This is not one of those electrical questions which should lead to vituperrious and acrimonious responses about current-carrying capacity of wiring and circuit breaker ratings vs start-up loads of equipment, etc.
I’m finally completing new wiring in my garage workshop to accommodate four 230 volt pieces of equipment; a 4 hp table saw, 4 hp joiner/planer, 3 hp band saw and 5 hp dust collector.
All the wiring and circuit breakers have been spec’d. The wiring is all 3 conductor 10 gauge in conduit outside the walls, breakers as recommended by the equipment manufacturers. Each piece has its own run of wiring/conduit, with breakers at the 100 A distribution box. The dust collector, of course will be on simultaneousy with any other piece (and probably fairly constantly as I go from one piece to another), but only one other piece of equipment will likely be running at at time.
Each machine has a flexible 3 conductor cord (“pigtail”) which will have a short run to the terminus of the conduit feeding it.
Here’s what I still have to decide, and would appreciate feedback. I’m thinking of terminating the conduit in 2 different ways.
First is to end each conduit run with a 230 V outlet (dryer type) and plug each machine in with a matching plug. To do any machine maintenance, I’ll unplug it. Simple, visually certain.
Second is to end each run with a “safety switch” (attachment) and “hard wire” the pigtails into that. The switch is as certain a shut off device as a plug/outlet. The handle is visually positive.
Any opinions one way versus the other?
Thanks,
Rich
Replies
Rich, I use and recommend the first method. You do not want or need a dryer type connection. Use a Hubbell twist lock receptacle and plug. If the Hubbell's are too expensive use Cooper twist lock devices available at your local BORG, they are about half the price of the Hubbell's.
Life is what happens to you when you're making other plans .
"Life is not a success only journey." Dr. Phil
Agree fully, except that any reputable brand of twist-lock plug and receptacle will do, and as most are made to NEMA standards, they will work interchangeably.Joe
Thanks guys,Twist lock devices for 30 Amp service are $20-25 each, plug and receptacle. Standard "dryer" type are 1/4 that cost. Why not use them?They're also readily available where I live. I'll have to order the twist lock, whatever brand I decide.Rich
Standard "dryer" type are 1/4 that cost. Why not use them? Because you are not powering a dryer. You paid thousands of dollars for your equipment why not get the proper power connectors. Lowe's should have twist lock L6-30 plugs and receptacles. Below is a link to L6-30 Hubbell twist lock new style connectors and 12' of 10/3 cable already wired for $12. Also, twist lock connectors work good in ceiling installations, that's what I have done with a couple of my machines.
http://cgi.ebay.com/Hubbell-HBL2621-L6-30-male-Twist-Lock-Plug-250-vac-30a_W0QQitemZ260290894828QQcmdZViewItemQQptZBI_Connectors_Switches_Wire?hash=item260290894828&_trksid=p3286.c0.m14&_trkparms=72%3A1205%7C66%3A2%7C65%3A12%7C39%3A1%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50
Life is what happens to you when you're making other plans .
"Life is not a success only journey." Dr. Phil
So long as the "dryer" receptacle and cord are rated for at least the amp draw of the motor they will work just fine. My Dad ran all of his tools on a 50-amp "dryer" style plug and receptacle, that were sized for his arc welder, for years. That 50-amp plug was more than adequate for any other tool he owned.
The equipment doesn't care what the plug looks like, just that it is getting the correct voltage, and can draw the correct amperage. Most of the "dryer" receptacles and cord/plugs are rated for at least 20-amps. The down side is they typically have five or six foot cords which are usually too short for use on tools.
The only advantage to the twist lock is that it is mechanically locked in and can not accidentally get pulled, or vibrate, loose.
"The only advantage of the twist lock is that it is mechanically locked in and cannot accidentally get pulled or vibrate loose.
That may not be an advantage in certain cases. I have a bad habit of moving a machine before unplugging. It worries me that I might move it beyond the cords length. I don't want to see whether the receptacle or the plug gives first.
You're absolutely correct the equipment doesn't care, however having a plug come loose for a dryer is not nearly as dangerous have having one wiggling loose and remaking while you are running a board through a table saw.
Jack
I think the benefits of the twist-lock are being overlooked. 1st, it creates a positive lock that prevents the plug from becoming loose in the socket, which happens. Think, have you ever accidently tripped over a cord? And 2nd, the ease of disconnecting versus that of a "dryer" type is unparalleled. If you are doing blade changes on a regular basis, the extra one time cost is justified. Whatever you decide, the use of a proper strain relief connector is more important. I prefer the "Chinese finger grip" type. If you look in an old machine shop or garage, notice the cracked insulation and sometimes loose fit of the box connector. My 2 cents.
Having spent 30 years in a Municipal power plant. I had LOCK OUT/TAG OUT safety pounded into my head. The manual disconnects are a great thing.
But at home,in my shop, I am using the Stab/twist lock method. But there are lockable boots you can install over the plugs if you really want to go to the effort. And you can make your own for that matter.
Work Safe, Count to 10 when your done for the day !!
Bruce S.
Bruce, others,Can you please elaborate. I assume that safety is increased by the ability to pull a device's plug out of the power receptacle. Yes? No? Is there some other safety that these connectors convey?What is the desirability of the locking nature of any of these and what is the difference between LOCK OUT/TAG OUT versus stab/twist lock.Why does a plug need to be locked into an outlet? Do plugs fall out on their own?I've asked in my earlier post what's wrong with using a home clothes dryer type of plug/socket. I've never seen the plug from my dryer come out of its outlet.Obviously I have little familiarity with the more sophisticated of these types of connectors.Rich
Edited 12/14/2008 9:38 pm ET by Rich14
First any kind of machinery needs to have a "disconnect" on it for servicing.That can be the safety switch or in many cases a plug and receptacle.And that includes in homes. Near your furnace there will be a toggle switch to kill the power and even most "built in" appliances like DW and GD are plug and receptacle connected.And when working on circuits and the breaker is tripped there is often only one person there or a piece of masking tape can be put over the breaker to warn others not to turn it on.In an industrial area there can be many different people around so OHSA requires a systematic system for not only disconnection equipment or circuits, but to also make sure that some one does not turn it back on while another person is working on it.That is called lockout/tag out. And it can include things like ways to lock breakers in the off position, places on the safety switch to put a padlock, and locking devices that you can put on plugs to keep them from being plugged in.That is different from the locking plug and receptacle. Those are designed to keep the plug from being accidently removed.And I don't see any need for them in your case. They are more often used where plugs might get pulled on such as construction sites or where there could be lots of damage from a piece of equipment being accidently unplugged..
William the Geezer, the sequel to Billy the Kid - Shoe
I went with plug and receptacle in my shop; could'nt justify the cost of twistlocks.
Rich,
I have mine wired with plugs and recepticles.
When I have both hands inside the table saw negotiating the arbor nut without having it fall into the cabinet, it's very reassuring to be able to see that unpulgged cord draped over the top of the saw.
It's a routine. Unplug machine and drape the bright orange cord with the bright yellow plug over the machine where I can see it.
Frank
Thanks everyone,That pretty much confirms what I was planning to do. The safety switch method of achieving safety seems like a good bet in my one man shop.That red handle is hard to mistake in the up or down position.There are still a few odds and ends to configure, so I'll put this off for a few more days.Rich
Rich, with the safety switch, you can buy a lock, and lock the power to the machines off.
I have all the 220-volt outlets in the shop on a separate subpanel with a lockable switch in between it and the primary subpanel, so that I can lock out all the 220-volt tools.
It is a really good idea if you have any children, or untrained adults, around who can get to the shop. <!----><!----><!---->
Or a lock on the sub-panel..
William the Geezer, the sequel to Billy the Kid - Shoe
Bill I ended up with what I have, because the previous owner had lockable disconnect installed for the outlet he had used for an air compressor.
When I bought the place, and started checking out the shop wiring, I found all sorts of issues with the grounds, and nuetrals.
To solve the issues, and get the 220 outlets for the power tools I wanted, without ripping the walls apart: I ended up running all new circuits in surface mounted conduit, and abandoning the existing receptacles.
To expedite the process, I kept the old cirucits, and panel active until after I had completed the the new system, and was ready to energize it. So, I bought a new breaker panel to use as a secondary subpanel, and since I already had a lockable diconnect that was rated high enough, I just wired it in between the primary, and secondary subpanels.
I can lock out everything, except: the receptacle for the garage door opener; one receptacle next to the subpanel, (that I plug the chargers for the cordless tools into); and the lights.
NEMA L6-20 or L6-30 (depending on amperage draw) twistlock plugs and receptacles. Have them on all my stationary equipment. They can be a bit pricy at your corner hardware store, but are reasonable if purchased on the web. There's a guy selling used ones in very good shape on ebay for $7 a pop. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260332431733
Thanks,That auction looks like a great deal. Wish I could use them, but I need 30 amp units.Rich
They come up on ebay all the time. Here are two L6-30's for $18 ... http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170289209164Just type in L6-30 into the search on ebay. You'll see them selling for ~$10-$14. Still less than $25+ you'll pay at the hardware store.
Got 4 L6-30 male units at another auction. 10 bucks each. Great deal. Now I need the female units. That'll be another auction, I need several types.Rich
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