On Sat, 11 Nov 2017 20:37:06 -0800 (PST), whit3rd
wrote:

On Saturday, November 11, 2017 at 12:17:01 PM UTC-8, Clare Snyder wrote:
We have a Canavac XLS970 central vac unit ( replacing our original
Beam) with an 8.4 inch dual stage Ametec-Lamb motor rated at 13.4amps.
It is running on about 50 frrt of AWG14 Romex on a 15 amp breaker.

The usual recommendation is to aim for no more than 2% voltage drop in
your connecting wiring.
14 ga copper reaches 2% drop in 30 feet, at 15A. So, your motor
might just be voltage-starved and trying to stall, when the breaker
pops.

The Kill-a-watt indicates a maximum draw of 12.3 amps, and a running
voltage of 115 volts with the hose connectes,and 114 running "open
ciircuit" or "full load". With the vac turned off the line voltage is
117. A 2% drop would be a drop of 2.2 volts, for a reading of 114.8,
and it's pretty difficult to "stall" a "universal" motor driving an
air turbine
The same motor, if it were REALLY 240V would only take half the
current (7.7A at 240V is the same motor power as 13.4A at 120V),
and thus by convention would be OK for 60 feet of wire,
so you might want to enquire with the manufacturer to see if the
motor can be re-strapped for the higher voltage.

It's a "universal" motor, iggy. They are NOT multy-voltage
convertible by their very design.

In other words, in addition to getting the 240V breaker, consider upping
the motor voltage as well.

Not possible. as noted above. A 240 volt and a 270 volt version are
avaiable (at about 50% higher price than the vacuum itself - so not
going to happen)
If the high-mag 15 doesn't solve the issue a high-mag 20 will take
it's place.

For near-term, check all the screw-down connectioins, if one is
loose THAT could be causing the motor to stall, and it only takes a quarter-turn
of the screw to fix. Don't get shocked!
All been checked, from one end to the other - (only 2 connections -
at the panel and at the outlet)
The entire house just went through a COMPLETE electrical inspection
when the panel was replaced under 2 years ago. - and that's on top of
my inspecting the circuit due to this issue.

Square D is aware of this problem and recommends the "high magnetic"
breaker as the solution

My point in this post was to bring to the attention of otherwise
knowlegable folks on this usenet group that double pole QO breakers
were ALL High Magnetic - so using 1/2 of the double pole breaker may
solve nuisance trips for "high performance" devices with high initial
startup draws - like compessors, AC units, central vacs, etc.