applying diversity

[leep82]

Currently on a job refurbishing a bungalow. The customer has completely changed the layout of the property taking walls out and putting new partition ones up. They have created an en suite in the master bedroom and require a power shower in here as well as the existing bathroom. Im working with an 80a supply and despite several attempts to get further info from the customer it hasnt been forthcoming. I have concerns about the loading of the potential two showers and any oven/hob ( again which i have no information on ). Just thought id see what peoples thoughts are on this situation particularly with regards to diversity and how to apply it.

Before i get shot down i always find it more helpful learning from other people than reading from a book. I see to many people when im reading through other posts leaving sarcastic responses to people asking genuine questions ( bet youre a joy to work with ). Better to ask a question than assume you know an answer/solution inly to be made to look foolish later?

 

[Andy78]

What are the power requirements of the power showers ? they generally don't pull a lot.

 

[leep82]

Unfortunately this is the info i can not get from the customer. Im thinking i may be best on insisting they go for smaller rated appliances to be safe. I dont want them to go and buy say two 10kw rated showers as the chances both showers getting at the same time are quite high as they have a guest room for relatives who stay over regularly.

 

[AndyL]

More info required from the client, you have to be a bit more insistent on this. Tell your client that without the complete information there is no way to design the installation correctly

 

[Spoon]

More info required from the client, you have to be a bit more insistent on this. Tell your client that without the complete information there is no way to design the installation correctly

or tell them that without the info you will put 32A breakers in for the showers & cooker and they will have to purchase the equipment to suit the breaker sizes.

 

[davesparks]

Just to clarify things, is it power showers or electric showers?
A power shower being a pumped unit which has hot and cold feeds and an electric shower being an electrically heated unit which has only a cold feed?

 

[leep82]

Believe me ive tried, i wired a new kitchen ring last weekend without a kitchen layout just went of the customers instructions and im just waiting to go back and have to move sockets that are in the wrong position, customers aware of this and are willing to pay for anything that needs moving, they are just so laid back its untrue

 

[Andy78]

Unfortunately this is the info i can not get from the customer. Im thinking i may be best on insisting they go for smaller rated appliances to be safe. I dont want them to go and buy say two 10kw rated showers as the chances both showers getting at the same time are quite high as they have a guest room for relatives who stay over regularly.

Well you stated power shower. These can be as little as 3A, now you are on about a 10kW electrically heated shower. Massive difference.
You can't do any cable calcs or diversity calcs until you have the info from the customer, tell them so.

 

[leep82]

Sorry for confusion i actually meant electric showers and not a heated unit with pump

 

[AndyL]

Yeah we have all had clients like that, but you need to cover yourself and just be a bit more professional. Don't install without a plan or at least confirmation of positioning. Sometimes you get lucky and they pay for alterations but it can easily turn into hassle and you don't get paid at all. There is another thread going on at the moment with that exact problem (from the clients POV)

 

[leep82]

Yeah this is the route i think i may have to go down, already put a seperate supply in for the cooker because of lack of info, was hoping i could just use the kitchen ring to supply it. Now ive lost a spare way in the CU but hopefully covered myself by installing a 4mm2 radial

 

[davesparks]

Yeah this is the route i think i may have to go down, already put a seperate supply in for the cooker because of lack of info, was hoping i could just use the kitchen ring to supply it. Now ive lost a spare way in the CU but hopefully covered myself by installing a 4mm2 radial

4mm for a cooker supply? That's pushing your luck isn't it?

I'd be very concerned about a design which supplies an electric cooking appliance via a ring final cct.

 

[davesparks]

Believe me ive tried, i wired a new kitchen ring last weekend without a kitchen layout just went of the customers instructions and im just waiting to go back and have to move sockets that are in the wrong position, customers aware of this and are willing to pay for anything that needs moving, they are just so laid back its untrue

Walk away from throb and leave some other mug to suffer this crap

 

[HandySparks]

4mm for a cooker supply? That's pushing your luck isn't it?

I'd be very concerned about a design which supplies an electric cooking appliance via a ring final cct.

Hmm. Maybe the OP actually means an oven, not a cooker. A small single oven might well be rated at less than 13A.

 

[mattg4321]

If you're doing that much work to a place, why the hell would you fit electric showers.

 

[leep82]

Sorry for the confusion once again, i of course meant oven when i was referring to supplying ot fro the kitchen ring main. This isnt a job i can walk away from now and although the customer can be hard work so far i have had no problems with payment

 

[davesparks]

Sorry for the confusion once again, i of course meant oven when i was referring to supplying ot fro the kitchen ring main. This isnt a job i can walk away from now and although the customer can be hard work so far i have had no problems with payment

Still not advisable to supply it from a ring circuit is it.

 

[Sparkie30]

I dont want them to go and buy say two 10kw rated showers as the chances both showers getting at the same time are quite high as they have a guest room for relatives who stay over regularly.

Well i think you worrying way to much pal, water pressure isnt powerful enough to run 2 showers at the same time unless some serious pumps are installed.

 

[davesparks]

Well i think you worrying way to much pal, water pressure isnt powerful enough to run 2 showers at the same time unless some serious pumps are installed.

Have you been to the property and tested the water pressure then?

 

[Andy78]

Convince them they want more reliable, more economical, mixer showers. Hassle from lack of info gets directed at the plumber, job done, down the pub.

 

[leep82]

Is it not? So oven arrives complete with 13a plug top and is less than 2kw and i cant plug it into the ring main?

 

[Sparkie30]

Have you been to the property and tested the water pressure then?

Yes i have 3 bar

 

[davesparks]

Is it not? So oven arrives complete with 13a plug top and is less than 2kw and i cant plug it into the ring main?

You will be hard pressed to plug it in to a ring main full stop. However you could plug it in to a socket one ring circuit, but that is considerably poor installation design to place such a load onto a ring, and the chances of it being less than 2kW are pretty remote considering the standard oven elements used are normally 2 - 2.4 kW.
Plus of course there is the consideration to the oven being replaced with a different unit in the future, as appliances are built with shorter and shorter lifespans these days. and less people appear to want to have them repaired, along with electricians seemingly not wanting to repair cooking appliances here days.

 

[davesparks]

Yes i have 3 bar

It might have been an idea to give this bloke a hand with his designs whilst you were there then. Or at least give us a clue in your post that you had actually measured the water pressure at the location.

 

[HandySparks]

Where the hell is Soul on Trent anyway?

 

[davesparks]

Where the hell is Soul on Trent anyway?

Sounds like the frozen north to me, somewhere the wrong side of the Watford gap

 

[HandySparks]

Sounds like the frozen north to me, somewhere the wrong side of the Watford gap

Wondered if it was something to do with "Northern Soul".

 

[Sparkie30]

It might have been an idea to give this bloke a hand with his designs whilst you were there then. Or at least give us a clue in your post that you had actually measured the water pressure at the location.

im a plumber, dont get involved with electrics. The clue is 3 bar.

 

[leep82]

whos been checking my profile out then, cheeky!

 

[HandySparks]

whos been checking my profile out then, cheeky!

No idea.

Location appears in the LH margin of the screen against every poster.

 

[leep82]

Apologies, not on the iphone app it doesnt.

 

[davesparks]

im a plumber, dont get involved with electrics. The clue is 3 bar.

What is 3bar a clue to?

 

[Sparkie30]

What is 3bar a clue to?

water pressure guv

 

[davesparks]

water pressure guv

I'm completely lost now.

You stated that the water pressure at the property is insufficient to run two showers, yet your profile location appears to be a long way from the OPs I think. So I wondered how you knew what the water pressure at his site is?
You might as well tell me that there isn't enough water pressure here to run two of those showers at once.

 

[Sparkie30]

I'm completely lost now.

you shouldn't be lost, you are in guildford

 

[leep82]

Anyways, i have actually given the oven its own dedicated supply so this is immaterial. I still fail to see why though, if i had known the type of oven and say it was only 2kw why it couldnt be plugged into the ring main. The ring main in question is a new circuit consisting only of 4 sockets above the worktops. Only other appliances will be kettle, microwave and toaster ( new kitchen ring is on different RCD to house ring, shocking design again there!! ). Can diversity not be applied also?

 

[leep82]

Doing a little more reading and found a rule of thumb equation to determine the maximum demand with diversity applied.

So the total value of all of the OCPD, multiplied by 0.4 seems an acceptable, as i say " rule of thumb "

So i have :-
3 x 6a circuits
3 x 32a circuits
1 x 20a circuit
1 x 16 a circuit

(6+6+6+32+32+32+20+16) x 0.4

150 x 0.4 = 60amps

As mentioned in the OP i have an 80a main fuse. The above OCPD do not include any electric shower circuits, am i right in thinking that diversity cannot be applied to showers?

 

[davesparks]

Anyways, i have actually given the oven its own dedicated supply so this is immaterial. I still fail to see why though, if i had known the type of oven and say it was only 2kw why it couldnt be plugged into the ring main. The ring main in question is a new circuit consisting only of 4 sockets above the worktops. Only other appliances will be kettle, microwave and toaster ( new kitchen ring is on different RCD to house ring, shocking design again there!! ). Can diversity not be applied also?

Again, it's not a ring main, that's a distribution circuit.

It may be me being old fashioned and not keeping up with the times, but it goes against the basics as I was taught them to feed a cooking appliance via a ring circuit. A separate circuit to feed the cooking appliances is the way I would go.
A ring circuit was, and is, designed as a circuit to supply multiple socket outlets for portable appliances spread over an area. A cooking appliance is a significant load which is on for long periods of time and I feel it is similar in this respect to an immersion heater or similar and should have its own circuit wherever possible.

 

[leep82]

What isnt a ring main?

 

[davesparks]

What isnt a ring main?

The circuit you are describing isn't.
A ring main is a distribution circuit, most commonly an open ring at 11kV
What you are talking about is a ring final circuit (rfc), or ring circuit

 

[leep82]

If you want to be picky i suppose, but i would like to think most people knew where i was coming from. Dont suppose your a member of the grammar police aswell are you

 

[leep82]

Would you also put any other appliances using more than 2kw on there own dedicated supply?

 

[sparksburnout]

I have just come back from the pub having enjoyed quite a few pints of a really nice guest ale. I can only imagine that the OP has done likewise on a regular basis. Dave your patience is worthy of some sort of award. Does the OP do this sort of work on a regular basis????

 

[davesparks]

I have just come back from the pub having enjoyed quite a few pints of a really nice guest ale. I can only imagine that the OP has done likewise on a regular basis. Dave your patience is worthy of some sort of award. Does the OP do this sort of work on a regular basis????

My patience is somewhat binary in its nature, as many around here will have noticed, it's either 0 - saintly or 1 -snapped.

I get the impression he's not been doing it very long

 

[davesparks]

If you want to be picky i suppose, but i would like to think most people knew where i was coming from. Dont suppose your a member of the grammar police aswell are you

Technical accuracy is an essential part of a technical trade such as this, to use incorrect terms suggests a lack of care or knowledge.

Not a member of the grammar police, but using core t terms, units etc etc was somewhat drummed in to me at college studying chemistry, physics and electronics at A level.

 

[davesparks]

Would you also put any other appliances using more than 2kw on there own dedicated supply?

If the load profile is such that I think it is worthwhile yes wherever possible I would.
Consider the load profile and portability of an oven versus that of a kettle, one is clearly suited to a plug and socket connection and the other a fixed supply.

 

[rolyberkin]

I have just come back from the pub having enjoyed quite a few pints of a really nice guest ale. I can only imagine that the OP has done likewise on a regular basis. Dave your patience is worthy of some sort of award. Does the OP do this sort of work on a regular basis????

Hear, hear!

 

[leep82]

So possibly dishwasher, washing machine, tumbledryer all on there own dedicated supply?

 

[leep82]

Also can i assume you have never referred to an IR test as having been meggered?

 

[sparksburnout]

So possibly dishwasher, washing machine, tumbledryer all on there own dedicated supply?

That's why you don't put the oven on the RFC isn't it?? So it's not overloaded by the appliances you just mentioned being on it PLUS the oven. Dear me.