In the case of adjustable breakers which value goes in the column for protective device
i.e. if it a a 200a breaker and it has been tuned down to 180a?
Hi guys just looking at some 2391 exam papers and came accross this question could someone help me on this as to how to work it out many thanks.
Refer to the measured values, tabulated below.
Circuit
1
2
3
4
5
6
7
8
Measured Zs
0.8
1.1
1.3
6.2
5.1
2
0.6
1.3
Calculate...
On an Installation Cert in the 'Max Permitted Zs' column should i put the tabulated values in the regs or should i put the corrected values(x0.8 rule of thumb)????
My guess would be corrected values as that would be max zs at ambient temperature at the time of test?
Cheers peeps,
Dan:cool:
Afternoon guys,
I thought id come on here and see if you have any more information what will be needed from me in my first assesment, iv read all the leaflets they send out, but just thought id ask as many of you as you have been having assesment for years and those who have recentley just...
Hello, can someone explain to me the 'rule of thumb figure' (0.8) when calculating max Zs value's from BS7671!?
Currently doing a PIR in a foundry where i measured the ambient temperature at 21 degrees at ground level, i bet you can add another 10 degree's higher up ...and that's on a good day...
Having just read some posts regarding Ra values of an earth rod, and some disagreement of the values to obtain, i thought i would post a little guide.
Earthing Design Considerations
hi if someone has a minute of thier time to help me out with this solution i would be most grateful?
Question: A length of circular section of conductor has a resistance of 2 OHMS. If its diameter was doubled what would its Resistance be ?
answer 0.5
i thought the answer would be 1 but the...
When testing its always been said that its important to take your Continuity reading (R1+R2) and that Zs can be calculated (avoiding working live)
So how many of you do all your correct R1+R2 values and then claculate there Zs and put this figure down on your test sheets?
Or are most of you...
installed a new dual rcd cu today and on completeing my tests I noticed the zs values were slightly above the max permitted by bs7671.
All my other readings, r1+r2s ect were fine and the ze was 0.2 off the top of my head.
took a zs reading off the load side of both rcds and both values came...
am looking at the question and am a bet lost now on answering it.....
The maximum permissible values of earth fault loop impedance for three circuits are 1.44 Ω, 0.92 Ω and 7.67 Ω. If the measured values for these circuits are 1.25 Ω, 0.68 Ω and 6.22 Ω, determine if the measured values are...
Hi, i am confused about how voltage drop is worked out and need an answer for the following please;
Work out cable size and cpc size you need when you have:
Cable length = 50 metres
Ib = 32Amps
to get a voltage drop that complies with regs i.e. below 5%(11.5 Volts).
It's wired in singles and...
ta-electrical
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aus
cable
formula
guide
help
help please
please
value
values
voltage
voltage drop
volts
Hi guys new to testing and about to do my first TT system tomorrow. Popped in today and did a quick Ze test and got 16.98 ohms. Zs values will not meet max values for 7671. Whats your thoughts guys. (what have I forgotten?). Pete
Hi there I have another question for you guys.What is the maximum Zs values for different circuit breakers i.e type B,C,D also where would we find them and why the difference?
could anyone help me with the short circuit capacity and maximum permitted zs of a BS3871 type 2 MCB please. And if using the sheath on a micc cable as cpc what do you put in the cpc mm2, is putting sheath acceptable.
Thanks Paul
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