older NEMA Type 10-50R vs. Type 10-30R

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Old 10-05-09, 10:19 AM
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older NEMA Type 10-50R vs. Type 10-30R

Hi,
In looking at new replacement appliances for our 17 yr electric 30 amp stove/range and 12 yr 220v/20amp electric dryer, I noticed the plug(pigtail) schematics now have a little upside down 'L' shape to one of the prongs in the 3-plug arrangement, where they're shaped like: \ /
where the right prong has a short-bar |

The older plugs/sockets we currently have on both the dryer and the range are exactly like what I've pictured - no little bar facing-left on the right-prong.
Will I still be able to get a pig-tail to fit the older socket or will I have to change out the socket as well?
thanks,
greynold99
 
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Old 10-05-09, 10:34 AM
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You might run into another problem. Many newer appliances now require a 4 wire cord, not the old 3 wire as they now separate the neutral and ground.

Check the appliance first to see if you can run it on a 3 wire outlet.

You may have to replace the outlet as well as the cable to the service panel to upgrade.
 
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Old 10-05-09, 11:01 AM
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Are you sure the old dryer is only 20 amps? All the electric dryers I have seen require a 30 amp circuit.

The plug and receptacle configurations are different to prevent someone plugging in an appliance of a different voltage or ampacity.

I am somewhat confused tho by the title of the post.
 
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Old 10-05-09, 11:46 AM
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Generally speaking you are allowed to re-use existing dryer (10-30R) and range (10-50R) circuits as long as the cable and breaker are both of adequate size and in good condition and you do not change the location of the appliance.

What troubles me is that the breaker sizes you have listed are not standard. Dryers are usually 30A and ranges are usually 40A or 50A. Please verify these sizes before proceeding.

The procedure for installing a new appliance on an old circuit would be to remove the new four prong cord (14-30P or 14-50P), purchase a three-prong cord (10-30P or 10-50P) for the appliance and install it per the manufacturer's instructions. Most appliances come with instructions for both three-wire and four-wire circuits; however some of the newer high tech models require a modern four-wire circuit so check the manuals carefully before you buy. There will be a bonding jumper inside the wiring compartment of the appliance which will need to be reconfigured to support the old circuit.
 
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Old 10-05-09, 11:54 AM
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Reply to PCBoss

You're probably right since as I'm thinking about it, the box has sockets for 2 of the older 20 amp screw-in fuses - one seemed to be for the motor that turns the inside drum and the other was for the heating elements. But I was reading the embossed lettering on the outside of the socket with a flashlight and a mirror, since it's placed in an awkward position to get to directly without having to pull the dryer out... Anyway it said - Leviton 20amp 125Volt/250Volt, but the prongs were oriented in that design of a 3-winged propeller - 2 @45 degree angles and 1-straight up. It's possible I could've misread - unless it means it's designed for max. 20amps on both prongs.
Greynold99
 
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Old 10-05-09, 01:27 PM
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You're probably right since as I'm thinking about it, the box has sockets for 2 of the older 20 amp screw-in fuses - one seemed to be for the motor that turns the inside drum and the other was for the heating elements.
Actually the heating element would normally require two fuses to provide 240 v. If you have a fuse box you may have a problem with powering new appliances. Can you post a picture of your fuse box.
 
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Old 10-06-09, 05:47 AM
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reply to Ben and Ray2047

I wanted to wait to reply until I checked my fuse box for the dryer... Afraid I can't post any pictures but it is the old style fuse box with a 'knife-switch' throw and it's the old glass fuses. However, I was wrong on the Amp rating -- the both fuses are rated 30 Amp - I got confused with the lettering on the Leviton socket receptacle and I might've gotten the Amp rating on that wrong as well since I was reading it upside down using a flashlight and a mirror.
Anyway, I checked the new Maytag dryer specs and it looks like it can work with either a 3 or 4 wire configuration.

Will I have any problem with getting a pigtail that only has the 3 'straight' prongs; without having one that has 'L'-shaped third-prong?
thanks,
Greynold99
 
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Old 10-06-09, 08:03 AM
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Replacement cords and receptacles are available in the old style at hardwares and home centers.

This is a 10-30R which should be used on an old 30A circuit for a dryer:


This is a 10-50R which should be used on an old 40A or 50A circuit for a range:
 
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Old 10-06-09, 08:33 AM
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Thanks Ben

Just what I needed... From your schematics it looks like the original owner used the 10-50R rated socket for the electric service to the dryer since the drawing is exactly what I see when I pull the plug. Will that be a problem with today's Electrical Code? Otherwise, it should be able to handle the amp rating since it is higher...
thanks,
Gary
 
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Old 10-06-09, 09:20 AM
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Yes it does handle the amp load, but it is a code issue. In practice I'm sure it would never be a problem but to be code compliant it does need to be changed to the 30A version.

The reasoning is that someone could accidentally plug a 50A appliance in and overload the 30A wiring and fuses. Except for maybe a portable welding rig the only other appliance with a 50A cord you would find around a house would be a range.
 
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Old 10-06-09, 10:51 AM
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You would have to buy a range cord for the dryer and tha larger wire might make it more expensive and harder to work with.
 
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Old 10-06-09, 10:57 AM
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Ben thanks for your help...

The only thing I wanted to point out to you in reply to your comment is -- remember how I had to 'read' the lettering on the Leviton socket for the dryer for the information on it -- Upside down with a mirror and a flashlight... There won't be any accidental connecting of a welder to that socket - it is mounted, I suppose, in the most convenient area for the dryer connection but the darndest for getting to it for anything else. So, I don't think it presents any other hazard and if the installers will wire up the dryer for it, I think we'll go with that for now. Gonna have to wait till I get some money set aside for replacing the fuse box and the socket.
Thanks again,
Gary
 
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