commercial electric shower power rating

Question

There are nine electric shower units connected to a landlord's Distribution Board. Assuming each unit is 7Kw, what level of diversity would be appropriate? These showers will be used by people who choose to cycle to work. The number of shower units is based on the cycle spaces available.

Sergio Fernandez · Accepted Answer

Several questions to ask 
 What are the operating time for the customer eg 9 to 5.30pm 
 Do people all start at the same time 
 What are the characteristics of the LandLord supply eg Single phase 100 amp or 3 phase 
 
 If there is only a 100amp single phase then that will limit it to 3 showers running at same time as 7kW being roughly 30amps. Need to check what else runs from the land loards supply at the same time. You will also need to factor in RCBO 30mA protection per shower if the leakage current accumulation may exceed 30mA. This depends on the MI (Manufacturers Instruction) and how much electronic circuitry the showers have as they are no longer purely a resistive load.

mapj1 · Answer

kWell you are well off the end of the normal OSG style diversity calcs here ;-) 
 In practice however it is quite correct to assume it will not all be in use at once, and that there will be quite a cool-down period for any one shower between users as folk get undressed and dressed etc. 
 It may be worth considering some sort of max load-lock-off circuit that sheds a non critical load, perhaps the water heaters, if the total load exceeds some limit, just in case one day, lots of people all arrive at once. Otherwise you are left rolling a dice somewhat, as it will depend on how the various tentant blocks are used - if they all insist on a 9AM start for example, or allow flexi-time is beyond your control. 
 Equally it will probably be fine for years, there are many blocks of flats with no such protection, ans if all the occupants showered at one it would be a disaster, but they never do. As a point of comparison street distribution assumes ~ 2kw per house if there are many or a tapered function for small nos, 
 as this graph 
 
 indicates - graph copied from here using the CREST model and showing large uncertainty (the long I-bar) but decreasing spread for large nos of houses per phase - but unlike an office block , for these households whose only point of commonality is they share a substation, there is no synchronizing factor - at a place of work there may be if the boss likes every one in place at the same time. Mike

commercial electric shower power rating

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