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Author Topic: How do you wire a 3 blade 220V clothes-dryer outlet (Nema 10-50) to Nema 5-15?  (Read 8003 times)
KK6BSB
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Posts: 8




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« on: November 12, 2013, 07:07:02 PM »

I am currently fabricating an AC adapter so I can use my old Stove 220V outlet for my liner amplifier. I've read the eHam blogs and searched the net but am still a little confused; if the top "blade" that goes into the older 3-wire-stove-outlet (Nema 10-50) is neutral and the bottom two "blades" are both hot, then how do I connect  to the newer NEMA 5-15 female at the other end which is neutral/hot/ plus ground?  I.E.,  which of the two "hots" from the NEMA 10-50 goes where on the NEMA 5-15 and do I need to run a separate ground-wire?

Thanks for any simple explanation is advance!!

73

KK6BSB
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KE4DRN
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Posts: 3721




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« Reply #1 on: November 12, 2013, 07:45:03 PM »

hi Tim,

Questions first, make and model of amp, can your amp run on 240
or only on 120?

The stove receptacle has no separate ground, it is shared with the neutral.

http://upload.wikimedia.org/wikipedia/commons/thumb/0/0d/NEMA_simplified_pins.svg/350px-NEMA_simplified_pins.svg.png

73 james

 
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TANAKASAN
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Posts: 933




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« Reply #2 on: November 13, 2013, 12:23:24 AM »

That's crazy! I count ten connectors for 240V operation and fifteen connectors for 110V, twenty five different connectors in total.

Why not just have eight connectors, four 120V and four 240V to cope with the different current ranges?

Tanakasan
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W9GB
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Posts: 2616




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« Reply #3 on: November 13, 2013, 06:53:43 AM »

Quote from: KK6BSB
I am currently fabricating an AC adapter so I can use my old Stove 220V outlet for my liner amplifier.
I've read the eHam blogs and searched the net but am still a little confused; if the top "blade" that goes into the older 3-wire-stove-outlet (Nema 10-50) is neutral and the bottom two "blades" are both hot, then how do I connect  to the newer NEMA 5-15 female at the other end which is neutral/hot/ plus ground?  I.E.,  which of the two "hots" from the NEMA 10-50 goes where on the NEMA 5-15 and do I need to run a separate ground-wire?
Tim -

NEMA 10 is a legacy throw back 240 VAC (30 or 50 amp) receptacle for stoves, ovens, and electric dryers.
Since 1996 (NEC Change), NEMA 10 is NOT to be installed in new residential homes.

NEMA 10 can NOT support 120 VAC safely (no separate Neutral and Safety Ground).
Traditional wire colors from service panel (before 1996) to NEMA 10 receptacle: Black, Red, White.
http://en.wikipedia.org/wiki/Electrical_wiring#Color_code

Wire the correct NEMA Outlet on a properly sized circuit breaker from your service panel.
http://en.wikipedia.org/wiki/NEMA_connector

NEMA 5 : 120 VAC (standard for US homes, good for 500-600 watt HF amplifiers)
http://en.wikipedia.org/wiki/NEMA_connector#NEMA_5
NEC wire colors used for NEMA 5:  Black (Hot, L1 or L2); White (Neutral); Green (Safety Ground)

NEMA 6 : 240 VAC (This is used for 1 kW and greater HF amplifiers, that have AC isolation transformer).
http://en.wikipedia.org/wiki/NEMA_connector#NEMA_6
Generally NEMA 6–series non-locking plugs are used for such appliances as large room air conditioners, commercial kitchen equipment, and the occasional home arc welder.
NEC wire colors used for NEMA 6: Black (Hot, L1); Red (Hot, L2); Green (Safety Ground)

NEMA 14 : 4-Blade Replacement for NEMA 10 (supports 240/120 VAC kitchen or laundry appliances,
 that traditionally do not have AC isolation transformers.)
http://en.wikipedia.org/wiki/NEMA_connector#NEMA_14
NEC wire colors used for NEMA 14: Black (Hot, L1); Red (Hot, L2); White (Neutral); Green (Safety Ground)
« Last Edit: November 13, 2013, 07:33:10 AM by W9GB » Logged
KG6WLS
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Posts: 507




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« Reply #4 on: November 13, 2013, 08:30:11 AM »

Most household 220V dryer outlets in the US are NEMA 10-30R (125/250V) - fed with #10 wire with a 2 pole 30A breaker.
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K8AXW
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« Reply #5 on: November 13, 2013, 10:18:40 AM »

BSB:  You can drive yourself crazy with these NEMA numbers, etc.  Plus you can overthink this situation.

Starting with your stove 220V socket.  You've identified the neutral pin and the two "hot" pins.

Just run a Romex 12-2 w/ground wire to your linear.  Whatever receptical/plug combination you use, just wire the neutral to the neutral on the new receptical  and either of the two "hot" wires to the "hot" pins on the receptical.  It doesn't make any difference which hot goes to either blade or pin.

This is no different than how I have my basement electric cooking stove and dryer hooked up.  I Just pull the pigtail from either one and replace it with the pigtail of the appliance that I want to use at that time.  You can do the same.....swapping out your stove power plug with the linear power plug.  If you ever wish to use both at the same time, I suggest you pull in a separate 12-2 w/ground for the amp.  Of course your amp must be wired for 240V.

It isn't necessary to run a separate ground wire. 

The only time I've been involved with 4 wire is with a portable generator being connected to the house system.

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AA4PB
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« Reply #6 on: November 13, 2013, 10:41:16 AM »

Actually, most 220V linear amps don't use a neutral connection. They use the two hot lines and the safety ground. The stove requires the two hot lines, a neutral, and a safety ground (4-wires). If its old wiring it may not include a separate safety ground. If the stove has 4-wires then connect the two hot lines and the safety ground to the amp. Leave the neutral unconnected.

If the stove has only 3-wires then connect the two hot lines to the amp. By code you need to add a separate line from the amp safety ground back to the panel box. As a practical matter, the neutral and the safety ground will be bonded together inside the panel box so you could just connect the amp safety ground to the stove neutral line. This won't make any difference because the amp is not pulling any current through the neutral anyway. The reason that present code does not permit using one conductor for both neutral and safety ground is that voltage drop on the neutral could cause the equipment case to be at a slightly different voltage than other grounds.
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KE4DRN
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« Reply #7 on: November 13, 2013, 02:06:54 PM »

Bob,

He wants to use a NEMA 5-15 receptacle, that is 120v not 240.
So he can not use both hots to the 5-15 device.

I hope his amp can be wired for 240v, that would make things easier.

73 james
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AA4PB
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« Reply #8 on: November 13, 2013, 02:16:23 PM »

Ahh, I didn't catch that his amp was 120V. In that case the solution is to use either hot (only one) for the hot side of the 120V and the neutral for the amp neutral connection. Since the amp is now drawing current from the neutral you MUST (according to code) have a separate safety ground. One solution would be to rewire the other hot in the panel to serve as the safety ground. In that case you must mark both ends of that black wire with green tape or paint so that someone working on it in the future will realize that it is being used as a ground.

I agree that if the amp can be rewired for 240V that would make the most sense.
 
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W9GB
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Posts: 2616




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« Reply #9 on: November 13, 2013, 05:08:57 PM »

Quote from: AA4PB
Ahh, I didn't catch that his amp was 120V. In that case the solution is to use either hot (only one) for the hot side of the 120V and the neutral for the amp neutral connection. Since the amp is now drawing current from the neutral you MUST (according to code) have a separate safety ground.
Bob -

THAT is the reason I gave a Complete Answer (and Education) for Tim, KK6BSB.
His proposed 120 VAC (NEMA-15R) receptacle usage is NOT proper from a traditional 240 VAC (NEMA 10-30R) kitchen appliance receptacle, due to the lack of a separate Neutral and Safety Ground.
==
Tim -

Look, this topic is personal for me.  IF this is beyond your understand or capabilities -- seek professional assistance -- especially if you have children in the household

The NEC 1996 and its adoption of NEMA 14 to replace NEMA 10 was due to an increasing number of Electrocutions -- found to be due to lack of separation of Safety Ground and Neutral with these circuits and appliances and attempted usage of 120 VAC devices from the circuit.  This is exactly what you were proposing.

The Insurance industry (P&C, Fire, Life) claims departments collect these morbid statistics for the actuaries and underwriters.  NFPA 70 : National Electrical Code (NEC) is developed and published by National Fire Protection Association (NFPA).
« Last Edit: November 13, 2013, 05:28:51 PM by W9GB » Logged
W6EM
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Posts: 787




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« Reply #10 on: November 13, 2013, 06:17:40 PM »

Quote from: AA4PB
Ahh, I didn't catch that his amp was 120V. In that case the solution is to use either hot (only one) for the hot side of the 120V and the neutral for the amp neutral connection. Since the amp is now drawing current from the neutral you MUST (according to code) have a separate safety ground.
Bob -

THAT is the reason I gave a Complete Answer (and Education) for Tim, KK6BSB.
His proposed 120 VAC (NEMA-15R) receptacle usage is NOT proper from a traditional 240 VAC (NEMA 10-30R) kitchen appliance receptacle, due to the lack of a separate Neutral and Safety Ground.
==
Tim -

Look, this topic is personal for me.  IF this is beyond your understand or capabilities -- seek professional assistance -- especially if you have children in the household

The NEC 1996 and its adoption of NEMA 14 to replace NEMA 10 was due to an increasing number of Electrocutions -- found to be due to lack of separation of Safety Ground and Neutral with these circuits and appliances and attempted usage of 120 VAC devices from the circuit.  This is exactly what you were proposing.

The Insurance industry (P&C, Fire, Life) claims departments collect these morbid statistics for the actuaries and underwriters.  NFPA 70 : National Electrical Code (NEC) is developed and published by National Fire Protection Association (NFPA).
The problem that created the hazard in 3-wire dryer and electric ranges is that they aren’t totally 240V loads.  The clocks, timers and lamps used on and inside them are 120V devices and they use the neutral for return current and it was bonded to the metal cabinet on each appliance..  Not like most all amateur linears that use only 240V-connected loads between the two hot legs.

For example, if the neutral conductor lug in the distribution panel or the receptacle became loose or otherwise intermittently connected, the surface of the appliance would then be connected and floating through the 120V connected accessory and anyone contacting a metal part could be shocked and injured or electrocuted by return 120V current.  Also, a separation of the neutral between the utility transformer and the residence service entrance would create a similar hazard, to the extent the grounding electrode (ground rod) resistance is more than a few ohms.

Insulating the neutral, as it is in every other appliance, solves this shock hazard problem should the neutral be interrupted.

Also, taping of branch circuit conductors to designate them for another purpose is only permitted on large branch circuit conductor sizes.  I think for No.2 AWG and larger conductor sizes, based on my recollection.  I could be wrong, however.

73.

Lee
« Last Edit: November 13, 2013, 06:33:19 PM by W6EM » Logged
KK6BSB
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Posts: 8




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« Reply #11 on: November 13, 2013, 11:35:36 PM »

Hi Fellow-Helpful-Hams!

Thanks for all the great replies and info which I think gives me the answer I need to construct this "pigtail". First off, the linear amp (Heathkit B220) is now wired for 220V so that makes things easier. Secondly, the solution I've come up with (thanks to your help) is this:  the 50 Amp, 3-wire, 240V male-stove-style-plug will be wired as follows to the standard issue 240V female plug on the other end using Romex 3-wire: 2 hots with the ground going to the neutral. I.E., the top vertical 50 amp blade is neutral to ground.The two slanting 50 amp blades (hots) go to the standard female plug as hots in any order.   Did I get it?

73

Tim KK6BSB
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N7BMW
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Posts: 115




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« Reply #12 on: November 14, 2013, 02:11:34 AM »

Rather than using Romex go to your local Home Depot or Lowes and buy a foot or two of four conductor generator cable.  Stranded generator cable is much more durable than Romex for a pigtail that is subject to flexing. 

An even simpler solution would be to put the stove style plug directly on the SB-220 power cord. 
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W9GB
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Posts: 2616




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« Reply #13 on: November 14, 2013, 04:23:16 AM »

Do NOT use Romex® for Drop cord for appliance usage -- from receptacle to appliance (HF amplifier or dryer).  
Romex® is a structural cable, it can not take flexing, etc. due to its solid conductors.

Grangier, McMaster-Carr and industrial equipment hardware stores sell proper CORDAGE,
sold by the foot.  Local Home Depot/Lowe's can be a mixed bag when dealing with
 240 VAC cordage (SJO, SJT, SJTO; 14-3 or 12-3)

March 2012 discussion (QRZ forum, Amateur Radio Amplifiers) of topic.
http://forums.qrz.com/archive/index.php/t-337347.html

w9gb
« Last Edit: November 14, 2013, 04:28:34 AM by W9GB » Logged
W6EM
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Posts: 787




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« Reply #14 on: November 14, 2013, 06:05:24 AM »

Another point that has not been mentioned here is that for very good reason, receptacles of a higher rating should not be used for 15A or 20A appliance loads.....like an amateur linear amplifier.  Why not?  Well, the reason stems from the fact that the circuit breaker back at the panel matches the receptacle rating.  So, a 50A breaker probably sits there, protecting all parts of the range or dryer appliance circuit up to and into the appliance.

If you come along and hook up AWG No. 12 or No. 14 appliance cords, and trouble develops, you could have more than what you'd expect to receive........a simple trip of the breaker.  Fire from extensive arcing and burning before the breaker clears the fault on the smaller wire.  How so?  A short inside the amp ahead of its fuses or failure of its fuses to operate.  The result:  Fried cord, cabinet, etc.  Much more damage than should happen, and a possible life or fire safety issue to boot.

Make sure that if you are going to try to repurpose an existing circuit (which I do not recommend doing), that the circuit breaker back at the panel is the proper size for the receptacle, plug, appliance cord and load you are connecting to it.

Best to have a qualified electrician help you out.

73.

Lee


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