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I'm being stupid but for some reason I can't remember the answer. I've seen main switches rated at 100a and some at 60a. If I was installing a main switch what would help me determine what size rating to use?

Apologies if I've asked this before because I fear I have but can't find the bloody answer!!
 
If it is a single device then the size then I wouldn't install one smaller than the upstream protective device i.e the DNO incomer cutout fuse.
If there are more than one such as in split load CUs then you can work out the size you require by looking at the circuits fed by them and applying diversity.
 
To ensure compliance, fit 100A switch disconnectors to all.
 
What max current rating RCDs come in "high integrity" consumer units? I thought one was 80A and one 63A for a wylex??
 
The output of cycle dynamos is (was?) AC, but with a very low frequency, proportional to the speed the bike wheel turned. The flickering is (was) the lamp extinguishing each time the output voltage crossed zero, that became perceptible to the eye once the frequency dropped below about 5Hz.

A commutator is a feature of DC motors and universal motors, often used in battery powered toys, auto electrics and both mains and battery power tools.

Commutation refers to the reversal of polarity of two conductors in a circuit.

Consider a car window motor. Within the motor, each time one pole piece on the rotor approaches a pole piece of the stator, the connections to the pole piece are reversed automatically by the motor commutator to drive the rotor past the stator pole.

The manual switch controlling the window motor also commutates, reversing the relative polarities of the rotor and stator connections to the motor to raise or lower the window.

An intermediate switch used in lighting circuits is also a form of manual commutator, reversing the connections between the two 'strappers'
 
What do we make of this.
Reg 559.10.3.3 states: A maximum disconnection time of 5s shall apply to all circuits feeding fixed equipment used in highway power supplies for compliance with reg 411.3.2.3 TN systems ot 411.3.2.4 for TT supply
so reg 411.3.2.4 states that a TT system shall have a disconnection time of 1s. What reg do you go by and why do they conflict?.
 
Have you looked to see if this discrepancy is resolved in the forthcoming Amendment?

If it isn't then you could feed this back via a DPC comment.
 
Thanks. How do I do that? So if it's a mistake , is it wise to go for the lower disconnection time?
 

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