MrCool 18K Mini split wiring help

[Lovthebass]

I have a MrCool 4th gen DIY 18k unit that I am going to install and just want to make sure I'm using the correct items.

It says in the manual for the 18k unit it is preferred to use 8 awg -



So I'm going to use 8 gauge wire from the panel to the unit but I want to make sure I am getting the right breaker and disconnect.

Can anyone point me in the right direction for the breaker, the outdoor disconnect & whip?

Thanks!

 

[PCustoms]

Ignore the manual completely.

Do you have the unit?

What does the label on the unit say?

I went through this a few months ago trying to determine fuse vs. breaker. All that matters is the label on the unit.

Btw, my 18k is on a 25A breaker and #12

 

[Lovthebass]

Ignore the manual completely.

Do you have the unit?

What does the label on the unit say?

I went through this a few months ago trying to determine fuse vs. breaker. All that matters is the label on the unit.

Btw, my 18k is on a 25A breaker and #12

I do have the unit but I didn't open it up yet.

I will when I get home from work tonight and post the label.

 

[PCustoms]

I do have the unit but I didn't open it up yet.

I will when I get home from work tonight and post the label.

Here's my thread:

Mini split wiring check-bad/unclear instructions

Quoting some of my posts from over in the HVAC sub forum as it's purely electrical: Check my plan for wiring a Mr. Cool 18k unit, as I think I'm wrong/their chart *****: 12-2 NM-B 25A breaker Non-fused disconnect Well physical unit arrived and, surprise, is marked differently then the...

www.garagejournal.com

Summary: these manuals ****, the specs are different depending where you look. Tag on unit rules them all

 

[Lovthebass]

Here's my thread:

Mini split wiring check-bad/unclear instructions

Quoting some of my posts from over in the HVAC sub forum as it's purely electrical: Check my plan for wiring a Mr. Cool 18k unit, as I think I'm wrong/their chart *****: 12-2 NM-B 25A breaker Non-fused disconnect Well physical unit arrived and, surprise, is marked differently then the...

www.garagejournal.com

Summary: these manuals ****, the specs are different depending where you look. Tag on unit rules them all

Ah, I see this can get confusing. I believe you have the same unit that I have but will confirm later.

So you used 12 gauge wire, 25 amp breaker & a non-fused disconnect I see.

Everything seems fine? How is the unit working for you?

Also, which disconnect did you go with?

 

[PCustoms]

Ah, I see this can get confusing. I believe you have the same unit that I have but will confirm later.

So you used 12 gauge wire, 25 amp breaker & a non-fused disconnect I see.

Fused disconnect.

Everything seems fine? How is the unit working for you?

Works good. Seems to have some harmonics, a few of my cheap LED light flicker when it's on. It's 86+ out right now and the far end of the house was 68 at lunch, so I'm happy.

Also, which disconnect did you go with?

I think GE, it was whatever Home Depot had in stock.

 

[mike93lx]

8 is a waste of money unless the run is 150+ feet.

I'd run 12

 

[Lovthebass]

Fused disconnect.



Works good. Seems to have some harmonics, a few of my cheap LED light flicker when it's on. It's 86+ out right now and the far end of the house was 68 at lunch, so I'm happy.


I think GE, it was whatever Home Depot had in stock.

Oh, I see the reply you got from MrCool that said a non-fused disconnect was OK.

What fuse size did you need to get for the disconnect?

I'm glad it's working good! I'm excited to install this.

 

[Lovthebass]

8 is a waste of money unless the run is 150+ feet.

I'd run 12

I have 10 gauge going to an electric heater halfway to where I would want to mount the disconnect box.

I'm going to decommission the heater so can I just connect to that wire once I disconnect the heater and run it to the disconnect box?

 

[PCustoms]

Oh, I see the reply you got from MrCool that said a non-fused disconnect was OK.

What fuse size did you need to get for the disconnect?

I'm glad it's working good! I'm excited to install this.

25A I believe.

It came down to it didn't matter what Mr cool told me via email, the label said X, you better do X to be compliant

 

[Lovthebass]

25A I believe.

It came down to it didn't matter what Mr cool told me via email, the label said X, you better do X to be compliant

OK, I will post the label later.

 

[mike93lx]

I have 10 gauge going to an electric heater halfway to where I would want to mount the disconnect box.

I'm going to decommission the heater so can I just connect to that wire once I disconnect the heater and run it to the disconnect box?

Yes. Go for it. I'd keep that run at 10 for the rest of the way. Make sure you keep the junction box accessible

 

[Lovthebass]

Here is the label on the side of the unit-

 

[Lovthebass]

Can anyone help on this? I was hoping to pick up what I need soon. Thanks!

 

[Raisedonadeere]

Something screwy about that manual. #8 would run a monster AC. I have 2 different 18k mini's hyper heat units, on 12ga and 15 amp breakers. I meant to use 20 amp breakers but had 15s when I installed and started using expecting the 15s to trip. Now, six years running. never a trip so I never installed the 20's. The data plate on my units look almost identical to yours.

For now just go by the minimum ampacity and realize that 12GA is good for 20 amp so 12Ga exceeds that. Run your wires, and settle later on what breaker to use.

 

[PCustoms]

Can anyone help on this? I was hoping to pick up what I need soon. Thanks!

Thought I responded yesterday, sorry.

Get a 30A rated disconnect and 2 30A fuses.

You mentioned abandoning an existing feed to a heater, how much (if any) do you need to add on?

What breaker is that wire on?

 

[Lovthebass]

Thought I responded yesterday, sorry.

Get a 30A rated disconnect and 2 30A fuses.

You mentioned abandoning an existing feed to a heater, how much (if any) do you need to add on?

What breaker is that wire on?

Last night I looked at what is there and the existing heater has 10/3 wire going to it. If I can use the existing 10/3 wire I would need to add about 25 feet. The total run would be about 45-50 feet.

Right now the breaker is 50A.

 

[mike93lx]

Last night I looked at what is there and the existing heater has 10/3 wire going to it. If I can use the existing 10/3 wire I would need to add about 25 feet. The total run would be about 45-50 feet.

Right now the breaker is 50A.

10/3? So a 4 wire connection? That needs to be a 30a breaker. A 50a would only be ok if it was a welder circuit

You only need 10/2 to get to the a/c

 

[PCustoms]

Last night I looked at what is there and the existing heater has 10/3 wire going to it. If I can use the existing 10/3 wire I would need to add about 25 feet. The total run would be about 45-50 feet.

Right now the breaker is 50A.

You sure it's 10/3?

I'd extend off that using 10/2 (cap the white wire on both ends) and reduce the breaker to 30A.

If starting from the panel, I think (would need to double check) you could run 12/2.

 

[Lovthebass]

You sure it's 10/3?

I'd extend off that using 10/2 (cap the white wire on both ends) and reduce the breaker to 30A.

If starting from the panel, I think (would need to double check) you could run 12/2.

I apologize, it is 10/2

2 wires and a ground.

 

[mike93lx]

I apologize, it is 10/2

2 wires and a ground.

Easy mistake to make.

Swap that breaker, for sure

 

[Lovthebass]

Easy mistake to make.

Swap that breaker, for sure

Yes, I know i need to change the breaker. So a 30A would be best?

 

[mike93lx]

Yes, I know i need to change the breaker. So a 30A would be best?

30a is max. I bet it would run fine on a 20a,but you won't gain anything by stepping down that far and a 30 will cost the same as a 20 or 25

 

[Lovthebass]

30a is max. I bet it would run fine on a 20a,but you won't gain anything by stepping down that far and a 30 will cost the same as a 20 or 25

I'm looking at this wire closer and the text on it says 8 gauge with a 10 gauge ground, sorry for the mistake.

So I can add onto this with 8/2 wire the rest of the way. Might be overkill but it's already half way there.

And the manual says 8 AWG is "preferred"

 

[mike93lx]

I'm looking at this wire closer and the text on it says 8 gauge with a 10 gauge ground, sorry for the mistake.

So I can add onto this with 8/2 wire the rest of the way. Might be overkill but it's already half way there.

And the manual says 8 AWG is "preferred"

Ignore the preferred junk. It's a waste of money.

I'd extend with no larger than 10. Personally, I'd likely do it with 12 and install a 20a breaker

 

[PCustoms]

If you have access I'd just run new 12/2.

Screwing around with #8, a junction box, wire nuts etc. would frustrate me.

EDIT: don't forget all junction boxes must remain accessible.

 

[Lovthebass]

I spoke to an electrician friend of mine and he said the following -

I can connect to the existing 8awg wire and keep going to the disconnect box.

Switch out the breaker to a 30 amp.

He said the disconnect doesn't matter, I can get any size unfused disconnect as long as I have a 30amp breaker.

Does all this sound correct?

 

[mike93lx]

I spoke to an electrician friend of mine and he said the following -

I can connect to the existing 8awg wire and keep going to the disconnect box.

Switch out the breaker to a 30 amp.

He said the disconnect doesn't matter, I can get any size unfused disconnect as long as I have a 30amp breaker.

Does all this sound correct?

That's the same as what we have been saying

 

[erik a]

Ignore the manual completely.

Do you have the unit?

What does the label on the unit say?

I went through this a few months ago trying to determine fuse vs. breaker. All that matters is the label on the unit.

Btw, my 18k is on a 25A breaker and #12

ditto

 

[PCustoms]

I spoke to an electrician friend of mine and he said the following -

I can connect to the existing 8awg wire and keep going to the disconnect box.

Switch out the breaker to a 30 amp.

He said the disconnect doesn't matter, I can get any size unfused disconnect as long as I have a 30amp breaker.

Does all this sound correct?

No, that's not correct. You need a fused disconnect

 

[Lovthebass]

No, that's not correct. You need a fused disconnect

He said if it's connected to a 30 amp breaker, a fused disconnect is not needed.

And If the breaker was bigger than 30amp, then a 30amp fused disconnect would need to be used.

Is he mistaken? If so, how?

 

[PCustoms]

He said if it's connected to a 30 amp breaker, a fused disconnect is not needed.

And If the breaker was bigger than 30amp, then a 30amp fused disconnect would need to be used.

Is he mistaken? If so, how?

Go read my thread I posted.

If the equipment tag says "max fuse", you need a fuse.

 

[mike93lx]

Go read my thread I posted.

If the equipment tag says "max fuse", you need a fuse.

There has been some debate on this here. I thought the same but was told be the real sparkies that it doesnt

 

[PCustoms]

There has been some debate on this here. I thought the same but was told be the real sparkies that it doesnt

Thanks for that shot...

I was told by them here that it does, so I returned my non-fused and bought the fused version.

 

[mike93lx]

Thanks for that shot...

I was told by them here that it does, so I returned my non-fused and bought the fused version.

I have no idea what the real answer is. I'd use one with fuses

 

[PCustoms]

I have no idea what the real answer is. I'd use one with fuses

That's where I landed.. didn't make any sense to me, but if the nameplate rules all it was simpler just to use them.

A couple quotes from my thread:

the nameplate is controlling. If it's wrong, they need a recall campaign to supply the correct nameplate.

Looks like they need to update their nameplate as thats what you should be basing the circuit off of

 

[Lovthebass]

If l use a 30 amp fused disconnect, it shouldn't hurt right?

 

[PCustoms]

If l use a 30 amp fused disconnect, it shouldn't hurt right?

Right

 

[Lovthebass]

So I finished installing the unit and it came out well. I used 8 awg wire, 30 amp fused disconnect and a 30 amp breaker. I also installed a surge protector. I must say it was very easy to install and the unit works great for AC so far. I’ll see how the heat is in the winter. Using 8 gauge wire was overkill and hard to deal with sometime, 10 gauge would be definitely easier to deal with. The build quality of the MrCool unit seems to be made well, if it heats well and lasts years then I believe it was a good buy.

 

[teknikfrog]

I bet when the data plate says "max fuse" it just means:

"some means of interrupting the power"

So a breaker on the circuit is completely fine. Fuse / breaker no difference. Obviously a fused disconnect adds some manner of protection but is not needed.

(Not an electrician)