Why do dryers and range/ovens use 120v for controls and motors?

[Electric-Light]

I see this as meritless. Back when 3 prong dryer receptacles were permitted and cabinet was bonded to neutral, a loss of neutral would cause the cabinet to become energized to 120v through the dryer's controls and motor.

Now that this isn't permitted, you'd need fourth wire for neutral.

You don't see condensing units with 240v compressor and 120v fan pulling from neutral to hot.

Even 1/25hp inducer motors, 75VA 24v control transformers in RTUs and blower motor in 240v window shakers are 240v and do not require a neutral.

 

[Dennis Alwon]

I don't know why either but you should know that there are some ranges, washers and dryers that are straight 240V. Why they all don't go this route is beyond me. 120V components must be cheaper.

 

[iwire]

Some one mentioned by using 120 for the controls the machine stops working if the neutral is open requiring the owners to have it fixed.

With stoves they used to include 120 receptacles on them.

 

[hillbilly1]

Another frequent poster here, sorry the name evades me at the moment, had the logical answer. They use 120 volt motors on theses appliances (some ovens have an optional fan motor too) because they may be used on 208 volt power also. This voltage is common in apartment complexes and condos. Apparently the motors are not dual voltage rated, also the motor may run slower causing the dryer or appliance to overheat when run at the lower voltage.

 

[Electric-Light]

Another frequent poster here, sorry the name evades me at the moment, had the logical answer. They use 120 volt motors on theses appliances (some ovens have an optional fan motor too) because they may be used on 208 volt power also.

As are RTUs, PTACs and windowshakers.

This voltage is common in apartment complexes and condos. Apparently the motors are not dual voltage rated, also the motor may run slower causing the dryer or appliance to overheat when run at the lower voltage.

Heating elements run at 75% power on 208v.

 

[kbsparky]

This goes back years and years ago when ranges utilized control switches for the surface elements.

The burners consisted of 2 coils, each of which were rated for 240 Volts.

When the control was set to "high" both elements were fed 240 Volts.
Medium high placed 240 Volts on one of the elements.
Medium placed 120 Volts on both elements, or put them in series with 240 Volts. Result was the same, either way.
Low placed 120 Volts on one element.
Warm placed both elements in series, fed with 120 Volts.

The range also provided a surface light, oven light, convenience outlet, and clock/timer assembly. I suppose that parts for these were much easier to obtain and use if they were rated for 120 Volts. So all those components needed 120 Volts, and with a dual-voltage supply, it was a no-brainer.

AS for dryers, it was common years ago to advertise and sell a unit that could be used on either 120 or 240 Volt supply. The motor would work either way, but drying time would be 3-4 times longer when connected to a 120 Volt supply. They never supplied a cord, since the manufacturer didn't know what supply would be used, and many appliances were direct connected in those days anyways.

Like the old 42 circuit rule, it takes years and years to wean off of it, even after the initial reason for the rule has been solved/dealt with.

 

[Electric-Light]

Gas stoves actually module by controlling the flow of gas. Do we have any stoves these days that instead of cycling on and off using bi-metalic thermostat in the switch, uses full cycle solid state modulation(as opposed to phase cutting so it wouldn't produce harmonics) so the power fed to the element is actually controlled?

 

[LarryFine]

As mentioned above, for 240/208v compatibility, plus the use of common consumer-replaceable bulbs.

Larger 240v motors (and bulbs) function better on 208v than small ones would, too.

 

[Little Bill]

As mentioned above, for 240/208v compatibility, plus the use of common consumer-replaceable bulbs.

Larger 240v motors (and bulbs) function better on 208v than small ones would, too.

Larry, I was beginning to believe you took off for the summer, like when regular season tv programming went off for the summer. But you didn't leave us with a cliff hanger.:lol:

 

[hurk27]

Some one mentioned by using 120 for the controls the machine stops working if the neutral is open requiring the owners to have it fixed.

With stoves they used to include 120 receptacles on them.

If the owners weren't being electrocuted because they got between the range and another grounded appliance:jawdrop:

I remember many electric ranges with convenience outlets, it was a god send to those who had a kitchen only fed with one 15 amp circuit back then, I remember my dad having all kinds of adapters in them so coffee pots, electric skillets, toaster, you name it could be used without blowing fuses, in Florida back in the "60's" we didn't have any natural gas, so everything was electric or propane,

 

[Cavie]

If the owners weren't being electrocuted because they got between the range and another grounded appliance:jawdrop:

I remember many electric ranges with convenience outlets, it was a god send to those who had a kitchen only fed with one 15 amp circuit back then, I remember my dad having all kinds of adapters in them so coffee pots, electric skillets, toaster, you name it could be used without blowing fuses, in Florida back in the "60's" we didn't have any natural gas, so everything was electric or propane,

FPL "Gold Medallion Homes". I installed door bells with this info on them. (boy,am I getting old!) Big publicity push back the by the power company and contractors. All Electric Homes. Now they pay us NOT to use electricty. Go Figure.

 

[iwire]

If the owners weren't being electrocuted because they got between the range and another grounded appliance:jawdrop:

I understand that.:roll:

 

[mtfallsmikey]

FPL "Gold Medallion Homes". I installed door bells with this info on them. (boy,am I getting old!) Big publicity push back the by the power company and contractors. All Electric Homes. Now they pay us NOT to use electricty. Go Figure.

Ahhh!.... I still have a gold medallion from PEPCO that came from a front door of an all-electric house, built in the late 60's. Has a miniature Reddy Kilowatt image empossed in it....I'm older than dirt too.

 

[kbsparky]

And the homes with gas heat and appliances in it were called "Forecast" homes.

 

[texie]

FPL "Gold Medallion Homes".

FPL "Gold Medallion Homes".

Wow-we're showing our age! I remember the FPL "Gold Medallion Homes" door bell button growing up in Miami in the 60's. It's laughable now that we have gone 180 degrees in the other direction. The young guys here must think we're pretty old but I'm kind of nostalgic.