Disconnect switch needed

[PT Doc]

I am going to be needing a single phase 240 v disconnect switch. This will only be used in the event of an emergency. I have a 240v circuit in my attached garage. 50 amp breaker is in panel on side of house. This switch will be installed in case I need to shut down the circuit and won’t need to go around the house. Satisfies code as well. Down line of the switch will be a rotary phase converter with 7.5 amp motor generating the third phase. This will power a milling machine that will have a 3hp 3 phase motor that is rated for 9.6 amps and about 20 amps on start up.

The readily available single phase disconnects are 30 or 60 amps. What should I use as a disconnect on this circuit?

Here are a few affordable choices for Home Depot:

https://www.homedepot.com/p/Eaton-6...connect-Molded-Case-Switch-DPB222RP/100193214

https://www.homedepot.com/p/Square-...kW-Non-Fuse-AC-Disconnect-QO200TRNM/202844936

 

[Norcal]

Either would work, but the SQ D model looks to be a little more generous with wiring space which is a plus in my book, I prefer safety switches but they will cost considerably more.

 

[PT Doc]

It’s a one time purchase so it’s not a big deal in the big scheme of things. I might just go that route and kill the power at the mill and at the location when I’m done.

 

[walta]

It looks like both of the linked disconnects will work.

If you only plan on a single 3 HP machine a phase converter will be a pain to get set up and take up to much space. Look at getting a VFD

Walta

 

[PT Doc]

It looks like both of the linked disconnects will work.

If you only plan on a single 3 HP machine a phase converter will be a pain to get set up and take up to much space. Look at getting a VFD

Walta

With a RFC installed I might end up getting more 3 phase machines. I then wouldn’t have an excuse to pass up a good deal. I have a KB Electonics vfd on my 3hp 3phaee powered belt grinder and it is nice but was quite costly. Will likely go with RFC this round.

 

[PT Doc]

60amp disconnect is the right choice for this circuit that has a 50amp breaker?

 

[DieselNut88]

I would use a commercial style disconect with appropriately sized fuses installed. They are more money though.

 

[Norcal]

60amp disconnect is the right choice for this circuit that has a 50amp breaker?

There is no issue.

 

[PT Doc]

I would use a commercial style disconect with appropriately sized fuses installed. They are more money though.

Something like this?

https://www.homedepot.com/p/Siemens...-Non-Fusible-Safety-Switch-LNF222RU/202315410

Why the recommendation for a fused disconnect rather than a non fusible like the one above? Thanks

 

[PT Doc]

There is no issue.

Thanks for clarifying.

 

[PT Doc]

Can anyone shed some light on fusible and nonfusible safety switches? Thanks

 

[Matt Matt]

Can anyone shed some light on fusible and nonfusible safety switches? Thanks

Disconnect is a knife switch. Fusible disconnect is a knife switch which can reduce the load for a particular situation or a particular machine.

They are more commonly used in industry with a distribution of higher voltage and three phase.

I have a 15 kVA step up transformer in one of my shops that takes 62A three phase and outputs 25 A three phase. After the disconnect and the 15 amp fuses that are in there(The disconnect is rated for 30 A) wiring afterward can be adjusted... most of my machines require less than 10 A at 600 V. So, feed lines are 14-4.

Remember you can pick fuses to step down from a knife disconnect maximum.And in most situations you’re allowed to change the wiring size afterward.

I like to use Square D fuse disconnect’s!

Edit; I like to use one fused disconnect per machine or one fused disconnect Per outlet.