Wiring Question

[Woodboy]

Just purchased a new cyclone (Laguna 2 hp) and I will follow-up hopefully with a Christmas present table saw (hope my wife is listening) - both 240V, one pulls 12 amps the other 13. Both have NEMA 20-6 plugs with a ground and the horizontal contact type mail plugs. I want to have a single floor outlet for both to minimize the cord issue. And of course, they run together.

In my wisdom, or foolishness when I built the room over a suspended floor I put a 30 amp circuit breaker in the box and even pushed 30 amp rated wire down underneath the floor. Even though the floor is suspended, it's a ***** to crawl down there (minimal clearance, very claustrophobic) - hence the pre-wire.

My problem - one 30 amp line, a 30 amp breaker and two machines that have plugs that do not fit a big 30 amp outlet. Plus they don't really make nice duplex floor outlets for those big 30 amp female plugs. Don't think I can put a 30 amp line into a 20 amp duplex outlet. Short of re-running two 20 amp lines under the floor and giving each just one outlet in the shared floor mounted box - what is the solution here? Or is just a single 20 amp line enough?

Any suggestions out there? I will hire my cousin-in-law the electrician to help me, because 240V scares me, but I want to do the spade work myself and have it teed up for him.

[LCHIEN]

technically you should quite easily be able to run 12A and 13A (total 25 Amps, max) loads on a single 240V 30A line with no problem, although there are no duplex plugs, you should be able to wire two outlets in parallel down a line.

I'm not aware of any Electrical code rules against this but electrically it seems OK to do so. I guess the issue you are having is , is it OK to have 20A outlets on a 30A branch? Maybe the people with electrician backgrounds can chime in. A lot of people probably have 15A outlets on 20A branches in their home.

I suppose the probable contention is that a 30A breaker will allow 30A to a "faulty" load plugged into the 20A outlet, over loading the outlet. I guess that's a Electrical code issue. The possible solution is to put a secondary breaker box at the location, housing 2 15 or 20A breakers each feeding a 20A outlet.

Lucky you, with the tools and all!

[JR]

I'm with Loring. Put another box down there, wired in parallel. Good planning on the false floor!

Of course, the electrical code is muy mysterioso, so it might not be strictly to code, but it should work just fine.

[jdon]

I guess the issue you are having is , is it OK to have 20A outlets on a 30A branch?

Can't speak re: 240V, but the analogous 120V situation is the norm. 20A circuits are common in households, but I've rarely seen a receptacle with 20A rating; the vast majority are 15A receptacles.

The difference is that the neutral slot in a 20A receptacle has a horizontal side arm (like a T on its side), whereas the 15A is a straight vertical slit. 15A plugs will fit 20A receptacles, but not vice-versa.

To me, it makes sense if the reasoning is that you can put loads less than the rated amperage of the circuit. Similarly, it would be logical to argue that it's okay to put multiple 20A circuits on a 30A 240V circuit, but I'm not an electrician, and code isn't always logical

However, check this out:http://www.sawmillcreek.org/showthre...-240V-circuits

[chopnhack]

Call you cousin in law and ask how he would like to proceed since he will ultimately be the one calling the shots on how this gets done. Let us know his answer!

[lrr]

[...]

Any suggestions out there? I will hire my cousin-in-law the electrician to help me, because 240V scares me, but I want to do the spade work myself and have it teed up for him.

I just installed a Laguna 2HP a few months ago. (By the way, I really like it. I think you made an incredibly intelligent choice ... )

I put it on its own 240V-20A circuit. I have my radial arm saw on a separate 240V-20A circuit, but that circuit has multiple outlets, so I can support a 240V table saw (maybe in the future -- I have a BT3100 now). My logic on this is that I would not run both 240V saws at the same time. I just wanted to avoid having multiple tools/devices on one circuit that could be running at the same time. Same logic holds for my compressor -- it is on its own 240V-20A circuit.

I did the same with my 120V circuits -- multiple circuits in the shop (and all with differently colored outlets to identify which is which). Although I primarily did this when I thought I'd just have regular shop vacs running at the same time as tools. This was the case for the BT3100 with a shop vac, and my Powermatic bandsaw (running on 120V, but it could run on 240V). Now table saw and bandsaw are connected to the Laguna cyclone.

[JimD]

They certainly make 20A 120V outlets. I put them in my shop for the 20A circuit for tools. They are not hard to find or expensive.

With respect to the question at hand, however, I would be inclined to put in two 30A outlets on the 30A 240V circuit and change the plugs on the tools. I would do this for the same reason I put 20A outlets in my shop. If you wire a 20A outlet into your 30A circuit you should be OK until you plug something else in that pulls more than 20A or you get an overload. Then the outlet is the weak link and may overheat. If you put 30A plugs on your tools, I do not see the problem. Over-rated is fine. Under-rated is a potential issue.

With respect to the breaker size I don't see that as any big issue. We plug devices that pull less than 5A into 15A or 20A 120V circuits all the time. It isn't great to put a load close to the breakers rating through a breaker. If you do, my experience is it will flip even though you are not technically above the rating. If a short occurs, it will not mean 10 more amps, it will double or triple or more the current. That is what the breaker is meant to protect, in addition to overheating the wiring - or the outlets from a more mild overload.

With respect to doing the wiring, I like to pull the breaker, do all my wiring, and then plug the breaker back in. When the breaker is out the line is most assuredly dead so you have zero risk (as long as you ran the circuit and know there is not another feed). You do not want to mess around when you have the cover off the breaker box plugging in or unplugging breakers. You have two live bars in front of you and could get quite a shock. But the breaker itself is not conducting. So as long as you keep your hands and your tools away from the conductors, it is not hard or terribly dangerous to plug and unplug breakers. 120V is about the same risk. They just plug to one bar while the 220V plug into both. Your hands and tools still have to get the same distance away from the risk. With the breaker engaged, a 220V circuit is worse for risk but I do not work on a live 220V circuit.

Jim