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[Douglas Cyr]

Photo album: https://imgur.com/a/QJPjxAD

Hello,

I have an event coming up at venue with a NEMA 10-50R receptacle side stage installed right underneath a breaker panel running into a 50 amp breaker. I need a high current/voltage outlet to power a Powersoft K20 DSP for the four subs I'll be using - it is an EDM DJ event so the subs will be pushed very hard, here are Powersoft's current draw specs:
Idle      115 V: 91 W – 1.3 A   230 V: 88 W – 1.17 A
1/8 of max output power @ 4 Ω      115 V: 1650 W – 15.8 A   230 V: 1625 W – 7.9 A
1/4 of max output power @ 4 Ω      115 V: 3250 W – 29.3 A   230 V: 3250 W – 14.7 A

The question: Is there a safe way to create an adapter to use this receptacle? I've metered it and it appears to be wired correctly (~120v neutral to each phase, 208v between phases):
https://imgur.com/Hejm8Ux

I think it won't work because the amp wants a ground, neutral, and a hot, while the receptacle has a neutral and two hots, but the venue owner says bands/sound people use this outlet all the time and that's why it was installed. My amp originally came with a single phase L6-20P plug.

Please take a look at the photo album and let me know what you guys think, I don't want to do anything dangerous for people or equipment but am curious if it's possible to make an adapter that will work here, my only other options here are 15/20 amp 120v receptacles.

Photo album: https://imgur.com/a/QJPjxAD

[Steve-White]

What I would do and what I would advise on a forum could be two different things.

That style of device and circuit is intended for use on 208V equipment only as it has a ground and no neutral.  However, they are used for domestic appliances such as clothes dryers and ranges that have 110V lamps in them.  However, that is in a residential setup on 240V.

 I don't believe that to be a legit setup for stage gear.  Maybe some of the other guys know more about that style plug on a 208V system.  To be legit it would probably need to be a 4-wire setup with separate ground and neutral.

There could be liability connecting to that - again, let's see what the other guys think about it.

[Douglas Cyr]

What I would do and what I would advise on a forum could be two different things.

That style of device and circuit is intended for use on 208V equipment only as it has a ground and no neutral.  However, they are used for domestic appliances such as clothes dryers and ranges that have 110V lamps in them.  However, that is in a residential setup on 240V.

 I don't believe that to be a legit setup for stage gear.  Maybe some of the other guys know more about that style plug on a 208V system.  To be legit it would probably need to be a 4-wire setup with separate ground and neutral.

There could be liability connecting to that - again, let's see what the other guys think about it.

Hypothetically speaking, would I be able to make an adapter that taps the neutral and a hot leg with a clamp lead running to the exposed ground wire above the receptacle and would I still get the 50a current rating? I know this is sketchy but I'm just curious for education purposes.

[Douglas Cyr]

Hypothetically speaking, would I be able to make an adapter that taps the neutral and a hot leg with a clamp lead running to the exposed ground wire above the receptacle and would I still get the 50a current rating? I know this is sketchy but I'm just curious for education purposes.

Also, the wiring diagrams I saw online showed their should be 245-250v between the phases rather than 208v I measured.

[Scott Holtzman]

Also, the wiring diagrams I saw online showed their should be 245-250v between the phases rather than 208v I measured.

The amp is setup for single leg service even at 230v so you are out of luck.  CPC 45 A AMP connector is on the back.  Please refer to page 5 section 4:3 for these details.  The wiring is H-N-G.  If it was a four wire connector at the venue you could accomodate this.  Don't even consider a bootleg ground.


Please also not downstream protection requirement from the manual "With K6, K8, K10 and K20 a sectioning breaker between the mains connections and the amplifier must be installed inside the rack cabinet. Suggested device is 32A/250VAC, C or D curve, 10kA."


The venue doesn't have any other high current connections?  I usually go hunting in the kitchen.  If not you will have to get a generator.






 

[Douglas Cyr]

The amp is setup for single leg service even at 230v so you are out of luck.  CPC 45 A AMP connector is on the back.  Please refer to page 5 section 4:3 for these details.  The wiring is H-N-G.  If it was a four wire connector at the venue you could accomodate this.  Don't even consider a bootleg ground.


Please also not downstream protection requirement from the manual "With K6, K8, K10 and K20 a sectioning breaker between the mains connections and the amplifier must be installed inside the rack cabinet. Suggested device is 32A/250VAC, C or D curve, 10kA."


The venue doesn't have any other high current connections?  I usually go hunting in the kitchen.  If not you will have to get a generator.

Thanks for this insight, I may have to look in the kitchen. I didn't notice the section in the manual about the rqckmount circuit breaker, where would I look to find one like they specify?

[Chris Hindle]

Also, the wiring diagrams I saw online showed their should be 245-250v between the phases rather than 208v I measured.

Douglas, you're seeing 2 legs of a 3-phase system.
220/240 is NOT possible without transformers.
Chris.

[Tim McCulloch]

A lot to unpack here...

First, Steve White's observations:  spot on, if Douglas is measuring 208V he's seeing 2 legs from a 3 phase service.  The 10-50 is listed for 125-250V operation which means this has no EGC.  I wasn't aware it was permissible in new work, but every jurisdiction can be different (or there was no permit and no inspection).

Second, Douglas, your question of a separate ground shows you payed attention to what each wire does.  Code says all wiring must be enclosed so Code says no.  I have seen what you are asking, done in locales where permitting and inspections are lax.  That should not be considered an endorsement, but an observation.

Finally, if none of your equipment requires 240V to operate the whole 208V from 3 phase is kind of a moot issue, other than being aware of it.  The primary issue here is the connector and wiring lacks the equipment safety ground.  It should be changed to a NEMA 5-50.  The venue and other users will resist because they have "Kludge Kords" built and changing all that is where the expenses really are.

[Helge A Bentsen]

ASSuming you can make a legal connection, my experience with Powersoft is that they run on anything.

My K20 run fine on 2 hot legs (230V between legs) or hot-neutral (230V between hot-neutral).

[Douglas Cyr]

ASSuming you can make a legal connection, my experience with Powersoft is that they run on anything.

My K20 run fine on 2 hot legs (230V between legs) or hot-neutral (230V between hot-neutral).

Interesting, and is there such a thing as +phase and - phase? Does it matter which phase goes to which terminal and is there a way to test that with a multimeter?

Also in this image:
https://bit.ly/3JQm1wt

What is going on what that ground wire running to the receptacle? What would that be connected to?

[ProSoundWeb Community]