Discussion on the use of 2 120vAC HF inverters to create 240vAC.

[RCinFLA]

I have 2 Trace sw4024 24v inverters same firmware revision but not installed yet. I do have an Onan QD 12.5kw generator with both legs fed to a 120v panel. I have a 50amp shore power cord connected through an isolator/switch/filter. I can get 120v to the panel from shore or the generator. But I want to get two 24v 200Ah LifePO4 batteries and install the inverters. Should I just parallel the batteries and stack the inverters? I downloaded a file that shows a connecting cable to stack the inverters. I really need some help such as a diagram. Thanks hopefully I need help.

Yes, series stack the inverter with DB25 connectors series stacking control cable and both inverters to same battery. Battery charging should be set up the same on both inverters. Bulk current to battery will be double, half contributed by each inverter.

I assume the DB25 series stacking control cable diagram is the one I posted before. Make sure the DB25 connector on inverters are cleaned and not filled with dust or bug droppings causing poor connections.

 

[EvRv]

Yes, series stack the inverter with DB25 connectors series stacking control cable and both inverters to same battery. Battery charging should be set up the same on both inverters. Bulk current to battery will be double, half contributed by each inverter.

I assume the DB25 series stacking control cable diagram is the one I posted before. Make sure the DB25 connector on inverters are cleaned and not filled with dust or bug droppings causing poor connections.

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Ok I have no problem wiring the cable. Could you be so kind as to present a block diagram of an example system? I am trying to power a diy Bus RV. I have the transfer switch that handles the ground bond and have the generator and a shore power 50 amp cable installed as well as a 120v panel that has some temp círcuits for receptacles and 3 roof ac units. But really need help getting a better picture. An RV setup with two inverters would be great.

 

[RCinFLA]

Ok I have no problem wiring the cable. Could you be so kind as to present a block diagram of an example system? I am trying to power a diy Bus RV. I have the transfer switch that handles the ground bond and have the generator and a shore power 50 amp cable installed as well as a 120v panel that has some temp círcuits for receptacles and 3 roof ac units. But really need help getting a better picture. An RV setup with two inverters would be great.

You don't really need a transfer switch. Just connect shore power to AC1 inputs and connect an external generator inlet port to AC2 inputs. Put AC breakers on AC 1 and AC 2 inputs.

Bigger issue is dealing with 240/120vac shore power and 120vac only shore power. It's the 120vac only shore power that is the issue with stacked inverters. Inverter's switch to AC input sync when it is present. I don't think feeding just one of the two series stacked inverters 120 vac will work. I have never tried it but pretty sure they will lose their cross 180 deg syncing to produce 240vac output. You could put a 120vac to 240vac/120vac auto transformer to feed both inverters, just adds more weight and cost.

Do you really need 240vac for RV? Carrying around 300 lbs for two SW4024 is a lot of weight. I'm thinking if your RV is so big it can use 8 kW, 300 lbs of inverters, and 240vac you can afford a newer more modern setup like a Victron system. SW's can do most of a modern Victron but it is 1980's tech when it comes to software and networking capability.

 

[EvRv]

You don't really need a transfer switch. Just connect shore power to AC1 inputs and connect an external generator inlet port to AC2 inputs. Put AC breakers on AC 1 and AC 2 inputs.

Bigger issue is dealing with 240/120vac shore power and 120vac only shore power. It's the 120vac only shore power that is the issue with stacked inverters. Inverter's switch to AC input sync when it is present. I don't think feeding just one of the two series stacked inverters 120 vac will work. I have never tried it but pretty sure they will lose their cross 180 deg syncing to produce 240vac output. You could put a 120vac to 240vac/120vac auto transformer to feed both inverters, just adds more weight and cost.

Do you really need 240vac for RV? Carrying around 300 lbs for two SW4024 is a lot of weight. I'm thinking if your RV is so big it can use 8 kW, 300 lbs of inverters, and 240vac you can afford a newer more modern setup like a Victron system. SW's can do most of a modern Victron but it is 1980's tech when it comes to software and networking capability.

Well I lost weight getting rid of the 8d batteries. Went from 8@150 to 2@63 pounds. Also If I could run both legs of 120v parallel stacked without 240? Now it's gotten messy. Isn't there a way 8 could just use an adapter cable to bring the same leg in twice like the adapter that converts 30 amp to the 50amp cord.

 

[Rednecktek]

Also If I could run both legs of 120v parallel stacked without 240?

Yes, you just run them in parallel to the same output lug. Your inverters will still need to communicate to sync the phase but that'll give you 60a @ 120v rather than 30a @ 240v.

 

[EvRv]

You don't really need a transfer switch. Just connect shore power to AC1 inputs and connect an external generator inlet port to AC2 inputs. Put AC breakers on AC 1 and AC 2 inputs.

Bigger issue is dealing with 240/120vac shore power and 120vac only shore power. It's the 120vac only shore power that is the issue with stacked inverters. Inverter's switch to AC input sync when it is present. I don't think feeding just one of the two series stacked inverters 120 vac will work. I have never tried it but pretty sure they will lose their cross 180 deg syncing to produce 240vac output. You could put a 120vac to 240vac/120vac auto transformer to feed both inverters, just adds more weight and cost.

Do you really need 240vac for RV? Carrying around 300 lbs for two SW4024 is a lot of weight. I'm thinking if your RV is so big it can use 8 kW, 300 lbs of inverters, and 240vac you can afford a newer more modern setup like a Victron system. SW's can do most of a modern Victron but it is 1980's tech when it comes to software and networking capability.

Well yes and no. I have begun lóoking at some of the Victron stuff but, I am hoping to use my inverters so that I won't even have to think about what 2 new Victrons would cost. Besides the Trace do have remote panels and even though not the latest, I can use what I have and spend money on other things that may be necessary Like new batteries.