Multiple Electric Showers

garlad

Hi,
Moved into a house with 2 electric showers installed. Never used one, but getting that room renovated now. I read a previous thread in this forum about needing some kind of switch in your fuse box to make sure both showers do not come on at the same time.
Checked my fuse box, but don't know what I should be looking for, so I took a photo to show you all(see attached). From what I can see, there are 2 RCD's, one for each shower unit.
Bit scared to turn them both on in case the house ends up with no electricity (or should the second one automatically switch off when second shower turned on?).
I think I need some kind of switch installed which will manage the 2 showers. Any advice?

Copper

If I was in that situation, the easiest thing to do is to turn everything off in the house, set the two showers to the lowest temperature setting and turn them both on for a few seconds. If they both run at the same time then you have no interlock, and you should get one installed. If only one shower runs at a time then you have an interlock and you're ok.

You have two RCBO's in at your board, more than likely one for each shower. Its impossible to tell if you have an interlock at your board without more pictures. Even if there isn't one at the board, there could be one mounted in the attic.

garlad

Thanks for info Copper.
Builder taken out upstairs shower, so when he puts in new one I'll test using your method.
If each is on a seperate RCD, does that mean if the two are on hot, one will cut out, or could the fuse blow cutting electriciy from whole house?
The idea of the interlock then is that you dont have to keep flicking the RCD switch back on after it cuts out?

Hoagy

Two showers on together will either
a) blow the main fuse for the house
or
b) blow the main ESB service fuse for the house
or
c) both.
The interlock unit is a necessity.

ircoha

OP: would it not be possible to test it now, by say putting a bulb on the circuit now disconnected and then turning on the other shower, it might be easier than blowing the fuse outside the house!.

I dont know what triggers the interlock, perhaps someone else will explain how they work and how they are wired.

For example, if u have 2 electric showers in two ensuites can u run one cable to the interlock and then 2 cables from it or do both have to have thier own trips and separate circuits with both cables passing through the interlock.

garlad

electrician coming out tonight.
Will let you know what he says

FX Meister

How old is your house? A number of newer houses have an enhanced ESB supply which allows you to use two electric showers. Could be a possibility

Copper

The interlock is an arrangement of contactors to prevent the simultaneous operation of both showers. Since only one shower can ever be on at a time, they can both be fed off the same RCBO and circuit.

If the sparks rigs up his own arrangement of contactors in the attic or at the board there will normally be a selector switch to choose which shower has power. A normal lightswitch is often used for this.

You can also get premade "priority units" to go in at the board. If these are used then one shower will always have a supply i.e it has priority. To use the other shower you can hit a selector switch.

Your mains is probably fused at 63 amps. On the lowest temperature setting most showers won't draw more than 25 amps so you will be okay to test them. The fuse is designed to pass momentary overloads anyway, if you draw 70 amps, the fuse won't blow straight away, it will take several hours to blow.

garlad

House 40 or 50 years old.
Electrician out last night, going to install some kind of box (presume its like this interlock). Box costs about €150 apparently. What it does is makes one shower the main shower. This will have the power. But if the second shower is turned on, it'll switch the power over if the main one is not being used.

FX Meister

Is he charging labour on top of the €150?

garlad

Yep, but hes a relative, so wont be much.
Hes done loads of stuff for us before

sundula

150.00 sounds reasonable enough for a pre-made shower priority unit

FX Meister

Just thought it seemed a little expensive but I don't have that much knowledge of them.