Shower install problem

[lloydy304]

I wire mobile decontamination units and we have a large unit that requires 4 electric showers.

Normally we use a standard metal 4way CU with rcd and mcb for each shower and its own 32A plugin inlet.

I would like to put all showers in the same board and have four 32A inlets coming from the board and each circuit separated inside.
It's possible all 4 inlets will be supplied by a onsite generator.
I can't seem to find any information on whether this is bad practice but also can not think of a reason why we can't do it.
The electrician who has just left the company said it was bad practice

 

[Wilko]

Hi Lloyds and welcome to the Forum !
My thought is loading within the CU may be a concern. OSG suggests diversity for instant water heaters at 100% + 100% + 25% + 25% but in practice at work or for emergency use you might need to run the lot together for some time, i.e. no diversity allowance. And this will likely exceed the CU and RCD ratings if you use a standard domestic type CU. Just a thought

 

[lloydy304]

Each rcd is rated at 63A the board will have four 63A rcds and four 40A type B breakers.
CU board neutral block and earth Block will not by used and a direct conection from 32A inlet to rcd mcb then shower switch.
No main switch will be used in the board.
I thought these new schnider boards were rated to whatever size main switch was required.
Board will be running less than 120A

 

[davesparks]

You will be creating an installation with four separate incoming supplies, with all four supplies coming in to the same enclosure without a single common main switch. add to this the fact that the generator will almost certainly be providing a three phase supply.
In my opinion this is far from ideal, and I would personally describe it as bad practice.
I think it would be far better to have it on a single incoming supply.
Your options for a single supply in my opinion are:
125A single phase inlet and hope that there will be that the generator will have enough other load on it to balance it.
Three phase inlet, probably 63A, and balance the load as much as possible.

 

[Pete999]

I wire mobile decontamination units and we have a large unit that requires 4 electric showers.

Normally we use a standard metal 4way CU with rcd and mcb for each shower and its own 32A plugin inlet.

I would like to put all showers in the same board and have four 32A inlets coming from the board and each circuit separated inside.
It's possible all 4 inlets will be supplied by a onsite generator.
I can't seem to find any information on whether this is bad practice but also can not think of a reason why we can't do it.
The electrician who has just left the company said it was bad practice

I should think if it's a decontam unit then there wouldn't be any diversity' as it's a 100% emergency application, just a thought

 

[davesparks]

I should think if it's a decontam unit then there wouldn't be any diversity' as it's a 100% emergency application, just a thought

The OP hasn't mentioned anything about diversity?

 

[Pete999]

The OP hasn't mentioned anything about diversity?

No but Wilko did, maybe I should have answered him direct sorry for any confusion

 

[westward10]

It sounds very confusing, I think from what I can make out there will be four separate supplies within the same enclosure.

 

[Lagentium]

Can you not just have 4 small DBs, each housing a main switch and RCBO marked up accordingly?

 

[davesparks]

It sounds very confusing, I think from what I can make out there will be four separate supplies within the same enclosure.

Basically he's planning to have four inlet connectors on one mobile unit, so yes four separate supplies in to the one mobile unit. And yes also those four separate supplies, of unknown phase distribution will be in one enclosure with no single point of isolation or means of guaranteeing that one inlet connector can't become live from one of the others.

What could possibly be wrong with that?

 

[HandySparks]

If you must have separate supplies, I would use a double pole RCBO, each in it's own enclosure.

 

[LankyWill]

Small 4 way TPN board should suffice, as stated above most building sites are fed from a 3ph transformer anyway. That way you could feed each shower on its own phase and still achieve one point of isolation.

Legrand 4 Way Three Phase(TPN) Distribution Board C/W MCB - http://electrical.com.ng/index.php?route=product/product&product_id=345

 

[HandySparks]

Small 4 way TPN board should suffice, as stated above most building sites are fed from a 3ph transformer anyway. That way you could feed each shower on its own phase and still achieve one point of isolation.

Legrand 4 Way Three Phase(TPN) Distribution Board C/W MCB - http://electrical.com.ng/index.php?route=product/product&product_id=345

Are you suggesting that the best price is to be found in Nigeria???

 

[Dave OCD]

Almost Will, except there are 4 showers. Your idea seems sound to me though.

 

[LankyWill]

Are you suggesting that the best price is to be found in Nigeria???

Silly Me