Electrical/EMS Question

[DonP]

I think I know the answer but here's the question anyway. If I have a TT wired for 50A but will never add a second AC and want to purchase an EMS, can I purchase a 30A EMS or does it need to be a 50A EMS?

[flybouy]

It needs to be a 50 amp. A 30 amp EMS in between a 50 amp panel and a 50 amp cable will become a fusible link and get damaged. Even without a second a/c unit I'll bet your using well over 30 amps.

[chuckster57]

If your trailer is 50A service, it has 2 legs of 120VAC. 30A only has 1 leg. The only way to know if BOTH legs are ok is to use a 50A EMS. You can’t “choose” to use one leg or the other.

[DonP]

Thanks guys but I guess I didn't explain properly. My TT is wired 50A because it's prewired for a 2nd AC. I will never add that and currently plug in to 30A shore power hookups unless the site is only a 50A site. I have the same equipment in this TT as I did in my 2013 Cougar TT, and it was wired 30A. I use an adapter on my 50A cable to use on a 30A site.

So again, do I need to purchase a 50A EMS or can I purchase a 30A EMS?

FYI, I know nothing about "legs or fusible links" I'm not an electrician and I don't understand what those terms mean, sorry guys.

[Javi]

No you can't. It must be a 50 amp

[rhagfo]

Originally Posted by DonP

Thanks guys but I guess I didn't explain properly. My TT is wired 50A because it's prewired for a 2nd AC. I will never add that and currently plug in to 30A shore power hookups unless the site is only a 50A site. I have the same equipment in this TT as I did in my 2013 Cougar TT, and it was wired 30A. I use an adapter on my 50A cable to use on a 30A site.

So again, do I need to purchase a 50A EMS or can I purchase a 30A EMS?

FYI, I know nothing about "legs or fusible links" I'm not an electrician and I don't understand what those terms mean, sorry guys.

Pretty impressive that you can run on 30 amp in a warm area. AC takes a bit and if you use electric to run refrigerator, or hot water, you stand a good chance of tripping the main.
Even if you can, and don’t pay extra for a 50 amp service, a 50 amp is likely a better connection.

[travelin texans]

After all the other answers & asking the same question twice the answer is still "if you have a 50 amp rv GET the 50 amp EMS". If you chose to only use the 30 amp pedestal you can still use the 50 amp EMS.
Not trying sound rude, but if the cost difference between plugging into a 30 amp site rather than 50 amp or the price differences between the 2 EMS units is that critical then rving may not be for you. There are areas where cost cutting is possible, in my opinion safety equipment is not one of them, it's an expensive hobby.

[DonP]

Originally Posted by travelin texans

After all the other answers & asking the same question twice the answer is still "if you have a 50 amp rv GET the 50 amp EMS". If you chose to only use the 30 amp pedestal you can still use the 50 amp EMS.
Not trying sound rude, but if the cost difference between plugging into a 30 amp site rather than 50 amp or the price differences between the 2 EMS units is that critical then rving may not be for you. There are areas where cost cutting is possible, in my opinion safety equipment is not one of them, it's an expensive hobby.

Well, you were. It was a simple question requiring a SIMPLE answer. YES or NO that is all I needed to know!

[DonP]

Originally Posted by Javi

No you can't. It must be a 50 amp

Thank you, Javi. That's all I need to know, ordering a 50A EMS now

[LHaven]

Originally Posted by DonP

Thanks guys but I guess I didn't explain properly. My TT is wired 50A because it's prewired for a 2nd AC. I will never add that and currently plug in to 30A shore power hookups unless the site is only a 50A site. I have the same equipment in this TT as I did in my 2013 Cougar TT, and it was wired 30A. I use an adapter on my 50A cable to use on a 30A site.

So again, do I need to purchase a 50A EMS or can I purchase a 30A EMS?

FYI, I know nothing about "legs or fusible links" I'm not an electrician and I don't understand what those terms mean, sorry guys.

A 50A circuit has two independent positive power connectors (legs); a 30A has one.

Even though your rig does not use more than 30A, the circuits inside it may be wired so that some devices/appliances/lights are assigned to one of those legs and the rest are on the other, so both legs have to work. It's not like one leg is reserved exclusively for your second AC and nothing else.

A 50A EMS monitors both those legs for happiness. A 30A EMS has only the connections capable of monitoring one of those legs, leaving the other unmonitored.

When you use a 50-to-30 adapter, it feeds both of your legs from the same single leg on the pedestal. So at best, your 30A EMS would protect half the stuff in your trailer, leaving the other half to fry. At worse, it would complain that there's something funny going on (like a GFI) and just shut down.

A fusible link is just a box full of smoke. Its job is to let out all that smoke when you screw up, to let you know you screwed up.

[HouseMouse]

Originally Posted by DonP

Well, you were. It was a simple question requiring a SIMPLE answer. YES or NO that is all I needed to know!

Yup.

[sourdough]

DonP I didn't see this mentioned;

There is a lot more difference between a 30A and 50A other than the seemingly small 20A difference. The 50A has 2 hot legs equaling 100 usable amps vs the 30A - very big difference. In a 50A trailer those 2 hot legs are split out in your power center and power 2 individual hot "sides" throughout the trailer so you can have more "stuff" plugged in and work vs having to disconnect this or that to prevent blowing a breaker. Lots more to it than the 2nd A/C. That was just so you know going forward; simple answer, get the 50A (but you sorta know why now).

[DonP]

Originally Posted by sourdough

DonP I didn't see this mentioned;

There is a lot more difference between a 30A and 50A other than the seemingly small 20A difference. The 50A has 2 hot legs equaling 100 usable amps vs the 30A - very big difference. In a 50A trailer those 2 hot legs are split out in your power center and power 2 individual hot "sides" throughout the trailer so you can have more "stuff" plugged in and work vs having to disconnect this or that to prevent blowing a breaker. Lots more to it than the 2nd A/C. That was just so you know going forward; simple answer, get the 50A (but you sorta know why now).

Thanks Sourdough, yes, I know why now and I even understand why. The last couple of responses are much better than maybe I should not be "RV'ing if I can't afford it". It was never about affording it was about understanding in term that I understand. Thanks again.

[sourdough]

Originally Posted by DonP

Thanks Sourdough, yes, I know why now and I even understand why. The last couple of responses are much better than maybe I should not be "RV'ing if I can't afford it". It was never about affording it was about understanding in term that I understand. Thanks again.

Just another thing neither here nor there but to think about with that 50A service; look at your power center to see how things are divided between the 2 50A sides. I have 2 A/Cs on mine but if I didn't the loads are unequally split in the event you add one. In other words, one side might have 2 or 3 heavy load items and the other might have one in anticipation of the addition of another airconditioner. Really doesn't pertain to anything other than for your knowledge of how they are breaking that power out.

[DonP]

Originally Posted by sourdough

Just another thing neither here nor there but to think about with that 50A service; look at your power center to see how things are divided between the 2 50A sides. I have 2 A/Cs on mine but if I didn't the loads are unequally split in the event you add one. In other words, one side might have 2 or 3 heavy load items and the other might have one in anticipation of the addition of another airconditioner. Really doesn't pertain to anything other than for your knowledge of how they are breaking that power out.

Power Center = Converter? What do I look for? To me there are just a bunch of breakers and fuses. I will not be opening that up to see what's behind them. Can I tell when I just open the door? I'm guessing no. Unless it's very simple electric I leave it alone and call someone. If I can't see it, I don't mess with it.

[sourdough]

The power center will be the brown door (probably) with the fuses and breakers in it. The converter is probably behind that if you pull it but no need to. Looking at the breakers there will be a big double pole 50A breaker in the middle. On either side are the items that are powered by each individual leg of power, hopefully they are labeled in a meaningful way (some look like a foreign language). Note what runs off each side just as an fyi. A 50A service can lose power to just one leg then those particular items will not work but the others will. Again, not really here nor there but I thought about it since we were discussing you getting a 50A trailer. Also, depending on what EMS you buy it will tell you the incoming voltage on each leg as well as the amperage being used on each leg. You can even use it (mine anyway) to figure out what kind of amp pull various appliances have. Again, just some things to help with figuring out the power and the new EMS.

[DonP]

Sent you a PM

[wiredgeorge]

Originally Posted by DonP

Sent you a PM

Breakers and fuses are the power center. Open the door on most power centers and you see the AC breakers and DC fuses. Somewhere (on mine it is behind but mine is likely different than most) is the converter. Power comes into the AC side. Then it goes to the converter via a big fat set of wires (black-pos, white-neutral, and green-ground). The converter takes AC and turns it into DC and the DC then goes to your fuses.

[LHaven]

Originally Posted by sourdough

Looking at the breakers there will be a big double pole 50A breaker in the middle. On either side are the items that are powered by each individual leg of power, hopefully they are labeled in a meaningful way (some look like a foreign language). Note what runs off each side

I've never owned a 50A rig. Are the legs arranged in two columns, or do they do even/odd positions like they do in residential?

[chuckster57]

Originally Posted by LHaven

I've never owned a 50A rig. Are the legs arranged in two columns, or do they do even/odd positions like they do in residential?

Here’s a picture:
https://www.camperid.com/wfco/wf-893...-50npb-30.html