14 new 9.5kw showers to be installed on existing supply

[sparky351355]

Got a job to install 14 x 9.5kw showers in a large property. There is an existing 100a 3phase supply, I've load tested the existing load and its generally pulling around 35A per phase with one only pulling around 10A (bit of a imbalance there. )I've worked out new load with diversity applied for the new showers but just after some numbers from some fellow tradesmen as there may be a couple of ways to determine the load, as a mains upgrade is on the cards and I want to make sure I'm not way off!!!!.

 

[telectrix]

go for power showers. 14 instantaneous showers is ludicrous.

 

[davethsparky]

What kind of property is it? I'm assuming its a load of flats or a hotel/guesthouse kind of thing?

When you say you've measured the current load was this a proper load survey conducted over a week or so, or was it sticking a clamp meter on it?

 

[Guitarist]

Can you apply diversity to 14 showers in this way? Is there no chance that they could all be used at the same time? Is the water supply adequate?

 

[sparky351355]

Power showers are a no go, believe me I've asked! The property is a sheltered accommodation ,it's two large houses knocked into one, as far as the load test is concerned I'm afraid it was the latter however there cannot be a great fluctuation on the load as there is no major appliances apart from a single phase extract hood , although probably a good 20a worth and the odd kettle/2kw heater, all cookers are gas and gas central heating.

 

[sparky351355]

Can you apply diversity to 14 showers in this way? Is there no chance that they could all be used at the same time? Is the water supply adequate?

Water supply not really my problem, I have just applied the diversity as per OSG for instantaneous water heaters!

 

[telectrix]

save water. shower with a 'friend'

 

[davethsparky]

Ok, is this 14 seperate bathrooms?

What is the expected use pattern? Do the residents follow a set routine of any sort? If everyone is likely to be using the showers all at the same time you're probably just a little bit buggered!

If they have gas fired central heating then there could be the possibility of them having one or more big mains pressure invented hot water cylinders which could supply regular thermostatic mixer showers.

 

[telectrix]

cut the accomodation to 13. in the spare room fit a humungous communal bath. boil up a few kettles.

 

[Guitarist]

Water supply not really my problem, I have just applied the diversity as per OSG for instantaneous water heaters!

Personally, I wouldn't apply diversity in this way. Like Dave, I am concerned that they could all be used at the same time.

 

[davethsparky]

As far as the current load goes, it's going to be much worse in winter!

Assuming 14 showers = 14 accommodation units of some form then you may be looking at 14 x 2KW heaters come winter time.

Depending on the actual people living there and the various rules about these things you may have to consider the requirements for limiting the max temperature of the water from the showers.

 

[sparky351355]

Ok, is this 14 seperate bathrooms?

What is the expected use pattern? Do the residents follow a set routine of any sort? If everyone is likely to be using the showers all at the same time you're probably just a little bit buggered!

If they have gas fired central heating then there could be the possibility of them having one or more big mains pressure invented hot water cylinders which could supply regular thermostatic mixer showers.

unfortunately I would Imagine a general rule would apply with showering , morning and night but these tenants do not work so I would imagine showering would be staggered. My question is really is wether the diversity would be applied by adding the total new load together or wether to apply as they are split across the phases as the reading is significantly different, any views?

 

[trev]

Just let the old buggers stink, problem solved

 

[sparky351355]

As far as the current load goes, it's going to be much worse in winter!

Assuming 14 showers = 14 accommodation units of some form then you may be looking at 14 x 2KW heaters come winter time.

very true dave!

 

[sparky351355]

Just let the old buggers stink, problem solved

They already stink trev lol, I must add there is already 3 x 8.5kw showers in communal bathrooms which would be removed , however this does not affect the load already measured!

 

[telectrix]

Just let the old buggers stink, problem solved

or take 'em to the council owned public swimming pool once a week. there's enough chlorine in there to kill half of them off.

 

[davethsparky]

You can't base anything on the load you measured as this measurement was only at a particular moment in time when you had the clamp meter on there. That doesn't give an accurate assessment of average or peak loads.

I would suggest you can't just assume showering times will be staggered, it will depend on the type of people in the sheltered accomodation. If they are people who have become institutionalised over their lives for whatever reason they may very well all follow the same routine either by accident or design.

 

[sparky351355]

You can't base anything on the load you measured as this measurement was only at a particular moment in time when you had the clamp meter on there. That doesn't give an accurate assessment of average or peak loads.

I would suggest you can't just assume showering times will be staggered, it will depend on the type of people in the sheltered accomodation. If they are people who have become institutionalised over their lives for whatever reason they may very well all follow the same routine either by accident or design.

Again true dave what I'm after here tho is as I said what load what you put for the new showers per phase?

 

[davethsparky]

I can't honestly say what I would put as the load per phase at the moment. I was taught a very old fashioned idea when dealing with 3 phases supplying single phase loads, basically keeping circuits on different phases separated, ie all simultaneously accessible sockets and lights on the same phase whilst still maintaining good phase balanceing.

So I would want to know which phase the wiring in each bathroom was connected to before deciding how many end up on each phase, and of course an accurate view of the existing loading and phase balance.

 

[i=p/u]

I've seen it quite a few places where certain room or area is all on 1 specific phase.

what about priority switching on a bigger scale