Can (3) 6-20r 20 amp 208v Duplex Receptacles be on a 60 amp circuit?

[cottora]

Can (3) 6-20r 20 amp 208v Duplex Receptacles be on a 60 amp circuit or is the breaker/circuit limited to the maximum amperage rating of the receptacle (20 amp)? Thanks

 

[LarryFine]

The latter; everything must be protected at their ampacity. . If you have three large loads away from the source, consider a sub-panel.

Hmmm. Maybe you can wire them on a single three-wire 20a circuit. What are the loads?

 

[cottora]

Thanks! The load will be 18 amps per duplex receptacle (server computers plugged into outlet). The idea was reduce the number of circuits/wire runs. Thanks

 

[tom baker]

But a multiwire branch circuit would have a common trip breaker, could not turn off just one receptacle.

 

[Dennis Alwon]

Look at 210.21 and the tables in that section

 

[cottora]

Look at 210.21 and the tables in that section

Does it matter that this isn’t a small appliance branch? It is an industrial classification with a known amperage of each plug (i.e. it is not a general use plug)

 

[hbiss]

Does it matter that this isn’t a small appliance branch? It is an industrial classification with a known amperage of each plug (i.e. it is not a general use plug)

I think using duplex receptacles like this makes them "general use " since anybody can plug something else into the receptacle. So if you can live with a common trip breaker you are talking about pulling three #12s. Can't get any easier than that.

-Hal

 

[cottora]

I think using duplex receptacles like this makes them "general use " since anybody can plug something else into the receptacle. So if you can live with a common trip breaker you are talking about pulling three #12s. Can't get any easier than that.

-Hal

There are 400 receptacles... we are talking about reducing the wiring/breakers/circuits by hundreds.

 

[hbiss]

Umm, your OP said 3 receptacles. :blink:

So these bit coin miners require 400 receptacles? You are looking at some serious distribution/ feeder/sub panel design work and installation. The least of your problem is how may conductors to the receptacles.

-Hal

 

[cottora]

Umm, your OP said 3 receptacles. :blink:

So these bit coin miners require 400 receptacles? You are looking at some serious distribution/ feeder/sub panel design work and installation. The least of your problem is how may conductors to the receptacles.

-Hal

The OP was referencing one of many circuits (they are all the same layout). Yes, we are getting 1MW service and have substantial cost in transformers/panels. But every little thing adds up and we have limited space.

 

[Little Bill]

I think using duplex receptacles like this makes them "general use " since anybody can plug something else into the receptacle. So if you can live with a common trip breaker you are talking about pulling three #12s. Can't get any easier than that.

-Hal

I'm not saying what the OP wants to do is correct, but I don't think 2-pole 208-250V receptacles would be a "general receptacle", especially with 6-20R receptacles.

 

[wwhitney]

Thanks! The load will be 18 amps per duplex receptacle (server computers plugged into outlet).

If the loads are sufficiently linear and identical, then I believe (3) 18 amp L-L loads wired in a delta would put 18 * sqrt(3) = 31 amps on each conductor of a 3-wire circuit. That seems like a problem, unless you can easily put a 20A OCPD at each receptacle.

Cheers, Wayne

 

[texie]

Thanks! The load will be 18 amps per duplex receptacle (server computers plugged into outlet). The idea was reduce the number of circuits/wire runs. Thanks

This sounds like a continuous load. The max continuous load on a 20 amp circuit is 16 amps.

 

[Todd0x1]

Have you looked into commercial PDUs? At the scale you are discussing you can probably get some custom ones made tailored to your requirements. For example something with a 100A 3ph input and 6x 2P 20A circuits (or 12x breakers to deal with continuous load) Are the computers in 19" racks or on shelves? Any reason youre not using 240/415v? That would cut the number of branch breaker poles in half (plus the other obvious benefits)

 

[hbiss]

I'm not saying what the OP wants to do is correct, but I don't think 2-pole 208-250V receptacles would be a "general receptacle", especially with 6-20R receptacles.

Any time I see a duplex receptacle I consider it to be for general use. Especially when they are all over the place.

Maybe for a lot of European equipment.

-Hal

 

[cottora]

Have you looked into commercial PDUs? At the scale you are discussing you can probably get some custom ones made tailored to your requirements. For example something with a 100A 3ph input and 6x 2P 20A circuits (or 12x breakers to deal with continuous load) Are the computers in 19" racks or on shelves? Any reason youre not using 240/415v? That would cut the number of branch breaker poles in half (plus the other obvious benefits)

From what we have seen, PDUs are expensive for our setup (i.e. 60 amp to eight 20 amp outlets is $800 remanufactured, we save two circuits/wiring/breakers/outlet). Computers are on shelving. Great idea on 240/415v. We assumed 115/208 because the equipment was readily available at decent prices.

Have you ever seen stand-alone breaker-receptacle housings? Not sure if it violates the tap rule but we could pull say 60 amp circuit ----------> 20 amp standalone breaker/6-20r duplex ---> Y Cable to Servers

 

[Todd0x1]

From what we have seen, PDUs are expensive for our setup (i.e. 60 amp to eight 20 amp outlets is $800 remanufactured, we save two circuits/wiring/breakers/outlet). Computers are on shelving. Great idea on 240/415v. We assumed 115/208 because the equipment was readily available at decent prices.

Have you ever seen stand-alone breaker-receptacle housings? Not sure if it violates the tap rule but we could pull say 60 amp circuit ----------> 20 amp standalone breaker/6-20r duplex ---> Y Cable to Servers

How many computers on a shelf?

 

[tortuga]

cottora From your tag line it says your an 'Energy Consultant', and (Not Design/Engineering).
Located in the great state of Georgia.
With all due respect the Georgia Code § 43-15-2. Defines the consulting your doing as the practice of engineering:

(10)"Professional engineering" means the practice of the arts and sciences, known as
engineering, by which mechanical properties of matter are made useful to mankind in
structures and machines and shall include any professional service, such as consultation,
investigation, evaluation, planning, designing, or responsible supervision of construction or
operation, in connection with any public or private utilities, structures, buildings, machines,
equipment, processes, works, or projects, wherein the public welfare or the safeguarding of
life, health, or property is concerned or involved, when such professional service requires the
application of engineering principles and data and training in the application of mathematical
and physical sciences. An individual shall be construed to practice or offer to practice
professional engineering, within the meaning of this chapter, who by verbal claim, sign,
advertisement, letterhead, card, or in any other way represents or holds himself or herself out
as a professional engineer or engineer or as able or qualified to perform engineering services or
who performs any of the services set out in this paragraph. Nothing contained in this chapter
shall include the work ordinarily performed by individuals who operate or maintain machinery
or equipment.

See
https://sos.ga.gov/plb/acrobat/Laws/09_Professional_Engineers_and_Land_Surveyors.pdf

I think the owners of your project should be employing a electrical engineer (or a design/build electrical contractor) whom you can bounce these important questions off of.

 

[ramsy]

1

 

[cottora]

cottora From your tag line it says your an 'Energy Consultant', and (Not Design/Engineering).
Located in the great state of Georgia.
With all due respect the Georgia Code § 43-15-2. Defines the consulting your doing as the practice of engineering:


See
https://sos.ga.gov/plb/acrobat/Laws/09_Professional_Engineers_and_Land_Surveyors.pdf

I think the owners of your project should be employing a electrical engineer (or a design/build electrical contractor) whom you can bounce these important questions off of.

It is my company's project and we have hired an Electrical Engineer. This type of setup is new to him and he mostly works on larger industrial applications where budgets are limitless. It has nothing to do with my consulting work (which is on the business side of Utility-Scale renewable energy projects for major utilities).