Shore power with a 240 volt system

[WiredForStereo]

I have a question about using a 240 volt system and shore power.

I've read up on all-in-one solar inverter/chargers, and higher voltage battery banks and 240 volt electrical systems are more efficient, produce higher power, and use smaller wires.

With many of these systems, if you want 240 volts, you just run two of them parallel.

So my question is: What if you're only getting 120 volt shore power, as in most campgrounds and RV hook ups (that I've seen)?

Does it work? Does the system compensate? Does one run two 120 volt shore power plugs?

[DeMac]

Never... Run two separate 120v services to achieve 240v. The breakers are not tied together, wont trip together. May be fed from different panels or xfmr or same brkr. Overcurrent, overheat, parallel service, arc fault, unbalanced neutrals, back-feeding, eddy current, etc.. are not taught at skoolie.net.

[Rwnielsen]

A 240 volt supply comes from a 2-pole breaker from a split phase panel. A 50 amp shore power receptacle is 240 volt. NEMA # 14-50r. A 30 amp receptacle is 120 volts, NEMA 5-30r. You could create a serious problem and possibly kill yourself getting 'resourceful' with outside electrical supplies. Phase to phase shorts are no joke.
Choose wisely

[Bert06840]

Originally Posted by WiredForStereo

With many of these systems, if you want 240 volts, you just run two of them parallel.

Not quite - SOME systems allow for synchronized cascading, the vast majority do not.

Also, you do *not* get 240V from running two 120V systems in series, which is what your post suggests (not parallel). Absence of frequency synchronization makes that even theoretically impossible in the vast majority of cases.

So my question is: What if you're only getting 120 volt shore power, as in most campgrounds and RV hook ups (that I've seen)?

Does it work? Does the system compensate? Does one run two 120 volt shore power plugs?

As said by others, even in the isolated case where you would get two 120V plugs wired to two separate phases; you really, really, really should not take a phase from each 120V plug and use the 240v between them.

You unplug one cord from the outlet, and the *prongs* will be live with power. It's against every rule ever written and outright dangerous.

The only practical way to feed a 240V system with 120V, is to use a transformer that turns 120V primary into split-phase 240V. Practical comes with a disclaimer here, because you are not going to be able to draw more than 1500W give or take from a 120V outlet, and if you have only 1500W on the load side, you are better off sticking with a 120V system.

I decided against a split phase 240V system, simply because I do not have any loads that justify it. And I don't even do shore power.

[WiredForStereo]

Originally Posted by DeMac

Never... Run two separate 120v services to achieve 240v. The breakers are not tied together, wont trip together. May be fed from different panels or xfmr. Overcurrent, overheat, parallel service, arc fault, unbalanced neutrals, eddy current, etc.. are not taught at skoolie.net.

Appreciated. Not relevant to my question.

[WiredForStereo]

Originally Posted by Bert06840

Also, you do *not* get 240V from running two 120V systems in series, which is what your post suggests (not parallel).

My post does not suggest this.

My post is in reference to all-in-one inverter/charger/MPPT units which run two units in parallel to make 240V.

How does one incorporate shore power in such a system?

[DeMac]

Originally Posted by Bert06840

Not quite - SOME systems allow for synchronized cascading, the vast majority do not.

Also, you do *not* get 240V from running two 120V systems in series, which is what your post suggests (not parallel). Absence of frequency synchronization makes that even theoretically impossible in the vast majority of cases.



As said by others, even in the isolated case where you would get two 120V plugs wired to two separate phases; you really, really, really should not take a phase from each 120V plug and use the 240v between them.

You unplug one cord from the outlet, and the *prongs* will be live with power. It's against every rule ever written and outright dangerous.

The only practical way to feed a 240V system with 120V, is to use a transformer that turns 120V primary into split-phase 240V. Practical comes with a disclaimer here, because you are not going to be able to draw more than 1500W give or take from a 120V outlet, and if you have only 1500W on the load side, you are better off sticking with a 120V system.

Maybe OP is missing it or more interested in debating.

[Rwnielsen]

Originally Posted by DeMac

Maybe OP is missing it or more interested in debating.

"engineer" remember?

[turf]

i think the op is confusing ac and dc. if you drop the zeros from his 120/240 question, he has scaled up a common dc solar post to AC voltage and posed a question.

ac and dc are not the same beast
the question is nonsensical
north america uses 2 x 120v lines to make 240v service.
you see twin inverter solar setups running 240,but its really 2 x 120v because each unit does 120. 2 inverters x 120v

your shore line is either:
30A - 1 x 120v
50A - 2 x 120v

a shore line will go through a transfer switch to your inverter. your inverter manual should tell you what it needs.

[Bert06840]

Originally Posted by WiredForStereo

My post does not suggest this.

My post is in reference to all-in-one inverter/charger/MPPT units which run two units in parallel to make 240V.

How does one incorporate shore power in such a system?

Which brand/model specifically? The ones that I have looked at are either natively split phase, or single phase 240V. Single phase 240V is in practice the global 230V single phase model as would be used in Europe and Asia.

Some of those you can parallel for more power, not for more voltage.

Surely there are countless ways to use inverters to take in DC and generate whatever phase arrangement you can dream of, including 3 phase power. Integrated, modular per phase, multiple modules per phase, and so on.

By the way, that’s how every variable frequency motor drive works, ubiquitous in industry. Or even an ESC in a brushless DC motor that you’d find in a cordless drill!

If you want 240V split phase shore power charging from an integrated unit, you’d be best off starting out with a unit that natively supports 240V split phase, and all your problems go away - just three wires instead of two.

But again, I’d make damn sure I *need* split phase. The only three loads that I can think of are an A/C, a range, and a washer. You can find plenty of 120V mini-splits and plenty of 120V washers. And do you really want to have a 8kW five-position stove and oven in a bus?

In a residential installation with 30kW of solar things are different, and there you may want a 2/3 phase installation, but I don’t think there’s a need for a 240V system on a *bus* for the vast majority of people.

You’re not going to run a 240V water heater or a dryer off your inverter, so if you want to haul a dryer around to be used when you’re in an RV park, you don’t have the switchover problem - use an extension cord.

[DeMac]

Originally Posted by Rwnielsen

"engineer" remember?

I understand your point, all too well.
‐---------------

Bert, You may save a life, here. Thanks for explaining.

[WiredForStereo]

Originally Posted by turf

i think the op is confusing ac and dc. if you drop the zeros from his 120/240 question, he has scaled up a common dc solar post to AC voltage and posed a question.

No, it will be a 48 volt DC system, and likely a 240 AC system, just need to work out a few questions.

[WiredForStereo]

Originally Posted by Bert06840

Which brand/model specifically? The ones that I have looked at are either natively split phase, or single phase 240V. Single phase 240V is in practice the global 230V single phase model as would be used in Europe and Asia.

Something like but not necessarily this: https://watts247.com/product/lv6548-...built-in-wifi/

Originally Posted by Bert06840

But again, I’d make damn sure I *need* split phase. The only three loads that I can think of are an A/C, a range, and a washer. You can find plenty of 120V mini-splits and plenty of 120V washers. And do you really want to have a 8kW five-position stove and oven in a bus?

That's a good question. Everything can be done with 120V, obviously. But also, since I have a big ol' bus sitting in my back yard with a 3+ kW solar array and a day's worth of kWh stored in a battery, might be nice to use it for something when it's not being lived in. Especially if I also put my big diesel generator in it. It could power the house in case of a power outage.

Originally Posted by Bert06840

...for the vast majority of people.

I've never been so confused as to consider myself one of the vast majority of people.

Originally Posted by Bert06840

You’re not going to run a 240V water heater or a dryer off your inverter, so if you want to haul a dryer around to be used when you’re in an RV park

Probably not a dryer, but maybe a water heater, maybe a heat pump, maybe a cookstove. Still trying to figure out the tech and logistics.

The easiest solution to my conundrum is obviously a 48 volt battery charger which is a separate unit from the inverters, then when I plug into shore power, I'm just charging batteries, and I can run each thing off the batteries in each thing's native voltage. No switchover necessary. It's only a backup anyway, solar will handle most power generation needs.

[Bert06840]

Originally Posted by WiredForStereo

But also, since I have a big ol' bus sitting in my back yard with a 3+ kW solar array and a day's worth of kWh stored in a battery, might be nice to use it for something when it's not being lived in.

Well, then I think you are going to end up wanting a grid-tied inverter system, which isn’t allowed anywhere code wise.

Especially if I also put my big diesel generator in it. It could power the house in case of a power outage.

You could have a transfer switch in your house and plug in your bus through an generator inlet for outages.

Probably not a dryer, but maybe a water heater, maybe a heat pump, maybe a cookstove.

For the water heater you are much better off using this:



And the most efficient heat pumps are 120V.

The easiest solution to my conundrum is obviously a 48 volt battery charger which is a separate unit from the inverters, then when I plug into shore power, I'm just charging batteries, and I can run each thing off the batteries in each thing's native voltage. No switchover necessary. It's only a backup anyway, solar will handle most power generation needs.

That’s what I do, but then at 24V, minus the shore power. I got a 450A alternator and don’t expect to be around “people” (I.e. an outlet) too much, and will charge up the batteries with the bus in the dark of winter. If I end up turning into an extrovert, I can add a 24V supply later.

[Rwnielsen]

If you're ever in the market for a big diesel generator I have one, actually two, already installed in my bus. I barely need one, 16 KW

[turf]

count the number of AC circuits you want and then choose.

5 or under i believe is 30A shore

6 or more is 50A shore.

usually the upgrade from 30a to 50a is the difference of running 1 air conditioner or 2.

50A shore is wired like like a panel in your house.

both your shore power and your inverter are wired to a transfer switch. the switch decides which one sends power to the breaker panel.

30A is cheaper and usually sufficient for small rv's. with a large bus, you may want to spend more and go with 50A shore power, but only if you are running twin a/c on the shore power. if you only want to charge the battery, you may get by with an 15/20a extension cord and a charger.

[Rucker]

Originally Posted by WiredForStereo

With many of these systems, if you want 240 volts, you just run two of them parallel.
?

A quick google search indicates that at least some inverters can be run in parallel to generate 240 VAC, providing they have a synch cable (I'm guessing that cable ensures the sine waves are 180 degrees).

Their SOURCE for the power is a 12V or 24V battery bank, NOT shore power.

I don't know if that is where the confusion lies?

[WiredForStereo]

Originally Posted by Bert06840

Well, then I think you are going to end up wanting a grid-tied inverter system, which isn’t allowed anywhere code wise.

I know that, which is why I'm not asking about it.

Originally Posted by Bert06840

You could have a transfer switch in your house and plug in your bus through an generator inlet for outages.

Of course, I'm not asking about transfer switches, I'm asking about AIO inverters and shore power.

Originally Posted by Bert06840

For the water heater you are much better off using this:

All options are on the table. I actually already own one.

Originally Posted by Bert06840

And the most efficient heat pumps are 120V.

Perhaps, I've not yet confirmed that for myself. I've heard claims made for both.

Originally Posted by Bert06840

That’s what I do, but then at 24V, minus the shore power. I got a 450A alternator and don’t expect to be around “people” (I.e. an outlet) too much, and will charge up the batteries with the bus in the dark of winter. If I end up turning into an extrovert, I can add a 24V supply later.

You do you.

[WiredForStereo]

Originally Posted by turf

count the number of AC circuits you want and then choose.

5 or under i believe is 30A shore

6 or more is 50A shore.

usually the upgrade from 30a to 50a is the difference of running 1 air conditioner or 2.

50A shore is wired like like a panel in your house.

both your shore power and your inverter are wired to a transfer switch. the switch decides which one sends power to the breaker panel.

30A is cheaper and usually sufficient for small rv's. with a large bus, you may want to spend more and go with 50A shore power, but only if you are running twin a/c on the shore power. if you only want to charge the battery, you may get by with an 15/20a extension cord and a charger.

None of this is relevant to my questions.

[WiredForStereo]

Originally Posted by Rucker

A quick google search indicates that at least some inverters can be run in parallel to generate 240 VAC, providing they have a synch cable (I'm guessing that cable ensures the sine waves are 180 degrees).

Their SOURCE for the power is a 12V or 24V battery bank, NOT shore power.

I don't know if that is where the confusion lies?

I literally posted a link to the type of inverter I'm talking about.

Check out other systems at https://www.mobile-solarpower.com/al...-packages.html