EMS still needed?

[67L48]

Originally Posted by BandJCarm

[...]Why would you not want an EMS? Are all those conditions not possible? [...]

I don't think it's about what the OP wants. I understood it was more about need. The question was whether or not the two devices were needed. As discussed above, the over-voltage scenario seems rare, though at least one person reported seeing it.

With low voltage, the appliances draw more current (Ohm's law). The increased amperage damages motors and other components. With over voltage, I'm not actually certain what the danger is to those components are (which isn't to suggest I think it's OK).

So, sure, for me, I would definitely want both. But, I only need the EMS, so that's what I got.

Originally Posted by BandJCarm

[...]I wouldn't get rid of a P.I. EMS for anything. If I got an Autoformer, it would not be for surge protection at all.........it would have one job only..........to boost low voltage.

I am not suggesting that anyone gets rid of their devices. If you have both, I'd recommend using both.

It's a probability vs possibility game. Is it possible to have low voltage? Yes. Is it probable? Yes, it seems so. The answers to those two questions for over voltage and for low voltage <94.5 VAC seem to be Yes/No. Those cases are possible but not probable based on the research I have done. Thus, I conclude that a person who already has an autoformer probably doesn't need to also get an EMS.

Others may have arrived at other conclusions based on their research or other opinions/beliefs.

Oh, and regardless of what you need or want, your autoformer does have more than one job. It boosts voltage and it offers surge protection. You may not care about the surge protection, but it's still in there.

[s1njin]

Glad I’ve kicked off some thoughtful conversation here. I suppose the hardwired EMS is the ideal situation with the Autoformer connected right at the pedestal.

I guess I need to find a place to easily hardwire the EMS. I don’t want to void any warranties.

[itat]

I imagine most people get the EMS first. I certainly did. I found that the EMS was shutting down power (due to low voltage) often enough that it became annoying somI bought the Autoformer strictly to boost voltage. The Auotformer plugs in first and the I plug the TT into the Autoformer.

And for an extra precaution I have a device to check for reverse wiring, open ground, etc. before I even back the trailer into the site.

[fr1rd831]

I have both a hardwired progressive ems and carry a Hughes Autoformer. I bought the auto former after a few trips that had my ems trip due to low voltage.

I check the voltage first with the ems. If there are no faults and power is above 115 I tend to leave the Hughes out. If the voltage is 110 before in turn anything on I will put the Hughes in front of the ems to get the voltage up to 120 ish.

I have yet to see an over voltage at RV parks but have often seen low voltage.

I don't use it all the time only when voltage is lower than I would like.

[itat]

Originally Posted by fr1rd831

I have both a hardwired progressive ems and carry a Hughes Autoformer. I bought the auto former after a few trips that had my ems trip due to low voltage.

I check the voltage first with the ems. If there are no faults and power is above 115 I tend to leave the Hughes out. If the voltage is 110 before in turn anything on I will put the Hughes in front of the ems to get the voltage up to 120 ish.

I have yet to see an over voltage at RV parks but have often seen low voltage.

I don't use it all the time only when voltage is lower than I would like.

Good strategy.

[FollowTheSun]

Originally Posted by s1njin

...
Is an EMS still recommended if you have one of these? ...
....

Yes, I would recommend installing an EMS after the Autoformer.
Finally, I found some technical information about Hughes Autoformer by way of their patient application. See https://patents.google.com/patent/US6087818. With this I am able to understand their design. The design is a simple 3-step voltage correction using a physical relay and an autotransformer. No saturable or resonant cores, no isolation. No fail safe disconnect, just pass through, for over-voltage (probably not an issue) or under-voltage (source less than 90 volts). Overall a very simple design that should not conflict with an EMS installed after the Autoformer. The EMS should still detect park wiring faults and disconnect when necessary. Additionally the EMS will disconnect when input voltages exceed (±) Autoformer's criteria.
See schematic:

[s1njin]

Both it is than. Looks like since my rig has the twist lock plug connector on the back, its hardwired or bust for me. I can't see putting the Autoformer on the pedestal, then the external EMS hanging off the Autoformer on the ground, and then the wire going to the coach.

[cavie]

Originally Posted by s1njin

Both it is than. Looks like since my rig has the twist lock plug connector on the back, its hardwired or bust for me. I can't see putting the Autoformer on the pedestal, then the external EMS hanging off the Autoformer on the ground, and then the wire going to the coach.

That's how it's done. If either one is not weatherproof you'll have to think outside the box as to how to weatherproof. My transformer is weatherproof. don't have an EMS.

[itat]

I don't have a picture of how I set it up but I can describe it.

- 30A (25 ft. long) extension cord plugged into the pedestal
- 30A Autoformer plugged into the extension cord
- 10' long, custom made 30A cord with the twist-lock end from the Autoformer to the TT.

The Hughes Autoformer is apparently not completely weather-proof so I bought a large blue recycling bin to put over it and place a landscaping block on the blue bin so it won't blow over. I use the included cable lock to lock the Autoformer to the stabilizer jack on the back corner of the TT near the power connector port.

If your power connector port is inside a bay, it would be best to put the Autoformer inside, out of the weather, if you have the room.

I also have this Prime Products AC Power Line Monitor to check the pedestal before I even back the TT into the site.

[s1njin]

Originally Posted by itat

I also have this Prime Products AC Power Line Monitor to check the pedestal before I even back the TT into the site.

I have that too - I leave it in the coach so I have a general idea of what's going on w/ the volts.

[s1njin]

So I decided to have my dealer install the hardwired Progressive EMS into my coach before I pick it up. This way it was a dealer install so I should avoid any warranty issues.

[RedLdr1]

Originally Posted by s1njin

This way it was a dealer install so I should avoid any warranty issues.

That is the one annoyance I have with Progressive.

I had ours installed behind the transfer switch so we are protected on both shore and gen set power.

[LandKKnight]

Originally Posted by s1njin

So I decided to have my dealer install the hardwired Progressive EMS into my coach before I pick it up. This way it was a dealer install so I should avoid any warranty issues.

What warranty issues are you talking about. If you have an ems on the pedestal, what would cause a warranty issue?

[s1njin]

Warranty issue with me hardwiring the EMS. No warranty issues to speak of with a pedestal unit.