New shower project, electric or not?

Hi
This is the start of an ongoing problem that needs to be resolved shortly. Normally this would be an easy one, I'd go for a thermostaic boiler fed one any day but...
I run a youth hostel, a huge sprawling 70 bed victorian mansion. Sounds fantastic (and it is) but I also have to maintain the place on a ridiculously small budget. I'm supposed to use "builders" and so-on but quite frankly if I did the place would be bankrupt pretty quick taking into account the amount of work it needs just to come up to standard.
One of the main problems is the ladies showers and loos. They were last updated in 1978 and even have painted plywood lining the showers instead of tiles. Therefore I'm ripping the whole room out and starting from scratch. The new window goes in this coming week and the skip has just been delivered. Tonight I'm working out my basic materials order for the local BM.
Part of the plan is to install 4 new showers, replacing the existing 2 electric ones. Part fo the problem is that these showers (both 7.5Kw) are painfully cold in the winter months. To my reckoning its a combination of things, first the water fed into them is extremely cold so doesn't get past 30 deg. C (measured last year) and the room is like a freezer so it feels cold anyway.
The easiest option would be to replace these with 4 x 10.5Kw showers and stick a storage heater in the room but I have just lifted a few boards and discovered an easily accessible 22mm hot feed. Running off it there is a T to the main kitchen sink, a T feeding 3 basins and another feeding 3 more in other rooms.
The first question (and I'm sure there will be more) is... what are the electrical implications of a 4x10.5Kw load (the existing showers are on seperate RCDs in a CU outside the room) vs. 4 showers fed from an already heavily used hot feed?
Electric or boiler fed?
Any comments?
Tony
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175 Amps! Do you have that available? Most domestic properties have a 100 amp supply maximum.
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What incoming supply have you got (electric) ? - 1ph / 3ph ? fused at ?
Depending on diversity (ie. do you envisage all four showers being in use at any one time) you may need to consider a larger supply.
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in it ;-) --- Its 3 phase (or a tleast I know the kitchen ovens are). I have no idea what the incoming supply is but its "big" and runs off to 12 "consumer units" each with an average of about 5-6 RCS in them (if that means anything!)
Sorry, I know nothing beyond wiring a spur or a simple light switch!
Tony
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It sounds like you might be best getting an electrician in to do a proper load assessment tbh... Because of the nature of the premises you may not have much scope for allowing diversity for load.
You might be able to take a stab in the dark at your present load requirements by using a clip-on ammeter during times of heavy use.
Something that might help pin down the size of supply - do you know if you have a CT chamber on your supply ? - where the cutout (main fuses) is/are, does it go to some sort of box with what is likely to be a ~1" diameter steel wire armoured cable, which goes to a panel with neon indicator lights and a meter on it ? There would be cables going directly into your consumer units or some sort of load splitting arrangement from this box.
If the cables from the cutout go direct to a meter and NOT through this sort of box, you are likely to have less than 100A per phase to play with, as meters aren`t generally made to take more than 100A directly - hence the use of a CT chamber for larger loads. The CT chamber will measure the amount of load on the main conductor and send a scaled-down output to a meter, ie. in a 300:5 CT - 300A in the main conductor would send 5A through the meter.
If this still sounds like double dutch, call your electricity supplier and ask what your declared supply capacity is.
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in it ;-) --- Hi Colin
Sort of sounds familiar. From memory (its all at the opposite end of the building) we have three "big green boxes", one with the meters in it, one with a big red "on-off" switch (which switches off the whole building) and another which has "big" RCDs for each part of the building. I'm assuming the latter feed the CUs, one is marked "kitchen cooker" others just areas of the hostel.
I don't intend to play with the electics for the showers myself, I'll get a proper electrician to do that. Possibly this sort of question is beyond a NG as no-one can see what we've got and I don;t know enough to identify it.
Thanks
Tony
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TonyK wrote:

Well that sounds like a vote for boiler fed, public liability as it is. Boiler fed would be better all round, especially if you already have a sizeable reliable calorifier. I assume 70 beds mean you must also cater for up to 70 showers taken in the morning, so reheat time for stored water should be factored here, but maybe this is something that you have no budget to address. Heat bank / thermal store fed thermostatic mixers would be ideal.
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TonyK wrote:

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You forgot one for each basin and one for the sink as well....
Cheers Clive
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TonyK wrote:

Aren't they supposed to be healthy outdoor types who keep clean by rubbing themselves all over in a snow drift? Sorry ... just daydreaming....
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