Do I need a breaker

[Dremel]

Old layout was main plug, 30 amp breaker then distribution.

New plan is main plug, progressive EMS, then distribution panels 30 amp breaker.

So, is that good, or do I need a breaker before the EMS ?

the EMS should shut down on a over or under voltage. And the breaker in the distribution box is next.

[daleyocum]

Usually you'd have a main breaker before the power gets to anything else. Whether it's worth it in your case would be for you to decide. After all there is a breaker outside of the trailer in the power box.

[rmkrum]

EMS is usually installed in the line between the pedestal and the 30 amp main in the trailer. Keep in mind breakers are there to protect the wiring. The EMS is designed to fend for itself. You don’t need an extra breaker before the EMS. It’s smart enough to shut down for over/under voltage, and the relay in it is plenty big enough to pop the pedestal breaker on over current conditions if your Main doesn’t.

[OTRA15]

Thanks Rich for those details . . . good confirmation of my gut feeling.

Peter

[JohnTF]

Breakers should on the load side .
The EMS is meant for the source side .

The load side should never exceed its rated value - if over it BREAKs
The EMS is not spouse to allow anything outside of its set values Min. / Max - from the source , if it sees a value above or below , it shuts down the source .

[cazual6]

IMHO: Breaker first.

Look at your house. From the POLE it goes to a MAIN Breaker, then individual Breakers then to your other stuff.

[rmkrum]

Originally Posted by cazual6

IMHO: Breaker first.

Look at your house. From the POLE it goes to a MAIN Breaker, then individual Breakers then to your other stuff.

Please note that house wiring is NOT the same as Travel Trailer or RV wiring standards in MANY details. RV wiring is to a different standard for MANY good reasons.

Pedestal breaker, to power cable, to internal EMS, direct to RV Main breaker is one correct way to wire an RV. Alternately, pedestal breaker, to portable EMS, to power cable, then direct to RV main breaker is also correct. Nothing else is necessary.

Note that there is NO ground to neutral bond connection allowed in the RV, and in a house, the ground to neutral bond is right there in the power panel. A very critical difference that the EMS is designed to check as a matter of safety. Note that the ground/safety earth connection is bonded DIRECTLY to the frame and shell of the trailer, and the neutral is floating. That is for safety. The EMS verifies that is properly connected, or immediately disconnects all three conductors in the shore power cable, ground, neutral, and Hot for safety.

The EMS is not there to only prevent over and under voltages, it tests for wiring errors that could connect the incoming hot line to the shell of the RV, and thus possibly kill someone standing on the ground and touching the trailer.

The reason for my strongly recommending the use of an EMS wired properly as above, either portable or built-in, is that MANY campground power pedestals are not wired correctly and can be dangerous to an unwary camper or family.

EMS and surge suppression is NOT just an added benefit--wiring errors in the campground or pedestal, and they do happen, are just waiting to cause an incident, injury or death. That's the bottom line..personally, I don't fully trust campground power unless my EMS and a multimeter check verify it is good.

Once bitten, twice shy, and believe me, in my rather long career in assorted workplaces working with all kinds of power distribution systems, I'm very careful.

[OTRA15]

Originally Posted by Dremel

. . .
New plan is main plug, progressive EMS, then distribution panels 30 amp breaker.
. . .

Would you please clarify whether you are planning on a portable plug-in Progressive unit or one installed in the trailer? That might simplify the discussion.

Thanks,

Peter

[OTRA15]

Originally Posted by rmkrum

. . .
Pedestal breaker, to power cable, to internal EMS, direct to RV Main breaker is one correct way to wire an RV.
. . .
Alternately, pedestal breaker, to portable EMS, to power cable, then direct to RV main breaker is also correct.
. . .
Nothing else is necessary.
. . .

Thanks for the additional details.

Pretty simple stuff, really.



Peter

[Dremel]

Putting in an INTERNAL EMS

"Pedestal breaker, to power cable, to internal EMS, direct to RV Main breaker is one correct way to wire an RV. Alternately, pedestal breaker, to portable EMS, to power cable, then direct to RV main breaker is also correct. Nothing else is necessary."

So I was planning
Pedestal breaker
to power cable
to internal EMS
direct to RV Main breaker ( the 30 amp breaker in my distribution box that then goes to the other breakers )

So I am hearing that there is NO need for an additional 30 amp breaker before the EMS inside the Airstream.
I thought it would be redundant, but wanted to hear.

[rmkrum]

Yes, your understanding is absolutely correct!



Besides, there is no really good way to add a redundant and unnecessary
breaker...

[Paprika]

"You don’t need an extra breaker before the EMS. It’s smart enough to shut down for over/under voltage"

Maybe I'm misreading, but this statement seems to imply that an EMS can do the job of a circuit breaker. But an EMS only protects against "surge, voltage, polarity and lost/open neutral protection" (quoting from PI's EMS-LCHW30 product description)--not against excessive current. It cannot do the job of a breaker.

[rmkrum]

You are absolutely correct to a point. The EMS does what is described. An extra breaker will not add any more protection. One at the pedestal protects the shore power cable on that end, and the main breaker in the panel protects against overcurrent at the panel. No need for an extra one anywhere.

The EMS/surge protection box is there for safety checking wiring connections, and not turning on if it sees something wrong. Further, it will shut off if it detects over or under voltage at any time. The surge protection is designed to absorb a surge, and if it is bad enough, blow the pedestal breaker.

That said, I note that the progressive EMS I have has an obvious current measuring toroidal transformer in it. I don’t know exactly how it is utilized, but it goes around the hot wire as specified in the installation instructions. At this point, I suspect it’s part of how the microprocessor in it detects wiring fault conditions.

And no, although I’m a geek, I don’t have the time to derive a schematic of the board or disassemble the code in the controller chip....

[Zil]

You are misreading. There is still a breaker after the EMS to protect the RV wiring. The same breaker that was originally there.

[Dremel]

Just to let readers know, My system is NOT the original 1969 version.
I will have a main breaker, it is in the distribution panel . First thing after the EMS.

The original AS layout had a main breaker on the wall next to the shore line plug in. I am eliminating that extra box.

The post was to see if I for some reason needed to protect the ems or the 4 feet of wire between the ems and the distribution box.

[OTRA15]

No, assuming that distribution panel has the correct master circuit breaker for the feed to the Airstream. [IMO]

[rmkrum]

Ditto. The breaker right at the power input can be eliminated. Just be sure to use the proper gauge wire (#10 or bigger) between the power input, the EMS, and your new main panel.

I'd suggest using stranded marine-type wire. No, it's not real cheap, but it is sealed against moisture, tinned to prevent corrosion, and stranded for flexibility. Over that short distance it's worth the money.

The usual solid wire Romex that Airstream uses can break due to vibration at the point the copper is usually nicked when it is stripped to make connections. Use a stripper that has the exact right size ROUND hole to strip the wire--it is less likely to nick the copper.