Page 43
VP-X Installation and Operating Manual
Rev. D (August 5, 2020)
5.21c Alternator switch
If installing a single alternator, the alternator switch can be a simple on/off
switch (SPST) wired to one of the inputs. You then associate (in the setup
menus) the Primary Alternator pin (J12-11) with that switch input.
Switch Input X
VP-X
Single Alternator Switch Inputs
If installing primary and backup alternators, you should use a switch that
mechanically allows either one to be on, but not both at the same time, and
has a center off position. We recommend a SPDT or DPDT ON-OFF-ON
switch for this purpose. The VP-X does not allow both alternators to run
simultaneously.
Switch Input Y
VP-X
Switch Input X
Dual Alternator Switch Inputs
In the designs above, when you turn off the master switch the alternator
stays running and may still provide power to the bus. You need to manually
turn off the alternator switch as well to shut off all power.
In the designs below, shutting off the master switch turns off both the battery
contactor and the alternator. This shuts off all electrical power with one
single switch (except for backup circuits and backup batteries as described
elsewhere in this manual).
How it works:
When the master switch is turned on, one pole of the switch
provides a ground to the battery contactor (which closes) and the other
pole provides a ground to the alternator switch. When the alternator switch
is turned on it grounds the alternator switch input pin which then turns on
the alternator. Turning off the master removes the ground from the battery
contactor and from the alternator switch which then causes the VP-X to turn
off the alternator.
VP-X
Alt Switch
Master
Switch
DPDT
on-on
SPST
on-off
To Battery
Contactor
J2, Pin 1-10
See PPS installation manual
for preferred method
Wiring for single alternator
VP-X
Alt Switch
Master
Switch
DPDT
on-on
SPDT
on-off-on
To Battery
Contactor
J2, Pin 1-10
See PPS installation manual
for preferred method
Wiring for dual alternators
• Wire the alternator switch(es).
5.21d Boost pump switch
If installing a single-speed boost pump (for most Lycoming, Jabiru, and Rotax
engines), the boost pump switch can be a simple on/off switch (SPST) wired
to one of the inputs. You then associate (in the setup menus) the boost pump
power pin with that switch input.
Switch Input X
VP-X
Single-Speed Boost Pump Switch Input
If installing a two-speed boost pump (commonly used on Continental
engines), use a switch that mechanically allows either one to be on, but
not both at the same time, and has a center off position (SPDT ON-OFF-
ON). A locking toggle switch is recommended so that the high boost does
