Testing 240V outlet and GFCI spa panel

[jlongstreet]

I recently had a 30A breaker installed, connected to a 50A spa panel and a receptacle. Yesterday, I realized I needed a different receptacle (I had an L14-20 receptacle, but my controller uses a 14-50 plug), so I replaced the receptacle. To check my work, I dug my multimeter out and tested it.

Here's the wiring inside the spa panel:

The blue wires are for neutral, red and black are the hot legs, green is ground. Service coming in from the 30A breaker in my subpanel on the left, load to the outlet on the right.

And here's the wiring in the outlet:

I tested voltage (with the breaker on) and continuity (with the breaker off) between each pair of terminals (X, Y hots, G ground, W neutral):

Voltage:
G/W: 0
G/X: 124
G/Y: 124
X/Y: 249
X/W: 124
Y/W: 124

Conductivity:
G/W: beep
G/X: no beep
G/Y: no beep
X/Y: no beep
X/W: no beep
Y/W: no beep

Is this correct? I understand that neutral is tied to ground at the main service panel, that's why I get conductivity between ground and neutral? And why I get voltage from the hots to ground?

I guess I'm confused about why this isn't a parallel grounding path. It seems wrong that I would have conductivity between ground and neutral, and voltage from the hots to ground.

 

[doug293cz]

Your test results are just what you should be getting.

Brew on

 

[kal]

Also pop the GFI and remeasure voltages. You want to make sure you get 0V between HOTS and GND as well as between the two HOTS.

Kal

 

[neild5]

What gauge is the wire both the feed and load? A 30 amp breaker needs a minimum of 10 gauge. Your wires look small.

 

[jlongstreet]

What gauge is the wire both the feed and load? A 30 amp breaker needs a minimum of 10 gauge. Your wires look small.

It's all 10ga stranded.

 

[LarMoeCur]

What gauge is the wire both the feed and load? A 30 amp breaker needs a minimum of 10 gauge. Your wires look small.

Good catch! The wires feeding the panel's bus do look smaller. Could just be the picture.

 

[jlongstreet]

Good catch! The wires feeding the panel's bus do look smaller. Could just be the picture.

The wires coming out from the breaker are the same wires (as in, physically the same lengths of wire) as the ones in the outlet, which don't look small, so it must just be the picture and the fact that there's a larger gauge white wire in the panel for the neutral bus. They're 10ga stranded. This is on a 30A breaker, so I can't exceed their rating.

 

[pdwittman]

I am getting ready to wire up a my system and did a search to see what others are doing...

Maybe there is a missing pic, but the poles on that breaker say 50A and those wires (especially if they are 10 Ga) are quite small for that kind of load.

 

[neild5]

He has a 30 amp breaker in the main panel. What the picture is showing the spa panel which is a 50 amp 240 volt GFCI breaker. Due to the amount of hot tubs that require 50 amp spa panels they can be half the price of a 30 amp 240 volt GFCI breaker. Since the breaker in the main panel is 30 amp the wires are protected.

 

[ajdelange]

Is this correct?

Yes

I understand that neutral is tied to ground at the main service panel,

Yes

that's why I get conductivity between ground and neutral? And why I get voltage from the hots to ground?

Yes

I guess I'm confused about why this isn't a parallel grounding path.

It isn't. Neutral and ground are only connected at the panel. No load current flows through the ground conductor. Any current that does is termed 'objectionable current' and its source must be removed.

This is when things are normal. Should there be a fault between one of the hots (or even the neutral) and any of the metal parts to which the ground wire (but not the neutral) is connected the ground wire and its connection to neutral at the panel provides a return path for that current. But this is objectionable current and the GFCI will trip.

It seems wrong that I would have conductivity between ground and neutral, and voltage from the hots to ground.

No, not at all. The grounded conductor (neutral) and grounding conductor must be interconnected somewhere if the grounding conductor is to be able to return fault current. As they must be interconnected it follows that there will potential between either of the hots and both the grounding and grounded conductors.

 

[Scout]

240 volt electricity is no more than two 120 volt supplies, they are just 180° phased apart. When one is at full positive, the other is at full negative. So to speak anyway. That's why you see voltage from hot to ground.

 

[jlongstreet]

I am getting ready to wire up a my system and did a search to see what others are doing...

Maybe there is a missing pic, but the poles on that breaker say 50A and those wires (especially if they are 10 Ga) are quite small for that kind of load.

Yes, they're 10AWG stranded. The circuit is on a 30A standard breaker, which isn't pictured. Unfortunately, probably just because there isn't much of a market for them, 30A GFCI breakers are significantly more expensive than 50A GFCI spa panels plus a 30A breaker. Add a short (~18") length of flex conduit and some 10ga wire, and it ends up being cheaper to protect a 30A circuit with a 50A GFCI spa panel than directly.

My understanding (which comes from my electrician friend who did the work) is that 10ga wire is acceptable for 30A in a short run, and that the fact that the spa panel could support 50A doesn't change that, since the main breaker is 30A.

 

[dyqik]

Yes, they're 10AWG stranded. The circuit is on a 30A standard breaker, which isn't pictured. Unfortunately, probably just because there isn't much of a market for them, 30A GFCI breakers are significantly more expensive than 50A GFCI spa panels plus a 30A breaker. Add a short (~18") length of flex conduit and some 10ga wire, and it ends up being cheaper to protect a 30A circuit with a 50A GFCI spa panel than directly.

For info, that's not true for all breaker styles. My BR type 30A GFCI breaker was $80, about the same as a spa panel locally.

 

[tmendick]

For info, that's not true for all breaker styles. My BR type 30A GFCI breaker was $80, about the same as a spa panel locally.

True, but for me, I would have needed to re run the dryer wiring for GFCI (currently only 3-wire) which would have cost more than using a spa panel with a 50A GFCI built-in