Maximum Demand Control

[Meshugga]

Hi All

I currently have the following installed on my yacht
7.2 kW solar panels
44 kW Lifepo4 battery bank
10 kW invertor 230 V
18 kW genset

I would like to install some sort of automatic load control so that large power drawing equipment cannot operate simultaneously while on inverter power. Obviously I already have suitable circuit breakers installed on all circuits and thus when the loads are exceeded, the breakers trip (works, but is a pain). Ideally, I would prefer to simply deny power to other circuits when one of the large power draw items is operating.

300 l/h Water maker: 4 kW
3 x Water heaters: 3 kW
Gally (dishwasher/toaster/kettle): 4 kW
Induction hob: 5 kW
Oven & microwave: 4 kW

Obviously I could install a 5 position selector switch, but I'm hoping that somebody can recommend a more elegant ((automated) solution.

Many thanks

 

[time2roll]

I think you are looking for a load shed device. There are sensing relays or even breakers that would seem to work. Everything I am familiar with is 120 volts so I can't suggest a specific solution.

120v relay based. Maybe this can be adapted or something similar for 230v.

 

[BentleyJ]

Interesting question, regarding the availability of "off the shelf" load control equipment, or more appropriately, lack thereof. I've often wondered why there is so little available.
The following assumes that when on shore power all of the high usage loads should be energized.
A DIY solution could be designed using a series of definite purpose contactors with 208/240V coils. https://www.supplyhouse.com/Packard-C240C-2-Pole-Contactor-208-240V-40-Amp

If you were to install 5 of these (1 for each of the aforementioned high usage appliances) They would be connected such that the coil of each contactor would be connected across the LINE side of the contactor and passing through a smaller, SPDT or DPDT control relay also with a 230V coil. The coil on the control relay would be connected across the output of the inverter such that when the inverter is ON it causes the control relay to change state interrupting the coil current to the 5 main contactors and none of the those appliances would be energized.

The downside is that when on shore power all 5 definite purpose contactors would be energized even when the appliances were not in use. This is a bit wasteful but its the simplest solution I can think of that would be reasonably easy to accomplish with easy to find parts.

Of course you could also install a bypass DPST toggle switch that would manually turn off the main contactors in an extended absence or non use period, you just have to remember to flip the switch back on when returning.

 

[Solar Guppy]

Hi All

I currently have the following installed on my yacht
7.2 kW solar panels
44 kW Lifepo4 battery bank
10 kW invertor 230 V
18 kW genset

I would like to install some sort of automatic load control so that large power drawing equipment cannot operate simultaneously while on inverter power. Obviously I already have suitable circuit breakers installed on all circuits and thus when the loads are exceeded, the breakers trip (works, but is a pain). Ideally, I would prefer to simply deny power to other circuits when one of the large power draw items is operating.

300 l/h Water maker: 4 kW
3 x Water heaters: 3 kW
Gally (dishwasher/toaster/kettle): 4 kW
Induction hob: 5 kW
Oven & microwave: 4 kW

Obviously I could install a 5 position selector switch, but I'm hoping that somebody can recommend a more elegant ((automated) solution.

Many thanks

This is the concept of what you could have installed, load shedding is what your looking for

 

[400bird]

Seems like a job for a load shed controller. I'm not super familiar with the operation or set up, but I'll bet it's what you're looking for.

PSP LSC-08 8 Channel Universal Stand Alone Load Shedding Controller

PSP LSC-08 8 Channel Universal Stand Alone Load Shedding Controller. In stock and available for immediate shipping. Free shipping and no sales tax outside of Wisconsin.

apelectric.com

 

[Vigo]

^Glad to learn a term for that so i can look into it!

I think another term you might look into is 'interlock'. You can make it so that one circuit cannot work if another one is already on, etc. Something like a current sensing switch on one circuit hooked to the electromagnetic coil of a relay/contactor on the other circuit. Even if you put current sensors and relays on both circuits it would work, just whichever one was turned on first would prevent the other one from turning on.

You can also use several different 'triggers' in series. Such as, for X circuit to be active, both Y and Z circuits must be idle/off (2 current switches in series). You can also use voltage switches such that 'X circuit cannot activate unless Y circuit is idle/off, AND voltage is above Z' (a current switch and voltage switch in series), etc.

It can all be pieced together with fairly cheap components but has the potential to become a rat's nest of wiring depending on how much functionality you are trying to build.