How to deal with uneven load on 240 volt generator?

[David Anderson]

Here is a pic of my ammeters and current transformers.  My genny output goes through the CT's first then to the disconnect.
This is the first time I've opened the CT box in 20 years.

David

[belfert]

What is the total KW of yours? Knowing that would make a difference in which way to go.

12.5 KW

[belfert]

Arrange your loads on your breaker panel to balance between the two phases as close as you can.

That is the issue here.  If you refer to my proposed schematic I attached essentially all of my 120 volt loads pass through my 120 volt inverter.  I can't split the loads and still have them go through the inverter.

[David Anderson]

What does  the other 120v leg of your genny feed now?

All my plugs in my coach go through my inverter, but all my heavy loads,  four electric heaters, electric water heater, 3 AC's are evenly split on the two legs. Only front AC can pass through inverter so I can run it off my alternator with genny off.

I can balance the phases by watching the ammeters.
One could balance the phases by calculating the loads from the mfg nameplate.
David

[belfert]

Right now, the generator is configured for 120 volt only so it has a jumper connecting the two legs togther to balance the load across the legs.

[David Anderson]

I just studied your diagram and realized that your set up is exactly like mine. All of my heavy loads are on the 240 V panel. They are closely balanced between phases.  I do not run the generator unless I'm using heavy loads
If I'm not running the generator then I just use the inverter on the batteries or I am hooked up to shore power.
I do have an automatic transfer switch.

[David Anderson]

Right now, the generator is configured for 120 volt only so it has a jumper connecting the two legs togther to balance the load across the legs.

Got it.
So do you have two 120 v wires (same phase) going to each lug in your breaker panel?
If so reconfigure so each output is now opposite phase to the other with 120 v output on each leg and 240v leg to leg. Wire big 120v loads on the first panel upstream the inverter that run off genny or shore power.

[belfert]

Besides my rooftop air conditioners, the only 120 volt loads not going through the inverter are my electric water heater, and a dedicated circuit with a single receptacle to plug in a large 120 volt load like an electric heater.

Nearly all of my 120 volt loads go through the inverter which means the generator is loaded unevenly.  The loads have to go through the inverter if I want them to be powered when on battery.

[bs4104]

You might think of a second tranfer switch too for some of your loads
new switch control by inverter/ gen out put
Bruce

[belfert]

I have a Victron Multiplus II 48/3000 inverter.  One option is to get a second Multiplus II that matches, and then the pair can run in split phase mode.  The Multiplus II 48/3000 has something like six different product numbers even though they are all called Multiplus II 48/3000.  The product numbers have to match.

My Multiplus II is somewhere between two and three years old, but I don't think I can buy a matching inverter with the same product number anymore.  I might have to buy two new inverters which will put me up into the $3,000 range.  I simply don't have $3,000 to spend on this right now.

[David Anderson]

Besides my rooftop air conditioners, the only 120 volt loads not going through the inverter are my electric water heater, and a dedicated circuit with a single receptacle to plug in a large 120 volt load like an electric heater.

Nearly all of my 120 volt loads go through the inverter which means the generator is loaded unevenly.  The loads have to go through the inverter if I want them to be powered when on battery.

I wired my coach just like yours except I'm 240V. I'm never more than 10 amps out of balance when genny is running.
I recommend the ammeters so you can monitor loads in real time.  20 plus uneventful years of usage is quality testimony.
David

[belfert]

My proposed setup is always going to be out of balance when any 120 volt load is used because basically 100% of the 120 volt load would be coming off of one leg.

[David Anderson]

My proposed setup is always going to be out of balance when any 120 volt load is used because basically 100% of the 120 volt load would be coming off of one leg.

That's true on my setup also. However most of my inverter loads are minimal or only on a short time ie, a hair dryer or microwave. You still need to balance your non inverter 120v loads on the 240v panel upstream the inverter panel as best you can.  The 240v loads if any don't require balancing. They use both phases.

That's why the ammeters are important to me.  If I'm more than 10 amps out of balance I can turn on a device to load up the low amp phase to bring them closer to balance.

I looked online and found these

https://www.bluesea.com/products/9630/AC_Ammeter_-_0_to_50A_with_Coil

I think I paid about $19 each when I installed them. They've  gone up in price.
It's got the wiring diagram on the site so you can see how the current transformers are wired.

[lovetofix]

My proposed setup is always going to be out of balance when any 120 volt load is used because basically 100% of the 120 volt load would be coming off of one leg.

You could get a standalone charger for your battery bank and put it on the other leg.
That way, any time you are running the generator the 120V loads are on one leg and the dedicated charger is on the other leg recharging your batteries. If that would exceed the C-rating of your battery bank you can turn the inverter charger down or off which would also decrease the load on the leg feeding your inverter and 120V loads.

[KF6-BusFan]

Do you intend to have (or do you already have) 240v shore power?

I would start by checking with the generator mfg to see whether unbalanced loads are an actual problem. Just because some people on the internet think it is, doesn't make it so.

If the imbalance is unacceptable to them, or the vibration is "too much", I feel like the most complete solution is going to be something like:

• 240v shore power
• 240v autoselect transfer switch between shore power and 240v generator
• feeding the 240v panel
• Convert water heater to 240v and connect at this panel
• 120v Victron is then being fed by one leg only, as designed
• Try it out in this configuration to check for generator vibration (as noted by another post)
• If needed or desired, insert autotransformer just before the Victron, to spread that single-leg load over the dual legs of the 240v system
• Program Victron to limit the battery charge current in order to not exceed the 28amp imbalance limit on the autotransformer. This is one of the larger loads on your 120v system and the only (?) one that is run for longer than a minute or two. Microwave ovens and hair driers are large, but short term, for example.

This has the effect of making electric water heating a non-battery function. If that's a problem, I personally would attack it by introducing either a combo electric/propane water heater or something similar. I like having two methods of heat anyway, but that's just me. I may be overthinking this part; if it's a 120v water heater it's probably something like 14 amps, so if you leave it downstream of the inverter that just means you can't run the microwave at the same time, basically; this is a not uncommon limitation even in 30-amp 120v shore power setups.

Many other options exist. I would start by checking the assumptions.