Clothes dryer heater element voltage selector

[oil pan 4]

This is for any one who might want to add a heater element selector switch to their clothes dryer.
For any one who might want to run lower power in summer and switch back to full power for winter months or if you need your work clothes dry now.

What does this mod do?
I keeps the clothes dryer operating normally every where except for the heating element. Powering the heater element with 120 volt power as opposed to 240 volt power cuts the heater element power consumption down to about 1/4 of what it originally was. Also operating at the lower temperature the heating element can last just about forever.
It can see it making clothing last longer too. You wont have oppressive hellish heat breaking down rubber stretch bands in underwear.
You might want full heat to shrink pants back down.
You might want or need to use less power for some reason, "turning the heat setting down" just cuts off the heating element sooner, it still draws the same amount of power when it is on.
Lots of reasons you might want to try this.

Here is a typical clothes dryer schematic.

This is before modding.

Here is what it looks like after it has been messed with:


My additions are to the right side of the drawing where it says "voltage selector switch".
This mod is very simple. You have 3 or 4 wires going to your clothes dryer. If it has a 4 wire cord ignore the dedicated ground and now its like working on a 3 wire.

All you need to know is how not to electrocute your self to death, get a heavy duty 3 way switch rated for up to 277 volts at 20 amps and a metal handy box, big or small handy box, it doesn't matter. 3 lengths of wire, 2 of which need to be 10ga.

You see the L1 side of the diagram, leave that alone, it powers the drum motor, timer and buzzer, L1 is usually a black or blue wire. Everything already on the Neutral gets left alone too. We will just be adding a wire to the N bundle.
The L2 side is what you want to mess with.

Before you touch anything you need to unplug the clothes dryer, not just flip the breaker. I recommend you flip the breaker before touching the plug and receptacle.

To find L2 all you have to do is disconnect one of the lines from the clothes dryers power cord, just disconnect it from the terminal board and wrap electrical tape around the lug and try to turn the machine on after you plug it back in and turn the breaker back on. If you try to turn it on and nothing happens then you unhooked L1 or didn't restore power. Safely reconnect the wire with power removed from the machine and try the other line.
When you disconnect L2 everything will work like normal, aside from the heater, there should be no heat.
Some times you will see "L2" stamped on the housing near the terminal board, other times the wire is marked L2 or is a red wire, but not always. L1 and L2 can also be called X and Y. To further confuse you.

When extending the wires don't use solid romex. Extend wires 6 to 8 inches past where you want the selector switch. Run the new wires inside or with the existing wire bundle.

Once you have identified L2 all you have to do is remove power, cut the L2 wire or remove the L2 terminal screw from the clothes dryer side of the terminal board and use a piece of 10ga wire to extend "L2" to where you want install your switch. We will call this wire "L2 line side" wire now. Try to use the same color wire or a red wire.

To extend one wire I just used a solderless butt connector, you can use a wire nut if you want, but you will still need solderless connectors later on.
Do not twist them and cover with electrical tape, it will get hot from the drum heat and fall off.

Now take the wire that used to connect the heater element to L2 power, we will call this "L2 heater side". Take the L2 heater side wire and extend it using a 10ga wire of different color or marked with electrical tape that is not red to where you want your switch.

The N or Neutral wires are almost always white.
Next run another neutral wire back to where you want the switch. Just unwire nut the group of neutral wires near the terminal board. If you add wire to the 3 or 4 Neutral wires going to the neutral bundle wire nut you will likely need the next size larger wire nut. If there is not bundle of neutral wires you are going to have to crimp a lug on your wire and connect the new wire directly to the N spot on the terminal board. This wire will switch one side of the heater element to 120v power and replace 240v with 120v. Powering the heater element with 120 power is only going to allow it to draw about 6 amps so this wire doesn't have to be 10ga. Good stiff 14 or 16ga multi stranded THHN wire will do fine.

Now that you have 3 wires. Hopefully a smaller white N wire, a red 10ga wire that eventually leads to hot wire prong on the dryer cord (L2 line side) and another 10ga wire that is any color but red that goes to the heater element (L2 heater side).

Your 3-way 277 volt 20 amp switch should have 3 terminal screws. One screw should be black or chrome color. This is your common. Take your non-red "L2 heater side" wire and connect it to the common. This is the wire going to your heater element.
The other 2 screws should be brass color these are your switched terminals. Hook the white N wire up to one side and the "L2 line side" to the other, it doesn't matter which one. This will switch your heater element between L2 power and N.

You might be wondering how to connect a stranded THHN wire to a switch?
Get forked or U shaped yellow sleeved 10ga solderless connectors for the 10ga wires and a blue sleeved 14 to 16ga connector for the N wire.
If you don't know how to do crimped connectors there are a few thousand Youtube videos on how to do it.

But you might be saying wait, the switch is rated for 20 amps, but my big clothes dryer heater element draws 22 or 23 amps. Yes, as long as you do not switch the heater element under load you will be fine.
If you have a dryer with a monster heating element you will need to turn off the clothes dryer, throw the switch and turn it back on or turn the selector to a "no heat" setting before you make your move.
My little apartment sized clothes dryer heater element draws 17 amps so I can switch it back and forth all day long.

You will know it works when the switch allows the dryer to discharge air hot as normal then the other setting will make the air kind of hot, but not hot enough to melt your flesh.

Also you might want to clean the lint out of the bottom of your dryer while you are doing this. I used compressed air blower and a cheater tank to remove a few pounds of lint.

[NiHaoMike]

The 120V trick gives about 1/4 power. If you find that too little, you can install a power diode in series with the heating element (and original 240V) to get 1/2 power. (Or you can use 120V and the diode to get 1/8 power...) Use plenty of heatsinking on the diode and put it right in the intake air stream so the heat coming off of it can be put to use.

Another thing that would work are the really heavy duty dimmers used to dim stage lighting, assuming you could find one cheap enough.

[oil pan 4]

Half wave rectified DC is a great idea.
A power diode could be added and controlled with a simple heavy duty SPST switch. Open the switch or turn it off to enable half wave DC, turn the switch on and allow full AC power to bypass the diode and flow like normal.

Don't forget to clean your clothes dryer. I found dryer lint that had been on fire in mine down near the heater air inlet.
I am not going to use the winter clothes dryer at all till it gets taken apart and cleaned too.

[bmxeroh]

How much is your dry time extended by this?

[oil pan 4]

Extend my drying time?
None, since so far every time I used it "dry" clothes the clothes were already dry when they went in there.
I rarely use my dryer to actually dry clothes during the summer, mostly just use it to remove lint and dog fur off work clothes.

Trying to remember back oh, 25 years ago when we lived in a house that didn't have a dryer receptacle my dad hooked up a dryer to 120v and you put a wet load of clothes and set it for the max dry time, an hour maybe 90min and one cycle even done with max time on the timer wouldn't quite completely dry them. I think this was mainly a problem during cooler wetter months in Virginia.
I am saying use 240v heater power and heat your home with the waste heat during the winter.

[mejunkhound]

every time I used it "dry" clothes the clothes were already dry when they went in there.

Every dryer I have ever had since 1967 already as an 'air only' setting.

[oil pan 4]

The no heat doesn't work so well on wrinkled blended fiber hospital uniforms. I don't think it will work to well on any bacteria of fungus picked up from line dry also.

[Servicetech]

Have you considered a relay and extra thermostat to automatically switch voltages based on drum temp? Use a 110f on/120f off (or similar) thermostat to switch 120 to 240v.

[oil pan 4]

Even better, use a hold in circuit, so when the drum gets up to temp and the element cycles off it will turn back on with 120v power.

That initial warm up with a drum full of damp or wet cloths on 120v is pretty much impossible.