Easy startup for A.C.

theoldwizard1 wrote:
People are hung up on the fact that the Easy Start is mounted directly to the starting capacitor and A/C motor windings. IT DOES NOT MATTER WHERE IS MOUNTED !

If it didn't matter, Micro-Air would have simply instructed users to connect it to the AC supply for the air conditioner - at any point.

There would be no need to open the A/C shroud - or even any need to go up on the roof.

You really think they'd make the installation process any more difficult than necessary?

THE LOCATION MATTERS.

The control circuit needs to switch in (relay?) a small value (LARGE power rating) resistor (probably a piece of copper wire) "in line".

NTC thermistors were often used rather than a high wattage resistor.

I believe that the MicroAire attached to the AC also provides some timing lockouts to prevent fan and compressor coming on at the same time etc. More options available when it’s wired in directly than just at post. Thats probably why SoftStarts ads refer to AC mounted as reducing surged current by 70% while shore post mounted only reduces 50%.

For you DIY EE, the "block diagram" on making your own easy start would be something like this :c

Detect that out have an "abnormal" current draw. Either a current sense transformer or a full wave bridge (filtered, into a resistor divider into you control circuit) across the "hot" lead.

The control circuit needs to switch in (relay?) a small value (LARGE power rating) resistor (probably a piece of copper wire) "in line".

Don't worry too much about the "resistor" power factor, it is only going to be in line for about 1 second.

After that 1 second, the relay open (the NC contacts close) and "ob la di, ob la da, life goes on" and any addition over current is handled by the main fuse/circuit breaker.

Like any good DIYer, there needs to be some "trial and error". Try some current detection circuits (the current transformer could be like 10 turns around the hot wire). If you use a relay, the contacts need to be seriously over rated (100A minimum). The "speed" of the relay could be an issue. You don't want to current limit too long as that starting capacitor is going to discharge one it is full enough.

wa8yxm wrote:
EZ Starts are very easy to install.

This plug in unit looks like it might be a power factor correction device Those are good too but I'm not sure they would qualify as an Easy Start.

A "true" easy start/soft start simply limits the inrush current required to charge the starting capacitor. This can be done with a current limiting resistor or by modifying the shape of the wave (shrink/chop).

People are hung up on the fact that the Easy Start is mounted directly to the starting capacitor and A/C motor windings. IT DOES NOT MATTER WHERE IS MOUNTED ! It just needs to detect that there is a sudden spike in current above a certain amount and then limit that current ! (This "spike" is so short and so fast that a typical fuse or circuit breaker can not respond.)

I remember "ELI the ICE man" ! My concentration was on digital circuits so I did not retain much about power electrical. I know industrial locations get a surcharge from the PoCo it there power factor is out of whack. I always thought power factor correction was a 3 phase "thing".

Good ole ELI.

Met him in 1967 in Navy electronics school.

ELI the ICE man

Say that to a young EE today and they are clueless what you are taking about. That phrase must have been a 70s thing.

They have an app for that though

I preferred the autoformer to the easy start.

EZ Starts are very easy to install.

This plug in unit looks like it might be a power factor correction device Those are good too but I'm not sure they would qualify as an Easy Start.

I've used them with some hardware (A dehumidifier) and it made a significant improvement in the unit's overall power needs.. A re-charge helped it to work better too (This is a refrigeration device like an air conditioner) back then you could by what you need to make it rechargeable at a hardware.

But will it work for "Soft Start".. Well.. Perhaps a little..
(The PF-correcors work by adjusting voltage to bring Voltage and current into phase.. Normally on a Motor (like an air conditioner) ELI the ICE man plays havoc with the relationship between Voltage and Current (ELI Voltage Leads on an Inductive load) so the correction device lowers the voltage or it can add some ICE (Current leads in a Capacitive load) Or Capacitance.

I do have a 2nd hand story about that.

Skibane wrote:

theoldwizard1 wrote:
In theory, a easy start could be wired as a dog bone between the post an the RV power cord.

No, it connects to several specific points inside the A/C, including the compressor run capacitor.

As a retired Electrical Engineer, I know it can be done !

Remember the old saying, "There is more than one way to skin a cat !". All you have to do is limit the "in rush" current used to charge the starting capacitor.