Maximum demand & diversity

[SafetyEICR]

Currently completing 2396 project (cant wait to see the back of it!!) Would just like to check im on the right wavelength when calculating max demand and diversity
DB1 Maximum Demand & Diversity


Lighting - 90% of total demand.


Total demand of lighting circuits is 50.48amps. After diversity has been applied the number changes to 45.43a


Sockets - 100% current of first circuit and 70% of remaining ring circuits.


Ring circuit 1 = 32a

Ring circuit 2-10 = 32 x 9 / 100 x 70 = 201a


32 + 201 = 233a


Heating - 100% full load of largest appliance and 75% full load of remaining appliances.


Curtain heater 1 = 26.08a

Curtain heater 2 = 26.08 /100 x 75 = 19.56


Hoist 32a switch fuse supply = 32 / 100 x 70 = 22.4a per phase x 3 = total 67.2a


Total maximum demand with diversity for DB 1 = 345.84a


Per phase = 345.84 / 3 = 115.28a


Sub feed ocp rated to 160a to allow for future additions to distribution board.


Sub feed cable size - 50mm XLPE singles enclosed in trunking.

 

[iamelectric]

Maximum demand & diversity

alright mate i was thinking of doing this course , whats it like , and how much did it it cost cheers

 

[SafetyEICR]

DB2 Maximum Demand & Diversity
Lighting - 90% of total demand.
Total demand of lighting circuits is 55.97amps. After diversity has been applied the number changes to 50.37a
Sockets - 100% current of first circuit and 70% of remaining ring circuits.
Ring circuit 1 = 32a
Ring circuit 2-9 = 32 x 8 / 100 x 70 = 179a
32 + 179 = 211.2a
Power - 100% full load of largest appliance and 75% full load of remaining appliances.
16a switch fuse = 16a
13a fce = 13 /100 x 75 = 9.75
Total maximum demand with diversity for DB 2 = 287.12
Per phase = 287.12 / 3 = 95.70a
Sub feed ocp rated to 125a to allow for future additions to distribution board.
Sub feed cable size - 35mm XLPE singles enclosed in trunking.

 

[SafetyEICR]

Re: Maximum demand & diversity

iamelectric - Hi mate, its a good course, gives you more of a understanding of why things are designed in such a way. Theres a lot to take in and the exam is certainly the toughest exam I've taken in my career. I did the course over 10 evenings, cost is approx. £500

 

[iamelectric]

Maximum demand & diversity

thanks for the info , whats involved in the exam , is it open or closed book

 

[i=p/u]

Much work in Glasgow iamelectric???

 

[iamelectric]

Maximum demand & diversity

my works busy , i have noticed on the job websites that works picking up again lot more companys advertising for sparks , y do u ask

 

[i=p/u]

Misses wants to move home, so looks like I could be going too...

Destination west Lothian ??

 

[iamelectric]

Maximum demand & diversity

unlucky , hope ur not a hearts supporter

 

[i=p/u]

Re: Maximum demand & diversity

Do they have football teams in Scotland... We hate the Celtic and wel take them anywhere lol

- - - Updated - - -

Football is boring now , like wiring lights just lol

 

[Richard Burns]

DB2 Maximum Demand & Diversity
Lighting - 90% of total demand.
Total demand of lighting circuits is 55.97amps. After diversity has been applied the number changes to 50.37a
Sockets - 100% current of first circuit and 70% of remaining ring circuits.
Ring circuit 1 = 32a
Ring circuit 2-9 = 32 x 8 / 100 x 70 = 179a
32 + 179 = 211.2a
Power - 100% full load of largest appliance and 75% full load of remaining appliances.
16a switch fuse = 16a
13a fce = 13 /100 x 75 = 9.75
Total maximum demand with diversity for DB 2 = 287.12
Per phase = 287.12 / 3 = 95.70a
Sub feed ocp rated to 125a to allow for future additions to distribution board.
Sub feed cable size - 35mm XLPE singles enclosed in trunking.

Maximum demand and diversity are very variable but as you are doing a project using the values in the OSG is the right approach. In reality using these figures would give very high values.
Sounds like you are in about the right area with your calculations.

I think you have missed one addition somewhere in example one as I get total of 391A using your figures.
For standard socket circuits I would use 100% of largest plus 50%of the remaining as they are standard circuits.
For the hoist you have used the MCB rating but if you have an actual current then you should use that in the calculation as FLC. Actually for anything except socket circuits if you have the rated current of the attached equipment then you should use that value not the MCB.

For example 2
Seems OK except for the socket circuits again.

Remember that to use XPLE singles rated at 90C the equipment to which they are connected must also be rated to 90C.

 

[Phoenix]

Informative reply, thank you.

 

[SafetyEICR]

Thanks for replies RB. Only reason I've not used rated current for the hoist is because we are simply told we need to supply to a 32a switch fuse. Not sure what diversity to apply? Again on mains panel we are to supply to a 63a switch fuse for HVAC and 45a switch fuse for Lift. again not sure on diversity. Have to take switch fuse isolator as design current.

 

[Richard Burns]

If you do not have the data then you are doing the right thing taking the worst case scenario, lifts are only partially covered by BS7671, but in general since each item is its own circuit then you work it out on the basis of the protective device, presumably inrush currents, etc. have already been addressed.
So your calculations are the best available.

 

[stigwart]

You would have to apply motor circuit diversity, haven't got my on site guide on me but I think it's 100% of first, 65% of second and 35% of the remaining circuits??