Wednesday, July 27, 2011

DIY: Hardwiring power protection to your RV.

Power surge protection is a cheap insurance for the RV in the long run. Although power surges are not very common nowadays, but when it happens, I know my electronic equipment's are protected. I opted for Progressive Industries EMS-HW30C hardwire unit with remote display, as pictured below. It is also available as a portable unit. The EMS-HW30C is a power protection all in one unit, it has a built in voltage protection, a time delay for the AC compressor, a 3 mode surge protection, reverse polarity protection, open neutral protection, open ground protection, AC frequency protection, and accidental 220 volt to PE EMS-HW30C.

Hardwiring the unit is pretty straightforward. Link to unit manual and installation instructions...EMS-HW30C Manual.

There is not much room for installation in RT Agile SS, I installed mine next to the automatic transfer relay unit. To hold the control unit in place, I use Scotch plastic Velcros. It's a special Velcro type fastener, both hooks and loops are made of plastic and they don't move once fastened. 

The unit was installed before the transfer relay to protect it, although you can install it after the transfer relay to protect both the generator and shore power. Progressive Industries recommended the first, reason is the generator usually has it's own protection's your choice. 

Wiring Diagram

Click on the picture to enlarge.

Plastic Velcro fastener

Automatic Transfer Relay removed.

Inside wiring of EMS-HW30C

Wiring connections of Automatic Transfer Relay.

Velcro attached to back of EMS-HW30C unit

Placement of ATR, Subwoofer, and installed Surge protector unit.

Remote display unit (Close-up). Note the error code card next to it. Comes handy when you need it.

Remote display unit


  1. Hi,

    Were you able to splice the PMS into the existing cable to the transfer box, or did you need an additional length of cable from the PMS to the transfer box?


    1. Hi Bob,
      I did not use an additional cable, I was able to splice the PMS into the existing wire, yours could be different though.

  2. I mounted the Display on Velcro behind the stove facing out the window. I did this for two reasons: 1. So that I can see the display when hooking up without having to go into the RV and 2. So the display did not light up the interior in the middle of the night. Since I mounted it with Velcro I can pull it off and lay it on the counter anytime I want to see the display inside. It is a bit hard to see through the tinted glass in bright sunlight. As for the PMS I needed to use 18” of additional 10/3 wire because I mounted it slightly differently. You can buy the wire by the foot at Home Depot.


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