Why four wire instaed of three for range and dryer?

[templdl]

4-wire for the dryer makes perfect sense if it was installed before the 1953 Code was adopted locally.
It might also have been because it used smaller wire?

Tapatalk...

I guess I missed the point of being installed before 1953.
Also, I can't speculate about the smaller wire size.
3w or 2w w/ a shared neutral has been a comonly approved method of wiring in our area up until the mid '80s or so as I can recall.
I personly don't think it's a good idea as it provides a good opportunity to turn neutral current on to the applence enclosure should the neutral connection back to the SE be inadvertantly opened or fail. If this should happed it can prove to be a shock hazard if someone touches the appliance and a ground.

 

[kwired]

It all comes down to profit, why sell a dual voltage motor when a single voltage motor is cheaper to produce? Would you install 4 lamp ballasts for a 2 lamp fixture at your own expense?







I'm a firm believer the NEC is about consistency, so it only makes sense to remove this once allowed acceptation?.

For a definite purpose motor - you are probably right, for a general purpose motor dual voltage is king of the market.

It does make sense to remove that once allowed requirement, what doesn't make sense was allowing it in the first place - or at least why it wasn't removed at least 20-30 years sooner than it was.

Just what was the third wire? Neutral or ground?

Seems to me the wire was a ground. The issue was that 220V appliances often needed 120v; ranges had convenience receptacles mounted on them (quite common in the 60's), ovens had lights, and dryers had their drum motors. This meant normal operation put current on the ground wire.

Or, perhaps, the wire really was intended as a 'neutral.' Consider that even today many homes lack any ground wires. and the original service lacks a ground bar. My house, built in 1957, was such a house. (Romex was the method). I've seen even commercial / government facilities built in the mid-70's (by exceptionally competent contractors) that use the pipe between panels as both neutral and ground.

When one such facility had a failure over a Thanksgiving holiday, it was a failure of the bonding between panels that proved to be the culprit. These days, we have all manner of electronics in our circuits. The effect is that 'power quality' -something unheard of in the 60's- is really important. Even our ranges and dryers have electronics in them. So, we really need to keep the neutral and the ground separate.

Third wire was a "grounded conductor" (neutral). If it were an equipment grounding conductor then it would be permitted to use a metal raceway as this conductor.

Last spring I bought a new 'budget' washing machine and it is amazing how light it is, how small the motor is, how little there is too it.

Main contributing difference between these new lighter units and the old heavy counterparts is the old ones had a steel tub, as well as a steel moving drum, and the older motor and transmission had to be bigger and more HP to drive that heavier drum. New water pump is usually a separate motor and pump but is a pretty light motor and a smaller non metallic pump and housing.

 

[templdl]

For a definite purpose motor - you are probably right, for a general purpose motor dual voltage is king of the market.

It does make sense to remove that once allowed requirement, what doesn't make sense was allowing it in the first place - or at least why it wasn't removed at least 20-30 years sooner than it was.



Third wire was a "grounded conductor" (neutral). If it were an equipment grounding conductor then it would be permitted to use a metal raceway as this conductor.



Main contributing difference between these new lighter units and the old heavy counterparts is the old ones had a steel tub, as well as a steel moving drum, and the older motor and transmission had to be bigger and more HP to drive that heavier drum. New water pump is usually a separate motor and pump but is a pretty light motor and a smaller non metallic pump and housing.

The way I understand it without the aid of a schematic was that very few if any components are actually 240v in the current appliances. Motors and control have been 120v and the 240v L-L is necessary because of the additional power that is available for 120v heating elements where you add 120v heating for additional heat utilizing the neutral as a home run for the 120v.
But, I'm sure that there are countless designs out there that actually utilizes an actual 240v L-L voltage.

 

[kwired]

The way I understand it without the aid of a schematic was that very few if any components are actually 240v in the current appliances. Motors and control have been 120v and the 240v L-L is necessary because of the additional power that is available for 120v heating elements where you add 120v heating for additional heat utilizing the neutral as a home run for the 120v.
But, I'm sure that there are countless designs out there that actually utilizes an actual 240v L-L voltage.

Maybe. I have seen ranges that have a neutral terminal but no conductors connected to it also - tells me there is no 120 volt load at all in those models, just a place to land the conductor in a "standard appliance cord".

 

[templdl]

Maybe. I have seen ranges that have a neutral terminal but no conductors connected to it also - tells me there is no 120 volt load at all in those models, just a place to land the conductor in a "standard appliance cord".

Yes, that would make sense.

 

[iwire]

For a definite purpose motor - you are probably right, for a general purpose motor dual voltage is king of the market.
.

Dryers do not use GP motors do they?

 

[templdl]

Dryers do not use GP motors do they?

The ones that I've seen are OEM types that are designed for the app!ovation but they look like they are designed around a GP motor.
Dryers may have capacitor start but but I believe may just split phase.
It would be interesting if the motors have a specific design for the rotor and stator the would provide performance specifically for the application but I doubt it.

 

[JDBrown]

The ones that I've seen are OEM types that are designed for the app!ovation but they look like they are designed around a GP motor.
Dryers may have capacitor start but but I believe may just split phase.
It would be interesting if the motors have a specific design for the rotor and stator the would provide performance specifically for the application but I doubt it.

"Minimizing costs" is the name of the game. The motors will be whatever's cheapest that will do the job. That's why gas and electric dryers use the same motor -- it streamlines the ordering process, the manufacturer can get better bulk discounts from the motor vendor, etc.

Oh, and I don't mean this as a knock against appliance manufacturers. This was just my experience from my internship a few years back. And it's not just motors; any time you're mass-producing products, those pennies saved/pennies earned add up really quickly. I remember doing a bunch of testing on control relays, and it drove one of the other interns nuts. He kept telling the engineers that we needed to use solid-state relays (which would have worked much better for the application), but he never seemed to understand that using a component that cost several dollars vs. one that cost several cents was just never going to fly.

 

[kwired]

The ones that I've seen are OEM types that are designed for the app!ovation but they look like they are designed around a GP motor.
Dryers may have capacitor start but but I believe may just split phase.
It would be interesting if the motors have a specific design for the rotor and stator the would provide performance specifically for the application but I doubt it.

I have never seen any such appliance with a GP motor. They have to be ordering them (I really doubt very many make their own) in large enough quantity to make it worth their customized order or else GP motors likely would cost less.

You have to remember that a GP motor will be built on standard frame sizes, but an OEM will often be based on a standard frame with modifications, such as different mounting means, different shaft characteristics, or added accessories

 

[RichB]

1. How likely would that be?
2. In the event that it did happen, wouldn't the ground be a more conductive path anyway? Granted, we don't know the length of the run, but in general, wouldn't the existing path be more conductive than my elbow?

Not arguing your point, just really curious about this now that it was asked of me.

btw, Happy Holiday's to those celebrating!

Electricity takes ALL paths-- as a kid I remember grabbing the stove and the metal sink at the same time cause it was fun to get the tingle that made your arms tighten up

 

[templdl]

I have never seen any such appliance with a GP motor. They have to be ordering them (I really doubt very many make their own) in large enough quantity to make it worth their customized order or else GP motors likely would cost less.

You have to remember that a GP motor will be built on standard frame sizes, but an OEM will often be based on a standard frame with modifications, such as different mounting means, different shaft characteristics, or added accessories

Mechanical design and/or electrical design? Yes, I'm well aware that the stator and rotor could be a common design but assembled in a frame with mounting provisions as specified by the OEM.
From an electrical and speed/torque perspective they would have the performance of a typical GP motor but the fram mounting provisions are per the OEM's specifications.
Yes, if you are saying the a motor built on a #56 frame would be defined as a motor with standard base dimensions, shaft dia. height and length, key dimensions, making the motor interchangeable with manufacturers. As such a GP motor may be designed and build to applicable NEMA standards.

 

[kwired]

Electricity takes ALL paths-- as a kid I remember grabbing the stove and the metal sink at the same time cause it was fun to get the tingle that made your arms tighten up

Yes electricity does take all paths, but in proportion to the resistance of each path. If you were to place a bonding jumper between the stove and sink in your example you do not get that tingle, as there is not enough resistance in the jumper to create enough voltage for you to feel what current is flowing through you. Yes there is some current still flowing through you but is so little you do not feel it, as your body's resistance is much higher than the bonding jumper is.

Should the sink have a fairly solid bond to the electrical grounding system you probably feel nothing either.

 

[iwire]

These motors are what I have seen in dryers

 

[kwired]

These motors are what I have seen in dryers

Pretty much very similar to all I can recall ever seeing too. Main difference from a GP motor is shaft specs, and the open design. There are open ventilation GP motors but not that open, this is designed to be inside the appliance and not exposed to the user or other environmental issues. Could also be an overall appliance weight advantage being another reason to use a motor as open as those usually are. May seem like no big deal for a single unit, but they add up for a truckload of appliances.

 

[templdl]

Wouldn't a naked picture as such be in violation of the T&Cs of the forum? That picture of the motor is as bare bones and you can get.

 

[iwire]

 

[GoldDigger]

Wouldn't a naked picture as such be in violation of the T&Cs of the forum? That picture of the motor is as bare bones and you can get.

I do not think that bare bones would be a problem. It is the sins of the flesh that are a concern.

 

[templdl]

I do not think that bare bones would be a problem. It is the sins of the flesh that are a concern.

Good point. I love it. I agree. At least they could have used a fig leaf as cover.

 

[ggunn]

Wouldn't a naked picture as such be in violation of the T&Cs of the forum? That picture of the motor is as bare bones and you can get.

I believe it's OK as long as uncovered male or female connectors are not displayed.

 

[templdl]

I believe it's OK as long as uncovered male or female connectors are not displayed.

This was my morning chuckle. I couldn't help but laugh.