Have you considered using a standard HVAC contactor and a delay on break timer? Seems like it would be a lot simpler and cost less to build. 4 parts total:
1: 24vac transformer
2: Delay on break timer (most are either 3 or 5 minutes fixed)
3: Standard HVAC contactor
4: Current switch (same as you are now using to break connection above certain amperage, you would use the NC contacts instead). You could also use a standard HVAC hard start relay if you could find one with the amperage you required.

Seems like it. But, as I've posted a few times before, they had no interest.

IMHO, the problem is firmware related. If you press the High Power on the remote,
or try to change the room temperature by more than 2 degrees, the controller goes nuts
and ramps everything up to full RPMs.
Shortly thereafter, one the outdoor unit's sensors activates and shuts it down.
You can see the sensors at the bottom of this pic. High Pressure switch and Over-Load relay.
http://i46.photobucket.com/albums/f1...CL/outdoor.jpg

My hack (upper right corner of this pic) stops the run-away before any damage can be done.
http://i46.photobucket.com/albums/f1...L/Untitled.jpg

The High Pressure switch and Over-Load relay get to take a break.. :)

So the objective of your circuit is to cut the juice to the compressor before the overload/high pressure switch activates? The 555 timer is a delay for the auto reset or to bypass the current switch during startup?

Yes, I don't want full RPMs, since I believe that my first system reached such
high pressure, that it blew a hole in the copper and all the R410A leaked out.
Here's the repair postings.
http://ecorenovator.org/forum/geothe...r-project.html

The 555 timer keeps the power off for about a minute, and simulates a grid failure.

At the end of a defrost cycle, the firmware always calls for full power,
which can be higher than 3.6KW. Which would normally cause
over-pressure or over-load.. (or a copper tube to burst).

By shutting it down at 10A and letting it recover, there are no high pressures
or over-loads..
During the typical defrost, the 555 will trigger once or twice and then,
the ice is gone and everything back to running normally..

Sounds like poor design that the copper would bust before the overlaod/pressure switch kicked the compressor off. Copper typically requires a LOT of pressure to bust, normally the compressor would trip on overload or throw a breaker first. Have you monitored the pressures when the unit is drawing excessive power? Have you considered replacing the pressure switch with somehting that has a lower pressure cutoff?

IIRC, when I was doing the repair job, I saw some pretty high pressures.
I was using a short loop (no indoor unit) for my tests.
I had to use the Cooling mode, because heating mode pressures were getting way up there..

I'm not sure about the design, but this basic model might be really old,
and when they upgraded to high pressure R410A, they might have
skipped upgrading the copper for the higher pressure..?.


Not going to change anything yet.. Back when I was an engineer, I learned a lesson.
If a device is working, don't 'fix' it..

These Sanyos are old models, but they are working very well (right now)..