Opinions on power connections for home shop machines

[ninefinger]

I'm looking for opinions and advice regarding connecting power to my new to me lathe and my mill. What is the "proper" electrical connections to make?
Hard wired with conduit and armored cable? Or is it acceptable to use a suitable plug and flex cord? Or either one is right? This is for Canada, in a basement workshop using 240 VAC, and the 2 machines have VFD's on them.. The largest is a 3hp VFD but its running a 2hp motor (mill), the lathe is a 2hp VFD running a 1.5hp motor. I do not anticipate running both at the same time so sizing the circuit for the largest of the 2 is my plan (the 3HP VFD calls for a 30 amp circuit)

I'm at a point where I need to rewire to accommodate the new lathe and I need to pick a method - or at least be informed before I call in an electrician.

I currently use a definitely not to code installation and I want to get much closer for insurance and safety purposes. To be truly in compliance I will need an Electrical Safety Inspection when all is done but if I can do the work myself then I'll be much happier.

Mike

 

[Entropy455]

The advantage to hard-wire (i.e. flexible conduit between an outlet box and your machine) is that you don’t need to purchase an expensive plug and receptacle. The disadvantage comes if you ever need to move the machine.

Match the full-load current rating of your machine’s motor with a breaker that either matches, or is slightly larger. Then select copper electrical conductors that are rated for the current (and voltage), and hook it up – either hard-wire, or with plugs. I recommend avoid using aluminum wire. . . . . .

Typically on 240 volt installations, the ground wire does not need to be the same size as the current carrying conductors. The ground can be smaller. Check your local code.

Does your machine have an on/off switch? If not, remember that electric motor switches are not rated the same as standard switches. The starting current on an electric induction motor is pretty intense. Even a 3-horsepower motor will burn up the contacts on a 20-amp non-motor rated switch. If you need an inexpensive and heavy-duty motor switch, I recommend purchasing a 3-phase switch. You’ll only use two of the three switch poles, and it will last for decades.

 

[f350ca]

Mike
I prefer a soft cord and plug. Im not sure if hard wired is code unless the machine is bolted down. Maybe a lathe or milll is considered heavy enough to be permanent. The plug gives me an extra degree of security if I have to work on the electrics of the machine. Unplug it and I know I can't get zapped or caught up in a belt or gear if a cover is off. In an industrial application you'd have a disconnect that can be locked out.
As for the VFD calling for a 30 amp service, that would be at rated capacity with a 3hp motor, for a 2 hp load you should only need a 20 amp service which can be fed with 12 gauge wire. Home depot should have 20amp 220 volt receptacles and plugins, They look like regular plugs with one spade turned sideways. The receptacles are available as single or duplex. I wired my cabinet shop and machine shop with them and it passed inspection.
If the wiring is surface mounted it needs to be armoured or in conduit if its below a certain distance from the floor, can't recall the distance. I run all mine in pvc conduit.
Hope this helps
Greg

 

[kvom]

For my mill, I put the VFD inside a NEMA box on the wall and hard-wired it with a cutoff switch. Then used flex cord to the mill motor (removed the switch box). I have a remote control unit for the VFD mounted to the mill that does all the power/speed control. This may be overkill, but the VFD is immune from shop dust and swarf. If I were to have the VFD mounted to the mill, I'd use flex cord and plug, making it easy to relocate the machine.

My lathe uses a RPC for power, and it's connected via SSO cord and plug.

 

[Stan]

You probably need advice from an electrician that is familiar with the codes for wiring machine tools (not just a house electrician).

You have to start from your entrance panel and depending on access will determine if you can run concealed wire or if it has to be on surface. Any wiring on surface has to be protected. If you are going to have any any 120 volt you either have to run multiple circuits from the entrance panel or else run a four wire circuit to a sub panel in the shop. The existing entrance panel may determine your choice depending on what breaker space and kind of breaker available.

You have to have a disconnect at each machine. If you hard wire to the machine then the simplest is a fused disconnect. The other alternative is extension cord to the machine using a plug and receptacle as the disconnect. If you are using a VFD you must be using three phase motors and three phase plugs and receptacles don't come cheap.

Questions like where do you get 120 volts for controls circuits or a machine light come into the equation. You can get 120 volts out of three phase but you can't plug a 60 watt lamp into a thirty amp circuit. These kinds of things are usually dealt with in the machine control panel, but you have to be sure.

Just for insurance reasons alone, you need a permit and an inspection.

 

[ShopShoe]

As has been stated on this forum many times, electrical connections vary greatly from location to location and jurisdiction to jurisdiction. My personal experience in three different jurisdictions in central Iowa, USA, is that if you study the alternatives in practical reference material (so you know the options by code) for your area and then call or visit your electrical inspector when he/she is not busy, then you will get brownie points for asking in advance and you will be told what will be allowed or expected no matter who does the work. In the US, anyway, there are options in the code and differences in local interpretation and local standard practices. What I should have also mentioned higher up in this post is that this is for a home shop situation, not business or industry.

I should also mention that nowadays you can usually find the general contact information and local permit/no permit information and ordinances through your community's website, so you can determine what you want to do from there. In my present town, I would need a permit, I would have to take a "homeowner" examination on the code, and I would have to pay fees for the above and have inspections. I believe that meeting with the inspector in advance would answer any questions as to what I would be able to do myself and what I would have to have an electrician do. The real issue would probably come up if I wanted to have an electrician do only part of the work: I don't know who would be willing to work with me on this.

 

[Dunc]

Just wondering...

If the motor/vfd combo requires "x" amps is it enough that the breaker is that value or is higher capacity required to allow for startup current?

 

[sunworksco]

I would use a twist-lock plug for my lathe.
They have more metal contact area and stay connected more securely.
You can acquire these through an electrical supplier.
Maybe "Homeboy" might stock?

 

[Maryak]

In Oz, machine tool lighting built in or directly attached is normally 32V DC. Helps prevent you electroplating yourself when the bit comes out and in passing attaches itself to the lamp it just broke.

Best Regards
Bob

 

[ninefinger]

Wow - thanks for all the replies. There are a few good points that I sorta knew but hadn't thought through completely such as a cutoff switch / disconnect if its hard wired. My mill is currently this way as the VFD doesn't have an "off" switch.

So I'm leaning towards what Greg (f350ca) says he did - seems very reasonable to have outlets surface mounted in conduit and plugs with flex cord to the machines. I will probably still add an off switch on the lathe and mill to turn off their VFD's when not in use, but if I need to work on the machine I can unplug it.

The cost isn't what has me concerned - I want it to be safe and convenient to use - this is my hobby space and I want it to be nice!

Plus, having outlets lets me plug in other devices if I so choose and need to (arc welder for instance - not likely but could happen - I'd rather keep welding in the garage for many reasons), etc.

I will be having my work inspected / permit acquired in accordance with local code - a house in the neighborhood recently burned and the owner had done some of his own wiring without any inspection - not sure on the cause yet but I did hear they aren't getting insurance money at this time....that has me wanting to cross my t's and dot my i's so to speak.

Mike

 

[kvom]

Breakers are designed to protect the wiring and should be sized as such. The breaker amperage can be higher than that drawn by the machine.

 

[f350ca]

Mike
The panel breaker can be used as an on/off switch if its within sight of the machine, if that applies in your case. I have a solid state phase converter wall mounted and hard wired to the panel with a 50 amp breaker. The inspector said no problem using the breaker for an on/off as it was in sight. Saves buying a disconnect.
Greg

 

[Stan]

Mike: Let us know what the local inspector required and what you ended up doing. There is usually more than one legal way and a 'good' inspector will give good advice. Some inspectors still belong to their local union and will discourage DIY work to the point of being miserable. They can find fault with anything that wasn't done by a union electrician.

 

[Omnimill]

I worked with an Electrician from Canada many years ago who came over here to work (UK) because he found working in Canada rather mundane. He told me that due to regs home owners weren't allowed to do much more than wire up a plug in Canada. Guess things have changed?

 

[Stan]

Every level of government can write electric code which cannot be lower than the federal cod, but may be tighter. Basically. it is only CSA approval that requires dealing with the Feds. Things like inspecting building wiring is done by provincial and sometimes municipal inspectors.
From this, you can see that there is a wide range of rules and regulations. In Alberta, as far back as the 1960s. I have been able to pull a permit and get the inspection done on my own home property. There are rigid requirements to work for the public. As an individual (not working for a contractor) you have to have a Masters ticket plus a business license to work even in your neighbor's house (a rule often ignored).

 

[ninefinger]

Well I have done some more investigating and I'm not really pleased with what I found out.

In Ontario a the governing standards are the Ontario Electrical Safety Code - but you the general public don't have free access to them - its $195 to buy a CD rom copy!

So even trying to do my own background homework on this is a real pain as I can't go to the source like I usually do to get myself informed. I also stumbled across an amendment to the code that specifically states a group of approved electrical devices does not constitute an approved device - meaning that when I get an inspector in to my house I'll probably need to explain my machines and get a safety inspection of them too - otherwise my house could be deemed a "clandestine laboratory" which sounds neat except its an the same level as meth lab!!!

Anyway - I am using VFD's that are single phase, 240 VAC in an 3 phase out. At least the VFD's have CSA markings on them. I'll install them in a nema box, proper start/ stop fwd/reverse and E-stop buttons and make proper power cords with twist lock connectors on them - that should be more than satisfactory for that part of the installation.

My last worry is that my panel will be deemed too small to add the circuit - it has breaker room but doing a "panel load" calculation will probably show me going over the top of my 100 amp service....

I will sort this out but I'm going to take my time to figure it out ...

Mike

 

[JorgensenSteam]

Mike-

I have seen some larger VFD's overheat when installed in an enclosure.
Do you have to enclose them or are they already in NEMA 1 enclosures?
You may need ventilating fans if you mount them in an enclosure.

My approach to adding wiring that I don't want a pesky inspector to look at is to install a large receptacle adjacent to the existing panelboard (maybe 50 amperes). I then run a temporary industrial cord overhead to the machine(s) I want to power, and install whatever on the end of the temporary cord, hanging it on the wall. If the inspector comes around, unplug everything, hide it, and explain the receptacle as a power outlet for miscellanous temporary loads.
It is also handy if you have to vacate the wife's garage and move to another shop.

But keep in mind that if you don't know how to wire things up safely, then the inspector may very well save your life.

I sometimes run large loads on my panelboard at the house, but turn off the dryer and electric range breakers so that I don't have all the heavy equipment on at the same time.

Also remember that many machine tool motors are lightly loaded.
My 1.5 hp mill motor is suppose to draw something approaching 20 amperes, but that is only if it is fully loaded, and I have found that for hobby work, the motor is generally very lightly loaded, pulling only a fraction of rated amperes.

My lathe tends to get pushed more to capacity, since I sometimes take heavy cuts there.

Use a green ground wire to every metal part, motor frame and metal enclosure, for safety purposes. The only safe electrical shop system is a well grounded system.