Mr.cool 36k @ 28-35A?

[dcg9381]

One of my buddies called, I've done mini-split systems with him before. He's finishing a bardo. The new Mr. Cool systems are kinda interesting as lines are pre-vacuumed. I suggested that he look at 24k system price points as I found them "less expensive" than large units, even if you had to move to multiple units.

He installed 12/2... And that was consistent with my experience with Daikin 24K units, less efficient, 17 SEER, that pull less than 12A continuous. I guess 24k is out of stock, so he's looking at 36k.

These are all 240V units. But their power requirement jumps to 6ga wire. I can't explain the difference in electrical pull... Can you guys?


Linky

 

[mm08822]

Who ever put this table together hasn't a clue what the first 2 coumns mean.
MCA = Minimum circut ampacity This value includes 125% for compressor FLAs plus 100% of the other loads (which is at least a fan).
12-2 NMB won't meet the 22a requirement. It should have been #10 NMB or 12 thhn in conduit.

The 36K will require #10 NMB and can have up to a 35A cb.

Of course if distance is long, then maybe go up a size but #6 is crazy.

 

[fitter30]

Here's a voltage drop calculator

Voltage Drop Calculator

Calculate voltage drop in AC or DC circuits, plus learn the formulas to calculate voltage drop for single-phase and three-phase systems.

www.inchcalculator.com

By adding a full ton of cooling it will not remove the humidity because of the shorten run time.

 

[dcg9381]

Who ever put this table together hasn't a clue what the first 2 coumns mean.

That's from the manual on their units. Here's the link

The 36K will require #10 NMB and can have up to a 35A cb.
Of course if distance is long, then maybe go up a size but #6 is crazy.

It's pretty explicit to me that it's a minimum of 8 awg for the 36k unit. Again, I don't quite get it as my Daikin 24k units with less SEER didn't have these requirements for power.. They run all day at less than 12A continuous, 20A breaker, 12 ga wire.

 

[mm08822]

As I stated, whoever put this table together (from Mr. Cool) doesn't know the NEC requirements and is creating requirements above and beyond what it requires. Is it a bad suggestion? No, but it undermines the entire concept of MCA.

The MCA concept was created so HVAC techs or electricians didn't have to do the calculations for multiple motor loads, etc.

 

[SVibs]

The values seem crazy. For instance: why is the MCA for the 9K and 12K units (19A) higher than for the 18K unit (18A) but the max fuse/breaker size is lower?

I just installed a 24K Senville Leto series and the MCA was 19A and MOP was 30A. I'd be curious to see what the condenser name plate values are. If your buddy is planning on pulling a permit, the name plate is what the inspector is going to use to determine what the wire size and breaker size should be.

 

[Bert_]

I would ignore the minimum and preferred size columns.

MCA and MOP is standard throughout the industry and all you need.

MCA means you need wire that is good for 28 amps. MOP means breaker size is 35 amps. You do not do anything else to those numbers, you don't add anything you don't multiply anything, it tells you exactly what to do.

If it needed 8 gauge wire then the MCA would be over 30. It's not so it doesn't need that wire. The table is wrong.

 

[sparky 1971]

It's kind of stupid that they give you the MCA and MOCP, then turn around and tell you to use different sized wires. I'm willing to bet that the preferred size isn't on the nameplate, and who in the blue hell is going to show up to wire the unit and look at the owners manual? I'm not. Someone is going to use all of the naughty words trying to land a #6 in there. If in conduit, I'm probably running #12 to each of those units. Some of them could be done in #14, but I probably wouldn't have it on hand. And...why is the MCA of the 9 and 12K higher than the 18K?

My mini split is a Bosch, I don't know how big, I told the supply house what I was doing and they sold me a unit. I haven't looked at the name plate, I just ran a 12/2 and put it on a 20 amp breaker.

 

[My Old Tools]

That's not what the manual with my 36k MrCool said. 10 ga. with 30a breaker. Been in 4 years.

 

[Kezorm]

And...why is the MCA of the 9 and 12K higher than the 18K?

Pretty sure the 9 and 12k units are 120VAC

 

[dcg9381]

MCA means you need wire that is good for 28 amps. MOP means breaker size is 35 amps. You do not do anything else to those numbers, you don't add anything you don't multiply anything, it tells you exactly what to do.

If it needed 8 gauge wire then the MCA would be over 30. It's not so it doesn't need that wire. The table is wrong.

Minimum Circuit Ampacity (MCA). 28A is required here.

What about consideration of "continuous duty"? Doesn't the 80% rule apply and limit 10ga wire to .8 * 30A = 24A @ 60c
As this thing needs 28A, I'd assume that's why they are kicking it up to 8ga minimum...

I mean I doubt this thing pull 28A continuous...

 

[mm08822]

Minimum Circuit Ampacity (MCA). 28A is required here.

What about consideration of "continuous duty"? Doesn't the 80% rule apply and limit 10ga wire to .8 * 30A = 24A @ 60c
As this thing needs 28A, I'd assume that's why they are kicking it up to 8ga minimum...

I mean I doubt this thing pull 28A continuous...

Minimum circuit ampacity includes 125% for compressor FLAs plus 100% of the other loads (which is at least a fan).

The continuous duty allowance is taken care of using 125% of largest motor which is factored into the labeled MCA value.

Also the mfr has no idea whether 60C rated wire or 75C is going to be used. Is it Al or Cu? Distance?

 

[Bert_]

Minimum Circuit Ampacity (MCA). 28A is required here.

What about consideration of "continuous duty"? Doesn't the 80% rule apply and limit 10ga wire to .8 * 30A = 24A @ 60c
As this thing needs 28A, I'd assume that's why they are kicking it up to 8ga minimum...

I mean I doubt this thing pull 28A continuous...

You aren't listening. You do not do any other addition or multiplication to the minimum circuit ampacity or max overcurrent protection!

The unit does not pull 28A. The manufacturer has already taken the current draw and multiplied it by 125%.

 

[sparky 1971]

Pretty sure the 9 and 12k units are 120VAC

In post #1, he states they are all 240 volt units. I dunno.

 

[Kezorm]

In post #1, he states they are all 240 volt units. I dunno.

The 1 ton unit is 120VAC. From same manual as shared above...

 

[mm08822]

Just read the nameplate and burn the manual.

 

[dcg9381]

In post #1, he states they are all 240 volt units. I dunno.

Sorry, the 36k unit was 240v for sure. Didn't look at anything below 24k.

 

[dcg9381]

Just read the nameplate and burn the manual.

I'd go for that, but some of us prefer to install the infrastructure before buying the unit.
I had him step down to 3 x 18K units, which work per "manual".

 

[mm08822]

I'd go for that, but some of us prefer to install the infrastructure before buying the unit.
I had him step down to 3 x 18K units, which work per "manual".

In this day and age of Chi-Chom **** galore flooding our markets, you have to scrutinize everything.