# 220-250VAC outlet wiring



## Amberwolf (May 29, 2009)

I know a bit of electrical house wiring, but not enough to be *certain* that I can safely do what I am asking about here.  So before I destroy equipment or fry myself, I'd appreciate feedback from those familiar with and experienced in such things.

My house has regular split-phase 220VAC service at the box, with most of the house wired as 110VAC on one phase or the other. Two accesible points in the house are wired to the 220VAC across the phases, with a NEMA 10-30 receptacle, as HHN (Hot-Hot-Neutral). One is for a clothes dryer, and the other is for the kitchen stove/oven, both on 40A/phase breakers. The air conditioner is also on there, on separate 50A/phase breakers, but there is no accessible receptacle; it's direct wired. 

The Sorenson DCS 55-55 lab supply I've got on loan has a NEMA L-6 plug on it, wired as HHG (Hot-Hot-Ground). It only needs 14A input with three phase, but with single phase like I have it'll take 20A (at max DC output, limited to ~2500W). 

Given that it is unlikely any conductor will break to cause a shock hazard, using the spare cord off a dryer I have here, is it safe for the equipment to wire from the NEMA 10-30 as Y-W-X to the NEMA L-6 as Y-G-X? Meaning, tie Equipment Ground to House Neutral, as there is no separate ground available in the receptacle configuration I have? 

I do realize that any internal equipment short by design or failure that allows neutral to short to case would then leave the case at whatever voltage Neutral is at, relative to ground, presenting a possibly fatal shock hazard; I'd be setting up the unit so contact with the case while attached to AC power is not easily possible even in my stupider moments (and impossible for the dogs to do so). 


If it's not safe to do the way I describe, I'll have to find an install a NEMA L-6 receptacle, and wire it up. 

This question is also posted at Endless Sphere, so I can confuse myself with as many opinions as possible. 
________


----------



## ElectriCar (Jun 15, 2008)

While it doesn't meet code to tie the neutral to ground at other than the first panel in a system, I wouldn't call it unsafe though it could become unsafe if the neutral connection is lost as your ground connection would also be lost. You said you had it on loan so what you're doing if temporary I would do if that's the only place I could get power.

For a permanent install you should install another breaker in the breaker box for another circuit. If it only requires 14 amps, use a double pole 20A breaker. Hope this helps.


----------



## TigerNut (Dec 18, 2009)

If your wall outlet has a grounded case (and if it's run with 10-3 plus a bare bonding wire right back to the electrical panel) then you could rewire it with a NEMA 14-30 socket (hot-hot-neutral-ground) and make up a short adapter cord that has the right transition to your 10-30 configuration.

http://en.wikipedia.org/wiki/NEMA_connector


----------



## Amberwolf (May 29, 2009)

ElectriCar said:


> While it doesn't meet code to tie the neutral to ground at other than the first panel in a system, I wouldn't call it unsafe though it could become unsafe if the neutral connection is lost as your ground connection would also be lost.


Unfortunately I don't have much other option; the age of the house (early 70s or late 60s) means that most rooms didn't even have grounds at all. Only a few outlets in some rooms had actual grounded outlets (although they are all the grounded type physically). I fixed that on as many of them as I could, but given the block wall construction I can't do anything about some, so they're just marked with red dots to remind me they're not actually grounded.  



> For a permanent install you should install another breaker in the breaker box for another circuit. If it only requires 14 amps, use a double pole 20A breaker.


There's no place in the box for more breakers.  But this is only a temporary thing anyway, even though it could be a fairly long temporary. 



TigerNut said:


> If your wall outlet has a grounded case (and if it's run with 10-3 plus a bare bonding wire right back to the electrical panel) then you could rewire it with a NEMA 14-30 socket (hot-hot-neutral-ground) and make up a short adapter cord that has the right transition to your 10-30 configuration.


Actually I also have a 14-30 cord someone tossed (probably pulled off a newer dryer or stove, swapped out to put the older kind on instead, since that's the package it was in when I got it brand new unused from Freecycle). But I don't have one of those receptacles, and my budget of zero necessitates using only what I already have or can get for nothing as discards or unwanted items. 

My stove outlet appears to have a grounded case, with standard solid bare 16-gauge (I think; can't tell for sure) copper. The red, white, and black wires to it's HHN connections on the actual receptacle are stranded copper where each strand in each wire is about 20-gauge, maybe 18, with the strands totalling up to a ~1/4" diameter wire. So heavy a gauge that it is VERY hard to bend the wire AT ALL. So it is probably a candidate for doing as you suggest with the 4-prong NEMA 14-30 receptacle. 


In discovering that the outlet on the stove end is (of course) a higher-current version of the HHN type plug, I realized it's got three straight blades rather than two straight and one L. I don't have a plug/cord for that one, so I have to use the one the dryer plugs into, which naturally is in a small utility room off the back family room (which was a back porch when the house was built, I think). This means I can't put any bikes right next to the power supply for charging/etc, so I'll have to run a longer charging lead than I would like, by a few feet. 

I went ahead and did it alone, since all it involved was wiring the cord/plug to the Sorensen, and then plugging that into the wall receptacle. Just to be sure, I left the breaker for that receptacle off at the main box during plugin, and only turned it on after. Then I went back inside and turned on the front panel switch of the Sorenson, which is a rocker that toggles the three panel-style breakers inside (one for each 220 leg). Powered right up, and verified no voltage AC or DC to case from floor, walls, objects, etc. 

Turned it off and pulled out the original powerchair motor I used on CrazyBike2, and wired that to the big bolt-on terminals on the back, braced the motor, and turned it on. Cranked voltage up to 24 (nominal for this motor) while turning up current limiting to let it have the full ~4A it takes unloaded. Pushed voltage up to 51V (which is where the OVP on the Sorensen happens to be set right now) and no problems, with the motor spinning very noisily away.  I don't have a way to load the motor down since it's not attached to anything, so I'll later wire up a cable that can run from the small utility room to the family room just outside it's door. 

Then I can connect that to CB2's mounted motor, and load it down to verify current limiting/etc at higher loads. Of course, that's after I fix CB2's drivetrain, which might be a while. 

In the meantime, I'll use it to charge up various batteries I have around, mostly SLA. Still building the LiCo pack, and that one I'm tempted to run charging wires out the window in the family room to the backyard and charge it out there. :lol:


----------

