DIY Inverter A/C Compressor
 

An old thread and something Xringer posted on another thread got me thinking. People spend a lot of money on Inverter A/C's but couldn't we Hack a window A/C compressor to do the same thing?

It seems so simple, just buy something like this :Amazon.com: MLCS 9410 20-Amp Heavy Duty Router Speed Control: Home Improvement

Then open up the A/C reconnect the compressor, and maybe the fan too? to the controller and you could run the compressor at any speed you desire. Getting longer run time at lower power or ramping it up when needed.

Adam

I asked Xringer to actually try hooking up his router speed controller to a sump pump to see if it worked. I don't recall hearing back from him...

I'm quite sure it will not work. Sump pumps and AC fans and compressors are AC induction motors. They rely on the fact that the current is alternating 60 times per second for their operation. They are cheap and strong and very reliable, but are not controllable by a simple router speed controller.

Routers use a universal motor that has brushes and a commutator. They are able to be controlled by a simple speed controller.

There is a device that might work for you, but it is not cheap... it is called a Variable Frequency Drive. They are usually for three phase motors, but I have seen them advertised for single phase motors, too.

They usually run about $300. You might find something on ebay cheaper.

If you don't believe me, Harbor Freight sells router speed controllers for about $25. Hook one up to your AC and see what happens...

Pretty inexpensive science experiment, I'd say.

-AC_Hacker

I'm not sure why you'd want to slow the compressor in your AC unit down. The sealed units are designed to achieve pressures at a certain RPM, with the motors efficiency similarly designed around that speed. Slowing the compressor, it seems would throw the entire system out of whack. Your efficiencies and power consumption would change drastically. You could if you wanted to experiment look for a belt driven compressor and use a DC motor to vary the speed.

mike

AC Hacker I think your're right. After doing more searching I learned basically what you just said. If I had a control laying around I'd try it out but I don't.

Vmike, the reason behind it would be to attempt to achieve something similar to the way a minisplit operates. Actually come to think of it, what's so efficient about slowing down the compressor like mini splits do?

Adam

You might be right. The pressures do bounce around somewhat with my Inverter compressor.
http://ecorenovator.org/forum/geothe...html#post14636

But, the system might have been designed to operate efficiently at different pressures.

Or, maybe something is seriously wrong with my Sanyo..?.

I have thinking about trying it on my drill-mill.
http://users.rcn.com/rlt59/Lathe/Jepeto.jpg
But, it's not high on my list yet. It's been a very busy summer so far.
My next projects are solar PV related & I still need to repair that old Sanyo.

Cheers,
Rich

Xringer,

The box on top of your mill is the step-pulley speed control set-up. Something like this is what an induction motor needs for selecting different speeds. If you really want to control speeds continuously, you will need to either get a variable frequency drive (at which time it would be best to replace your existing motor with a 3-phase motor), or replace your motor with an appropriate DC motor and then get a DC speed controller that is compatible with that motor.

In any case, your router speed controller will not work with your existing setup...try it for yourself.

-AC_Hacker

You may be correct. The mill-drill motor is an induction type, (with startup cap).
I just used a flash light and mirror to check out the blower motor
on the old wood stove (that's been sitting unused in the fireplace for many years).
And, it looks like induction type, but no capacitor. I've used a lamp dimmer to control it (works fine).

I don't have a router, and I wonder what kind of motor they use.?.
I'm assuming those are regular brush type motors. Like a circular saw.

Variable speed hand drills use brushes, and I'll bet the trigger unit contains
a circuit, much like a light dimmer..

If that motor is actually an induction motor, it relies on the alternating current to make it go. If it is an induction motor, using a light dimmer or a router speed controller will not change the speed, just reduce the torque.

There is an induction motor type called 'shaded pole' that does not use a cap to start, but it is still an induction motor and will need a variable frequency drive for speed control.

This from wikipedia:
-AC_Hacker

You said it will run at reduced torque with a light dimmer or similar controller, reduced torque would cause a compressor to slow down, just like Xringer found, does this damage the motor? Or could this still be a viable, although not "proper"(is any of the things being done with a/c's in these threads?) method for motor speed control?

Adam