Shower wiring

Buford T Justice

Hi

Was working in a house today and I noticed that they have two electric showers.

Nothing odd there really, until i noticed that the two showers are doubled into the same double pole 40A Trip (Not sure if its an MCB or and RCBO).

This is wrong, obviously and these showers need a priority unit. I've looked at drawings that have been posted here before, and I have a question. Should there just be one 40A RCBO in line before the non priority unit, and the respective outputs of the np unit feed direct to the showers, or should there be another mcb / rcbo in there somewehere?

Also. Is there any benefit to using double pole RCBO's instead of single pole?

Also,

Randyleprechaun

Why aren't you sure whether it's an MCB or an RCBO??????

One RCBO will do with the priority unit, it should be already in the proprietary unit(bought of the shelf). A control MCB for the control wiring is also needed/provided.

I have posted an alternative way of doing this before, mightn't be too easy to find it again but try a search.

Randyleprechaun

I've found that original thread

http://www.boards.ie/vbulletin/showthread.php?t=2055595071

I've also attached the original sketch that I did. Excuse the sketch, it's a bit rough and ready but you'll get the idea.


It's a good simple system and is, or at least was allowed by the regulatory bodies.

Isolators required in the circuit that is normally being fed while the contactor is off, and would probably be better to put one in the other circuit too.

The argument was made the last time this was discussed that it's not really a slave/priority setup, and that argument has merit, as if you are in the "slave" shower, turning on the "priority" shower wont kill the power in the slave one. But anyway, it's still a simple effective solution to the problem and cuts out the need for a costly off the shelf unit.

Also, my diagram mentions using 6mm2 cable, probably better off using 10mm2 for all if doing new installation.

Buford T Justice

Randyleprechaun wrote: »

Why aren't you sure whether it's an MCB or an RCBO??????

One RCBO will do with the priority unit, it should be already in the proprietary unit(bought of the shelf). A control MCB for the control wiring is also needed/provided.

I have posted an alternative way of doing this before, mightn't be too easy to find it again but try a search.

Not sure because I didn't bother to take a close look as I was only killin time waiting for the rain to die off. I only noticed the two showers doubled into the one trip, and I've kinda seen enough then. Checked it today and it an RCBO.

Need to make the call to the landlord now and break the bad news to him about the guy that fitted the shower.

With the drawing you have attached there, am I right in saying that after the timelag switch opens again at the end of its time, the power will be cut to the slave shower regardless of the shower being off or on?

Randyleprechaun

Yes, thats correct, when the timer times out, the power reverts back to the priority shower. if it's set to 10-15 mins , that should be plenty for any shower.

Bruthal

Randyleprechaun wrote: »

Yes, thats correct, when the timer times out, the power reverts back to the priority shower. if it's set to 10-15 mins , that should be plenty for any shower.

Id say the one with the time delay at it is electrically the priority shower. Which ever shower can electrically overide the other is the priority one i would of thought. Because if someone is in the non timer one and someone can now enter the time delay one they can take priority. Not that its any major deal. But in a priority unit bought in electrical shop the shower which can overide the other one is the priority one. ie- the priority one cant be interrupted during use.

Randyleprechaun

Probably right Rob, still, it's a cheaper and simpler method of interlocking the 2 showers!!!!

Bruthal

Randyleprechaun wrote: »

Probably right Rob, still, it's a cheaper and simpler method of interlocking the 2 showers!!!!

Yes its a decent way alright. Not sure if simpler though, as a current sensing priority or non priority unit just has to be installed at the board. No extra switch wiring to the timer controlled shower location. But if a new shower is going in anyway and the timer operating switch is going there then it would work out well.

cast_iron

Randyleprechaun wrote: »

Probably right Rob, still, it's a cheaper and simpler method of interlocking the 2 showers!!!!

Would a contactor capable of taking 10sq cable not negate the bulk of the cost saving? And the time-lag switch alao?

Just curious, as I'm not sure on prices for any of the gear involved.

M cebee

i'm a veteran of the old link(when i was davelerave):p

you'd prob be using the 4-pole 63amp( ac1 rated contacts)
there'd be no bother with the 10sq with 40 or 63 i'm sure

'non-priority automatic' is the handiest but the manual priority with the timelag is another option

.G.

wierd that.

I only said to myself the other day I wonder why davelerave dosen't post anymore:)

M cebee

lost my :pac:details in the cyberattack

SP rcbo's are prob ok for general use on TN supplies

they don't clear the N-E fault so they wouldn't be allowed in all cases- i think

ebuy

Randyleprechaun wrote: »

I've found that original thread

http://www.boards.ie/vbulletin/showthread.php?t=2055595071

I've also attached the original sketch that I did. Excuse the sketch, it's a bit rough and ready but you'll get the idea.

I have a similar setup to "Randyleprechauns" diagram that I'm trying to understand.

After the contactor there is a 40A Double pole switch at each of the showers. (one is a wall mounted switch, the other a ceiling pull switch).

There is no timelag switch at either shower. It looks like switching one of the 40A Double pole switchs energises the coil and closes the N/O contacts, allowing the 2nd shower to be used.

Does anyone know how this circuit might look?

Bruthal

ebuy wrote: »

I have a similar setup to "Randyleprechauns" diagram that I'm trying to understand.

After the contactor there is a 40A Double pole switch at each of the showers. (one is a wall mounted switch, the other a ceiling pull switch).

There is no timelag switch at either shower. It looks like switching one of the 40A Double pole switchs energises the coil and closes the N/O contacts, allowing the 2nd shower to be used.

Does anyone know how this circuit might look?

If there is a contactor before each 40A shower isolator, they will have to be N/C contacts on them for the isolators themselves to activate the interlock contactor setup.

So when one isolator is switched on, it will switch power on to its own shower as normally would happen, but it will also energise the contactor of the other shower, so its N/C contacts now open, so the other shower cant now be used. The disadvantage is, the isolator must be turned off again to enable the other shower to be used then, and vice versa if the other one was used.

If N/O contactors were used before each shower isolator, then the isolators themselves would have no power to them, so they would do nothing when either is switched on. But the N/O contactors can be used in a timing setup and momentary switches.