Inverter/Charger Bypass Insufficient

[CarlCruzin]

I purchased a 4kw 48v low frequency pure sine inverter/charger/transfer for my upcoming build. Considering the cost of the Victron unit that had many great features ($2700), I decided to try a less expensive route ($900) with a couple compromises to see if it will work for my purposes.

My RV has a 50A service, and a 5.5kw generator. The inverter bypass is only rated for 3600w pass through, which is not ideal seeing that it is less than my RV's service and generator output and in some circumstances a bottle neck.

So I'm thinking I may need to wire a type of parallel bypass if that is possible? I can't bypass the unit all together because I will need to utilize the built-in battery charger.

 

[snoobler]

50A service is 120/240VAC split phase, and your generator is likely the same.

Is your inverter 120/240VAC split phase?

What inverter?

 

[CarlCruzin]

4000W DC 48V Pure Sine Wave Inverter With Charger

Sungoldpower 4000W DC 48V Pure Sine Wave Inverter With Charger. Hightlight: This Pure Sine Wave Inverter is a combination of an inverter, battery charger and AC auto-transfer switch. GFCI socket, low frequency, low Idle Current, BTS cable, remote control. This 4000 watt inverter requires 120VAC...

sungoldpower.com

 

[snoobler]

That unit is not compatible with 50A shore power.

 

[CarlCruzin]

That unit is not compatible with 50A shore power.

Thank you for that information. It sounds like I need to research RV wiring further.

I sent a message to sungold to see if I can return this one and order the split phase.

I'm wondering if the split phase will have the same bypass limit per leg of 120v and not pose the same problem?

 

[snoobler]

Not sure, but then you're looking at only being able to plug into 50A shore power. You won't be able to feed 30A shore power since it's single phase.

50A shore power is basically the same as a residence. 120/240VAC split phase. Neutral down the middle with L1 and L2 legs feeding difference circuits. L1 to N is 120VAC, L2 to N is 120VAC and L1 to L2 is 240VAC, but nothing in the RV uses 240VAC.

When you plug into 30A power, L1 and L2 are shorted, so that you still feed 120VAC to all circuits, but L1 and L2 are 0V to each other.

You could use your existing inverter as 30A shore power. Install another transfer switch at the output of your existing one (assuming you have one selecting between shore/genny) such that if the inverter is on, it's supplying power to the trailer like a 30A supply. If 50A or genny are active, the transfer switch cuts the inverter out, and you could easily feed in just one leg of your shore/genny output to your inverter input.

This would allow 30A, 50A shore or genny input that would charge your inverter batteries, but the inverter output would be disconnected from AC panel.

There are other options.

 

[CarlCruzin]

I have some good news! The supplier is willing to exchange the unit since it is unused, so I will be ordering the split phase 4kw inverter/charger.

Not sure, but then you're looking at only being able to plug into 50A shore power. You won't be able to feed 30A shore power since it's single phase.

50A shore power is basically the same as a residence. 120/240VAC split phase. Neutral down the middle with L1 and L2 legs feeding difference circuits. L1 to N is 120VAC, L2 to N is 120VAC and L1 to L2 is 240VAC, but nothing in the RV uses 240VAC.

When you plug into 30A power, L1 and L2 are shorted, so that you still feed 120VAC to all circuits, but L1 and L2 are 0V to each other.

You could use your existing inverter as 30A shore power. Install another transfer switch at the output of your existing one (assuming you have one selecting between shore/genny) such that if the inverter is on, it's supplying power to the trailer like a 30A supply. If 50A or genny are active, the transfer switch cuts the inverter out, and you could easily feed in just one leg of your shore/genny output to your inverter input.

This would allow 30A, 50A shore or genny input that would charge your inverter batteries, but the inverter output would be disconnected from AC panel.

There are other options.

 

[snoobler]

I have some good news! The supplier is willing to exchange the unit since it is unused, so I will be ordering the split phase 4kw inverter/charger.

Does the new unit accept 120VAC single phase input on one leg? If not, you won't be able to use 30A shore power to charge the batteries with the inverter.

 

[CarlCruzin]

Does the new unit accept 120VAC single phase input on one leg? If not, you won't be able to use 30A shore power to charge the batteries with the inverter.

That is an important consideration. I am checking with them now