3 phase supply to communal shower block

[bobbert]

Hi Guys,

Looking for a little advise regarding installation of new supply to feed a communal shower block at a local Girl Guides Camp.
The owners have just had the supply upgraded from single phase to 3 phase on my advise as their new power requirements are now much greater with the arrival of their shower block.

The shower block is a porter-cabin type of affair with 4 8.5Kw electric showers, 3 3Kw over-sink instantaneous water heaters, a couple of frost guard heaters and lighting with a couple of extractors. In total i calculate the max load to be just shy of 44.5Kw.

The shower block came from an industrial site and is currently wired as single phase feeding 2 CUs.
I'm proposing to run 3 phase to the shower block, add a third CU and juggle the loads equally across the 3 boards.

Given the loading I'm torn between running 16mm or 25mm 4core SWA back to the supply. Any input guys? ... as looking at the big red book, 16mm would just about do it but it does cut it fine. Cable run is only 6mts and will be clipped direct.

The next problem I have is what size breaker to fit at the supply end ...
As the site has new 3 phase supply there is no existing 3phase board as yet.
I need to fit one and then run submain out to shower block.
Most standard load 3 phase boards only allow a maximum rating of 63A for the MCBs and I'm feeling that this will be too small for the shower block.

I've calculated the max load as everything on at the same time due to the fact that the shower block will be used by guides/scouts during both summer camps but more importantly WINTER Camps.
The way I see it, everybody could all turn up at once to shower/wash on a cold day so I can't really justify using diversity can I?

Based on this, I'm thinking that the submain will need to have overload protection of 80A if this is the case then I'm faced with the problem of finding a TPN board that will allow me to fit an 80A 3pole MCB.

Anyone else had this problem?
I've installed TPN boards before that have high-load outputs but these have been seriously pricey and I can see this becoming a problem.

I know that Hager do 80A 3pole MCBs but I don't know what boards they fit into.

Any suggestions on where I can find such a board without it costing the earth?
Supply to site is TT so I'll need the option of RCD main incomer too which I know most boards do now anyway.

Thanks guys ... this one has left me tied in knots

 

[Engineer54]

That's 63A for EACH phase, which will be more than ample for your 45KW loading in this shower portal cabin

 

[john999uk]

I am probably totally wrong here but with 4 x 8.5KW showers on 3 phase that's 1 shower per phase plus 1 shower. So 2 showers on 1 phase. So that's 17Kw on a single phase. As OP said can't allow for diversity as all showers might be used at same time. Am I right in assuming a 63amp mcb is capable of 14.5Kw i.e. 230x63. So a 63amp mcb is not capable of handling the load.

 

[Engineer54]

Actually i did make a mistake in my metal arithmetic on this one.... lol!!
So yes it would have to be an 80A protective device supplying this shower block...

Sorry all.... :smiley2:

 

[BlueToBits]

Have you considered water pressure? We hardly get enough water pressure for 1 shower in the summer, let alone 4 and 3 wash basins, all in use at the same time.

Why not fit 7KW showers? They will also help with both power and water demand.

 

[bobbert]

Thanks for all your advise guys!

Amazingly this place has amazing water pressure even though they are in the middle of nowhere... I think they have a water main coming from a nearby farm which I'm guessing has a some kind of pumping station.

The showers are already in situ so I can't really see them going for boiler changes.

Any ideas with regards to a board that will take an 80A 3 pole MCB ??? ... this part is giving me a headache

Thanks again all!

 

[westmac]

You won't find an MCB above 63A anywhere, you'd have to move into MCCB territory if you wanted it to be re-settable.

I haven't looked but are you allowed multiple phases in a room containing a shower?

I would suggest that you temporarily wire one of the showers up and see what load it takes, the amount of power used depends on the desired water temperature and the temperature of the incoming water.

 

[Simlec]

When did we go back to the red book?

 

[Brightspark2]

Square D or Schneider as you might call it now, do a MCB board at the bottom to each side is a din rail which accommodates various equipment including a small MCCB which is sort of made for it. You then fit 1 module through connectors in place of the MCB and drop down with tails to your MCCB.

I have no details to hand but have a look at the Schneider dist boards.

 

[HandySparks]

the amount of power used depends on the desired water temperature and the temperature of the incoming water.

Which showers work like that then? I thought they usually had one or two fixed power settings and the temperature control was by varying the water flow.