On 10/31/2013 08:36 AM, Pavel314 wrote:
Our greenhouse heater wore out after a number of years so we bought a
replacement. It's essentially the same heater except that the new one
is a different color and the plug is a different configuration. The
old one has one round pin and two flat blades, with the blades at an
angle to each other and above the round pin. The new one also has one
round pin and two flat blades but the blades are lined up with each
other, so I have to replace the receptacle with one that matches the
new plug. Not a major project, just a minor annoyance and expense.

I've seen other 220 volt plug configurations; some have an L-shaped
blade instead of the round pin, others have four blades in a circular
pattern which lock when turned, etc. Is there any practical reason
for all these variations?

Yes, different standards and current capacities:

http://www.mikrocontroller.net/attac...eceptacles.gif

Jon