Automatic Dryer Plug Switcher?

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kevinleaf

Well-known member
Joined
Jun 3, 2013
Messages
178
My situation is: I have a 220v EVSE from Lear / Fisker and it works great. However I am living in a rental property and don't want to make any permanent changes to the house wiring. It would just be too much trouble and too expensive for the short time I will be here (perhaps a year). The charger has a drier plug and that works just fine, except I have to switch it out every night with my clothes drier.
Of course this is a pain:
  • These plugs are not meant to be plugged and unplugged every day.
    Its inconvenient
    Its ugly
    Its not all that safe
    I often forget to switch the plugs at night and wake up with a dead car in the morning

I thought about making some kind of a dual plug setup with an automatic switchover. If the clothes dryer is in use the power goes to the drier. If it is not the power goes to the car. This way when the drier's cycle is done it switches back to charge my car, even if it finishes when I am asleep. In the simplest case it could be a manual switchover with a standard light switch, and at least I don't have to plug / unplug the drier every night.

The current sensing switch or manual light switch would have to control a relay of some kind. I was looking for something DPDT (double pole double throw) capable of 20a per leg, with 120v coil voltage to keep it simple. To keep the cost down I was looking for a surplus relay or something salvaged from an oven or HVAC equipment. I'd really like to keep all the parts under $100.

For the auto-switch: there are current sensing setups I have seen. With some simple circuitry I could rig this to the relay.

Opinions / ideas?

[edit: fixed spelling of that machine that dries clothes)
 
I bought one of these devices just to keep in my trunk to make a 220 line when i'm at a friend's house that does not have a 220 Line.

Maybe it will work for you and You won't need to switch anything out every night,

http://www.quick220.com/-P-103.html" onclick="window.open(this.href);return false;
 
kevinleaf said:
My situation is: I have a 220v EVSE from Lear / Fisker and it works great. However I am living in a rental property and don't want to make any permanent changes to the house wiring. It would just be too much trouble and too expensive for the short time I will be here (perhaps a year). The charger has a drier plug and that works just fine, except I have to switch it out every night with my clothes drier.
Of course this is a pain:
  • These plugs are not meant to be plugged and unplugged every day.
    Its inconvenient
    Its ugly
    Its not all that safe
    I often forget to switch the plugs at night and wake up with a dead car in the morning

I thought about making some kind of a dual plug setup with an automatic switchover. If the drier is in use the power goes to the drier. If it is not the power goes to the car. This way when the drier's cycle is done it switches back to charge my car, even if it finishes when I am asleep. In the simplest case it could be a manual switchover with a standard light switch, and at least I don't have to plug / unplug the drier every night.

The current sensing switch or manual light switch would have to control a relay of some kind. I was looking for something DPDT (double pole double throw) capable of 20a per leg, with 120v coil voltage to keep it simple. To keep the cost down I was looking for a surplus relay or something salvaged from an oven or HVAC equipment. I'd really like to keep all the parts under $100.

For the auto-switch: there are current sensing setups I have seen. With some simple circuitry I could rig this to the relay.

Opinions / ideas?

Detecting if the dryer is running is probably the easiest part, as you can monitor the status of the knob, LED light, or just use a current sensor (example 1, example 2).

I recommend you try posting this question on the CocoonTech forums (which is all about DIY automation) as well, you will probably get a few more good responses.

It's a very interesting idea for sure, and might have other applications. I guess there might be a code issue, not sure why else a device like this doesn't exist.
 
This would be a great feature to build into an EVSE. The EVSE could feed through to either a dryer or electric water heater. In the case of the water heater it could interrupt charging periodically and apply power to the water heater, then detect when the load diminished (ie elements shut off) and go back to charging. For the dryer you would just have a button to direct power to the dryer for say, an hour, or until (near) zero load is detected for some period of time.

No idea if UL or the likes would approve such a thing though.
 
It will need to be manually switched. While on the EVSE there is no power to the dryer to draw current and vice a versa.

The cleanest way would be to make a box with a contactor in it and a small control switch. You can get 50A contactors on Ebay for around $30 shipped.

If you used a low voltage contactor and a power supply you could remote the switch.
 
Never mind, I was thinking you were switching the power. What you are doing is leaving the dryer connected and removing the EVSE load when the dryer turns on. This should be simple, Just make the sensor sensitive enough to see the motor since the element cycles on and off.

Worst case you could use the GFCI circuit from the OpenEVSE design and only use one wire. You would need to tweak the burden resistor since it will likely trip on the processor current.
 
GlennD said:
Never mind, I was thinking you were switching the power. What you are doing is leaving the dryer connected and removing the EVSE load when the dryer turns on. This should be simple, Just make the sensor sensitive enough to see the motor since the element cycles on and off.

Worst case you could use the GFCI circuit from the OpenEVSE design and only use one wire. You would need to tweak the burden resistor since it will likely trip on the processor current.
If you're going to leave the dryer connected, it will likely also be drawing power to run the electronics in the dryer. You'd want something that would detect a draw of more than an amp or so and disable the EVSE. The nice thing about this is that someone can use the dryer and the car would stop charging, then restart again after the dryer finished.
 
Interesting question. I'd think you'd be fine just making a simple 'Y' adapter and charging your Leaf using the end timer. What are the chances that you'll be running the dryer between ~2 and 6 am or whenever the car charges?

But otherwise I think you could fairly simply make this work with a current sensing relay - perhaps one like this. Get a box to make a Y adapter, and pass one of the hots going to the dryer through the current sensor. If you can get a relay with a normally closed (NC) contact that opens when current is flowing to the dryer, that'd be ideal, otherwise you could add a second relay to achieve the same purpose.

Rather than using the relay to interrupt power to your EVSE, I'd just open up your EVSE and access the pilot wire. Configure it such that the pilot wire is broken when current flows to the dryer and closed otherwise. This way you won't need a big relay capable of switching a lot of current, and you won't be needlessly power-cycling your EVSE and/or dryer all the time.
 
Thanks for the feedback! I'm glad others have enthusiasm for this idea as well.

Contactors: if anyone has ideas of one that would work please let me know.

Dryer vs drier: You are right. The word drier is for "Although we both fell in the lake my clothes were drier than yours were" vs the machine which is a dryer. http://grammarist.com/usage/drier-dryer/" onclick="window.open(this.href);return false;

My particular drier is very old school and has no electronics at all. It probably draws 0.01 amps or less while not doing anything, as opposed to even the "cool down" cycle of the machine which is probably 5a or more. So no problem detecting that.

"switching dryer every night": I have two small kids who barf on things regularly, so there is almost always something to wash ;-) Realistically we probably use the dryer only 2-3 days a week but it feels like every day.
 
This was one of the options we explored when installing our EVSE. Our options were limited due to load calculations. The electrician called it a "load switcher", or "transfer switch". This was to be a manual switch.

Ultimately our city would not sign off on the permit so we came up with another option that worked.

I know I've run across someone doing this type of switch (manual) on the forum; probably back in early 2011 or so.
 
So I think a simple low cost and low complexity solution would be to make a Y junction box (dryer plug into a junction box that is connected to a second junction box where each have 30 amp plugs).

Then use an off the shelf current sensor that has a switch in it for when there is current, should be easy to find as I have one laying around. Unfortunately integrating it into the EVSE is only simple if the EVSE supports an external input to control it or it's an OpenEVSE.

Whatever you do I would not want to cut power to the EVSE when it was under load as the car may not like this so the fact that you have a mechanical dryer if it were to get interrupted it would start back up once the car was done.

So I guess in your case since I doubt you'll be able to easily control your EVSE you'll need a relay/contactor to cut power to the dryer.
 
I think fooljoe's suggestion of opening the pilot is the best solution. You could have the current sensor open the line.

This has the advantage of a clean shutdown with no glitches. The OpenEVSE RTC switches to -12V which when you consider the diode in the charger is the same thing.
 
you cannot have the dryer and the evse on the circuit at the same time. It creates the possibility of overloading the circuit. What I would do is use a Double pole, double throw relay in a box that switches the line to either the evse or the dryer. Connect the control coil to a cord connected to a 5-15 plug on the other end. Plug that end into a programmable wall timer. Figure out the times you want either to work and set the timer.
 
johnrhansen said:
Plug that end into a programmable wall timer. Figure out the times you want either to work and set the timer.
You could also use one of those countdown knobs used for things like jacuzzi heaters at hotels. Assuming you can get one with a long enough fuse, i.e. 90-120 minutes you could just crank that, set the dryer, and then when it runs out it will click back over to the EVSE. This would be more appropriate to the dryer use-case than a programmable timer and wouldn't prevent a charging opportunity if the kids don't barf one day.

Edit: http://smile.amazon.com/Intermatic-FF6H-6-Hour-Spring-Brushed/dp/B000B8WJZU/ref=pd_sim_hi_7?ie=UTF8&refRID=1TVK5S512PD0FHXE0T2H" onclick="window.open(this.href);return false; or something like this might work too... http://smile.amazon.com/Leviton-LTB02-1LZ-Incandescent-Resistive-Inductive-15-30-60-120/dp/B00313JXBK/ref=smi_www_rcolv2_go_smi?_encoding=UTF8&*Version*=1&*entries*=0" onclick="window.open(this.href);return false;
 
Putting the power lines on a DPDT relay (would be a great application for the relay the Juicebox comes with) would work okay, and I like the countdown timer idea. The problem I foresee is maybe someone who's not so EV-savvy (wife?) comes along and decides to switch over to the dryer while you're in the middle of a charge. Then you get a hard shutdown of the power to the EVSE and error codes in your EV or possibly even real damage to your charger (although I'm sure that's very unlikely.) Plus I could imagine the wife complaining about the dryer not working because she forgot about setting the timer, or it's a time when it wasn't preset for the dryer to be on, etc.

While switching the power lines is the "pure" solution of guaranteeing that only one appliance is powered at a time, I'm sure using any such device would never pass an inspection anyway. Cutting the pilot when the dryer pulls current is really just as good of a guarantee that charging and drying won't happen simultaneously, and it gracefully stops charging that might already be happening. Plus you don't need a large relay and you don't have to set any timers or throw any switches manually.
 
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