The core issue (in simple terms)

Most single-phase PV battery backup systems can only supply about:

  • 20–25 A @ 230 V

  • ≈ 4.6–5.7 kW max

But a normal house can easily try to draw far more than that when everything is connected.

If the system goes into island mode (ESB gone):

  • The inverter becomes the “grid”

  • It cannot supply high-power appliances

  • If you haven’t limited what loads are connected → the system is electrically unsafe

What are “large loads”?

Typical Irish examples:

Load Current
Electric cooker 30–45 A
Electric shower 35–45 A
EV charger 32 A
Heat pump 20–30 A
Immersion 13 A

Now imagine just two of these trying to run in island mode.

👉 The inverter cannot supply them safely.

What happens if there is no load shedding?

One or more of the following:

  1. Inverter overload / shutdown

  2. Repeated nuisance trips

  3. Overcurrent without proper protection

  4. ADS failure in island mode

  5. Fire risk or equipment damage

From a compliance perspective:

  • You have violated Clause 433.1 (overload protection)

  • You have violated Clause 8.82.7.1 (generator capability vs load)

  • And potentially Clause 411 (fault protection integrity)

Safe Electric is explicitly warning you about this now.

What “load shedding” means in practice (for you)

Load shedding = making sure large loads cannot be supplied in island mode.

There are three accepted ways to do this.

✅ Option 1 – Essential Loads Board (BEST PRACTICE)

You:

  • Move only critical circuits onto a backup board:

    • lights

    • sockets

    • broadband

    • fridge

  • Cooker, shower, EV, heat pump stay on main board

  • Changeover only feeds the essential loads board

👉 This is the cleanest and safest solution
👉 Very hard to fail inspection with this

✅ Option 2 – Automatic Load Control / Smart Relays

You:

  • Use inverter-controlled relays / contactors

  • When island mode starts:

    • cooker

    • immersion

    • EV

    • heat pump
      are automatically disconnected

This must be:

  • Fail-safe

  • Tested

  • Documented

👉 Acceptable, but more complexity = more risk if badly done

❌ Option 3 – Do nothing (RED FLAG)

You:

  • Leave the whole house on backup

  • Rely on “the inverter will trip”

  • Or tell the client “don’t use the cooker”

👉 This is now explicitly non-compliant

Safe Electric is saying:

Design it so misuse is impossible — not just unlikely.

Why Safe Electric cares so much about this now

Because:

  • Clients will turn things on

  • Inspectors see:

    • EV chargers running in island mode

    • cookers on backup

    • heat pumps on single-phase batteries

And when something trips, overheats, or burns:

  • They look at your design

  • Not the client’s behaviour

One-sentence takeaway

If a single-phase backup system can’t safely supply a load, that load must be physically prevented from being connected in island mode — not just “advised against”.