2 showers in a property

[daniel hill]

hi all

i have been to look at a job today and they are wanting 2 9.5kw showers installed
there is already a cooker circuit int the property so relly only one shower wants to be working at once
is there any simple way of doing this i heardd some one mention an "interlocker" or somthing dont have a clue

any thorts

thanks danny

 

[Had8Lives]

Not heard of an interlocker for showers before. You could use a contactor so that one shower is isolated if the other shower isolator is switched on. Might be easier (unless they've already bought the showers) to have two less powerful showers.

 

[daniel hill]

how would you do this with contactors and diagram
and yes they have allready purchased the showers and cant take them back as i think they fell of a wagon if u get me

 

[Darkwood]

Putting contactors on the shower supplies is an option and simple in principle but not ideal in domestic really ordering 2 showers before working out the parameters of the installation is where you went wrong here, that aside it is possible to run each supply through a contactor but it is what you control the contactors with that is the main question, my option would be 2 current monotoring relays controlling the contactor. If current monitor relay detects current in shower circuit 'A' then it drops out power to contactor 'B' and vice versa.
2 contactors
2 current sensing relays
2 sets of current transformers
enclosure
Im afraid it could cost more than the showers altogether so unless customer flush with money its a solution but an expensive one.
Alternatively controlling from shower switch wire would be problematic as if a pull switch was left on it would stop the other shower working altogether without the aid of a timing device but again expensive and not ideal.
A change-over switch is cheapest one supply in and run each shower circuit out, it allows the use of one shower at a time and is cheaper with just one supply for 2 showers.
Again its not ideal and more an industrial/commercial solution for a domestic job, the customer would have to choose the shower through this switch before showering and if second person wanted other shower then they may accidentally cut other shower off while someone in it.
Keep spare shower for future and just one shower to this job, unless you can get a boiler/tank fed shower as shower no2

 

[sparks1234]

Whats all the fuss about, has nobody here heard of diversity?

 

[Darkwood]

Whats all the fuss about, has nobody here heard of diversity?

Not got enough circuit info to do all that im assuming hes worked it out thus looking for a alternative solution.

 

[claire_r]

thought you werent allowed to use diversity on shower circuits?

 

[ezzzekiel]

Whats all the fuss about, has nobody here heard of diversity?

yes and we understand it,
you arent allowed diversity on a shower and even if you were 2 x 9.5kw showers running at same time is a heavy load..

Lighting - 66% of total current demand for each circuit
Power - 100% of the first ring circuit + 40% of all other circuits
Cooker - 10A + 30% of remaing rated current + 5% if the CCU has a socket outlet
Shower - No diversity allowable
Instantaneous water heater - 100% of largest heater + 100% of second largest + 25% of of any others
Thermostatically controlled water heater - No diversity allowable
Underfloor heating - No diversity allowable

 

[Graeme Harrold]

Whats all the fuss about, has nobody here heard of diversity?

Even if diversity was allowable I still wouldnt do it. We run two 9kW at home and the frequently are on at the same time. If on a single circuit then you would have to interlock on whilst the other is running via a contactor.

Putting contactors on the shower supplies is an option and simple in principle but not ideal in domestic really ordering 2 showers before working out the parameters of the installation is where you went wrong here, that aside it is possible to run each supply through a contactor but it is what you control the contactors with that is the main question, my option would be 2 current monotoring relays controlling the contactor. If current monitor relay detects current in shower circuit 'A' then it drops out power to contactor 'B' and vice versa.
2 contactors
2 current sensing relays
2 sets of current transformers
enclosure
Im afraid it could cost more than the showers altogether so unless customer flush with money its a solution but an expensive one.
Alternatively controlling from shower switch wire would be problematic as if a pull switch was left on it would stop the other shower working altogether without the aid of a timing device but again expensive and not ideal.
A change-over switch is cheapest one supply in and run each shower circuit out, it allows the use of one shower at a time and is cheaper with just one supply for 2 showers.
Again its not ideal and more an industrial/commercial solution for a domestic job, the customer would have to choose the shower through this switch before showering and if second person wanted other shower then they may accidentally cut other shower off while someone in it.
Keep spare shower for future and just one shower to this job, unless you can get a boiler/tank fed shower as shower no2

Keep it simple with a master slave relationship. There will be one shower that is used more frequently and use this supply to disconnect the other. Might cause a few arguments with someone showering in the slave shower being cut short by someone hopping into the master

 

[mechelec]

How about two mechanically interlocked contactors controlled by 10 A pull switches (or lower as each is switching only the contactor coil) in the respective shower rooms. The supply to each switch is via a 3A fuse in contactor enclosure and the NC contact on the other showers supplying contactor thus each one will be mechanically and electrically interlocked

 

[Darkwood]

How about two mechanically interlocked contactors controlled by 10 A pull switches (or lower as each is switching only the contactor coil) in the respective shower rooms. The supply to each switch is via a 3A fuse in contactor enclosure and the NC contact on the other showers supplying contactor thus each one will be mechanically and electrically interlocked

Wouldn't you have problems if one pull sw was left on then other switch would be useless until first switch turned off, and on the test cert the functionality of switch etc box might get a cross in the box due to this issue.

 

[Des 56]

The diversity given values of Domestic installation are guides to assist calculation of maximum demand,but if they are taken as absolute values of consumption then a majority of new installation in the land would have values higher than the 100 amp main isolators
Two 9.5KW showers and a cooker circuit and it would seem the loads are greater than the capacity
You dont state the cut out fuse size or the size of tails

If it is 80 or 100 amp and 25mm tails then I would have thought you will experience no problems whatsoever
If it is 60 amp and 16mm tails then with these loads running at the same time and upwards of 90 to 100 amp fully loaded, the period of time that the overload contiues for would be the main factor
Given that the cooker will be unlikely to be at full load for the vast majority of its use and the showers ditto,additionally they would be running for short periods,the actual loading may be way below what the calculations state
Use a clamp meter to measure each load,it will probably be well withion what the system can handle
1361 60 amp fuses are very tough little creatures and dont give up the ghost very easily
I would say that having two showers , they will pose little problem in the real world

 

[daniel hill]

tell me if i am an i idiot but could yo do this with a two way pull switch and a 1 way pull switch

feed in to the master pull switch(the two way) l1 to the contactor in the main shower room and l2 to the onsweet pully(1 way) then in to another contactor

when the pull is pulled it will turn on the contactor for the master bath room and when turned of will let the on sweet one be used

would this work as it only allows one shower to be used at a time

or if not this instead of a the two way pully put a time 2 way switch on and set the time to say 10 mins then if they need the shower in the on sweet it is avalibul just then the argument of when some 1 in the onsweet shower and some 1 hits the button

thanks des that is all that i relly wanted to no wouldent want to start getting involved in contactors to be honest am only a house basher

 

[ezzzekiel]

most new builds tend to have shower in bathroom and one in onsuite in master bedroom with no problems, but as des said they would be 25mm tails on 80a/100a service fuse

and as most cutouts tend not to have the size fuse thats written on the carrier as this is the rating of the carrier not the fuse its carrying (just learned this interesting snippet)

 

[sparks1234]

The diversity given values of Domestic installation are guides to assist calculation of maximum demand,but if they are taken as absolute values of consumption then a majority of new installation in the land would have values higher than the 100 amp main isolators
Two 9.5KW showers and a cooker circuit and it would seem the loads are greater than the capacity
You dont state the cut out fuse size or the size of tails

If it is 80 or 100 amp and 25mm tails then I would have thought you will experience no problems whatsoever
If it is 60 amp and 16mm tails then with these loads running at the same time and upwards of 90 to 100 amp fully loaded, the period of time that the overload contiues for would be the main factor
Given that the cooker will be unlikely to be at full load for the vast majority of its use and the showers ditto,additionally they would be running for short periods,the actual loading may be way below what the calculations state
Use a clamp meter to measure each load,it will probably be well withion what the system can handle
1361 60 amp fuses are very tough little creatures and dont give up the ghost very easily
I would say that having two showers , they will pose little problem in the real world

I knew someone with a bit of experience and capable of a bit of engineering judgement would come along sooner or later.

 

[saveloy]

Please correct me if I have this wrong.

Just looking at the time current charcteristic curves for a 100A BS 1361 fuse (as mentioned by DES) and it shows that said fuse can take a current of around 180 Amps for a time of over 6000 seconds before operating.
6000/60 = 100 minutes . So in theory the installation would have to have a load of over 180A running continuosly for over 1 hr and 40 mins before the main fuse would blow.

Have to agree with DES that 2 showers should'nt pose much of a problem

(unless the house is a hostel for tramps)!

 

[daniel hill]

(unless the house is a hostel for tramps)!

haha well the house will be for students

 

[saveloy]

haha well the house will be for students

One shower will be one too many if its for students

 

[daniel hill]

that is verry truee

 

[Darkwood]

Please correct me if I have this wrong.

Just looking at the time current charcteristic curves for a 100A BS 1361 fuse (as mentioned by DES) and it shows that said fuse can take a current of around 180 Amps for a time of over 6000 seconds before operating.
6000/60 = 100 minutes . So in theory the installation would have to have a load of over 180A running continuosly for over 1 hr and 40 mins before the main fuse would blow.

Have to agree with DES that 2 showers should'nt pose much of a problem

(unless the house is a hostel for tramps)!

In the long run your probably right it wont be a issue but relying on trip times when exceeding rated current of device is bad practice, but you, me and many others will realise that in reality it shouldnt be a problem in this instance.
I myself stick to the reg's even though ts possible to get away with a lot more without undermining the integrity of the installation but the clear concience when signing the design of installation on the cert keeps my mind at ease.