Shore power breaker question

[brooks340]

I am planning the installation of a hard wired EMS and a 3000w inverter. If I wire the EMS in line before the inverter do I need to wire in a 50A breaker? Would the EMS act as the protection for the inverter, and eliminate the need for the breaker?

[PNW Fireguy]

No, the inverter requires it’s current carrying conductors to be protected by an appropriately sized current interrupting device. An EMS does not fit that definition.

[brooks340]

Would you put the breaker before the EMS or after. I plan to run shore power into the EMS then to the inverter and back to the fuse panel.

[PNW Fireguy]

Before the inverter.

[mhs4771]

You have me completely confused. An inverter works off 12VDC, if you put it between your EMS and the Power Distribution Panel you won't get any power, just a burnt Inverter.

[brooks340]

The GOPower IC3000 inverter has both DC and AC inputs. The DC input from your batteries gets inverted to AC power and fed thru to your distribution panel and then through out your rig. The AC power, from either shore power or generator, is fed into the inverter which acts as a switch to apply AC thru to the distribution panel when the DC power used for inversion is either interrupted or insufficient. I am going to install a hardwired EMS between the shore power input and the inverter to ensure consistent, safe AC power. What I'm asking is, should I install a 50A breaker in the AC inout line, either before the EMS or between the EMS and the inverter.

[jetskier]

I don't know why you'd need an additional 50A breaker. The shore power circuit at the post should have a 2-pole, 50A breaker protecting it and the trailer has it's 50A breaker internally in the distribution/fuse box. Unless you want to be able to use the 50A breaker before the inverter as a switch, I guess you could mount another small panel with the breaker only.

[brooks340]

I wonder if I'm overthinking this a bit. I know the breaker on the power pole is there for this purpose but we all know campground power poles can be hit and miss. I was concerned that a voltage surge or over current situation might imperil the inverter without a breaker on the input feed line. It would also act as a switch as you mentioned. I think for the sake of a $100 breaker and subpanel I might just go ahead and do it. Power would go thru the EMS, then thru the breaker and then feed the inverter.

[jetskier]

Don't forget a hardwired EMS has the relay/contacters that won't pass current until it determines the line voltage is good and all the connections are present and wired correctly (grounds, neutrals, etc).

[sourdough]

I'm not understanding the additional breaker. The EMS will protect you far better than another 50A breaker and just introduce another place for problems. Unless you just really. The EMS eliminates the worry about campground power.

[mhs4771]

OK, just looked up that model Inverter, interesting concept feeding the inverter with the 240 VAC main input line. The biggest issue will be making sure you do some serious energy management when operating the entire unit on a 3000 watt inverter will be worse than operating on a 30 amp circuit. How big is your battery bank to support the inverter?

[jetskier]

Originally Posted by mhs4771

The biggest issue will be making sure you do some serious energy management when operating the entire unit on a 3000 watt inverter will be worse than operating on a 30 amp circuit.

agreed. I can see the issues when the shore power kicks off and an AC is running.

Here's a link to the thread I did on isolating the inverter circuits from the main trailer panel.

https://www.montanaowners.com/forums...ad.php?t=75474

I've modified some of it since then to balance out the two lines better. I found a tandem dual 30/50A breaker to replace the 2-pole center breaker. The inverter subpanel is more balanced and gets both legs of AC power when on shore power. Remember, the RV main panel is all one phase each side of center. It doesn't work for conventional 2-pole breakers.

[jetskier]

Here's the breaker I was referring to:

https://www.amazon.com/dp/B000VYKYR4..._2RgpFb0JNTMZ8

I use the 30A part to feed the ATS on the shore power side and the inverter feeds the other input. The output goes to my subpanel with all the receptacles. This keeps the inverter from powering the washer/dryer, ACs, converter circuits.

[bcrvman]

Originally Posted by mhs4771

OK, just looked up that model Inverter, interesting concept feeding the inverter with the 240 VAC main input line. The biggest issue will be making sure you do some serious energy management when operating the entire unit on a 3000 watt inverter will be worse than operating on a 30 amp circuit. How big is your battery bank to support the inverter?

On my inverter, only one leg goes thru the inverter the other leg goes direct to the RV main panel. In a boondocking or power outage situation with no grid power only half the panel is powered with up to 3,000VA or 2,400W. If you plug a generator in, then you get L2 powered as well.

Sitting here watching TV we use about 200W mostly the residential fridge. I did move a couple of circuits around, so the unpowered circuits are one AC, Washer, Dryer, Hot Water, Furnace. None of those are needed for boondocking and in an emergency my pair of Honda 2,000W inverter generators give me enough to handle any of that. 400Ah of lithium provide days of power and if the sun is shing the 680W of solar extend our stay.

[PNW Fireguy]

One of the biggest benefits of the IC3000 is that it passes through both legs at 50A. Another option to allow people to determine what their power needs are and how best to achieve them.

[bcrvman]

Originally Posted by mhs4771

OK, just looked up that model Inverter, interesting concept feeding the inverter with the 240 VAC main input line. The biggest issue will be making sure you do some serious energy management when operating the entire unit on a 3000 watt inverter will be worse than operating on a 30 amp circuit. How big is your battery bank to support the inverter?

Since most if not all of this type of unit is a charger/inverter, you have to feed the AC in to operate the charger. The better units called 'hybrid' allow using some battery power to augment the AC as in the case of a 30A feed. My 'inverter' is also a 120A charger and will pass 50A on one leg. The inverter can only produce 20A so the other 30 would come from the grid.
HOWEVER, these units cost a lot of money and need a serious battery bank to be useful for boondocking so are mainly of interest to full timers. My objective was to be able to boondock for up to 5 days. My daily usage is about 2.5kWh per day.