NIC PIR Certs
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It's on the schedule of items tested on the forms I use (Tysoft EasyCert), not the actual EIC or PIR.
612.14 gives two methods:
Measuring a circuits impedance or checking design criteria (yeah right!).
612.14 gives two methods:
Measuring a circuits impedance or checking design criteria (yeah right!).
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R1 + R2 will give the volt drop. If we take a 2.5mm (1.5mm earth) radial at 20 amp we know the limit is 32 meters and the R1 + R2 will have a maximum of 0.75 ohms so I would think doing the calculation and verifying on the form makes sense. Rather easy to produce a chart and so easy for someone latter to show you got it wrong one would be silly not to ensure it passes.
Problem is with Zs as so easy to get parallel earths which mess up the reading we all know often Zs - Ze does not equal R1 + R2 it should I know but very rare that it does and with that in mind will Zs - Ze be accepted?
Eric
Problem is with Zs as so easy to get parallel earths which mess up the reading we all know often Zs - Ze does not equal R1 + R2 it should I know but very rare that it does and with that in mind will Zs - Ze be accepted?
Eric
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Are you suggesting we measure voltage at the accessory terminals under load conditions?
The circuit may not be under load conditions at the time so how could the voltage reading be relevant to volt-drop?
It would be interesting standing in a running shower, cover off (shower cap on - pink one) and £600 tester hooked up to the supply terminals
Back to 525.1 - ....under normal service conditions....
It would be interesting standing in a running shower, cover off (shower cap on - pink one) and £600 tester hooked up to the supply terminals
Back to 525.1 - ....under normal service conditions....
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For an immersion heater I can see how you can turn it on and measure voltage but I can’t see how you can do that with a selection of sockets with variable load.
I use excel on my PDA but how many electricians carry a PDA or laptop. And although easy to calculate once excel has been set up I would not want to work it out on the back of a fag packet.
I suppose the point is design and installation are separate and although as an electrician we are trained to install should we also be doing the design? And I remember as set of houses that the installation was carefully designed and half way through the builder changed from beams with knock outs for wires and pipes to plain wood beams so 1/3 rule came in and three houses were completed before anyone realised as a result with too much cable in each ring.
A full set of meters is now regarded as tools of the trade maybe now a PC is a necessary tool of the trade as well?
Eric
I use excel on my PDA but how many electricians carry a PDA or laptop. And although easy to calculate once excel has been set up I would not want to work it out on the back of a fag packet.
I suppose the point is design and installation are separate and although as an electrician we are trained to install should we also be doing the design? And I remember as set of houses that the installation was carefully designed and half way through the builder changed from beams with knock outs for wires and pipes to plain wood beams so 1/3 rule came in and three houses were completed before anyone realised as a result with too much cable in each ring.
A full set of meters is now regarded as tools of the trade maybe now a PC is a necessary tool of the trade as well?
Eric
Am I right in thinking that without knowing Ib for every circuit, for an installation with single or multiple submains feeding the final sub circuits it's impossible to either measure or calculate in accordance with 612.14 (i) (ii)?
How do you think a tester tests Zs?
As it's not normally required during Initial Verification, the assumption is that the Design has been worked out accordingly.
So we move onto PIRs. In the absence of accurate design diagrams to refer to, what can you do?
Measuring the circuit impedance might help to verify design figures, if they are available. But they would give you a good indication if measured correctly.
But neither BS7671 nor GN3 offers much in the way of this.
As it's not normally required during Initial Verification, the assumption is that the Design has been worked out accordingly.
So we move onto PIRs. In the absence of accurate design diagrams to refer to, what can you do?
Measuring the circuit impedance might help to verify design figures, if they are available. But they would give you a good indication if measured correctly.
But neither BS7671 nor GN3 offers much in the way of this.
Surely you're not suggesting that accurate diagrams are not available?
I hope the NIC don't want to see a graph attached to the PIR showing maximum cable length v current for different conductor cross-sectional areas with different percentage volt drops for specific nominal voltages, conductor temperatures and wiring systems for every circuit
The circuit may not be under load conditions at the time so how could the voltage reading be relevant to volt-drop?
It would be interesting standing in a running shower, cover off (shower cap on - pink one) and £600 tester hooked up to the supply terminals
Back to 525.1 - ....under normal service conditions....
525.1 also states that you must have the product standard relevant to the equipment. That's before you even get to thinking about normal service conditions.
By the way, hands up those who think Zs tests are 'very' accurate? Testing in general is not a fine science. Tolerance of test equipment alone would surprise many. Add in the effects of varying/dirty mains and it's not hard to see that live testing might be considered by some to be nothing more than a reasonable indication. But that's what we have to play with.
I hope the NIC don't want to see a graph attached to the PIR showing maximum cable length v current for different conductor cross-sectional areas with different percentage volt drops for specific nominal voltages, conductor temperatures and wiring systems for every circuit
I think even the NIC won't be going that far. Then again, maybe they've produced something in their (sorry the ESC) Technical Manual.
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