Mini split disconnect

[Ska23]

Im currently having a mini split system installed and originally ran 10 gauge wire, red, black and green inside 1/2” pvc conduit from the panel to the disconnect but now decided to install a Fujitsu system instead which only requires a double pole 20 am breaker. Is this ok? I know it wont burn up the wire but is it acceptable to use such a heavy gauge for such a low amperage system? The company installing the mini split system said they would get an electrician for roughly $600 dollars so I decided to run the wire myself and my electrician said he will connect it to the panel for $50. No brainer. Just want to make sure its correct before I get the electrician here to hook it up. I attached the Fujitsu electrical requirements for reference. Any advice would be greatly appreciated.

 

[Lonnies Performance]

The wire will be fine... it is only 1 size over the minimum rated wire.

 

[Ska23]

The picture isnt clear.
The panel states:
Maximum operating current : 13.7
Starting current: 9
MCA: 17
Maximum breaker: 20
10 208/230v 60hz

I have the 20amp double pole breaker. Just want to make sure the wire is ok. The wire is already installed and dont want to waste money for additional wire. Also I can only find a 60 amp disconnect. Is this acceptable?

 

[Ska23]

Also is the double pole breaker correct? The 10 in the previous paragraph is meant to for single phase

 

[Terry D]

There is nothing wrong with the wire that you have. Just install a 2-pole 20 amp breaker. The 60 amp disconnect is fine, It can be a non-fusible, no need for a fusible one here. Im not sure you can even get a 30 amp disconnect anymore, everything I buy is 60 amp.

 

[Ska23]

Thank you very much!

 

[rlitman]

...Also putting in a 60 amp fused disconnect when a unit only calls for a max of 20 amp like your unit calls for, can allow it to over amp way worse than you should which can damage stuff.

Um, no. There's no harm or risk in using oversized wires. The only difficulty could be if the wire were so oversized as to not fit connectors.

 

[rlitman]

Did I say anything about "oversized wires"?

Putting a 60 amp fused disconnect (with 60 amp fuses) on a unit that calls for a 20 amp fuse / breaker allows up to 60 amps before the breaker kicks or the fuse pops. So allowing for an extra 40 amps BEFORE a fuse or breaker trips allows for the possibility of more damage instead of the breaker / fuse going out at 20 amps......


To OP: You can use a 60 amp fused disconnect, and get these little adapters to make the smaller fuses work to use the 20 amp fuses if you want. Or just get the smaller 30 amp disconnects which take the smaller fuses in the first place.

Again, this doesn't make sense. There's no need for fuses here, the fuse size isn't even relevant, and fused disconnects, even 60A fused disconnects, don't come with fuses.

In a situation like this, you can buy shunts rather than fuses, if you happen to really want to use a fused disconnect, since only the upstream breaker size matters. But you're throwing out money.

But the smart thing to do would be to buy one of those $6 AC disconnects that doesn't have fuse positions.

 

[The Cobbler]

a disconnect can definitely be higher amperage rated than the feed amperage size.
zero safety issue. code compliant. what else is there to say?

 

[rlitman]

Never said a fused disconnect comes with fuses, you just love making stupid assumptions..

Now for my own assumption.... I'd be willing to bet when telling someone who doesn't know what they're doing to get a 60 amp fused disconnect that they're popping 60 amp fuses in there with it because someone "told me to use a 60 amp fused disconnect".

The upstream breaker size isn't all that matters. I have seen multiple times where a breaker doesn't kick even though whatever it's feeding pulls more than the breaker is rated for. Having another layer of protection to prevent your AC from getting hit with too many amps (or overheating from a compressor trying to start with a bad capacitor for example) is only going to help you and may prevent damage which may cost you a lot of money.

A quick google of shunts said, "While shunts serve to remedy an open circuit, fuses work to prevent damage due to a short circuit or any other dramatic increase in current." Which seems to back me up as a fuse works to "prevent damage due to a short circuit" like I have been trying to say.

Also a 30 amp fused disconnect is like 15 bucks and a few bucks for each fuse. So for around 20 bucks I'd rather have a fused disconnect, but do whatever you want at your own house.

Give it a rest. A 60A fused disconnect is sized by the lugs, NOT the fuses you stick into it. And again, fuses aren't bringing anything to the party here except another point of failure.

Making the claim that you've seen breakers not trip at the rating means you do not understand time trip curves. Time to hit the books.

 

[The Cobbler]

You can use one rated for whatever amperage you'd like, .

correct. it goes without saying equal to or larger than the feed breaker size

but just use the correct fuses If you use anything larger than 20 amp fuses (in this case) then they're not really serving their purpose of protecting the unit like it's supposed to.

a disconnect's purpose is simply to disconnect the feed from the equipment. it has nothing to do with protecting the circuit. think light switches, they simply disconnect the circuit, they have no overload protection in them.

Someone else said they don't think they make 30 amp fused disconnects and all I was doing is stating that they do.

but in this case, that information is irrelevant

 

[Norcal]

Fusible A/C pullout discos come in 30A & 60A models, non-fusible are 60A, which are the most economical choices, I prefer safety switches but are damn expensive compared to pullout discos, which can be had for less then $20.