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When do hot water unit installations require an RCD and an Isolation switch?

When do hot water unit installations require an RCD and an Isolation switch?

Stop the confusion! Do you need to install an RCD and an Isolation switch when swapping or replacing an existing Electric Hot Water unit?

Answer! NO RCD or Isolation Switch required, if…

»  the element is the same size!  e.g. 2.4 kW HW replaced by 2.4 kW

»  there are no changes or alterations to the circuit cable or circuit breakers e.g. reconnect the same existing cables.

»  the HW unit was 350 litre and went to a 450 litre and if the element is the same size!  e.g. 2.4 kW HW replaced by 2.4 kW

YES RCD or Isolation Switch is required, if…

»  the HW unit is upgraded from say – 2.4 kW element to 3.6kW element

Pictured here is my personal Rheem Hot Water system, around 28 years old and still going strong, well electrically.

Hi I’m 28 years OLD! Do I need an RCD or Isolation switch? 

The plumbers may say something different (what rust marks?).  I plan to have the unit replaced shortly (my order is in with Reece). As you can see, there is no isolation switch outside, additionally, there is no RCD on this circuit.

Now if I keep to the same circuit and keep to the same size element which is around 3.6 kW then I can call out a plumber with a restricted electrical licence to complete the replacement.

If I want to upgrade the unit and upgrade or extend the cables for the circuit – then I would be required to call an electrician or in my case dust off the tools and meters and complete the electrical installation, install a new isolation switch and RCD.

Because we are only replacing the 3.6 kW size element electric hot water unit for the same 3.6 kW size element electric hot water, then I do not require an RCD or Isolation switch at the new hot water unit. (yes like for like replacement)

I am still amazed almost two years later, there are electricians and plumbers who still do not understand this new rule, or maybe they are trying to profit from their interpretation.

The new rule is very clear it is NOT retrospective, in other words it covers NEW installations not existing as I said above unless the existing wiring changes or the appliance is electrically say a 2.4kW to 3.6 kW larger element and circuit in size

Now there is no reason why an RCD and Isolation switch should be fitted.

This RCD/Isolation install must only be completed by a full licenced electrician as a restricted electrical licenced person is limited to only disconnecting and reconnecting and/or locating and rectifying  (fault finding service), with NO installation of fixed wiring or switchboard work.

I just wonder if the new Rheem Everhard unit will last as long as this baby! Maybe I will look at an extended, extended & extended warranty.

The extract from New AS3000 Wiring Rules
Updated 5th June 2020

An explanation from the Electrical Safety Office – E-alert 

(New hot water unit installs – RCD protection on all hot water units)

This rule does not apply for existing installed hot water units or direct like for like replacement hot water.

There are two new requirements for Electric Hot Water units.

These rules only apply to NEW INSTALLATIONS ONLY not existing or like for like replacements.

The new AS3000:2018 Electrical wiring rules as published;

»  A new hot water installation will require an Isolation switch to be installed near the Hot Water unit.

»  All new installations or altered circuits/sub-circuits with hot water units are required to have an RCD (Residual Current Device) 30 mA installed.

There is a concern with the new RCD (Residual Current Device) rule for Hot Water units, the householder could experience false tripping. False tripping can be prevented – if the electrician makes certain the Hot Water Unit is installed on a dedicated circuit. If the unit is a standalone circuit/RCD, there should not be any false tripping. i.e. If there were 2-3 hot water units, each Hot Water Unit should be powered by an individual and dedicated RCD and circuit.

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