Wiring a home in Nigeria

[Oriahig]

We are building a house in Nigeria and need to install cooling only units. Voltage in Nigeria is 230. Each aircon unit is from 1600 to 2200Watt. We need to install 14 air conditioning units. My questions are,
1) what cable size do I need to run this aircon units to the Distribution Panel (DP)- distance of 20Metres to DP?
2) Must they be connected parallel of one another and protected by single MCB for each aircon unit?, what MCB size?
3) The distance between the house where the Consumer Unit (Distribution Panel) is located and the incomming supply is 110metres. What cable size and type should we use? The average temperature in Nigeria is 32*C +or-
4)We plan to bring in 100A each tripple phase from the incommer supply but use single phase MCBs to distribute since we wont be having a TP appliance. Is this allowed?
Thanks

 

[plugwash]

We are building a house in Nigeria and need to install cooling only units. Voltage in Nigeria is 230.

I don't know what regs nigeria work to but i'm assuming that as a former british colony they are similar to british ones though possiblly based on older british ones. Contacting a local expert would be a very good idea. The following information is based on british regs

Each aircon unit is from 1600 to 2200Watt. We need to install 14 air conditioning units. My questions are,
1) what cable size do I need to run this aircon units to the Distribution Panel (DP)- distance of 20Metres to DP?

If there is only one unit on a circuit i'd think 2.5mm would be plenty. You may get away with smaller but I wouldn't bother.

2) Must they be connected parallel of one another and protected by single MCB for each aircon unit?, what MCB size?

I would wire a seperate circuit for each unit and use 10A breakers.

3) The distance between the house where the Consumer Unit (Distribution Panel) is located and the incomming supply is 110metres. What cable size and type should we use? The average temperature in Nigeria is 32*C +or-

I don't have a figure offhand but its going to be big because of volt drop issues. Remember you have to add up volt drops over differrent stages of the wiring so you don't want too much drop on this step. I'd think 75mm cable should do it.

4)We plan to bring in 100A each tripple phase from the incommer supply but use single phase MCBs to distribute since we wont be having a TP appliance. Is this allowed?
Thanks

It is perfectly normal to have single phase breakers in a three phase board.

 

[JohnD]

I'd think 75mm cable should do it.

ae you sure you meant 75mm?

 

[Oriahig]

Thanks a lot plugwash.
I think Nigeria complies to the British Electrical Standards. But the Electricians there reading their own "common sense" meanings in implementing the British regulations. This often result in wastage or failures due to compromising. For example, our current electrician wants to use 4mm cable to run each (separate) circuit for the aircon. 2.5mm for 13amp sockets circuits, and 1.5mm for lighting circuits. What do you think?
Since we are installing 14 aircon units, is it allowed to connect 2 aircon units (separate) circuits into one 20A breaker? This will reduce the number of breakers to 7 instead of 14.
We plan to use 25mm-4core armoured cable to connect the 110m distance of supply to consumer unit. Is this alright?
Thanks a lot

 

[plugwash]

ask him for a copy of his volt drop calculations, if you don't understand them post them here, if he says he hasn't done any find someone else. 25mm seems a bit small but my calculations were very rough. Remember you have to add up volt drop along the different stages and you are allowed 4% drop overall. One possibility is he may not be basing his calculations on the full 100A supply rating but on the load he has calulated, this is ok per regs but may make expansion very difficult.

4mm for the aircon circuits sounds like overkill to me if there is only one unit on each.

Putting two units on one 20A breaker is fine from a cable protection point of view if using 2.5mm or higher cable and other calcs bear out but if doing this you should protect the individual units with FCUs.

 

[Oriahig]

Thanks Plugwash.
Is 13amps FCU enough to protect each airconditioning unit?
Also what is the least cable size I can use for single electric fan oven? 4mm ok?

Regards

 

[Stoday]

There are times when it's prudent to take a wider view on volt drop calculations.

The regs allow + or - 4% on an installation; the distribution company can allow + or - 10%. Now, if the incoming supply is from a nearby substation, within only a few meters of the incoming supply, there's very little distribution network & it won't need its 10% allowance. So you could find a volt drop of more than the 4% on your installation acceptable.

The rating of the aircon units is based on full load running, not the starting load. The starting current can be six or more times higher than full load, or it can be soft start and have little more when starting. It sounds as though your electrician, in choosing 4mm cable, has assumed you don't have soft start aircon units.

 

[Oriahig]

Thanks Stoday, so does that mean that we can use 25mm armoured cable for the 110m distance? There is a transformer on the line about 30metres from where our incomer terminates.
The other thing I need to know:- can we use 13amp fcu for the aircon switch?

Thanks a lot
Regards

 

[Stoday]

We plan to use 25mm-4core armoured cable to connect the 110m distance of supply to consumer unit. Is this alright?

Plugwash gave his view that 25mm was a bit light. I expanded that view to say that maybe local circumstances suggest it's OK.

You & your electrician have to decide. If it dosn't work you can then blame your electrician. You are paying him to take the responsibility.