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

 

[kingeri]

I would honestly push for a different solution. 14 x 9.5kw showers is not the way forward. I would struggle to apply diversity here as well, who's to say the showers won't be used all at once, ok maybe not now but in the future? At the very least, why not look at 7.5kw showers for a start! What's the need for 9.5's?

 

[sparky351355]

I am planning to split the load over 3 phases fed from a consumer unit on each floor via main dis board, the rooms don't have there own c/us so this makes thing a little simpler, diversity as follows:-

14 x 9500=133000
133000/3
44,330/230=192A

div=
2 x100% + 3x25%

 

[davethsparky]

How exactly are you planning on connecting two thirds of a shower to a phase?

 

[Sintra]

Good luck with your sub mains and ct's etc for that lot. Sounds absolutely crazy what you are trying to do.

 

[i=p/u]

Get 14 showers connected and be happy with his decision

 

[kingeri]

I wouldn't even consider it. And you say that the water supply isn't your concern but it would be when the showers don't work due to lack of pressure........wouldn't it? I've seen this happen with only two showers in use!

 

[i=p/u]

Not everyday do you say call in the plumber

 

[Guitarist]

Have to agree. 14 electric showers in this situation seems like a crazy way to go.

 

[i=p/u]

I remember doing a washing facilities at caravan park , probsly 10 power showers were used and had a tank out back 4 times size of oil tank.. And massive pump buried out the back........ Mechanical

 

[sparky351355]

Might be worth me raising a concern over the water issue agreed! However i will have 375 A to play with here I'm sure a supply of that size and I'm sure the chances of even 50% of the showers being on at the same time ( even assuming that the the shower is at full wack(9.5kw)) this is manageable , when all that we have is low energy communal lighting and a couple of t.v.s running.

 

[telectrix]

install a 10KVA generator (2 stroke) outside each shower room. not only will that sort out the loading problem, but starting the buggers with the pull cords will keep the old buggers fit.

 

[sparky351355]

How exactly are you planning on connecting two thirds of a shower to a phase?

I'm not with you dave. It would be 2 5's and a 4.

 

[davethsparky]

You calculation in post number 22 was:

14 x 9500=133000
133000/3
44,330/230=192A

You added up the total KW of 14 showers then divided by 3 and calculated the per phase current from that. To achieve this in the real world you will have to connect 4.66 showers to each phase.

 

[telectrix]

You calculation in post number 22 was:

14 x 9500=133000
133000/3
44,330/230=192A

You added up the total KW of 14 showers then divided by 3 and calculated the per phase current from that. To achieve this in the real world you will have to connect 4.66 showers to each phase.

easy when you've cut out the cable entry and wet-pants has butchered out his pipe entry then melted away half the plastic casing with his blowlamp, that's 0.34 of the 5 showers gone, leaving 4,66.

 

[sparky351355]

I will get 1 three phase shower that will sort it!!!!!!

 

[Guitarist]

Might be worth me raising a concern over the water issue agreed! However i will have 375 A to play with here I'm sure a supply of that size and I'm sure the chances of even 50% of the showers being on at the same time ( even assuming that the the shower is at full wack(9.5kw)) this is manageable , when all that we have is low energy communal lighting and a couple of t.v.s running.

Unless switched to "economy mode", which nobody does, these showers always pull "full wack".

 

[sparky351355]

So nobody is going to come up with a load per phase then !

 

[Marvo]

I think that many instant shower units is a crazy idea. You could run just 3 x 200 litre 4kW hot water cylinders, one on each phase with 5 or 6 showers piped from each cylinder. It would probably cost a fraction of the price and would draw a fraction of the peak load.

 

[davethsparky]

So nobody is going to come up with a load per phase then !

How many rooms are on each floor? as you have suggested you will be going for one phase per floor that will dictate how many showers end up on each phase.

 

[i=p/u]

Share them equally, If fuse blows it blows but you told them to go with power showers..

 

[davethsparky]

Ok i'll play the game here.

Assuming they are split as equally as possible (5,5,4) and as you used 230V in your earlier calculation i'll assume they are rated 9.5KW at 230V.

Total connected load on L1 = 5 * 9.5KW = 47.5kW = 197.9A

Allowable diversity if you consider thsi to be a boarding house = 100% FLC of largest 2 appliances + 25% FLC of all other appliances
Current for 1 * 9.5KW unit = 39.6A
Load after diversity = (2*39.6)+(3*(39.6/4)) = 79.2 + 29.7 = 108.9A

However you could consider these to be individual dwellings in a block then you take 100% FLC of the shower in each dwelling so we get back to 197.9A.

Either way that's going to be a bit much for your existing 100A supply

 

[7029 dave]

you can not applly dievesirty to intantaious water heaters

 

[davethsparky]

Why not?

Guidance note 1 table H.2 lists diversity for Water-heaters (instantaneous type) as 100% f.l. of largest appliance + 100% f.l. of 2nd largest appliance + 25% f.l. of remaining appliances.

 

[i=p/u]

So ok all that's been said , people's opinions , what would you do? , would you do the job or would you say get a plumber in

 

[ruston]

Why not?

Guidance note 1 table H.2 lists diversity for Water-heaters (instantaneous type) as 100% f.l. of largest appliance + 100% f.l. of 2nd largest appliance + 25% f.l. of remaining appliances.

So does the OSG , it's thermostatically controlled that no diversity is allowed.

 

[ruston]

So ok all that's been said , people's opinions , what would you do? , would you do the job or would you say get a plumber in

I would just like to know what the DNO would have to say about it .

 

[davethsparky]

"here's your bill for the new supply, thankyou very much"

 

[ruston]

"here's your bill for the new supply, thankyou very much"

Sticks in my mind that you have to notify them of load increases over a certain level, although I can't remember what it is lol.

 

[davethsparky]

Yes but with the load after diversity being more than the existing incoming supply (100A TP) without even considering the existing load I kind of assumed that conversation would be happening anyway.

 

[ruston]

Yes but with the load after diversity being more than the existing incoming supply (100A TP) without even considering the existing load I kind of assumed that conversation would be happening anyway.

Fair enough , I confess to not reading the whole thread ,it was just something niggling in my mind that you had to notify them of additions over a certain level.