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

 

[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.

 

[andekoch]

I agree with darkwood. I also tend to stick to the regs re loading as it lets me sleep easy at night, if a fire was started due to a cable fault caused over time by going over the cables rated capacity for a period you will be hauled over the coals for your design.

 

[saveloy]

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.

Couldn't agree more with all you said darkwood. The situation described is not ideal and if alternatives can be found then thats the course I would take. I can see these scenarios becoming more and more frequent though!
Almost every property I go into has the cu full up and customers want to add another couple of ccts and a few more amps!! Just have to wave me magic wand and all will be fine.

 

[mechelec]

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.

That is the whole point in that you do not want then both to be on at the same time

 

[Darkwood]

That is the whole point in that you do not want then both to be on at the same time

I got your reasoning to why you suggested your method but its not without its flaws as i said if you leave a pull switch on after your shower then someone using the second shower wont be able to without travelling to the first shower to pull the switch to off then back to there own shower. i tend to find people leave the shower pull on all the time and just switch it on and off at the shower itself, so when ticking the functional testing box it would need a 'x' in it as its not a practical method as the pull switches wont always work.
Although your method would work if the switch operated a pulse timer instead thus it would return to normal state after say 15mins.

 

[mechelec]

I got your reasoning to why you suggested your method but its not without its flaws as i said if you leave a pull switch on after your shower then someone using the second shower wont be able to without travelling to the first shower to pull the switch to off then back to there own shower. i tend to find people leave the shower pull on all the time and just switch it on and off at the shower itself, so when ticking the functional testing box it would need a 'x' in it as its not a practical method as the pull switches wont always work.
Although your method would work if the switch operated a pulse timer instead thus it would return to normal state after say 15mins.

I can see what you are saying but it is a poor method to use in a domestic situation anyway but at least it is foolproof.

 

[alba]

i have never seen this, anytime i have seen two showers there has been a main electric shower and the other a thermostatic pumped power shower.

 

[johnstantine]

Personally I'd be inclined to put in contactors mechanically/electrically interlocked, because although time/current graphs say main fuse can run over rated current for a bit without blowing it doesnt mean that the fuse isn't slowly breaking down. And you can't really rely on customer not to run both showers together.