Shop wiring ?

[mmcmdl]

I've gone full circle these past 40 years . I'm starting to lay plans out for the garage after moving out of the basement years ago . I have a 10HP RPC on hand once again . If I remember correctly , the RPC was connected to the main panel and then to a quick disconnect box . From the disconnect box , the outlets to the machines were then mounted on the walls for each piece of equipment . Does this sound correct ? It's been a long time ago and a master electrician hooked it up for me . Just trying to get it straight again . My largest motor may be a 3 horse and I will only be powering 3 or 4 smaller machines , the BP being the largest . Like I said at the start , I'm getting back to what I started with 36 years ago .

So , as far as breakers and wire sizes . I know the breakers protect the wiring . What would be the requirements of such a set up ? I'm almost at the point where I can begin this project once again . TIA . Dave

 

[Karl_T]

The best way to do this is get a small 3 phase load center and install it as a sub panel. Then one circuit per machine with the correct circuit breaker.
The RPC goes on its own circuit also. As to wire sizes and breaker sizes, need the FLA number from each motor.

Here's one panel. You can do WAY better on pricing shopping used. I suggest the square D Q0 240 volt panel for ease of breaker price and availablity.

Square D Load Center, 12 Spaces, 125 A Amps, 208Y/120/240V AC, QO Circuit Breaker Type QO312L125G | Zoro

Order Square D Load Center, 12 Spaces, 125 A Amps, 208Y/120/240V AC, QO Circuit Breaker Type, QO312L125G at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.

www.zoro.com

 

[mmcmdl]

I'm going to take pics of my panel in the garage , the panel down the other basement and the breaker boxes ( fused ) that I have on hand . The original breakers may still be in the basement main box but I can't remember . Trying not to burn the garage down or get magic smoke from the machines .

The machines involved will be the BP , Hardinge DSM-59 and a future HLV-H along with a 3 phase HB saw . Everything else will be single phase 110 .

 

[Reddinr]

So, I have a bunch of Square-D 3-Pole breakers that I can spare. They are old and dusty but kept dry and never used. They require a "bolt-on" style distribution panel (Type QOB or QOD if I remember right), not a plug-on-only "QO" panel. I have some 20A, 30A, 60A ones. I don't have 15A I don't think. They are mostly "HACR" type made for heavy inrush currents like compressors, motors and the like.

Model: Square-D, Model QOB, HACR New, these run in the $80-90 range. Will trade for something interesting you don't need that I can use (related to machining).

If you are interested, please do check if you can get a QOB/QOD panel cheap enough to make it worth it to you. It would suck to have a bunch of breakers but nothing to put them in.

Come to think of it, anyone else need breakers? I have many varied ones 2-4 pole. Some UL panel breakers, some UL/IEC Types (European, DIN rail mount). I am on a mission to clean out my attic.

 

[Reddinr]

I just reread your post. The RPC is 10HP you said. I looked up a 10HP RPC, maybe 14-15 Amp rated? Some name-plate reading is in order. My breakers are possibly too big.

What is the three phase current rating of your biggest machine? If it is less than or equal to 12 Amps, and a one-man shop, I would do the following.

Single Phase Panel [2-POLE CB} ---> 10HP RPC ---> 15A-3Pole CB --> OUTLET ---> OUTLET ---> OUTLET ---> OUTLET

The only benefit of a CB distribution panel for this low current would be to isolate each machine. If you are plugging them in then you can just unplug each one as needed.

This advice does not consider all the state/local electrical codes that might apply. For example, some circumstances might require a disconnect switch within x feet of a machine etc.

 

[Eddyde]

I agree with Karl T, Installing a sub-panel is the best, easiest way to do it, to code.

 

[Reddinr]

It would be great to meet code. It may be difficult to meet code though, depending on the specific RPC. For example, if the RPC is not a UL Listed device. Some RPCs are listed but for use on only for one machine. So, there is code compliance on one hand and safety on the other.

 

[Eddyde]

It would be great to meet code. It may be difficult to meet code though, depending on the specific RPC. For example, if the RPC is not a UL Listed device. Some RPCs are listed but for use on only for one machine. So, there is code compliance on one hand and safety on the other.

True, I should have said "Code", meaning reasonably safe, not necessarily to the letter of the law...

 

[CJ5Dave]

Wondering if a 15 amp breaker will run a 10 hp phase converter. I have a homemade converter with a 5 hp idler motor. It runs a 3 hp 3 phase lathe. I used a 20 amp breaker for the disconnect. When the weather got hot last week the breaker started tripping and I had to upgrade to 30 amp.

 

[Reddinr]

Regarding 15A Breaker to power the input of the RPC. Probably not. When I had an RPC, the input breaker was about 2X the output breaker if I remember right. I was speaking about the output side branch protection to the machine(s). Also, 15A on the load side may not be correct either, maybe 20A is more appropriate. More information is needed about the machine ratings, the RPC ratings etc.

Eddy - I'm thinking that this sort of set-up would take the average residential electrical inspector outside his comfort zone regardless of how it is done. I think that the distribution panel method and the multiple receptacles on one branch circuit method could be safe and reliable for a one-man home shop. This is especially true if only one or two are running at once.