitrogen easier to detect a leak with? Im not questioning the use of it, I am just curious why. Does one need a license to buy nitrogen? And where would I get it from if I do plan on trying it myself? If I do have to vac/charge the system, I want to do it right the first time.

I dont know about laws regarding nitrogen in your area..

We'll nitrogen check on bigger systems with several possible leaking points or places that would be hard to get to for a future fix.

Standard Ductless piping usually have very few connections and vacuum check has been working fine for years.

Of course It's never a bad thing to push nitrogen in there but we found it to be unnecessary for regular, out of the box ductless installs.

There's a big difference between having success and doing something incorrectly. Lots of people do things wrong all the time and never have issues.

There is no law determining whether nitrogen is used for leak checking or not. Anyone can buy dehydrated nitrogen. Getting an 80 pound cylinder and a regulator is probably out of the cost envelope for a DIY guy installing one system. NEVER use compressed air or any other gas to leak check.

A decent HVAC training course should tell you not to use vacuum to leak check. If there's a leak, you risk contaminating all the components that have been under vacuum. A vacuum can hold small leaks shut that would normally be detected under pressure. I've run into it many times over the years. I go to check a newer system that has a low charge. I find the leak and repair it. The installer tells me there's no way he had a leak. It held a vacuum for DAYS...

Tommy

 

[justinjoyal]

There's a big difference between having success and doing something incorrectly. Lots of people do things wrong all the time and never have issues.

There is no law determining whether nitrogen is used for leak checking or not. Anyone can buy dehydrated nitrogen. Getting an 80 pound cylinder and a regulator is probably out of the cost envelope for a DIY guy installing one system. NEVER use compressed air or any other gas to leak check.

A decent HVAC training course should tell you not to use vacuum to leak check. If there's a leak, you risk contaminating all the components that have been under vacuum. A vacuum can hold small leaks shut that would normally be detected under pressure. I've run into it many times over the years. I go to check a newer system that has a low charge. I find the leak and repair it. The installer tells me there's no way he had a leak. It held a vacuum for DAYS...

Tommy

I agree that pressurizing with nitrogen is the better way, there is no doubt.

We don't do it for different reasons and don't have problems.

 

[DavidGT650R]

I used to be a plumber, I never worked with HVAC but we worked with gas lines very often. We would test the lines before hooking up the gas by removing the house side of the gas meter line and attaching a gauge to it, then taking a simple bicycle pump and pumping pressure up to 3.5 PSI. We would leave it sitting for about a half hour before checking it. If it had dropped pressure at all, we would take soapy water (or an actual leak detector spray) and spray down all the fittings until a leak was spotted. Sometimes it was an extremely tedious task when you're in an old house and looking at tons of different connections. But I know what I'm looking for, even the smallest of bubbles. Instead of checking with nitrogen, would it be conceivable for me to attempt to do this the same way I would do a gas line? I mean there will only be 2(possibly 3) connections to deal with. One at the interior unit and one at the exterior unit, assuming I dont break the line when I bend it(in that case it would be leaking pretty good) making turns. Plus the pressure in an A/C line will be a lot higher than 3.5 PSI Im assuming. Put yourself in my position, would this be something you would try if you didn't have all the pressure testing/charging tools. Or would it be best to just try to call a tech out to do all that for me, assuming they will. They could refuse to charge it I suppose. What do you guys think?

 

[CTyankee]

I didn't read all the posts, but for the Mitsubishi, I believe you need to purchase your system from an authorized dealer for full coverage under their warranty

 

[LS6 Tommy]

I agree that pressurizing with nitrogen is the better way, there is no doubt.

We don't do it for different reasons and don't have problems.

Hey, please don't take me as being judgemental. I didn't mean to come across that way. I'm just sharing the things I've learned over the last 25+ years as an HVAC tech and instructor. If your ways are working with a high succes rate I guess I shouldn't have been so harsh with my wording.

Tommy

 

[fastjohnny]

Guess we've been doing it wrong for 20+ years. Say that to hundreds (thousands?) of satisfied customers with trouble-free units. ;-)

Nitrogen will be used in some cases but definitely not all the time.

Justinjoyal, are you pulling a sub 500 micron vac on your installs?

Dry nitrogen would be a tool to help pull moisture from a system to achieve this. Not saying you don't know this, but to clarify for the sake of discussion for use of nitrogen.

Background: I'm not an HVAC tech, but do have plenty auto AC experience and have mobile AC certification.