Mate in Linwood was using a dodgy old electric drill in his garden. Cord had nicks in it but he figured itd be fine. Hit a damp patch and the drill shorted - current went straight through him into the ground. Lucky for him his switchboard had RCD protection. It tripped in like 20 milliseconds. He felt a decent zap but wasnt hurt. Without that RCD he'd probably be dead cause the fault wouldve kept running current through him til someone found him or the breaker eventually tripped. He came into our workshop next day still shaken up, wanted to say thanks cause wed installed his RCDs couple years back. Said he never really understood what they did til one saved his life. Now he tests them every month without fail.
Thats what RCDs do - they save lives. Simple as that. Every house needs them.
What RCDs Actually Do
RCD stands for Residual Current Device. Some people call them safety switches cause thats basically what they are.
They monitor electricity flowing out on the active wire and compare it to current coming back on the neutral. Should be the same amount going out and coming back. If theres a difference - even tiny like 30 milliamps - it means current is leaking somewhere.
That leak could be going through a person whos touched faulty equipment. Could be leaking through damaged wiring into ground. Either way its dangerous.
When an RCD detects that leak it cuts power instantly. Like in 0.03 seconds or less. Fast enough that you might feel a tingle but not fast enough to kill you or even really hurt you.
Without RCDs if you touched faulty gear the circuit would keep running current through you. Your muscles seize up so you cant let go. Current keeps flowing til either someone shuts off power or the circuit breaker trips from overload - but that takes way longer and by then your probably dead.
RCDs are different from regular circuit breakers. Circuit breakers protect wiring from overload and short circuits. RCDs protect people from electric shock. You need both.
Why RCDs Are Required Now
Building code requires RCD protection on all circuits in houses built or renovated after 2003. Houses older than that often dont have them.
The reason for the requirement is simple - RCDs save lives and prevent injuries. Before they were required heaps of people got shocked or killed by faulty electrical gear.
Statistics showed that countries with mandatory RCD use have way fewer electrical deaths and injuries. New Zealand adopted the requirement cause it works.
Even if your house is older than 2003 you should retrofit RCDs. Its not required by law if you havent done major renovations but its smart safety.
Insurance companies like RCDs too. Some give discounts on premiums if you got proper safety switches installed.
If your selling a house buyers will want to see RCD protection. Pre-purchase inspections pick up missing RCDs and buyers either walk away or demand price reductions to get them installed.
Types of RCDs
Few different types of RCDs depending on whats being protected.
Fixed RCDs install in your switchboard. Protect entire circuits - everything plugged into that circuit gets RCD protection. This is the standard type we install in houses.
Portable RCDs plug into outlets. You plug your equipment into the RCD. Good for people using power tools where theres no fixed RCD protection. But not a substitute for proper fixed RCDs.
RCD outlets have the RCD built into the outlet itself. Protect just whats plugged into that one outlet. Sometimes used outdoors or in bathrooms where extra protection is needed.
Most houses use fixed RCDs in the switchboard cause they protect everything on those circuits and dont rely on people remembering to use portable ones.
RCD Configurations
Different ways to configure RCDs in your switchboard.
Single RCD protecting all circuits. Cheapest option but has a downside - if the RCD trips everything loses power. Can make it hard to figure out whats causing the trip.
Multiple RCDs protecting groups of circuits. Better option. Maybe one RCD for kitchen and laundry, another for bedrooms and living areas. If one trips you still have power to other areas.
RCD on each circuit. Best protection but more expensive. Every circuit has its own RCD. If theres a fault only that circuit loses power.
We usually recommend at least 2 RCDs for average houses. Splits protection so a trip doesnt kill all your power. More circuits need more RCDs but you dont necessarily need one per circuit.
Did a house in Shirley where they had old single RCD protecting everything. It kept tripping randomly and theyd lose all power. We installed a second RCD and split the circuits. Now when theres a trip they can figure out which half of house has the problem and they always have some power.
Installing RCDs in Existing Switchboards
If your switchboard doesnt have RCDs we can retrofit them.
First we check if theres space in your switchboard. RCDs are wider than regular breakers so you need room. If theres no space we might need to upgrade to a bigger switchboard.
We shut off power to the circuits were working on. Install the RCD in the switchboard. Rewire the circuits to run through the RCD instead of directly off the main bus bar.
Test the RCD to make sure it trips at the right current levels and within the right time. Has to trip between 15-30 milliamps in under 40 milliseconds.
Label the RCD so you know what circuits it protects.
Whole job usually takes 2-3 hours depending on how many RCDs were installing and how complicated the switchboard is.
Some old switchboards are too small or too old to retrofit RCDs properly. In those cases we recommend upgrading the whole switchboard which gets you modern RCD protection plus other benefits.
Common Reasons RCDs Trip
RCDs tripping can be annoying but theyre doing their job protecting you. Common reasons they trip:
Faulty appliances leaking current. Washing machines, dryers, kettles - any appliance can develop faults that leak current to earth. The RCD detects it and trips.
Damaged power cords. Frayed cords, crushed cords, cords run over by stuff. Damage exposes wires and creates leakage.
Moisture in outlets or equipment. Water conducts electricity. Moisture in outdoor outlets or bathroom areas can cause RCD trips.
Old wiring with degraded insulation. Insulation breaks down over time specially in older houses. Creates small leaks that add up.
Too many appliances with minor leakage on one RCD. Individual leaks might be under the trip threshold but add them together and it trips the RCD.
If your RCD trips regularly get an electrician to find the cause. Dont just keep resetting it cause that fault could hurt someone.
We do fault finding where we isolate circuits and test appliances to find whats causing trips. Usually pretty quick to track down once we start methodically checking things.
Testing Your RCDs
RCDs need testing to make sure theyre working properly. They can fail and if they fail you got no protection.
Test button on the RCD is what you use. Push it and the RCD should trip immediately cutting power to those circuits. If it doesnt trip its not working and needs replacing.
You should test RCDs monthly. Takes 10 seconds. Push the test button, RCD trips, flip the switch back to reset it. Done.
Most people dont test monthly cause they forget. At least test them every few months. Better than never testing them.
We also do proper RCD testing with special equipment that measures exact trip current and time. This tests that RCDs not only work but work within the right parameters. Should trip between 15-30mA in under 40ms.
Annual testing by electricians is smart specially for rental properties where landlords are liable for safety. We test, document the results, and replace any RCDs that dont meet standards.
Had a customer in Burnside who never tested their RCDs. When we tested them as part of a safety inspection one RCD didnt trip at all. Been faulty for who knows how long. They had no protection on half their circuits. Replaced it that day.
When RCDs Need Replacing
RCDs dont last forever. They wear out and need replacing.
Signs an RCD needs replacing: wont trip when you push test button, trips randomly for no reason, trips at wrong current levels when tested with proper equipment, physical damage, old age.
RCDs should last 10-15 years normally but can fail sooner if they trip a lot or if theres electrical problems that stress them.
If an RCD wont reset after tripping could be its failed or could be the fault is still present. We check both - test if RCD is working and find the fault if thats the issue.
Replacing RCDs is straightforward. Shut off power, remove old RCD, install new one, test it, done. Usually under an hour.
Cost for replacing one RCD is $200-300 depending on type and switchboard accessibility.
RCDs for Outdoor Circuits
Outdoor circuits absolutely need RCD protection cause outside youre exposed to moisture and standing on ground that conducts electricity.
All outdoor outlets should be on RCD protected circuits. Garden tools, pressure washers, hedge trimmers - all that stuff needs RCD protection.
Pool equipment and spa areas have special requirements. RCDs for pools need to be more sensitive - 10mA instead of 30mA. Extra protection cause water and electricity dont mix.
Outdoor lighting circuits should have RCD protection too specially if lights are in gardens where people might touch them while wet.
We install RCD protected outdoor outlets all the time. Either add them to existing RCD protected circuits or add new RCD to switchboard for outdoor use.
RCDs vs GFCI
Some people ask about GFCI which is what they call RCDs in America. Same thing just different name.
GFCI stands for Ground Fault Circuit Interrupter. Does the same job as an RCD - detects current leakage and cuts power.
In New Zealand we use the term RCD but if you see GFCI in documentation or on equipment its the same thing.
RCD Protection for Rental Properties
Landlords have legal obligations around electrical safety including RCD protection.
All rental properties should have RCD protection on circuits. Its part of making the property safe and habitable.
Landlords are liable if tenants get injured from electrical faults that RCDs would have prevented. Not worth the risk - install proper RCD protection.
We do lots of work for landlords bringing rental properties up to standard. Install RCDs, test existing ones, provide documentation that the properties meet safety requirements.
Tenancy inspections sometimes pick up missing RCDs. Better to get them installed proactively than have it flagged during inspection.
Cost of RCD Installation
RCD installation costs depend on whats involved.
Installing one RCD in existing switchboard with space - $250-400 including RCD, labor, testing.
Installing multiple RCDs - $500-800 for two RCDs depending on configuration.
If switchboard needs upgrading to fit RCDs - $2000-3000 for full switchboard replacement with modern RCD protection.
RCD outlets for outdoor or bathroom areas - $150-250 per outlet installed.
Annual RCD testing service - $80-150 depending on how many RCDs need testing.
These are rough prices. Every job is different. We provide quotes once we see your switchboard and know exactly whats needed.
RCDs in Commercial Properties
Commercial properties need RCD protection too. Requirements are similar to residential but scale is bigger.
Offices, retail shops, restaurants - all need RCDs on circuits. Specially important where staff and public are using equipment.
Construction sites require portable RCDs on all power tools. Site supervisors responsible for making sure this happens.
Industrial properties with heavy equipment need RCDs configured properly for the electrical systems. Three phase circuits need three phase RCDs.
Regular testing and documentation is more important in commercial cause of liability and OSH requirements. We help businesses set up testing schedules and keep records.
How RCDs Prevent Deaths
Worth understanding exactly how RCDs prevent deaths cause it shows why theyre so important.
Electric shock from mains power (230V in NZ) can kill in seconds. Current flowing through your body causes muscles to contract. Your heart is a muscle - electric current disrupts it and causes cardiac arrest.
Amount of current matters. 30 milliamps through your body is enough to cause serious harm or death. 100 milliamps is almost always fatal.
Without RCDs if you touch faulty equipment current keeps flowing through you. You cant let go cause your muscles have seized. The circuit breaker might eventually trip but that takes seconds or longer - way too long.
With RCDs the current cuts in 0.03 seconds as soon as 30mA leaks. Youll feel it but its not enough time or current to cause serious harm. The RCD literally stops the shock before it can kill you.
Studies show RCDs reduce electrical deaths by 80-90%. Thats huge. Simple device that costs a few hundred dollars saves lives.
Common RCD Myths
Some misunderstandings about RCDs worth clearing up.
Myth: RCDs prevent all electrical accidents. No - they protect against electric shock from earth leakage. They dont protect against contact between live and neutral, dont prevent fires from overloads (thats what circuit breakers do), dont make bad wiring safe.
Myth: If you have RCDs you dont need circuit breakers. Wrong - you need both. Circuit breakers protect wiring from overload. RCDs protect people from shock. Different jobs.
Myth: RCDs trip all the time for no reason. If RCDs tripping theres a reason - faulty equipment, damaged wiring, moisture somewhere. The RCD is doing its job detecting problems. Get an electrician to find the cause.
Myth: You only need RCD protection outdoors. No - faults can happen anywhere. Indoor appliances can leak current too. All circuits should have RCD protection.
Myth: Testing RCDs is optional. Testing is how you know they work. Non-working RCD gives you false sense of security. Test them regularly.
Future-Proofing with RCDs
When installing RCDs its worth thinking ahead.
Install RCDs that are rated higher than your current needs. If you might add circuits in future the RCD should be able to handle extra load.
Use quality RCDs not cheapest ones. Good brands last longer and are more reliable. Worth the extra cost for safety equipment.
Consider installing extra RCDs even if not strictly needed. Gives you flexibility if you renovate or add equipment later.
Keep documentation of RCD installations and tests. If you sell the house buyers and their inspectors will want to see it.
RCDs and Solar Systems
Solar power systems need special RCD considerations.
Solar circuits need RCDs same as any circuits. But type of RCD matters - some RCDs dont work properly with DC current from solar panels.
We install Type A or Type B RCDs for solar systems depending on setup. These handle both AC and DC leakage currents properly.
If your adding solar to existing house we check your RCDs are compatible. Might need upgrading if youve got old RCDs.
What to Do When RCD Trips
If your RCD trips heres what to do.
First check what caused it. Did you just turn something on? That appliance might be faulty. Did it trip randomly? Could be moisture or damaged wiring somewhere.
Unplug everything on that circuit. Reset the RCD. If it stays on start plugging things back in one at a time til it trips again. That tells you what appliance is the problem.
If RCD trips immediately when you reset it even with everything unplugged theres a fault in the wiring or the RCD itself. Call an electrician.
Dont ignore tripping RCDs. If it trips regularly theres a problem that needs fixing. Continuing to use faulty equipment is dangerous.
Dont try to bypass or disable RCDs. Seen people do this cause they got sick of trips. Incredibly dangerous - removes the only protection against electric shock.