What Happens When (120V ~ 240V)

[2edgesword]

I didn't want to keep asking this question in a tread started by someone else but the idea that a 120V surge protector would allow 240V into a rig baffles and bothers me. Most surge protectors goes through a diagnostic phase checking voltage, polarity, proper ground, etc. Under want circumstances would any 120V surge protector allow 240V to get passed through to the RV?

[morleyz]

Originally Posted by 2edgesword

I didn't want to keep asking this question in a tread started by someone else but the idea that a 120V surge protector would allow 240V into a rig baffles and bothers me. Most surge protectors goes through a diagnostic phase checking voltage, polarity, proper ground, etc. Under want circumstances would any 120V surge protector allow 240V to get passed through to the RV?

Are you talking about an EMS or a basic surge suppressor only? Every EMS I'm aware of has a low and high voltage cutoff. A miswired 30amp plug (2 hots and a neutral) would never power the rig through the EMS. A properly wired 30amp could never supply 240V because it has 1 hot, 1 neutral, 1 ground.

A 50amp plug actually supplies two distinct 120V circuits and the EMS is aware of this. It should treat each leg individually for low/over voltage. In the rig, those circuits are still two distinct 120V circuits with separate breakers.

Your only risk should be a miswired 30amp plug (typically a home dryer plug) with NO surge suppressor, which would supply 240V. I'm not sure what is going on in the other thread, but this seems like the only scenario where 240V could hit the RV.

[2edgesword]

Originally Posted by morleyz

Are you talking about an EMS or a basic surge suppressor only? Every EMS I'm aware of has a low and high voltage cutoff. A miswired 30amp plug (2 hots and a neutral) would never power the rig through the EMS. A properly wired 30amp could never supply 240V because it has 1 hot, 1 neutral, 1 ground.

A 50amp plug actually supplies two distinct 120V circuits and the EMS is aware of this. It should treat each leg individually for low/over voltage. In the rig, those circuits are still two distinct 120V circuits with separate breakers.

Your only risk should be a miswired 30amp plug (typically a home dryer plug) with NO surge suppressor, which would supply 240V. I'm not sure what is going on in the other thread, but this seems like the only scenario where 240V could hit the RV.

I understand the distinction you're making regarding a surge protector and EMS. I have always used an EMS for better protection and for monitoring voltage/current. It was surprising to me that the type of error made, mentioned in the other thread, resulting in a severe over voltage condition would not be recognized by one of these pole mounted units and prevent 240V to be passed through to the RV. Even the basic units check for correct polarity. Wouldn't the polarity check have identified the incorrect wiring?

[morleyz]

240V at the RV should not be possible unless your EMS is defective. Assuming you're specifically talking about the SG 35530, it should shut off power if polarity is reversed or if voltage is over 132VAC. The only way to wire a typical home outlet or a typical 30amp RV outlet for 240V would be to connect the hot to hot and neutral to hot with a ground/neutral on the ground. That EMS unit should not power the RV in any of those conditions. If that is really happening, you'll need to take that up with Surge Guard as I would think that is the purpose of their device, not just a whiz bang extra feature.

[Cavie]

Keep in mind that 50 amp RV service IS 240 volts delivered to your 50 amp rv main breaker. 30 amp is only 120 volts. A properly wired 30 amp 3 wired service can NOT pass thru 240 volts to a 30 amp 120 volt breaker.

[Lake Huron]

This is the thread in reference

https://www.jaycoowners.com/forums/f...ake-79735.html

I too have been thinking the same thing. How could a protection device allow 220V thru a 30A plug?
Must be defective??

[2edgesword]

Originally Posted by morleyz

240V at the RV should not be possible unless your EMS is defective. Assuming you're specifically talking about the SG 35530, it should shut off power if polarity is reversed or if voltage is over 132VAC. The only way to wire a typical home outlet or a typical 30amp RV outlet for 240V would be to connect the hot to hot and neutral to hot with a ground/neutral on the ground. That EMS unit should not power the RV in any of those conditions. If that is really happening, you'll need to take that up with Surge Guard as I would think that is the purpose of their device, not just a whiz bang extra feature.

I was not referring to any particular EMS or surge protector so nothing to take up with Surge Guard. I have used a number of their units (EMS) and they have protected my rig from low voltage and would not pass through power to the rig if reverse polarity or a ground issue was present. I asked the OP in the other thread about the make/model of the surge protector mentioned in that thread but never got a response.

[2edgesword]

Originally Posted by Cavie

Keep in mind that 50 amp RV service IS 240 volts delivered to your 50 amp rv main breaker. 30 amp is only 120 volts. A properly wired 30 amp 3 wired service can NOT pass thru 240 volts to a 30 amp 120 volt breaker.

At a minimum I would think any 30A 120V surge protector or EMS would recognize an issue where you have two hot wires but that appears not to have occurred with the incident mentioned in the other thread.

[morleyz]

Originally Posted by Cavie

Keep in mind that 50 amp RV service IS 240 volts delivered to your 50 amp rv main breaker. 30 amp is only 120 volts. A properly wired 30 amp 3 wired service can NOT pass thru 240 volts to a 30 amp 120 volt breaker.

True, but a 50 amp converter will actually work on anything 120-240. If only one leg is hot it'll still work and wouldn't malfunction at 240 either.

[morleyz]

Originally Posted by 2edgesword

At a minimum I would think any 30A 120V surge protector or EMS would recognize an issue where you have two hot wires but that appears not to have occurred with the incident mentioned in the other thread.

Going to call BS. Any EMS is going to prevent you from damaging your 30amp RV by plugging into a dryer outlet. Either the EMS malfunctioned or it wasn't used properly. It's a primary function especially on 30amp where there is so much higher risk because the same receptacle is commonly used at different voltages.

My opinion would be they probably tried troubleshooting by bypassing the EMS and maybe embarrassment, etc. came up with the unlikely theory. I'd be going after the EMS manufacturer if that really happened.

[Cavie]

Originally Posted by morleyz

True, but a 50 amp converter will actually work on anything 120-240. If only one leg is hot it'll still work and wouldn't malfunction at 240 either.

It is not a 50 amp converter. It's called a 50/30 dog bone adapter. It uses 1 leg of 50 amp and puts 120 volts on the 30 amp leg of the 120 service. There is nothing to malfunction.

[RetiredOne]

Originally Posted by Cavie

It is not a 50 amp converter. It's called a 50/30 dog bone adapter. It uses 1 leg of 50 amp and puts 120 volts on the 30 amp leg of the 120 service. There is nothing to malfunction.

That's not what he's referencing. He's claiming that if a 50 amp RV service only had one leg hot (120 volts), it will still operate, (one side of the buss). At 240 volts, it would be both sides of the buss (120 x 2)

[Cavie]

Originally Posted by RetiredOne

That's not what he's referencing. He's claiming that if a 50 amp RV service only had one leg hot (120 volts), it will still operate, (one side of the buss). At 240 volts, it would be both sides of the buss (120 x 2)

Yes. That is correct. A loose/burned connection is the only why to have one dead leg.