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Thank you. Life has been strange at times and I generally have had no free time for forums unfortunately. Hopefully things may change soon. Thought I could slide in a question without anyone noticing!

Hi Just posting to ask if anyone would know of an Independent Connection Provider who would cover NE Hertfordshire for a small TP supply cable install. I have a customer who needs a TP supply installing and the UKPN cost is eyewatering, he has tried to contact some ICPs but they are not...

You would need to be able to make some assessment of the installation method for your 6mm² twin and earth cable. If the cable is entirely surrounded by insulation for a distance then you would be limited to 20A, though most other methods would allow a 32A breaker. Without this information you...

I would tend to concentrate on Doc Hudson's lost Neutral, presumably if all sockets show Line Earth reverse the neutrals are not connected at the board. Oh and all the neutrals will be at line potential! Normally you have: L-N 230V,  L-E 230V,  N-E 0V A Line Earth reverse will Give L-N 0V...

Going back to basic electronics the voltage dropped over a resistor is only dependent on the current and resistance i.e. V=IR. The same principle applies when the "resistor" is a cable. Therefore the value of volts dropped is correct for each section and the total is then compared to 230V to get...

You add the volt drop for each section together to find the total volt drop from origin to end of circuit. I did this diagram earlier to show calculation of volt drop for varying cables in a circuit. Obviously it would usually be larger csa cables first and smaller csa toward the end, and the...

The volt drop is measured from the origin of the installation to the end of the circuit (or the worst case point in the circuit if it branches or is a ring). Volt drop is generally only considered during the design stage so the voltage would be taken to be the nominal supply voltage of 230V...

So you have done all that except the fifth one to resolve the adiabatic equation for confirming the cpc size. I also missed your post of "Thank you, that's helped. Would you say the Design Current to be 16A, then your In could be 20A? I will have another go at the calculation, just so I...

From table 54.7 a 2.5mm² conductor is OK, so however you calculate the adiabatic equation it should come out as suitable. You can't put 2.5mm² into an equation, square it multiply it and divide it and then reverse the process to get the same answer you put into the equation as it is...

You have your supply generator as a source and the neutral is earthed (resistance to earth 7.1Ω?).  This earth path is only transferred to the building via the Neutral conductor so it is using a TNC conductor.  I do not know the rules for this under the rail regulations but not permitted on the...

You are told it is a 16A circuit, you are not given the design current, if you specify a type B 16A BSEN60898 then maximum Zs @70°C is 2.73Ω Ze is 0.11Ω, therefore R1+R2 must be less than 2.62Ω @70°C. From the installation method (singles in conduit) and assuming maximum current as you do not...

The first bit is OK with some overkill on the currents and cables but compliant and workable. For the second why have you used 0.4s as the trip time with a fault current of 2090A? Your cpc size would usually be expected to be smaller than your line conductor csa when using the adiabatic equation.

You are correct with reading the R1+R2 value from table I1: 2.30 mΩ/m for a 16mm² line and cpc. Tabulated value x length gives the R1+R2 at 20°C in milliohms. To get the R1+R2 value at maximum normal conductor operating temperature (70°C) multiply by 1.2. To get the value at 35°C multiply by...

Feel free to post a synopsis of the lighting and we can provide feedback on the design. I am not sure how much design for loading you need to include in this question.  A cafe can be a very heavy load and might need two circuits on its own in order to ensure availability of power to a...

If you look at appendix 3 of BS7671 the tables beside the graphs give the Ia, minimum disconnection current to use. For a 6A type B it is 30A as given on page 370.

A dishwasher will be heating the water most of the time during the wash cycle so the maximum load would be drawn at most times when it is in operation. Therefore the design current is 32A. Since you have been given that figure it should not be necessary to use any other value. In other...

When you are working out the design current for a circuit you are attempting to ascertain the expected current draw in normal use on that circuit. If you have a domestic house with only one lighting circuit then you would generally expect that say in the early evening downstairs lights will be...

The correction factors you have applied are correct for a cable installed on a surface, installation method C, but you say in the post above the cable is buried which is installation method D. The Zs value given is for a type B 32A breaker but you state a type C 32A breaker. Could you show...

I think you may be approaching the situation form the wrong direction.  You are looking at how dangerous is this whereas you should be looking at how safe is this? You should be looking at a cable and checking what current it is permissable for it to handle and then work from that current and...

Some of the LED floodlights can be internally rewired with 4 core flex.  The deeper units have a standard driver inside and can be interrupted on the pir output.