SINGLE PHASE LOAD SHEDDING

Depending on the exact requirements, it is often possible to use "shower priority units" For example, connect an electric cooker in place of the "high priority" shower and connect immersion heaters or space heaters, via a small consumer unit in place of the "low priority" shower. Then, whenever the cooker is in use and drawing more than say 10 amps, the space heaters or water heaters are isolated.

Multiple units may be used if desired. For example, use of cooker "A" isolates two immersion heaters, use of cooker "B" isolates 5 or 5KW of space heaters.

EV chargers are available that monitor the total current used by the whole installation, and pause or reduce charging when this current would otherwise be excessive.

...I want to use load shedding so that the single phase supply capacity is not exceeded. I am looking for a simple 3 phases device with current coils..

You've confused me already John - single phase or 3-phase? Or a 3-phase device you can also use on single phase?

   - Andy.

Are you looking for one large device to shed all loads, or many devices distributed locally near the non-essential loads?

Worth noting though that your description does seem to fit the scope of an EREC G100 CLS? Even if no generation (currently)

This particular job is for a large single phase installtion where a new 3 phase supply is not available.

It is a domestic installatiuon with a 100A single phase supply. The supply may be 100A but I suspect that the authorised supply capacity may be only 80A.

The device will have a one or more current coils on the supply and will control contactors in the supply to one or more heavy loads to  isolate them to prevent the overloading of the supply.

I am looking for suppliers of this type of kit to get their data sheets to evaluate their suitability.

JP

John, is this Schneider device the sort of this which you are looking for. They may be cheaper elsewhere!

There are plenty of current monitoring/load shedding relays about - e.g. https://uk.rs-online.com/web/p/monitoring-relays/8577072?gb=s but it's can get quite "interesting" quite quickly once you move past the "when a high load high priority load is on, disconnect all the low priority loads" kind of logic. What seems simple - e.g. switch off large load when overall current > 80A (and therefore turn it back on when overall current is <80A) can easily get into an unstable oscillating state (you probably already thought of that, but just in case...)

On the subject of load shedding heat pumps - like a lot of compressor driven stuff I suspect they won't appreciate just having its power removed unexpectedly - mine came with "ESCO" contacts (intended to respond to a DNO signal to shed load) and an option for separate peak (constant) & off-peak (timed) supplies ... either way, plan to run at least one extra cable - which might have to go to the outside unit or the indoor controller.

  - Andy.

AJJewsbury said:

What seems simple - e.g. switch off large load when overall current > 80A (and therefore turn it back on when overall current is <80A) can easily get into an unstable oscillating state (you probably already thought of that, but just in case...)

That occurred to me too. I suppose that it could be addressed by having a relay/contactor which opens on loss of power and needs to be re-closed manually.

Manual reset probably isn't ideal from a consumer's point of view (flat EV in the morning because one of the teenagers had a late night shower and neglected to press a button afterwards?). Interestingly that Schneider unit seems to take a not dissimilar approach - but resets automatically after 5 or 10 mins (so if the overload remains it will keep reconnecting, overloading, then disconnecting ... which doesn't seem ideal). If you want to avoid a "smart" system (that can dynamically adjust according to the actual loads) I would have thought it would be simpler to measure the side you're *not* disconnecting - with a margin to allow for the disconnectable load. So say you had a 20A low priority load and a 80A supply, you'd disconnect when the priority loads exceeded 60A (i.e. the 20A margin no longer remains) and reconnect once it had dropped below (with a time delay if you wish). You could cascade such an arrangement for several low priority loads if you wished. E.g.