I’m in the planning phase of rewiring my garage shop.
The current 50-amp feed is adequate for the loads I foresee, which are two 3-hp motors, (dust collector and one machine), and the lighting.
There are currently four 20-amp 110-volt pug in circuits, two of which have ground issues, and one with reversed polarity on some of the plugs. Two of the plugs I pulled to correct the polarity issue have aluminum wire, so I am guessing that much of the rest of the wiring is too.
My basic idea is to run surface mounted EMT, to avoid tearing into the walls. Up to here, every thing is within my skill and experience level.
We have frequent short duration drops of the power in the winter. I was cutting some 5/4 maple last year, and the power dropped. I immediately reached for the off paddle, but before I could get things shut down, the power came back up. I managed to keep control of the board and avoid a kickback, but it still scared the **** out of me.
What complicates it for me, is that I want to put in some type of latching relay set up on the feed to all the plug in circuits, and have things set up so that if the power goes down and then comes back up, the tools will stay off until I relatch the relay. I also want to have a key switch to keep the kids from “working” with the power tools when I’m not there. I have the mental image of what I want, a feed from the subpanel, through the relay to a second subpanel, and then wire the receptacle circuits from there. The control power for the relay can come from the original subpanel.
I’m out in the boonies, and the older guys at the hardware store I will be buying my pieces/parts from all retired this year. The folks that are still there are good on the day to day stuff, but this is a little beyond them.
So, any advice on what I need, parts wise, or references to read would be greatly appreciated.
Thanks
Replies
If your machines are older, you can replace the switches with magnetic ones, which will stay off when the power comes back on. Grizzly sells them and they're not terribly expensive, considering the safety aspect.
A sub-voltage drop-out falls into the industrial controls category is my guess. I wonder if Grainger might have something. Do you have their catalog? It's huge.
Otherwise if there's a Graybar anywhere nearby you could definitely talk to them and get what you need, or likely any other electrical suppy house.
The idea of individual magnetic switches is a pretty good one. Maybe easier to deal with.
Ed
What you propose is not all that difficult, but I do suggest you find an electrician to do it. I mean a REAL electrician - not a handy type that's pulled wire in a few houses. Someone with control or Ansul experience.
Probably the easiest thing to do is to put all the circuits you want to control on a separate panel. 50 amps is well within the range of readily available magnetic starters. Then you can have a locking 'stop' button added- or simply padlock the disconnect switch.
Newer starters have electronic overloads - these will also protect the equipment from low voltage, and other hazards for which we have never had protection.
Yes, you can use a '3 phase' starter on a single phase system.
As for momentary power spikes ... before you try to add a "UPS" or some such item, have an electrician check out your service and your garage feed. It is very possible that there is a bad connection somewhere.
Reno, the connections at the house are good. It isn't just me that has the fluctuations, and momentary drop outs, it is the whole town. We are in the mountains and isolated. There are a couple of feeds in to here. One goes over the continental divide, the other just a few high mountains.
So fair as real electricians with controls experience, there might be a couple that work at a mine around here, but there isn't a lot of industry that uses controls around.
The only tricky part to this whole scheme is the relay system.
"Tricky" is more a matter of experience, than anything else. Let me try to explain a simple way to do this, in greater detail. First, you decide what circuits you wish to have 'locked out.' These you run to a separate panel. For the sake of this discussion, let's assume that you decide this panel needs to be fed with 40 amps of power. Before this panel, you place a motor starter that can handle 40 amps of 240v. If I recall correctly, that would be a "size 1" NEMA starter. your #8 wires that feed the panel pass through the starter.
The starter is - by definition - a contactor (big relay) with overload elements attached. If you get one with electronic overloads, these will also protect you from low voltage, and a few other things as well. It's pretty important that the loads all be 240v, or VERY well balanced; if you can't do that, the older style 'heaters' are a better choice. Now, the starter has within it a magnetic coil that is energized when you push the 'start' button. All it takes is a moment of the contacts in the switch to be closed for the coil to stay energized; from there the coil is wires so as to keep itself energized, and the power 'on.'
This means that even a moments' interruption of power to that coil - caused by power failure or the 'stop' button being pushed - and the coil will stop holding the relay closed ... your machines will stop, and remain stopped until you push the 'start' button again. These coils come in different voltages. Make sure the guy at the supply house knows that the coil - and all your controls - will be 120 volts. You will use 120 volts, because it is available in your system. Again - and this is a preference of mine - for simplicity's sake, supply the control power from a different circuit in your primary panel ("upstream"), rather than by tapping off the starter feed. Before the 120 is delivered to the "start" button, you can insert a keyed switch. Or, as mentioned, "Stop" switches are available that allow you to lock them in the 'stop' position. One of the Mine guys ought to find this to be very basic. One last note: The 'overloads' in the starter are NOT a substitute for having properly sized breakers or fuses. The two devices are there for different purposes. You still need the breakers.
Other things to consider:
I wired my shop with 2 lighting circuits and (2) 20A power tool/receptacle circuits (GFCI protected from the first receptacles to everything downstream.) Plus the dedicated 240V circuits for the band saw and dust collector. That way, lights don't dim when tools power up. And an overloaded breaker on a tool won't leave you in the dark.
In this area everything is EMT. I like it. The wiring is protected, and I like the neat appearance. I went overkill on wiring, and wired everything with 10 gauge solid copper. My FIL was helping, and he was cussing making all the connections. Some BIG wire nuts needed for that!
As far as keeping the kids safe, you could run the receptacle/tool circuits from the panel through lockable box with a switch on it, sort of like a disconnect. In my basement, I would just hit the test button on 2 GFCI receptacles to kill the power to all receptacles and power tools (except for the 240V bandsaw). Since they were mounted on the ceiling, I didn't have to worry about the kid figuring it out, or even if he did, reaching it.
And don't forget, you can't have too many receptacles. Double duplex boxes every 4-6' ought to do it.
Pete Duffy, Handyman