3 X single phase showers

[David Rann]

I've been asked to price 3 X 7kw showers. There is a three phase board about 40 meters away. Can anyone see an issue with 40 amp three phase MCB with 10mm four core swa to a sub board then 3 X 32 amp rcbos for each individual shower.

Cheers

 

[sparks1234]

I'm guessing you can't get RCBO's for whatever board you have already installed, can't see any problem but what are you going to do with the spare ways? , might they get used for something else in the future? and take the total load up past the 40 amp MCB?

 

[chris gray]

Deleted comment as never saw replies

 

[David Rann]

That's on whoever installs after I presume. And I will put dedicated shower board. Someone suggested that I could have current issues down the neutral?

 

[Pete999]

That's on whoever installs after I presume. And I will put dedicated shower board. Someone suggested that I could have current issues down the neutral?

What do your cable calculations show?

 

[David Rann]

Volt drop fine.

 

[Pete999]

Volt drop fine.

Please show calcs for an answer

 

[Wilko]

Hi - if I understand correctly you plan to have one shower per phase to spread the load. This means you will need L and N for each shower (i.e. each 10mm L needs its own 10mm N).

 

[westward10]

You won't achieve correct discrimination between the 40 and 32A devices, with overcurrent yes but not fault current. Not the end of the world but not the best circuit design.

 

[westward10]

Hi - if I understand correctly you plan to have one shower per phase to spread the load. This means you will need L and N for each shower (i.e. each 10mm L needs its own 10mm N).

The triple-pole is a submain to another board for the showers.

 

[Andy78]

Will you be using shower priority contactors ?

 

[Deleted member 26818]

I've been asked to price 3 X 7kw showers. There is a three phase board about 40 meters away. Can anyone see an issue with 40 amp three phase MCB with 10mm four core swa to a sub board then 3 X 32 amp rcbos for each individual shower.

Cheers

Yes, I’m thinking 16mm2.

 

[David Rann]

Sorry I'm confused why would you need shower priority contactors? And are you saying you can't use a sub board?

 

[Wilko]

The triple-pole is a submain to another board for the showers.

Got it - in the case where the 4 conductors are the same ccc but fully loaded and all the loads are single phase only then N will be flogged surely (?).

 

[Andy78]

Sorry I'm confused why would you need shower priority contactors? And are you saying you can't use a sub board?

You might not need to use them. Was just asking as curious. I have no knowledge of the type of installation, type of use, existing capacity etc.