Ems

[Scott'n'Wendy]

I'm going to pull the trigger on an EMS for the trailer soon. I'm partial to the portable, 'plug into the post' style. Just because in my career as an electrician, you don't want your sacrificial devices installed in the thing you are trying to protect.
Granted, in my career it was 1000's of volts not 120/240. But to those of you that have hardwired EMS's, why? Other than theft I'm not sure I see an advantage. School me.

[Country Campers]

Peer pressure for me. I have had 3 other RV's and countless of others that we camped with over the years that have never had any kind of electrical protection. After joining a Forum after our GD purchase and reading how others have had issues I thought I would get one. I have the hard wired installed under the bottom drawer in the hutch so I have easy access to it and the power panel if there is ever a need to remove it from the system in the driving rain sometime. We have just started our 4th year and have yet to have an electrical problem that the EMS has shut down power. I think with the aging infrastructure at most campgrounds this may be a good investment. I like the hardwired one as I do not have to remember to plug it in or even unplug it when I leave , I found one somebody left at the post one time.

Brian

[Cate&Rob]

I'm going to pull the trigger on an EMS for the trailer soon. I'm partial to the portable, 'plug into the post' style. Just because in my career as an electrician, you don't want your sacrificial devices installed in the thing you are trying to protect.
Granted, in my career it was 1000's of volts not 120/240. But to those of you that have hardwired EMS's, why? Other than theft I'm not sure I see an advantage. School me.

I have the portable one . . . for exactly the reason you describe. But . . . after buying this, I learned (through the experience of another forum member) that this location misses an important part of the connection . . . the power cord and its connection to the trailer. The EMS can only see problems upstream. As it turned out, the cord to trailer connection lost the neutral which caused the L1 to L2 voltage to damage several appliances in the trailer. The EMS at the post showed that shore power was correct. Bottom line . . . The on-board unit can see everything feeding the panel. To buy this again, I would choose the hardwired version.

Rob

[howson]

I'm going to pull the trigger on an EMS for the trailer soon. I'm partial to the portable, 'plug into the post' style. Just because in my career as an electrician, you don't want your sacrificial devices installed in the thing you are trying to protect.
Granted, in my career it was 1000's of volts not 120/240. But to those of you that have hardwired EMS's, why? Other than theft I'm not sure I see an advantage. School me.

One less thing to store when not in use. I also like the display in the camper as I often reference it when we're on a "power diet" and the DW wants info on how much power she's using in the kitchen.

You're not asking to be convinced to get an EMS, just which type, but allow me to pontificate for a moment.

Unlike Brian, my EMS has saved me twice from electrical problems. Granted, both times were MY fault (oops) but it did it's job. Installing the EMS was one of the very first mods I did to my trailer.

An EMS is like an insurance policy--hopefully you never need it, but it sure is great to have it if "that day" arrives. Read d2reid 's latest thread where the EMS identified a really bad pedestal power situation. Without an EMS he could have easily smoked something in his camper.

[Dnmatt]

We have the hard wired unit mainly for ease of use, the inside display and no chance of theft. Ours has gone off at 2 places, once for over voltage (around 135 V) and once for low voltage (around 107 V). Prior to installing we noticed our phone chargers going bad frequently, I don't know if a coincidence or not but haven't had one go bad since installing the EMS.

[ncitro]

I'm going to pull the trigger on an EMS for the trailer soon. I'm partial to the portable, 'plug into the post' style. Just because in my career as an electrician, you don't want your sacrificial devices installed in the thing you are trying to protect.
Granted, in my career it was 1000's of volts not 120/240. But to those of you that have hardwired EMS's, why? Other than theft I'm not sure I see an advantage. School me.

I did hard wired for the same reason as Rob. There was a forum never a few years ago that had a bad shore cable that did a lot of damage. I think it happened twice if I recall right before he figured out the issue. My understanding is some of the portable units now protect the downstream connection as well but I don’t have any first hand experience there. It’s super convenient to not need to connect the EMS every time, and the display has a switch to bypass it. I would think it would need to fry pretty hard to lock me out of power, and if it did it would be easy enough to bypass.

[Guest]

We use the progressive industries portable unit. It saved our AC during a heat wave and low voltage situation which payed for itself on that one incident. Can bypass in 30 seconds and never mess with the trailer side connection while hot, which I believe accounts for most failures there.

https://www.amazon.com/Portable-RV-S...9441376&sr=8-2

Jim

[Scott'n'Wendy]

Thanks for the feedback, I have one other EMS related question,
If you have to plug into pedestals that are say only 15amp, or a generator for that matter, do the 'dog bones' etc play nice with EMS systems? Either portable or permanent? I'm thinking a two leg 50amp EMS unit might have an issue with single leg feed? Even if the single leg is jumpered to both legs in the dog bone? Do you HAVE to bypass them in certain power feed situations?

Oh ya, I haven't looked yet but how hard is it to get at the power feed to the trailer from inside? Can you access from the basement?

[Cate&Rob]

Scott'n'Wendy

I have used my two leg 50A portable EMS adapted down to a single 15A and it functions correctly. I have never bypassed or removed the unit (except at home where I am confident of the power source). To bypass this safety device seems like asking for trouble. Ours has shut off power several times at different campgrounds for over and under voltage. The power has to have a bonded neutral and ground at the source, for the EMS to work correctly. (A potential issue with generators that is easily remedied).

On a 303RLS, there is space behind the electrical panel accessible behind the aft wall of the pass through storage. The shorepower feed can be removed from the panel and rerouted to a hardwired EMS. Use new wire from EMS to panel and the EMS can then be removed and the shore power reconnected to the panel (if you ever wanted to do this).

ncitro As Neil notes above, newer portable EMS units are supposed to be able to "see" a downstream missing neutral.

OffToHavasu To quote Curtis (from a discussion "elsewhere" a long time ago) following is the reason why a lost neutral connection on a 50A supply can do so much damage. (For those who want to know the "why" . . . )

"Utilities provide 240 volts to your main service panel, whether that's your home or main panel at a RV park. To supply lower power loads they center tap the secondary winding in the utility transformer (I'm getting geeky here). This makes it possible to derive two legs of 120 volts each. From the three conductors run to your house you can derive 240 volts across the two hot legs, or 120 volts from either of the two hot legs to the centertaped neutral. As this neutral connects to the centertap in transformer, earth driven ground rod at the power pole or ground level transformer, and the grounded leg of the higher voltage primary leads supplying the transformer, it is called the grounded conductor. This conductor is also connected to earth at one point in the house, or other building.

Should this neutral conductor fail, the circuits on one hot leg become series paired with the other hot leg. As resistance is unlikely to be balanced, the side with the greatest resistance will get the biggest share of the voltage.

Imagine two 60 watt light bulbs each connected to one leg of the 240 volt supply, and the neutral, or grounded conductor. Each works fine. Should a connection fail on the centertapped neutral, the perfectly balanced 120 volt bulbs now in series will evenly divide the 240 volts. No change in voltage at either bulb.

Changing this scenario by substituting a 25 watt bulb for one of the above mentioned bulbs, they work fine with the neutral intact, when it fails they become a series circuit sharing 240 volts as resistance is not in balance, voltage isn't either. The 25 watt bulb resists the flow of electricity more than the 60 watt. It will get the greater share of 240 volts. It will quickly burn out, breaking the circuit. Both bulbs go dark, only one is burned out. This is the case in why Paul's TV blew up. It had the lease amount of resistance, so the voltage went up."

Rob

[OffToHavasu]

Scott'n'Wendy

i have used my two leg 50a portable ems adapted down to a single 15a and it functions correctly. I have never bypassed or removed the unit (except at home where i am confident of the power source). To bypass this safety device seems like asking for trouble. Ours has shut off power several times at different campgrounds for over and under voltage. The power has to have a bonded neutral and ground at the source, for the ems to work correctly. (a potential issue with generators that is easily remedied).

On a 303rls, there is space behind the electrical panel accessible behind the aft wall of the pass through storage. The shorepower feed can be removed from the panel and rerouted to a hardwired ems. Use new wire from ems to panel and the ems can then be removed and the shore power reconnected to the panel (if you ever wanted to do this).

ncitro as neil notes above, newer portable ems units are supposed to be able to "see" a downstream missing neutral.

OffToHavasu to quote curtis (from a discussion "elsewhere" a long time ago) following is the reason why a lost neutral connection on a 50a supply can do so much damage. (for those who want to know the "why" . . . )

"utilities provide 240 volts to your main service panel, whether that's your home or main panel at a rv park. To supply lower power loads they center tap the secondary winding in the utility transformer (i'm getting geeky here). This makes it possible to derive two legs of 120 volts each. From the three conductors run to your house you can derive 240 volts across the two hot legs, or 120 volts from either of the two hot legs to the centertaped neutral. As this neutral connects to the centertap in transformer, earth driven ground rod at the power pole or ground level transformer, and the grounded leg of the higher voltage primary leads supplying the transformer, it is called the grounded conductor. This conductor is also connected to earth at one point in the house, or other building.

Should this neutral conductor fail, the circuits on one hot leg become series paired with the other hot leg. As resistance is unlikely to be balanced, the side with the greatest resistance will get the biggest share of the voltage.

Imagine two 60 watt light bulbs each connected to one leg of the 240 volt supply, and the neutral, or grounded conductor. Each works fine. Should a connection fail on the centertapped neutral, the perfectly balanced 120 volt bulbs now in series will evenly divide the 240 volts. No change in voltage at either bulb.

Changing this scenario by substituting a 25 watt bulb for one of the above mentioned bulbs, they work fine with the neutral intact, when it fails they become a series circuit sharing 240 volts as resistance is not in balance, voltage isn't either. The 25 watt bulb resists the flow of electricity more than the 60 watt. It will get the greater share of 240 volts. It will quickly burn out, breaking the circuit. Both bulbs go dark, only one is burned out. This is the case in why paul's tv blew up. It had the lease amount of resistance, so the voltage went up."

rob

flashback!!

[Country Campers]

Scott'n'Wendy

As Rob has stated everything is accessible from the pass thru false wall. It is also accessible from removing the lower drawers in the hutch and also removing the power distribution box. I did as Rob has suggested removed the incoming power line and added a piece from the EMS to the power panel , this makes is easy to remove for the next RV if I choose.

Brian

[howson]

I'm on a 15A outlet as I type this response...no issues with the EMS. I've never had an issue with the Progressive. Of course, with my generator a bonding plug is required (well known issue).

[TucsonJim]

I'm partial to the portable version of EMS myself. I have frequently used it to check another camper's pedestal when they are having electrical problems.

Jim

[Guest]

The portable EMS is not needed for a 15amp home power source or with a generator. I used to be somewhat concerned about theft but then again, I've never locked it to the pedestal.

Jim

[Scott'n'Wendy]

flashback!!

That's quite a choice of wording, considering we are talking electricity...Lol