I can confirm that you can easily see past the impellor on this pump. This
is actually an indication that the impellor is not optimized for the pump
casing, however it is adequate to do it's job very well. This also allows it
to allow flow to past even if it ever seizes, although I don't expect that
to ever happen again since I've made a very small mod to correct this.
After reading Davies Craig reply I'm considering a series installation as
it would allow for redundancy without the addition of another possible
failure mode from the T/flapper valve. My only concern is that I've worked
hard to reduce or eliminate all possible restrictions to my system and am
loathe to introduce another by having a standby pump in the line. However it
would be simple for me to measure any change as I have a flow meter.
As for wiring options, I would recommend having the main pump controlled by
the controller and a second pump controlled by a temperature switch, but
with a bypass switch allowing manual activation on 1 or both of these pumps.
Everything that I removed from my old mechanical system totalled 12lbs, so
even with an additional pump weight is still half.
In order to take best advantage of this system an adapter block is required
to allow complete removal of the waterpump. I made my own which was a bit of
work, but somebody with a mill could probably make them easily. (If I wasn't
so darn busy I'd buy a mill and make a bunch to try to pay for it:-) Meziere
make a nice looking one, but it requires 2 return hoses and appears to be a
little restrictive from the picture.

S. Todd Bartrim
Turbo 13B RV-9Endurance
C-FSTB
http://www3.telus.net/haywire/RV-9/C-FSTB.htm

   "Whatever you vividly imagine, Ardently desire, Sincerely believe in,
Enthusiastically act upon, Must inevitably come to pass".

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