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Old 01-05-2009, 01:15 AM   #1
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Code on Changing a plug to larger size


I am trying to help someone figure out how to power an espresso machine. They are in a temporary home where they are not able to easily pull a new branch circuit in.

The machine currently has a NEMA 20A 3 prong 240 Plug on it.

Is there any code that would prohibit that plug from being changed to a standard 3 prong range plug and using the range receptacle for power?

Thanks
Jamie

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Old 01-05-2009, 01:24 AM   #2
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Code on Changing a plug to larger size


Quote:
Originally Posted by jamiedolan View Post
I am trying to help someone figure out how to power an espresso machine. They are in a temporary home where they are not able to easily pull a new branch circuit in.

The machine currently has a NEMA 20A 3 prong 240 Plug on it.

Is there any code that would prohibit that plug from being changed to a standard 3 prong range plug and using the range receptacle for power?

Thanks
Jamie
probably, yes. Changing the OE plug to a non-OE and different rating plug would technically kill the UL rating and as such, against code to use.

The OE is designed with the 20 amp circuit. There may not be adequate protection to handle the possible limitation of the 40 amp breaker for the range circuit. (yes, I now, the breaker is designed to protect the feed conductors but equipment is often designed with the least amount of protection in mind and the allowance of the up to 40 amps if something should happen may be a problem. Probably not but....)

Don't tell anybody I said this but if it were me, I would change the plug AND the breaker. While not 100% legal, it would be protected as designed and the plug would be rated higher than OE so it would not be damaged.

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Old 01-05-2009, 01:39 AM   #3
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Code on Changing a plug to larger size


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Originally Posted by nap View Post
probably, yes. Changing the OE plug to a non-OE and different rating plug would technically kill the UL rating and as such, against code to use.

The OE is designed with the 20 amp circuit. There may not be adequate protection to handle the possible limitation of the 40 amp breaker for the range circuit. (yes, I now, the breaker is designed to protect the feed conductors but equipment is often designed with the least amount of protection in mind and the allowance of the up to 40 amps if something should happen may be a problem. Probably not but....)

Don't tell anybody I said this but if it were me, I would change the plug AND the breaker. While not 100% legal, it would be protected as designed and the plug would be rated higher than OE so it would not be damaged.
Thanks for your response. When I see 3 prong 240V plugs like either of these, are the appliance always going to be using only 240 (120 line to line) or could an older appliance with one of these plugs also want some 120 and use the neutral?

I was just concerned if the likely uninsulated ground leg could end up carrying current.

Was this a problem with past setups? is this part of why they require 4 wire setups now? Because it seems like a 3 wire setup on a true 240 connection does give you a clear fault path.
Thanks
Jamie
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Old 01-05-2009, 01:45 AM   #4
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Code on Changing a plug to larger size


What does the nameplate say? If it says 240 V, then it doesn't need a neutral. If it says 120/240 V then it does need a neutral. If the 6-20P that is on it now is original, then it is straight 240.

How about an adapter? A range plug that feeds a 6-20R. That way, you don't have to alter the plug or the circuit. Sure, the overcurrent device is oversized for the equipment, but I think altering the circuit or plug is a bigger potential problem than making an adapter for TEMPORARY use.

Even better, but more costly, would be to make a whole subpanel unit that plugs in the range outlet. A $12 four space panel and range plug is all that is needed. Attach a handy box to it with a nipple, add the appropriate receptacle and breaker, and you are covered all the way around.

Last edited by InPhase277; 01-05-2009 at 01:47 AM.
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Old 01-05-2009, 01:46 AM   #5
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Code on Changing a plug to larger size


Quote:
=jamiedolan;207172]Thanks for your response. When I see 3 prong 240V plugs like either of these, are the appliance always going to be using only 240 (120 line to line) or could an older appliance with one of these plugs also want some 120 and use the neutral?
In an dedicated circuit such as a range circuit (make sure it is btw), the neutral and ground in the manner you would be using them are interchangable since the circuit is going directly to the panel (please tell me there is only the MAIN panel in this house) and attached to the bonded ground and neutral (remark the neut as a ground for the time being) On a plug for the coffeemaker, there is apparently no 120 needed or you would have a 4 wire plug.

Quote:
I was just concerned if the likely uninsulated ground leg could end up carrying current.
as long as it is as I clarified above, it would not be any different than having a EGC and no neutral.

Quote:
Was this a problem with past setups? is this part of why they require 4 wire setups now? Because it seems like a 3 wire setup on a true 240 connection does give you a clear fault path.
the reason for adding the 4th wire is, of course a dryer and many ranges use 120/240. They were using the neut as a ground and a neut. What that causes is, the metal frame of the appliance is connected to the neutral. There was a possibility of a difference of potential between that and some other grounded metal. That would, obviously, cause a shock. If for some reason the neut/ground was lost somewhere between the applicance and the panel, the frame of the appliance would actually become energized compared to any grounded metal.
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Old 01-05-2009, 02:19 AM   #6
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Code on Changing a plug to larger size


Thanks for the help. Nap; I will advise them to verify the circuit is a dedicated run.

It sounds like he will be able to make up a cord that is going to work. I tried to find a 240V 20A fused plug / receptacle, as that would have been perfect, but have been unable to locate what I had in mind online. (kind of like what you saw them put in for sump pumps and such), just a handy box with a fuse and a receptacle, but one for 240V.


Thanks again for the help and information.

Jamie
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Last edited by jamiedolan; 01-05-2009 at 11:20 AM.
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Old 01-05-2009, 02:40 AM   #7
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Code on Changing a plug to larger size


Quote:
Originally Posted by nap View Post
the reason for adding the 4th wire is, of course a dryer and many ranges use 120/240. They were using the neut as a ground and a neut. What that causes is, the metal frame of the appliance is connected to the neutral. There was a possibility of a difference of potential between that and some other grounded metal. That would, obviously, cause a shock. If for some reason the neut/ground was lost somewhere between the applicance and the panel, the frame of the appliance would actually become energized compared to any grounded metal.
Same problem they have with pools and voltage gradients? I see, a 4 wire system with a clear "ground" / bonding path also helps reduce the possibility of shock due to voltage gradients.

So how important is grounding really, aren't we really talking about bonding being what keeps people safe because it prevents any of the metal in a building from being at a different voltage than other metal?

So in a perfect situation if everything metal was properly bonded, then it would not matter if we used a 4 wire system because there would be no shock hazard due to voltage gradients? But the 4 wire system gives us that extra safety of insulating the current since we know everything doesn't get bonded (grounded).

Interesting.

Jamie
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Old 01-05-2009, 08:28 AM   #8
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Code on Changing a plug to larger size


Quote:
Originally Posted by jamiedolan View Post
Same problem they have with pools and voltage gradients? I see, a 4 wire system with a clear "ground" / bonding path also helps reduce the possibility of shock due to voltage gradients.

So how important is grounding really, aren't we really talking about bonding being what keeps people safe because it prevents any of the metal in a building from being at a different voltage than other metal?

So in a perfect situation if everything metal was properly bonded, then it would not matter if we used a 4 wire system because there would be no shock hazard due to voltage gradients? But the 4 wire system gives us that extra safety of insulating the current since we know everything doesn't get bonded (grounded).

Interesting.

Jamie
If everything was bonded, yes I can see were you wouldn't get shocked.

You still could have current flowing through the ground...not really safe.

Last edited by rgsgww; 01-05-2009 at 08:31 AM.
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Old 01-05-2009, 11:47 AM   #9
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Code on Changing a plug to larger size


Quote:
Originally Posted by jamiedolan View Post

So in a perfect situation if everything metal was properly bonded, then it would not matter if we used a 4 wire system because there would be no shock hazard due to voltage gradients? But the 4 wire system gives us that extra safety of insulating the current since we know everything doesn't get bonded (grounded).

Interesting.

Jamie
There is no perfect conductor, so there will always be a voltage drop on current carrying conductors. So a neutral bonded stove could potentially have a different voltage on the frame than the refrigerator next to it. If you could jumper the stove to the fridge to sink to the dishwasher to the microwave, then the problem would be eliminated. Instead of running a wire around the kitchen, we do it with the "ground" wire in each appliance's circuit.
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Old 01-05-2009, 04:34 PM   #10
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Code on Changing a plug to larger size


Quote:
Originally Posted by jamiedolan View Post
I am trying to help someone figure out how to power an espresso machine. They are in a temporary home where they are not able to easily pull a new branch circuit in.

The machine currently has a NEMA 20A 3 prong 240 Plug on it.

Is there any code that would prohibit that plug from being changed to a standard 3 prong range plug and using the range receptacle for power?

Thanks
Jamie
Why is this difficult? Change the wall receptacle to a 20 amp 240v receptacle and change the breaker.
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Old 01-05-2009, 04:44 PM   #11
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Code on Changing a plug to larger size


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Why is this difficult? Change the wall receptacle to a 20 amp 240v receptacle and change the breaker.
Thanks, Yes that would be the easiest. It's a situation where the property owner doesn't want to have changes made to the current range setup. So the adapter or plug change seems to be the only realistic solution.

This actually seems to come up somewhat frequently as many of these espresso machines as 240v. People bring a machine to someones party / event, more to an apartment temporarily, etc, and the only 240 plug available is the range or dryer outlet. Most of the machines are 20A or 30A at the most.

Thanks
Jamie
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Old 01-05-2009, 04:51 PM   #12
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Code on Changing a plug to larger size


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Originally Posted by jamiedolan View Post
Thanks, Yes that would be the easiest. It's a situation where the property owner doesn't want to have changes made to the current range setup. So the adapter or plug change seems to be the only realistic solution.

This actually seems to come up somewhat frequently as many of these espresso machines as 240v. People bring a machine to someones party / event, more to an apartment temporarily, etc, and the only 240 plug available is the range or dryer outlet. Most of the machines are 20A or 30A at the most.

Thanks
Jamie

Ranges are 40-50 amps, dryers are 30 amps, I hardly ever install a straight 20a/240v receptacle, except for woodworkers. Let me know if you find an adapter.
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Old 01-05-2009, 06:13 PM   #13
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Code on Changing a plug to larger size


In general it is not a good idea to change plugs on things to something different than what it came with. The plug is that way for a reason.

I've seen a lot of damage done to electrical equipment from people replacing plugs instead of having an electrician install the proper circuit and outlet.

As to apartments... Well that is why I bought a house. Now I can fix my truck in the driveway or install new wiring to my heart's content!

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