Shower Electrics MCB vs RCD

[bmouthboyo]

Hi Everyone,

I am currently looking to upgrade my current electric shower with a power shower.

Whilst doing some research on what I currently have and how I can go about the upgrade I noticed that my current shower has a MCB at the CU. I believe the shower should be protected with a RCD however, is this correct?

This is my current CU:

Is there a RCD further down the line in the switch that hangs from the ceiling or is this something I need to get replaced? Is it as simple as swapping a MCB out with a RCD?

Not going to start ripping wiring out don't worry, just like to know how it's all meant to work.

Thanks

 

[ericmark]

You have an isolator, then 2 x MCB, then 2 x RCBO then 4 x MCB.

The RCBO is an RCD and MCB combined, likely best way to do it, today you can also get spark detection built in, and can have surge protection devices, (SPD) and the RCD can come as many types, and tripping currents.

Your problem is likely finding devices to fit that box, so likely will need a consumer unit change.

So a RCD measures current in and current out, and assumes if not equal then some must be going to earth. Because using AC some current will always leak due to inductive and capacitive linking, so it is considered 30 mA is a good compromise protection v tripping with no real fault, but the more you split up the circuits the less likely to trip with no real fault. They come as type AC, A, F, B, and S, in real terms today we fit type A RCBO's which will work with up to 6 mA DC, but without DC detection we have no idea if within 6 mA, so really only valid for EV charging and Solar panels, if they don't feed anything else.

A type B will handle more DC, but not found a single width RCBO which is type B for RCD, but loads are type B for the MCB part.

So the MCB comes in three types now, B, C, D, which relates to the magnetic part of the trip B = 5 times thermal rating, C = 10 times, D = 20 times so a B32 MCB trips in fullness of time at 35 amp, but will trip in 0.01 seconds at 160 amp, so we need to insure with a direct short 160 amp will flow, so ohms law 230/160 = 1.44 ohms approx, give 5% extra for safety, so 1.38 ohms is considered max loop impedance (call impedance with AC and resistance with DC) but the cheap plug in testers with loop pass at around 1.9 ohm, so it needs expensive test gear.

Since a new consumer unit needs registering not really worth doing DIY, and the electrician doing the work should explain this, but what we have is a balance between cost and protection and chance of tripping when it shouldn't.

I went for all RCBO as a freezer full of food is not cheap. That's easy to see, but the SPD is more abstract, we have no idea when an LED bulb fails if due to a surge or not. If you have never lost equipment like video recorders, TV and LED bulbs then likely not required, but if they have failed a SPD may help, I fitted one to be on safe side, but no one really knows if needed.

 

[EFLImpudence]

Which shower are you planning to buy?