H
holmslaw
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Another Pair of Eyes would be appreciated
- Thread starter oharaf
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These are design figures and represent the absolute maximum figures given the test conditions referenced in BS7671. BS7671 makes this clear at the foot of the Zs tables in Chap. 41. As such, the maximum figure entered on the sheet should be the maximum permissable figure taking into account ambient and conductor operating temperatures and it is against this value that the measured value is compared.
If you prefer not to measure conductor temperatures, ambient temperatures and re-calculate using correction factors, the OSG figures are the ones to use as they make a generous allowance for variables.
Not sure if it's required on this form (mine are different) but do you not need to put in R2 values for the main equipotential bonding conductors?
Looks very neat!
Good luck
R2 refers to a circuit protective conductor, not a bonding conductor. By all means enter a resistance value for bonding conductors if you wish, but don't refer to them as R2 values.
I stand corrected , thanks for pointing that out. In defence, I was instructed to put the value in the R2 column. 'Gas equipotential bonding conductor' etc went in the Circuit designation column, leaving a few rows spacing from the numbered circuits.
, thanks for pointing that out. In defence, I was instructed to put the value in the R2 column. 'Gas equipotential bonding conductor' etc went in the Circuit designation column, leaving a few rows spacing from the numbered circuits.Sponsored Links
Gary, the preference is to test RCDs at an appropriate point(s) in the circuit. I seem to recall ERA (or someone) mentioning this in an RCD paper. Testing on the terminals can give odd/incorrect readings and with some RCBOs very odd.
So I would say that the RCD should be tested from each individual circuit and the readings to be entered accordingly. These will vary, perhaps most after the first test, but they should be substantially the same. I wonder if he tested kitchen sockets first?
I can't quite make out the figure. Is it 1.08 or 1.82 or 1.92??
Parallel paths. But in domestics, I usually only ever come across this on shower circuits when the shower is just the other side of the wall.
I stand corrected
You should be commended for measuring them and noting the results.
1.92
GN3: The test is made on the load side of the RCD between the line conductor of the protected circuit and the associated cpc. The load should be disconnected during the test.
Couldn't that mean at the load terminals of the RCD with the outgoing circuit disconnected?
I also realise it could mean, for example, at the supply terminals of a cooker isolation switch with it in the OFF position.
Wow. I wonder if the reading was measured from the front via an adaptor. Marbo sockets in particular are very flaky if measured this way. MK always rock solid though and Crabtree always good.
r2? I would hope it was end-to-end resistance of the cpc at the consumer unit!
Gary, you're not wrong. It's just that there can be problems testing directly on terminals. I've always tested in circuit as I believe it's always best to make testing as realistic as possible. Doing so also 'repeats' other tests in a round about way i.e. cpc to CU. I know there has been a debate about this and also load on or off but the penny isn't dropping. If it drops I'll get back.
I always thought that the entered figures on certs where it says Max Permissable Figures are those directly from BS7671 i.e. uncorrected. Maybe I have picked this up from the NICEIC?
The corrected figures in the OSG/GN3 are for a copper conductor with an operating temperature of 70deg C measured at 10 deg C, outside those figures further correction is required.
I guess the way to look at it is to ask why is the info requested on the test sheet? Seems little point putting a figure which may not be applicable. Especially as that figure is recorded in a British Standard anyhow. The purpose of entering the measured value is to record the value and also to check it against the 'max' figure to ensure it is below it. If you put the design values down, you would also have to note that the testing conditions were appropriate to use the figures.
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