Beware The Safety Switch Trap Burning Battery Budgets

Unless your house was built in the last couple of years, installing a house battery will likely require at least some switchboard upgrades.

It’s a basic electrical regulation so why are some solar battery salespeople ignoring the need and setting expensive traps in the process?

Does Your Switchboard Require An Upgrade?

At the heart of this problem is the humble safety switch. They’ve been around for decades but since 2023 the AS3000 rules mandate they shall be updated to the latest type if any significant work is done on your wiring.

Installing a solar battery means you are changing the supply, so every downstream circuit needs a compliant Type A residual current device. No ifs or buts.

Of course this can be expensive. Switchboard rebuilds start at $1000 and that’s a significant price differential when your competition is quoting on a power system without including all the required work.

So customers are rightly upset when there’s a hidden premium to pay on install day, because the sales team conveniently forgot and the electrician is obliged by law to do the work.

Make sure to confirm with your installer whether an upgrade is needed before you sign on the dotted line.

Safety Through Balance

Say you have a toaster that’s using 8 amps of current. What flows out to the appliance on the active wire must come back via the neutral wire. If you drop that toaster in the bath, some of the current will “leak” out of the circuit.

The imbalance, measured between active and neutral by the current transformer, will throw the safety switch open, disconnecting the supply.

Thanks to electricaltechnology.org for the image

It doesn’t take much to stop your heart, so RCDs will trigger at only 30 milliamps.¹ So whether it’s the toaster using 8 amps, or my Dad’s welder using 28 amps, the circuit only has to leak a tiny 0.03amps to trip the RCD.

Name Calling Begins Here

“Safety switches” do pretty much the same thing. They go under a few different names, like earth leakage circuit breaker (ELCB), residual current circuit breaker (RCCB) residual current device (RCD) or residual current breaker with overload (RCBO), so the names are often confused.

At 40 odd years not the oldest I’ve seen, but this outlet gave earth leakage protection to several others in the house.

Of course “pretty much” isn’t a term covered in the rules and there’s nothing like a room full of pedants electricians to start quoting chapter and verse from “the good book” or more precisely AS/NZS 3000:2018 Amendment 2.

A cheap builder’s new house switchboard has 2 pole RCDs for earth leakage protection. Downstream of these are two or three standard circuit breakers to protect the final sub circuits from overload.

If you want “whole home” backup in the board pictured above, sadly everything except the red toggle is likely going in the bin.  Installing 7 RCBOs will free up 6 poles you may need for consumption metering, solar circuit breakers or an EV charger.

AC/DC

Now everybody is rocking solid state power handling equipment, we need devices that will cope with both kinds of music.

Ordinary alternating current (AC) powers things with a predictably shaped wave, which ebbs and flows 50 times per second. These smooth curves make up the grid frequency of 50 Hertz, which keeps your oven clock on time.

However the modern world is full of batteries which need direct current (DC), solar panels which supply DC, and variable frequency drives which power LED lighting and flexible appliances. For instance, when you see an air conditioner with an “inverter” sticker or a ceiling fan with a “DC motor” then it relies on a solid state power supply.

Remember when your electric keyboard or portable home phone(!) had a plug pack on the wall, which felt so heavy? Like it was solid metal? Well it was. There was a steel and copper transformer in there.

The green curve is what you get from mains electricity or a transformer. Inverters make less refined “waves” depending on the need.

These days your cordless everything charger has comparatively little metal inside it. It uses lightweight high frequency switching devices to boost or buck voltages. Conversions are done by incredibly fast electronics, chopping up the nice smooth AC coming from the wall into all kinds of crazy square waves and reforming them into just what the technician ordered, almost.

The thing is that solid state power supplies often leak a bit of electricity here and there.

In theory, the top image shows you can switch things on/off really fast to make waves, but in reality, things can get lumpy, spiky & leaky, as seen in the lower oscilloscope measurement.

Type A versus Type AC

Older RCDs called Type AC can cope with nice smooth AC waves but they are effectively blind to DC pulses which might leak from  solid state power handling equipment.

Newer Type A RCDs will trip if they see a 6mA DC pulse on top of the standard AC waveform.

While Type B RCDs will trip if they encounter smooth DC from something like an EV battery. Most wall chargers or EVSE equipment has this built in, however there are specific breakers available for EV circuits.

So When Is The Difference?

AS/NZS 3000:2018 Amendment 2, published on 30 April 2021, introduced Clause 2.6.2.2.2, to better protect against pulsating DC residuals from modern electronics, solar inverters, and EVs.

• There was a 24-month grace period for installing either Type AC or Type A RCDs.
• From 30 April 2023, Type AC RCDs were prohibited in new installations, alterations, additions, and certain replacements.
• Even a 3 year old house may require a switchboard rebuild.

You may need your glasses on to read the tiny pictogram, so if the battery sales team ask for pictures, make sure these are legible.

Poles Apart

1990 might feel like yesterday, but after 30 years switchboards will need work. I like to point out it’s a good opportunity, especially if you’re putting a whole package of upgrades together and using a green loan to pay for them.

If your electrician is swearing about poles, don’t worry, they’re not ranting about migration from the EU. Switchboards are sized to suit  miniature circuit breakers (MCB) and each 17mm section is considered a pole. If your ‘board is pretty packed, then removing old 2 or 4 pole RDCs can create space needed for new solar circuits.

Happily there are now RCBOs to offer individualised circuit protection. Not only are they more compact, a single fault doesn’t take out a cluster of three circuits, or your whole house.

However even cheap junk RCBOs cost $30each, so a modest single phase upgrade board might use $500 in parts alone.

Here we’ve superimposed a hybrid solar inverter to show partial home backup. Arrowed in blue, TWO downstream circuits, have Type A RCBOs. The single RCD would be grandfathered as compliant last century.

Site Inspections Solve Problems

Adding an unexpected additional expense on installation day might sound like an opportunistic tradie is taking you for a ride, but the real shonks are those foisting responsibility onto electricians without giving the customer the whole picture up front.

It’s important to understand and document what you’re buying and what’s in the fine print in terms of exclusions.

Originally 6 ceramic fuse circuits, 10 poles have been added in 9 enclosures. This is guaranteed to be a mess.

If you’re keen on having power during an outage, write down what you want to have working  and get the salespeople to sign off on it.

Whether it’s partial blackout protection, ie lights, fridge and internet or it’s the whole house, including the rainwater pump, stove and the air conditioning, everyone must be on the same page.

Starting at the top, with a 1970s/80s switchboard that had a single RCD added for rental rules. This board now has whole home backup with RCBOs throughout and the two pole RCD reused for the oven/induction stove.

Batteries Mean Updates Are In Order

When you get a quote for a heat pump, EV charger, air conditioner, solar power system or battery, make sure you’re getting the whole story. Adding one piece of the puzzle with no real plan will always be more expensive.

Ad hoc installation of different brands of equipment means rework and compromise that can easily leave you with a lot of expensive but dysfunctional gear.

So make sure you confirm if a switchboard upgrade is required before locking in an install, so you can factor that into the cost.

For more on switchboard upgrades, read our explainer on why they are vital for all-electric homes.