EV charger installation, sized to what your supply will carry

Hanging the charger on the wall is the easy part. The job is everything behind it: whether your supply can carry another 32 amp circuit, what Ergon will allow on a single phase connection, and how the cable gets from the switchboard to where the car actually parks. The question is nearly always the same, the car arrives in three weeks and what has to happen first, and the honest answer is that somebody has to look at your board before anyone can tell you.

What decides whether a charger goes in cleanly is not the charger. It is the switchboard, the mains, what the supply has spare and what the network will allow, and that has been our work since 2007. Boards and mains upgrades, load logging on buildings already running close to their limit, sub-metering that bills the right lot, and the Ergon paperwork that goes with all of it. A charger is a dedicated circuit on a compliant board with a connection the network has approved. Same job, newer load.

Up here that matters more than it does down south. A lot of houses around Port Douglas, Craiglie and Mossman are on older boards that were never sized for another heavy circuit. And a very large share of the parking in this town is common property in an apartment block or a resort, which changes the question completely.

Single phase, and the 20 amp rule in Queensland

Most houses around here are on a single phase supply, which puts you at a charger up to about 7 kW. That is somewhere near 40 km of range for every hour it is plugged in, depending on the car, so it fills the battery overnight with hours to spare.

The catch is a Queensland one and it surprises people. Under the Queensland Electricity Connection Manual the general equipment limit on a single phase connection is 20 amps, and anything above that has to have active device management on it. That includes the common 32 amp 7 kW units. So a 20 amp charger goes in and that is the end of it. A 32 amp charger goes in under one of three arrangements: an economy tariff using a network device, a primary tariff with basic active management via a network device, or a primary tariff with a dynamic connection. Which of the three is available depends on your site. We work that out and lodge the paperwork before we quote, so nobody finds out afterwards that the charger has to run at half speed.

Three phase skips the device management altogether

Worth knowing before you rule it out. Ergon allows a dedicated 22 kW three phase charger, 32 amps per phase switched simultaneously across all three, to be connected without any of the arrangements above. No network device, no dynamic connection, nothing winding it back at peak times.

On a house the catch is the car rather than the wiring. A 22 kW charger only charges faster if the vehicle can take it, and most electric cars sold in Australia cap out at 7.4 kW or 11 kW on board, so bringing three phase in purely for a charger is rarely worth the money. If three phase is already at the property it is the cleaner connection by a distance. On a resort or a block of units, where the supply is three phase already and there are several chargers to feed, it is almost always the answer.

What has to be at the switchboard

The Wiring Rules want a charger on its own dedicated circuit, not sharing with anything, with its own protection and a safety switch (RCD) suited to the equipment. Where the charger cannot detect a DC fault itself, the safety switch upstream has to be a type that can. Better units handle that internally and cheaper ones do not, so if you have already bought a charger online, tell us the model and we will check it before anything gets ordered around it.

Then there is capacity, and that is where the surprises live. A 32 amp circuit is a serious load on top of the hot water system and the cooking. If the board is a rewirable ceramic fuse board, if there is no room left on it, if the existing circuits have no safety switch protection, or if the mains are undersized, that gets sorted first. Plenty of boards are fine as they are and we will tell you so. If yours is not, our switchboard upgrades page sets out what is involved.

Apartment blocks, body corporates and resort car parks

An owner wants a charger in their bay. The bay is either common property or exclusive use, and either way the cable has to cross common property to get there. In Queensland that makes it an improvement to common property, so it needs body corporate approval, and whether the committee can approve it or it has to go to a general meeting depends on what it costs.

Committees are right to be cautious, and from the body corporate work we already do, the real reason is rarely the one said out loud. It is that saying yes to the first owner, on a cable run designed around one bay, quietly makes owners two through eight harder and dearer. Design the building once, then let owners connect to it one at a time.

• Find out what the building actually has spare. Not what the drawings say. We log the main switchboard over a week and hand the committee a real maximum demand figure, so the decision gets made on numbers instead of opinions.
• Load management, so the supply stops being the reason to say no. A managed system shares whatever headroom exists across every charger and winds them all back together when the building is busy. Six managed chargers will often fit where two unmanaged ones will not.
• Meter every charge point to the lot that uses it. Who pays for the electricity stalls more of these projects than anything technical. Metered properly the argument never starts, and the body corporate is not quietly funding one owner’s fuel.
• Size the infrastructure for later, not for now. Tray, spare ways and a sub board put in on the first visit cost very little next to going back into a finished basement a second time.

We write these quotes the way a committee has to read them: scope, cost, why it is needed, what happens if it is deferred, and what it does to the next six requests. Same as we do on strata and body corporate work already. If the answer is sub-metering, that is our metering work. If the answer is that nobody knows what the building has spare, that is power quality logging.

Guest charging at a resort

Guests turn up in electric cars and ask at reception where to plug in. The engineering is the same as a block of units, but the decisions are different: where the chargers go so staff can see them, how they survive a reversing hire car, how you stop one guest sitting on a charger for two nights, and whether charging is free, included in the tariff or paid for. We do a lot of work in resorts and accommodation already, so staging it around guests and bookings is familiar.

BH Electrics is a licensed Queensland electrical contractor, licence 82270, based in Craiglie. Brad and Leanne Sims run it, with four electricians and two apprentices, and we are fully insured. Installation work comes with a Certificate of Testing and Compliance. Ring by 2pm on a business day and a commercial job gets attended that day.

Sources: Ergon Energy, EV charging and connections, Queensland Government, improving common property and lots and WorkSafe Queensland, certificates of compliance. Standard: AS/NZS 3000, the Wiring Rules, 2018 edition.