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Old 09-03-14, 10:25 PM   #8
oil pan 4
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I have lots of 220 volt extension cords, fluke325 amp clamp and out side sub panel with easy access to the lines.
And I have 2 clothes dryers, the inside one that never gets used during warmer months is full size, the outside one is a smaller apartment sided one.

What do you want to know?

Here is what I can tell you about electric clothes dryers with out doing any additional tests.
The minimum plug requirement for a clothes dryer is NEMA 10-30. The 10-30 has 2 lines and an L shaped neutral/ground.
Newer homes have the NEMA 14-30 cord. It has 2 lines a neutral and a dedicated non current carrying ground. I don't really see the point. NEMA 10-30 worked fine for 50 or 60 years.

Clothes dryers do have 120 volt requirements. I know this because I have resurrected a few over the years. You have 3 things in there that use 120 volt power:
Buzzer
Timer
Drum motor

The drum motor ends up using up to around 400 watts.

The small apartment sized dryer uses about 17 amps of line to line power when the heater elements are on. Then one leg of line power has about another 4 amps on it.
The full size dryer uses closer to 21 to 22 amps of line to line power plus another 400 to 500 watts on the line to neutral that power the little stuff.

When you adjust the temperature of the dryer you aren't reducing peak power consumption at all. The cooler setting just uses a different set of thermostats to cut power to the heater coils at different temperatures. Most dryers have 2 settings, I think I have seen up to 4 heat settings.

I don't use much power with my dryer, I line dry the clothes, weather permitting (dust storms here) and then put the dryer on about the 15 minute setting, gives about 5 minutes of heat and just air tumbles the rest of the time. That's a huge savings compared to 30 or 40 minutes of heat. I do that to make cloths less stiff and gets the white shepherd mix dog hair off blue and black hospital uniforms.

I do this because it saves power and keeps hours of run time off the machine. I don't like fixing dryers or buying dryers so I like it when they last a real long time.

You should be able to run your dryer off purely line to neutral power.
My dad talked about doing this when I was a kid and understood nothing about electricity because "that house didn't have any 220 volt plugs" and said "that the dryer takes for ever to dry clothes only running off 120 volt power". I don't think it was a 120v dryer, originally.
Then I figure if you use hot attic air you could run the heaters with 120 volt power to slightly further warm the prewarmed attic air and not have it take forever to dry clothes.
A heavy duty "SPCO" switch could be used to enable or disable 220 power as opposed to rewiring the back of the machine every time you want 220v or 120v power. I have only thought about doing this, have not tried it yet and pretty sure I know how to wire it up.

A standard full size clothes dryer heater element is rated for 5100 watts at 230v. Ohms law tells us that a 5100 watt heater is going to draw about 22 amps and offer about 10 Ohms of resistance. This resistance is due in part to electron mobility decreasing with increased temperature.
So we will assume at the heater element operated on 120 volts and at lower temperature will offer a little less than 10 Ohms of resistance.
So we will figure the 5100 watt 230 volt heater element running off 120 volts will consume only up to about 1400 watts.
That reduces heater power down to about 1/4 of what it originally was.

The Ideal setup:
Have one clothes dryer set up inside. Have it draw attic air during warmer months and use Line to Neutral power for the heater elements during the summer. When its winter flip the switch and run full power to the heater element and have the dryer draw air from inside the house and discharge it into your house. I figure if you run your dryer like a normal person that's at least 15,000BTUs of free heat.
If you blow 15,000BTUs of fully usable heat out of your house during the cold winter you are just another wasteful person who hates the earth. I don't care if you drive a prius.

How much CO2 does it produce? Who cares. Worry about how much of your hard earned money its burned up.
Its safe to assume if you are saving money through saving energy you are producing less plant food.

Last edited by oil pan 4; 09-03-14 at 11:12 PM..
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