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Old 01-16-2013, 06:05 AM   #1
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Default Spa box wiring with 10-30R (3-wire)

Apologies if these questions have been asked before...I've been searching for some time now and believe I know what my plan is, but am curious about a few things.

The previous owners of my house switched the dryer from electric to gas, so I have an unused 10-30R (3-wire 240v) in the basement that's still live. I'd like to use it to power a single 5500W heat stick using these instructions for the control panel: http://www.instructables.com/id/Elec...-system/#intro

Obviously, I need GFCI protection. My understanding is that I can't just switch the breaker in my panel to a GFCI one, as there's no true ground running to it (3-wire outlet). I can't find a 240v 30a GFCI cord under $150 (let alone a 3-wire one), so I was looking at spa panels at home depot.

A few questions:

1) I'd like to plug the spa box into the 10-30R (3 wire). This means the spa box isn't connected to any true ground, but as far as I can tell, this is okay, as the spa box acts as an "effective ground" and if anything shorts the power will "instantly" be cut anyway. Is my understanding of this correct? As far as I can tell, this only actually protects the 240v line such that if I were to use anything that pulls at 120v from the wires I'd need a GFCI for that line as well?

2) As a follow-up to that, "instant" is relative, and I've seen that for it to be safe, the panel would need to trip the GFCI in under 5ms. Is there any way to confirm a given box would do this? None of the boxes on HD's website have anything about a response time. Is this just an industry standard on any new box thus it's not a worry?

3) Any spa boxes I see at HD have max wattages of ~240 watts. This is on a "50 Amp 240 Volt" box. If something's running at 50 amps and 240 volts, that makes it 12000w, which means this box can't handle anywhere near a 5500w heat stick. What does the 240 watt max actually mean then?

4) The spa box is 50amps, but I'm never going to pull more than 30amps from it (all the outlet is anyway). Knowing this, if I'm running 15' of line from the outlet to the spa panel, then 3' of line from the spa panel to my controller, do I definitely need to use #10 wire, or is #12 okay?

5) After all of this, this diagram: http://www.instructables.com/file/FBYO7DFGX5XKQ6Q will work fine for me, with the exception that going from the 30A breaker into the spa panel is actually only 3 lines?

6) Any reason to not disassemble the spa box, and wire everything (spa box and controller) all in one box?

7) I'm kind of stuck on this page: http://www.homebrewtalk.com/f170/sup...01/index8.html worrying that this whole thing is still potentially dangerous. What if I used a standard 3-plug cord with the ground connected inside the spa box and the hot and neutral terminated, and plugged the other end into a standard outlet? Would that alleviate the potential code violation? I'm not worried about a fine, I'm worried that the code is there for a reason - safety, and $20 worth of wire would make it a bit safer.

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Old 01-16-2013, 06:10 PM   #2
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As I understand it, you have two hots, a neutral and no ground at your 10-30R outlet? What type of cabling is it? Romex, conduit, etc.? Gauge?

Are you planning to use 110 from this circuit? If not, what about using the neutral wire as a ground? Attach it to the ground bus in the main panel and wrap it with green tape on both ends. Now you can wire a safe, 220 outlet with a 220 GFCI breaker in the main panel.

There are errors in the HD specs on the spa panels. A 50amp/240V panel should be listed with 12kW power rating.

A 5500W/240V element will draw 23amps. You should use 10gauge wire for 23amps and the 240 outlet should/could be 6-30R, which is a 240/only outlet rated for 30amps.

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Old 01-16-2013, 10:32 PM   #3
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look here the second post has a diagram on how to wire it to that outlet.
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Old 01-16-2013, 11:05 PM   #4
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That makes a ton of sense. My current plans have no need for the 110V anyway.

The line feeding the outlet says on it "Columbia 10/3 with ground type nm 600V (UL)". From my research, that's a 3 wire romex.

The spa boxes start at $65 and then I have to wire it. I have a GE breaker box. Since I have to open the breaker box anyway, is there any reason I can't just replace the current 30a breaker with this http://goo.gl/yfyg4 and plug my control panel right into the new 6-30R and save some time and be fully GFCI? I would put an emergency shut-off on my control box then.


Any permits typically required for this?

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Old 01-16-2013, 11:58 PM   #5
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10/3 with ground means there are 3 current carrying conductors (hot, hot & neutral) plus a ground (usually bare copper). Maybe the ground has not been cut back and you can use this existing wiring for a 240/120 circuit if you need it. Have you opened up the receptacle and main panel to survey your existing wiring?

The 5500w/240v/23amp heat stick requires a circuit protected with a 30amp breaker, like this.

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Old 01-17-2013, 04:26 AM   #6
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Haven't opened anything yet. I'm going to run to home depot in the next few days and will pick up everything I could potentially need and return whatever I don't use. Then I can install it all at the same time.

I assume that if the wire is a true 4 wire with an intact ground, I should just go L14-30R instead?

Thanks for the breaker link too. $30 cheaper than amazon.

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Old 01-17-2013, 03:08 PM   #7
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Quote:
Originally Posted by chuckda4th View Post
.......I'm going to run to home depot in the next few days and will pick up everything I could potentially need......
That might be a tall order. I have a good knowledge of electrical issues and I would guess this project, for me, would be, at least, a two tripper to lowes.
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Old 01-17-2013, 05:25 PM   #8
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Quote:
Originally Posted by chuckda4th View Post
I assume that if the wire is a true 4 wire with an intact ground, I should just go L14-30R instead?

That would give you the most options in case you want to add some 120 V control circuits later.
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Old 01-17-2013, 06:16 PM   #9
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Quote:
Originally Posted by chuckda4th View Post
Haven't opened anything yet. I'm going to run to home depot in the next few days and will pick up everything I could potentially need and return whatever I don't use. Then I can install it all at the same time.

I assume that if the wire is a true 4 wire with an intact ground, I should just go L14-30R instead?

Thanks for the breaker link too. $30 cheaper than amazon.
Absolutely change to 14-30 if you can.

Also, why not survey up front and maybe you won't have to go back? Could be me though. I hate returning stuff if I don't have to.
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Old 01-18-2013, 01:40 AM   #10
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I'm really glad this thread was made when I was looking into this. I currently don't have 220 but am going to make it soon. I'm going to do a 3 wire circuit 14-30? I was going to run 6 gauge to the spa panel so I can run 50 amps if wanted but after looking at my breaker panel, I only have 100 amp service to my house. Would 30amps be enough for a heater element and a 120 circuit? Without popping the breaker all the time?

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