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I'm not an electrical engineer, but I play one on TV. Can you help me be more realistic?

Our facility has three items that run on three phase 208 and plug in at a temporary building using CS (California Style) connectors. We are in the process of speccing a new building. To give the users maximum flexibility in where to put their stuff, I want to scatter five of these receptacles around the new building. I just realized that the three equipments do not have the same CS connectors, oops.

Two of them have a CS8365, and the other one has a CS6365. UH-OH! We have the competence to change out the connectors to match each other, but before I recommend that, I want to better understand the differences to make sure I don't create a safety problem.

Here are some data on both of these connectors:

https://www.hubbell.com/hubbell/en/Products/Electrical-Electronic/Wiring-Devices/Locking-Devices/50A-Twist-Lock/CS8365/p/1634245

https://www.hubbell.com/hubbell/en/Products/Electrical-Electronic/Wiring-Devices/Locking-Devices/50A-Twist-Lock/CS6365/p/1634242

I can see in the description that one of them claims to be for 250 "delta" power while the other claims to be for 125/250 power. That's all good, and I think I understand it, until the next sentence--they both claim to be "3-Pole 4-Wire Grounding". Now that does not make sense....the 125/250 one seems to be claiming to have a neutral, so how does that add up with still only four conductors?

Now, my bottom line questions:

Would it be safe to remove a CS6365 from a Harrington Hoist VFD246 series crane and replace it with a CS8365?

Alternatively, would it be safe to remove two CS8365 from a Toyota forklift battery charger and a Grainger Speedaire 13G709 air compressor and replace them with CS6365?

As far as I can tell, all three of these devices are straight 208 three phase, with no need for a neutral or 115 power, but I give the model numbers to let you all educate me if needed.

Thank you for your time!

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  • \$\begingroup\$ Hire an Electrician. \$\endgroup\$ May 5, 2020 at 6:13
  • \$\begingroup\$ the shape and orientation of the L slots is different \$\endgroup\$
    – jsotola
    May 5, 2020 at 6:30
  • \$\begingroup\$ Tony Stewart-- should I hire the same electrician that decided to use the CS6365 for a three phase application, now that I know from Harper that the CS6365 is intended for split phase? \$\endgroup\$ May 5, 2020 at 13:06

3 Answers 3

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Be careful -- receptacle type usually reflects voltage and phasing

First, the "250V" rating relates to socket insulation limits. It has nothing to do with expected/conventional voltage on them. (You can't exceed it obviously).

The CS6365 is for split-phase 120/240V power, and its NEMA equivalent is NEMA 14.

The CS8365 is for 3-phase delta 208V, its NEMA equivalent is NEMA 15.

That is plainly stated in their catalog (if you know what to look for).

I leave it to you to look up the bolded phrases.

By the way... all 208V installations are actually "wye" (120V line to neutral), and can be used either wye or delta. It is quite common for 120/240V split-phase appliances to be used in 120/208V 3-phase territory. They simply attach 2 phases and 1 neutral, so the 120V sections work normally, and the 240V sections get sqrt(0.75) less voltage than they are used to. Resistive loads can live with this, they simply work at 3/4 power. Motor loads, you'll have to check the nameplate to see what they can accept. However, the important part is these 120/208V 2-of-3-phase appliances are wired up NEMA 14 - same as 120/240V split-phase.

But why on earth do some have a different connector?

The worrisome thing is that some of your machines have the different connector. Usually, that means this machine requires a different voltage. It's like if you go to plug in your RV and it has a TT30 type connector, that always means it is a 120V/30A RV. An RV with a NEMA 14-50 means it wants 120/240V split-phase.

So on these machines that have CS6365 -- look very, very closely at their labeling, nameplates and the like. In fact, post them here. You need to assume the CS6365 is correct and the machine is 120/240V split-phase (or 120/208V) requiring neutral, until clear evidence on the unit proves otherwise. Don't fall to wishful thinking.

I suspect that converting these to 208V delta would be a mistake. You must assume they have sections which require 120V line to neutral, won't like 208V there, expect 240V line to line, and may be able to tolerate 208V line to line. If that's the case, then you need to provision sockets with this H-H-N-G wiring.

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  • \$\begingroup\$ I think you have got it, good find! This is strange though because the current building doesn't have 120/240 split phase, it only has 208 three phase. That CS6365 receptacle is supplying 208, no doubt about it, reads about 212 on a meter, and is fed by the same three phase breaker panel as the CS8365 receptacles. Maybe it is only getting two of the three phases though, I will need to verify. \$\endgroup\$ May 5, 2020 at 13:00
  • \$\begingroup\$ They often use neutral + 2 phases of 208V as a substitute for 120/240V. For instance, any household dryer or range will work just fine on that (albeit a bit slower). Try measuring all six voltages. \$\endgroup\$ May 5, 2020 at 15:55
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Change the CS6365 from a Harrington Hoist VFD246 series crane and replace it with a CS8365. Reasoning behind that is the CS8365 will only be expected to work with 250V lines, so you are restricting the equipment a little bit, but it's perfectly safe. Changing the CS8365 to CS6365 opens the possibility that the equipment could be plugged into a supply it's not rated for, potentially causing issues.

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  • \$\begingroup\$ Since 208V is always wye, able to provide both 208 delta and 120/208 2-of-3-phases+neutral... I suspect the two connectors accurately reflect the power needs of the devices. Converting a 120/208 device to 208 delta would be bad. \$\endgroup\$ May 5, 2020 at 7:51
  • \$\begingroup\$ Harper, I'm afraid I don't share your optimism that the old work was done correctly. It's starting to look like the electrician who installed the crane's receptacle botched the job by using the wrong product. Note that the same person probably installed the plug on the equipment also, that kind of hoist does not come already connectorized. \$\endgroup\$ May 5, 2020 at 14:01
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I’m going to accept Harper’s answer because it is the “correct” answer for most future readers.

I’m also writing my own answer for the small portion of future readers whose situation is the same as my own.

The difference is Harper’s answer is correct in the case where previous electrical work was done correctly, but that is not the case for me.

The electrician that installed the CS6365 several years ago made either a careless mistake or a poor choice. The Harrington crane I verified 100% in its schematic that it requires three phase power with no neutral, which is exactly what the CS6365 is putting out.

This is actually a potentially dangerous situation, so we are going to replace the 6365 receptacle and plug with 8365.

Dmitri thanks to you also, and I am going follow your recommendation, but for different reasons than you suggested.

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