MRCOOL DIY Mini Split, Seriously, I Think...

[Slowbra]

Ingrams seem to have decent tech, and parts, support just based on what I've read on here.



Costco do have a very generous return policy but I'm not sure how useful that'd be for a fixed installation where repairing in place would be better than ripping the whole thing out and returning it.

That is a fair comment. Their techs are pretty nice and knowledgeable . Hopefully they’re just as nice on the warranty side as they are on the pre-sale side.

If the warranty side (since they handle all MrCool for the US) provides the same level of service then the cheaper option prevails right?

 

[ItBurnsWhenIPee]

Ordered my 24k DIY today. Home Depot has them for $1,461 + tax. That's a few hundred cheaper than just about anywhere else.

Metal 24x30x10 (12 or so at peak) steel frame building. One 9x9 door (insulated) and one insulated man door. Walls and ceiling have like...R3 or R5 between the sheet metal and frame. I'll probably insulate better soon, but that's what I've got right now. Hopefully, 24k BTU will knock it down well enough. I've been using an 18k BTU window shaker for 10 years that won't quite keep up, so it should do a decent job.

Now to figure out where to mount the thing LOL

 

[GJuny]

is the electrical connection straight forward? Only a few times was it discussed in this thread. Can someone elaborate as to what is needed? Not my strong suit.

 

[jmarkwolf]

is the electrical connection straight forward? Only a few times was it discussed in this thread. Can someone elaborate as to what is needed? Not my strong suit.

Depending on local code, you will need/want a 220V/20A "disconnect box" for an 18K BTU Mr. Cool. If this isn't your "strong suit" have an electrician do it.

Hooking up the power to the actual compressor unit is easy and well described in the docs, and the internal air exchanger is powered by the external unit via the line set.

 

[Git]

When I installed my Mr Slim, I just bought this kit from eComfort (where I bought the Mr Slim)

Basically, you run your circuit, usually with some sort of romex/sheathed cable, to the disconnect box which is located close to the compressor. Then you come out of the box with the flexible 'whip' and make your connections

You need something like this at the outdoor unit:

 

[randyandrewsberg]

Enjoying my new 24k install. It is a great feeling to work in a climate controlled shop. I knew it would be quiet running, but it's amazingly quiet. If you are thinking about it, make it happen. I'm glad I did it now instead of waiting longer because it seemed like a luxury or a waste of money.

Sent from my XT1635-01 using Tapatalk

 

[Lindy911]

Did you need to do insulation too?

 

[randyandrewsberg]

My shop was already well insulated including the doors. I just needed to run the electric, hang the indoor unit and hang the outside unit up high out of harms way.

Sent from my XT1635-01 using Tapatalk

 

[Lindy911]

Thanks. I’d like add AC, but I only have bare studs and no ceiling, so Looks like I need to manage that first.

 

[ItBurnsWhenIPee]

Has anybody seen a line cover set/kit that's more than 14' or so? Pretty much all of my lines will be outside, and I'd rather not buy two kits if I can avoid it.

 

[SALIV8]

Has anybody seen a line cover set/kit that's more than 14' or so? Pretty much all of my lines will be outside, and I'd rather not buy two kits if I can avoid it.

You can buy one kit, and then piece the straight lengths together and fittings as needed.
This is probably the cheapest kit I found when I was looking.

https://www.highseer.com/products/p...-a-professional-finish?variant=24481992245312

 

[39CAMC]

Another sizing and how does this work with other AC systems question...

We have a older (1951) house that was originally ~1000 sq ft. It has a 13x25 addition on the back. THe house wasn't built with central AC but was converted in 1991 to central AC using the existing heating ductwork.

As the addition (which we use as a family room) is on the back of the house, it only has one supply duct and one return.

Given 1950 (for the house) and 1960 (for the addition) insulation standards, the back room is generally warmer in the summer and cold in the winter. We make it tolerable with a fan in the summer, space heater in the winter.

With these DIY units down so cheap, it has occurred to me that if we added one to this room, it might help quite a bit.

My main question is do I have to worry about this additional unit in the family room screwing up the balance of the rest of the house HVAC? The entry to that addition is large and the middle of the house is fairly open floorplan.

Off the top of my head, I don't see a downside, but I don't want to create some situation where all the sudden the main unit doesn't run enough and we lose humidity control or something. Of course, its an old house, old HVAC so nothing is really peak efficiency anyway...

TIA,

DaveW

 

[SALIV8]

I don't think you would have anything to worry about regarding the whole system. If anything it would obviously lower the return temps from this room so might help in other areas a bit.

I'm just a diy'er but love my minisplits.

And I highly recommend them. I don't have a mr cool, but recommend a higher efficiency unit- you will hardly know it's running and it only slightly increases your electric bill for some awesome comfort.

 

[Blstr88]

I just finished the install on a 24k unit in my home too, and we're halfway through doing an 18k at my parents' lakehouse.

Very easy straight forward to install, just take your time and think each step through as you go through it.

Im not super comfortable with electric, especially going into my breaker panel...but my dad is, so he gave me a hand. Super easy. In addition to the Mr Cool unit, I purchased a 220v breaker (30 amp for the 24k, I believe as someone said its 20 amp for the 18k), about 25' of 10 AWG wire (12 AWG for 18k), an outdoor disconnect (all my hardware store had was a 60amp. This isnt a protection device so going over on amperage shouldn't matter...its rated to handle up to 60amp so the 30 amp required will be fine). I also bought a "pigtail" from my hardware store at the same time to connect the outdoor unit to the disconnect. All that stuff was had for probably about $100.

Basically just de-energized my panel, install the breaker, run the wire from the breaker to the outdoor disconnect, connect the outdoor AC unit to the disconnect via the pigtail, and then make the connections between the inside and outside units. Really quite straight forward.

I built a wooden platform for mine so it sits about 8" off the ground, and I intend to build a small roof over it to keep the rain off it.

 

[jjrbus]

Another sizing and how does this work with other AC systems question...

We have a older (1951) house that was originally ~1000 sq ft. It has a 13x25 addition on the back. THe house wasn't built with central AC but was converted in 1991 to central AC using the existing heating ductwork.

As the addition (which we use as a family room) is on the back of the house, it only has one supply duct and one return.

Given 1950 (for the house) and 1960 (for the addition) insulation standards, the back room is generally warmer in the summer and cold in the winter. We make it tolerable with a fan in the summer, space heater in the winter.

With these DIY units down so cheap, it has occurred to me that if we added one to this room, it might help quite a bit.

My main question is do I have to worry about this additional unit in the family room screwing up the balance of the rest of the house HVAC? The entry to that addition is large and the middle of the house is fairly open floorplan.

Off the top of my head, I don't see a downside, but I don't want to create some situation where all the sudden the main unit doesn't run enough and we lose humidity control or something. Of course, its an old house, old HVAC so nothing is really peak efficiency anyway...

TIA,

DaveW

Just another homeowner trying to get by. People seem to be doing this all over the net and not reporting any issues. I have 3 separate mini's in my house and I see no interference between them. Also some people have more than one HVAC system in their mansions.

I would be tempted to experiment with closing the ducts to the room off to see what happens. Not permanently at first.

I have cheap electric in my area and did some of the online calculators for high efficiency units and the pay back periods were over 10 years. Hardly seems worth the extra investment and exposing myself to what could be more technical issues. Mini's are more computer than HVAC!

 

[alxmlr789]

My 24k has been working well for about a month now. Still can’t figure out when these mini splits shut off and turn on lol. It’s a mystery.

I keep my shop at about 83 when I’m not using it and pop it down to 80 when I’m working on a car. It keeps my 35x30 shop well cooled and at about 47% humidity, which is more important Best part it only costs about 3-4 bucks a week according to my power logger. Should cost me less when i insulate my second (12x10) overhead door.

 

[jjrbus]

My 24k has been working well for about a month now. Still can’t figure out when these mini splits shut off and turn on lol. It’s a mystery.

I keep my shop at about 83 when I’m not using it and pop it down to 80 when I’m working on a car. It keeps my 35x30 shop well cooled and at about 47% humidity, which is more important Best part it only costs about 3-4 bucks a week according to my power logger. Should cost me less when i insulate my second (12x10) overhead door.

I would guess when the outside unit is running, they are on, when the outside unit is not running they are "off". Other than sitting outside with a clipboard and writting down when they start and stop, how would we check running time?

 

[bored350]

Other than sitting outside with a clipboard and writting down when they start and stop, how would we check running time?

One would have to be pretty ambitious to undertake such a project IMO, but I would imagine monitoring/data logging current draw changes of the system would identify compressor start/stop times.
A second data point of ambient temperature would likely be helpful as well.

Sent from my Moto G (5) Plus using Tapatalk

 

[Browneye]

Has anybody seen a line cover set/kit that's more than 14' or so? Pretty much all of my lines will be outside, and I'd rather not buy two kits if I can avoid it.

I used plastic rain gutter for mine. I think it was about $8
One got painted, the other is pending...

 

[Browneye]

Another sizing and how does this work with other AC systems question...

We have a older (1951) house that was originally ~1000 sq ft. It has a 13x25 addition on the back. THe house wasn't built with central AC but was converted in 1991 to central AC using the existing heating ductwork.

As the addition (which we use as a family room) is on the back of the house, it only has one supply duct and one return.

Given 1950 (for the house) and 1960 (for the addition) insulation standards, the back room is generally warmer in the summer and cold in the winter. We make it tolerable with a fan in the summer, space heater in the winter.

With these DIY units down so cheap, it has occurred to me that if we added one to this room, it might help quite a bit.

My main question is do I have to worry about this additional unit in the family room screwing up the balance of the rest of the house HVAC? The entry to that addition is large and the middle of the house is fairly open floorplan.

Off the top of my head, I don't see a downside, but I don't want to create some situation where all the sudden the main unit doesn't run enough and we lose humidity control or something. Of course, its an old house, old HVAC so nothing is really peak efficiency anyway...

TIA,

DaveW

I kind of depends on where your thermostat is for the main hvac unit. In any case, your minisplit will do what it needs to do in that room regardless of what the rest of the house is doing.

I think you'll love it. We put two of them in and they're silent, efficient, and super easy to live with. Cheap to put in too.

 

[Browneye]

On wiring...
Technically, per code, you need a fused disconnect for the outside power connection. We had a licensed electrician in here recently that wanted to get technical about it. Frankly, I think the UL Listing for them just happened to get worded that way, although the code does say if it says 'fused' then the disconnect is supposed to have a fuse in it. MrCool does say 'fused'.

I also believe there's a fuse on the board, so if the unit decided to fry itself it likely would blow it's own fuse first. And if it's connected to a properly breaker'd and wire-sized circuit there's no danger.

Anyway, if you want to be completely safe and to code hire an electrician. Well, it's no guarantee, but you get the point.

 

[39CAMC]

THanks everyone for the input. The thermostat for the main unit is as about as far away as it could be from the room that may get the mini split. Blocking the vent (eventually) in the family room is a spectacular idea as well.

Thanks again!

DaveW

 

[Blstr88]

On wiring...
Technically, per code, you need a fused disconnect for the outside power connection. We had a licensed electrician in here recently that wanted to get technical about it. Frankly, I think the UL Listing for them just happened to get worded that way, although the code does say if it says 'fused' then the disconnect is supposed to have a fuse in it. MrCool does say 'fused'.

I also believe there's a fuse on the board, so if the unit decided to fry itself it likely would blow it's own fuse first. And if it's connected to a properly breaker'd and wire-sized circuit there's no danger.

Anyway, if you want to be completely safe and to code hire an electrician. Well, it's no guarantee, but you get the point.

The instructions do say fused but I saw zero reason why the disconnect would need a fuse...the unit is hooked up to its own dedicated 30 amp breaker, any fault in the system would trip the breaker. Having a breaker and fuse is just unnecessary redundancy.

Im no electrician so excuse me if this is dumb...but maybe it makes a difference depending how far the breaker panel is from the AC? As in, if its far enough away by having a fuse right there at the disconnect its faster acting and protects the AC better? I can't imagine 20' or 100' of wire would change how quickly the breaker reacts to a fault...but like I said, Im no electrician, I have no clue.

I ultimately went with a non-fused disconnect. If you're wiring your AC into a dedicated breaker and thats sized correctly I think thats all the protection you need.

 

[alxmlr789]

I would guess when the outside unit is running, they are on, when the outside unit is not running they are "off". Other than sitting outside with a clipboard and writting down when they start and stop, how would we check running time?

Since I’m using a power logger, i can tell what times of the day it’s running and not, the inside fan is running always. But mainly I’m talking about the why of the outside fan. Like my unit yesterday was reading 78 indoor temp, set to 83. But the outdoor unit was running. Typically when registered temp is 2 degrees under set temp, the outdoor unit fan kicks off, so yesterday was weird.

One would have to be pretty ambitious to undertake such a project IMO, but I would imagine monitoring/data logging current draw changes of the system would identify compressor start/stop times.
A second data point of ambient temperature would likely be helpful as well.

Sent from my Moto G (5) Plus using Tapatalk

It also seems like the compressor has different amperage draw levels. I’ve seen it steady at .5a per leg when set temp has been reached (actually when it’s 2 degrees under set temp), 2.65a when it’s mildly cooling - say when it’s 83 in the building and i set it to 80. I’ve seen 5.5a, 7.65a then when it’s full bore it’s pulling up to 12a per leg is the highest I’ve seen. All of these numbers I’ve seen for extended periods of time so there must be different ramp levels based upon what the inverter is doing.

 

[jjrbus]

Speaking of electrical, I have read fairly often that mini's are sensitive to electrical surge. It is often stated that most today have a computer or expensive TV plugged into a surge protector. Well a mini is more computer than HVAC so it only makes sense to protect them.

To me the whole house surge protector made sense so I added one to my panel.

 

[jjrbus]

Since I’m using a power logger, i can tell what times of the day it’s running and not, the inside fan is running always. But mainly I’m talking about the why of the outside fan. Like my unit yesterday was reading 78 indoor temp, set to 83. But the outdoor unit was running. Typically when registered temp is 2 degrees under set temp, the outdoor unit fan kicks off, so yesterday was weird.



It also seems like the compressor has different amperage draw levels. I’ve seen it steady at .5a per leg when set temp has been reached (actually when it’s 2 degrees under set temp), 2.65a when it’s mildly cooling - say when it’s 83 in the building and i set it to 80. I’ve seen 5.5a, 7.65a then when it’s full bore it’s pulling up to 12a per leg is the highest I’ve seen. All of these numbers I’ve seen for extended periods of time so there must be different ramp levels based upon what the inverter is doing.

You are right, the units modulate, so it only makes sense the compressor would be drawing different amounts of power. My Daikins start on low and ramp up to the needed btu. The 9,000 can go as low as 4,400 and up to 11,000 btu. This is a great feature as I have a 9k in a room that would use a 5,000 btu window unit. Seems to be working ok.

However it is claimed that mini's are more efficient running at higher outputs. My electric bill in FL for last month was $85 which is about 1/2 of what central air would cost. So the efficiency does not seem to be a major issue.

 

[alxmlr789]

You are right, the units modulate, so it only makes sense the compressor would be drawing different amounts of power. My Daikins start on low and ramp up to the needed btu. The 9,000 can go as low as 4,400 and up to 11,000 btu. This is a great feature as I have a 9k in a room that would use a 5,000 btu window unit. Seems to be working ok.

However it is claimed that mini's are more efficient running at higher outputs. My electric bill in FL for last month was $85 which is about 1/2 of what central air would cost. So the efficiency does not seem to be a major issue.

Yeah my unit never goes ABOVE the set temp unless i open one of my giant doors so it must be working just fine. I don’t need to be in 70 degree air wrenching around in the garage. I’m good with 80-85. I really like the constant dehumidification of these units. They really allow for some good dry air to keep a spray foamed building happy for not a lot of money.

 

[Browneye]

The instructions do say fused but I saw zero reason why the disconnect would need a fuse...the unit is hooked up to its own dedicated 30 amp breaker, any fault in the system would trip the breaker. Having a breaker and fuse is just unnecessary redundancy.

Im no electrician so excuse me if this is dumb...but maybe it makes a difference depending how far the breaker panel is from the AC? As in, if its far enough away by having a fuse right there at the disconnect its faster acting and protects the AC better? I can't imagine 20' or 100' of wire would change how quickly the breaker reacts to a fault...but like I said, Im no electrician, I have no clue.

I ultimately went with a non-fused disconnect. If you're wiring your AC into a dedicated breaker and thats sized correctly I think thats all the protection you need.

Agreed absolutely. Just stating electrical code as we have some nit-picky licensed electricians reading that want to make a point.

I didn't use a fused disco either. And he went on to say my daughter, whom is a licensed commercial electrician, beyond journeyman now crew lead, doesn't know what she's talking about, didn't explain it right, or I just misunderstood. I didn't think it was any of that. She explained you 'breaker' the wires - all of that has to match, and there are accepted wire sizes for circuits and breakers. You want the breaker to trip before the wire overheats. Duh.

Anyway, carry on...

 

[alxmlr789]

I went with a fused disconnect only because i can't read well in Lowes apparently. I thought i was buying non fused but upon installation, i realized it was a fused box. Oh well, extra 2 bucks. I'm on a 25A breaker, 10GA wiring with a 30A fuse on a 24k unit, have not had any power issues.

 

[3rdgendslmech]

So not to deviate from this thread too much but I'm going to be buy an Advantage unit probably next month and I'm either going to DIY the install or have my friend who is licensed to the hookup/leak check. I'm going to do everything else including wiring and disconnect.
My question is with these units being run by a circuit board, how many of you guys are running a surge protector either for this circuit alone or for the whole house/garage?
I know they're (surge protectors) becoming more popular since a lot of newer home appliances are run off of mini computers, inverters, and control boards. I'm pretty sure my homeowners covers surges but I like to avoid a hassle if I can.

 

[PoorOwner]

So not to deviate from this thread too much but I'm going to be buy an Advantage unit probably next month and I'm either going to DIY the install or have my friend who is licensed to the hookup/leak check. I'm going to do everything else including wiring and disconnect.
My question is with these units being run by a circuit board, how many of you guys are running a surge protector either for this circuit alone or for the whole house/garage?
I know they're (surge protectors) becoming more popular since a lot of newer home appliances are run off of mini computers, inverters, and control boards. I'm pretty sure my homeowners covers surges but I like to avoid a hassle if I can.

I have a surge protector on each one. It's wired at the disconnect.
There are some that are installed at the main panel, but I think closer the appliance is better.

 

[3rdgendslmech]

I have a surge protector on each one. It's wired at the disconnect.
There are some that are installed at the main panel, but I think closer the appliance is better.

That's what I'm reading too. A lot of manufacturers recommend putting it as close to the device as possible.

 

[MattT]

Agreed absolutely. Just stating electrical code as we have some nit-picky licensed electricians reading that want to make a point.

I didn't use a fused disco either. And he went on to say my daughter, whom is a licensed commercial electrician, beyond journeyman now crew lead, doesn't know what she's talking about, didn't explain it right, or I just misunderstood. I didn't think it was any of that. She explained you 'breaker' the wires - all of that has to match, and there are accepted wire sizes for circuits and breakers. You want the breaker to trip before the wire overheats. Duh.

Anyway, carry on...

First off I ain't no lektrishun, licensed or otherwise. You are the only one dragging worthless credentials into this conversation.

You, and your source, clearly know nothing about peak let through current or clearing time. It's way above y'alls pay grades and I ain't gonna waste my time attempting to explain it to people who already know everything.

Yeah the breaker will protect the wiring. The equipment manufacturer specifies fuses to protect the equipment.

I really don't know why anyone would compromise on these DIY units to get a warranty then void it by disregarding the manufacturers installation instructions just to save $20

Carry on

 

[jjrbus]

I would send a written letter to Mr Cool and ask about the fused disconnect, makes no sense and may be an error. Actually sounds like something that would have to be added in 3rd world countries. It may only be $20 but to my way of thinking is just something else to go wrong.

 

[MattT]

I would send a written letter to Mr Cool and ask about the fused disconnect, makes no sense and may be an error. Actually sounds like something that would have to be added in 3rd world countries. It may only be $20 but to my way of thinking is just something else to go wrong.

It makes perfect sense once you understand the differences between circuit breakers and fuses. With a short a decent fuse will probably limit the current to less than the available fault current and break the circuit in less than a half cycle. With a breaker the unit will probably see the full available fault current for a couple cycles which will be much more damaging. Kinda like the difference between 1 stick of dynamite and eight or more.

Yeah fuses are one more thing to go wrong but they're cheaper than condenser units............

 

[jjrbus]

It makes perfect sense once you understand the differences between circuit breakers and fuses. With a short a decent fuse will probably limit the current to less than the available fault current and break the circuit in less than a half cycle. With a breaker the unit will probably see the full available fault current for a couple cycles which will be much more damaging. Kinda like the difference between 1 stick of dynamite and eight or more.

Yeah fuses are one more thing to go wrong but they're cheaper than condenser units............

Shouldn't the Mr Cool have a fuse inside?

 

[LS6 Tommy]

Guys, just to get to the short and sweet of it, code does not dictate whether you use a fused or non fused disconnect. Code requires you to follow the manufacturer's installation instructions. If the instructions say the disconnect needs to be fused, it needs to be fused and any decent inspector should fail it if a non fused disconnect is used.

Tommy

 

[Browneye]

First off I ain't no lektrishun, licensed or otherwise. You are the only one dragging worthless credentials into this conversation.

You, and your source, clearly know nothing about peak let through current or clearing time. It's way above y'alls pay grades and I ain't gonna waste my time attempting to explain it to people who already know everything.

Yeah the breaker will protect the wiring. The equipment manufacturer specifies fuses to protect the equipment.

I really don't know why anyone would compromise on these DIY units to get a warranty then void it by disregarding the manufacturers installation instructions just to save $20

Carry on

I don't know how we could all survive without you.

Perhaps this thread from MikeHolt.com can clear it up for our dear readers:
https://forums.mikeholt.com/showthread.php?t=144721

Basically UL says if a breaker matches the capacity of the disconnect amperage requirement you're good to go, fuse or breaker.

EDIT: This thread on HVACTalk basically says the same thing: https://hvac-talk.com/vbb/showthread.php?1132271-Are-fuses-in-disconnect-necessary

EDIT2: Another thread on the same forum...same subject...same players.
https://www.garagejournal.com/forum/showthread.php?t=334111&showall=1\

 

[Mr onetwo]

plus 1 on what Tommy just said........just for reference

 

[bones1]

I have two Frederich Breeze models that do not require an electrical box on the outside of the home for power to the unit. The power comes from the inside unit, which is plugged into a wall outlet and travels down with the refrigerant and drain lines in a plastic sheath. I want to add another unit but the Breeze units are not sold anymore and I was wondering if anyone has run wire to their Mr Cool outside unit in the above fashion. I cannot run wire to an outside box without major work I was told by a couple of experts but wall plugs are everywhere.