Installing an iVAC Contactor
August 11, 2020
iVAC Technical Support: 800-775-5579 Ext. 4
Page 1 of 6
For larger dust collectors or ones that draw too much inrush current at start up you will need to install
an iVAC Contactor along with your Pro Switch or Switch Box. Without the contactor the amount of
current drawn by your dust collector will destroy the relay inside the iVAC Switch. From this point on in
this document, iVAC Switch means either the Pro Switch or Switch Box.
Contactor is a fancy word for a really big relay and, like a relay, a contactor has two inputs and one
output. The first input is for the contactor coil which generates the magnetic force required to close the
contacts. The second input is for the power to run the dust collector and the output delivers the power
to the dust collector when the iVAC Switch tells the contactor to close its contacts. iVAC supplies the
control cable that connects to the contactor coil. You must supply the cables for the power circuit.
The iVAC Contactor has a 115 volt ac coil so you must use a 115 volt Pro Switch (or a Switch Box) to
control it. The 115 volt Pro Switches in production at the time of writing this article are the S11520-A-
NA and the S11520-A-NA-MRT. Either of these is suitable for use with the iVAC Contactor. Any of the
obsolete Pro Switches whose model number begins with S115... is also suitable. The MRT option is for
larger dust collectors. Before ordering a Pro Switch whose model number ends with MRT be sure you
understand this option and that you want it. See the document “
High Power Dust Collectors and
” under the Tech Advice tab on the ivacswitch.com website for an explanation of
this option.
It is important that you not add too much additional cable to the dust collector power circuit when
installing a contactor and that you use cable of adequate size for your dust collector. A good rule of
thumb is to use cable of the same type and wire gauge as supplied with your dust collector and to keep
the additional wire to less than 10 or 12 feet long. If you have to add more wire it’s a good idea to use
one wire gauge larger than that supplied with your dust collector. If you have to add more than 25 feet
of cable you should consult a licensed electrician to be sure the wire used is adequate.
The contactor coil draws very little power so much smaller cable is sufficient for this purpose and it can
be quite long without causing any problems. If you need more cable than iVAC supplies just add a 16
gauge extension cord.
Where you install the contactor in the dust collector power circuit depends on whether or not your dust
collector has a magnetic switch (often called a magnetic starter). Some dust collector manufacturers
use an off the shelf magnetic switch and others build the same functionality into their proprietary
control circuitry. If your dust collector has a remote control or a timer it almost certainly has the
magnetic starter functionality built in.
The Magnetic Switch Test
A sure fire test to determine if you have a magnetic starter or not is to plug the dust collector into power
and turn it on. While it is running, pull the plug out of the wall socket. Do not turn the dust collector
off. When the dust collector has stopped plug it back into the power source. If the dust collector starts
