shore power inlet front of 5ver, EMS protection

lockmup68 · August 10, 2017

2007 Teton, has gen prep package (automatic transfer switch and wiring to the location of where gen set is mounted).

Just wanted to make sure I'm not under thinking this, I have the gen prep package, ATS is already installed, the wiring is in a junction box near the front of the basement. To add a front shore power plug, I think I simply wire in new shore power plug to the existing wires in the gen prep junction box. What am I missing?

2nd question, I have a progressive industries hardwire EMS. I assume this should be wired in AFTER the automatic transfer switch, that way either power input source (front or back input) will be protected.

I want a front plug for several reasons, namely, the genset is on the truck vs. mounted on the trailer, and secondly, many power pedestals are now closer to the front of the trailer vs. the rear where you want to park in the spot. I hate pulling the 50 amp extension cord as it seems I am frequently just 3 feet short in cord length.

Thanks,

TheLongWayHome · August 10, 2017

From my understanding of what you are trying to do, others have done something similar. Jack Mayer has a two shore power sources (front, back) going to a transfer switch and then through the Progressive Industries EMS (EMS-HW50C). I'm sure he will comment.

I'm looking at a new coach design and would do something similar. My only concern is having the TS (PD52) as a Single Point of Failure (SPOF) before the EMS systems. Could use two EMS systems, one of each source line, before the transfer switch. That would provide EMS protection, power usage monitoring to both lines, but more expensive. So curious on what other power distribution approaches people suggest (Jack, oldjohnt, etc.)

Kirk W · August 10, 2017

1 hour ago, lockmup68 said:

To add a front shore power plug, I think I simply wire in new shore power plug to the existing wires in the gen prep junction box. What am I missing?

The only negative that I can think of for this approach would be that when you use power from the secondary source to the ATS it means that the coil of the ATS is energized for as long as you are using that power source. For most users that is of little consequence because a generator is not typically used constantly for months at a time, while the shore power cord might be. The effect could mean a somewhat shorter lifespan for the ATS but I have never seen any data on that so I doubt that it would be very significant, but might be something to consider.

1 hour ago, lockmup68 said:

2nd question, I have a progressive industries hardwire EMS. I assume this should be wired in AFTER the automatic transfer switch, that way either power input source (front or back input) will be protected.

2

That is correct in order to be protected when using the front cord. While most generators are supposed to not need such protection, I'm not sure that I entirely believe that and I know that I would want it in the circuit when using the front cord to connect to a shore power pedestal.

Ronbo · August 10, 2017

You have it correct

Bobi and Dick McKee · August 10, 2017

I have had 2 rigs over 6 years and that is exactly how they are wired with no problems.

Jack Mayer · August 10, 2017

Both shore powers to an ATS, rear shore primary. Then output from ATS to Progressive, then from progressive to loadcenter. No issues with that at all....it is done all the time.

GeorgiaHybrid · August 10, 2017

I have a 50 amp plug in the front as well as the gen set on one transfer switch. The plug is primary and the gen set is secondary on that switch. This is then run to the rear of the coach as a secondary input on the main transfer switch. The rear 50 amp connection is the primary on that transfer switch. From there it goes to the Progressive Industries surge and then to the load center. That way I can have front or rear hookups or run the gen set without changing anything.

oldjohnt · August 10, 2017

If I'm correctly understanding what you're doing, it works for me as the fine gents above, and I'm over safety conscious remember.

As you use shower power much more then the Genset, I see that obviously as PRIMARY input to the ATS with the Genset as Secondary (covers Kirks valid concern) and ATS output to the EMS (so genny or utility is protected) then to your distribution panel.

Is the ATS a two or a three pole?? IE does it switch Neutral as well as the two hots ?? I'm assuming the Genset, as most larger units, has a bonded Neutral.

John T

Mark and Dale Bruss · August 10, 2017

ATS switches three wires. Many ATS relays are powered to make contact, a relay for each source. Very few are double pole where off is shore and on is generator.

We had two input connectors with a ATS between them. The output went to the ATS for the generator. Our EMS plugged into the power pole.

We used an ATS between the two input connectors so that when one was in use, the other was dead to prying kiddy fingers.

oldjohnt · August 10, 2017

1 hour ago, Mark and Dale Bruss said:

ATS switches three wires

Mark, that would be my expectation as necessary to switch two hots and the Neutral on a 50 amp 120/240 system. That way single point grounding is maintained and the Genset has the typical for larger units bonded Neutral, works for me. Its possible to switch only the Hots but that's another story. Indeed if two shore power connections are tied together you need it configured so no live pins might be exposed YIKES

John T

ALLOY · August 11, 2017

If the EMS is before the TS won't it protect the circuit board in the transfer switch.

Some TS use terminal strips to connect 6ga wire. On the other side of terminal strip fom the 6ga there are 2-10ga wires. If the load is not balanced the neutral may carry more than the 10ga is capable of.

mptjelgin · August 11, 2017

NuWa offered this as a factory option, with front and rear sockets for the 50 amp power cord. Both sockets went to an ATS, with the EMC wired in after the transfer switch. Very handy...