Consider we have an RCD+MCB protection for a circuit.
if we follow the tables for Zs values of a 10A, MCB, type C, the maximum value shall be 1.75 Ohm, this happens when 100A current flows ( as per MCB breaking curve). When the RCD disconnects the circuit in much less current, why...
Where can I find the max Z's value for a BS3871, type 3, 32A MCB?
Iv had a look through BS7671 and done some searching online but I cannot find it. IV found some tables with listed Zs values for a 3871 but I have no idea where they originate from or how old
right I get a bit confused with working out the Tabulated values (I am training and have exams tomorrow for Initial verification) on the Ze and Zs anyone on here what to explain how this works on the earth loop impedance, please can someone explain what I am overlooking ?thanks, Jules I...
I'm in the final stages of completing my electrician course, and I find myself confused (again) by EFLI.
In the textbook provided is this:
see below for each circuit.
Calculate the maximum Zs for each circuit:
Complete the table.
The answers given in the textbook are said to...
So I've been told by the NICEIC not to use the 80% rule for max Zs (even though that's the table provided on the inside of the cert books). They want me to use the 100% values from table 41.3 in the BYB. Not a problem.
However I can't seem to find a table for the BS EN 3871 MCB's in there...
Repairing a 2kw convection heater in our workshop office and I'm getting zero resitance on the min/max dial at any setting. What is the value for min and max as need to lever the spacing to get a resistance but don't know if it's too much or too little
I was doing my r1+r2 tests on a lighting circuit yesterday in a 6 bed house over 3 floors. Approximately 20 points not including switches. Mainly pendants but some light bars etc and almost all LED or low energy halogen type bulbs. Closed circuit r1+r2 values range from 0.88 on ground...
I know that the 80% values are applied in regards to operating temperature etc but NIC paperwork asks for the max permissible values of bs7671.
So when do you guys apply the tabulated values?
I've done commercial condition reporting in the past with a company that used their own test sheets...
Hi for a ring circuit, is there any need to measure and enter R1 + R2 values on a schedule of results ? Because an r2 value is already measured (together with r1 and rn). If I needed a ring R1 + R2 value to calculate ZS (although i would find ZS with a socket tester so really no need; but if I...
I have a ring circuit where the Zs reading taken is higher than maximum allowed values.
the circuit is protected by a 32a RCBO type C device, Zs = 1.43.
I have currently have tightened terminations which has brought it to its current value.
as i have been out of the game for a while...
Iv been given the scenario:
6 circuit earth fault loop impedance values were recorded. Each circuit has type B cb.
referring to the maximum values, show by calculation if these values are acceptable.
so I can't do zs =ze+R1/R2 because they've not provided me with ze.
doing some research it...
So, when I did my 2391 I&t course I was told to use to values in table 41.3 of the regs for max ZS value for rcbo which provide earth fault, and over load protection. Recently a colleague of mine said you should use the value in table 41.5 which states a max permissible ZS of 1667 ohms. I don't...
Struggling on this one.
Anyone know where I can find the Min PSCS Values of Type gG fuse,10A 500V (10 x 38mm)? IEC 269-2
I've got a load of 230v lighting circuits protected by them but google is not my friend today......
So disconnection time of 0.4 seconds?
Hi I have a Fluke 1653b and it claims to have Pass/Fail indication on RCD's ?? Where? Is this on the auto mode?
I can only get it to auto test then I have to scroll through all the measurements. There is no mention of this feature in any of the manuals?? Help!!!
I have continuity measurements on a ring final circuit of: L/L 1.4, N/N 0.78, E/E 1.7
Loose connections somewhere?
There is a new CU with RCD.
Insulation resistance measurements are good.
There is a boiler added into the circuit as a spur.
Any suggestions or comments?
:) :) :)
Much though I don't like it, once in a while I use a second hand MCB - for one that has long since gone obsolete and new ones are unavailable. What about testing used MCBs before reusing them, does anyone actually do this?
I just tested a 5A MCB at a couple of values of loading, it seemed to...
Hi can somebody shed some light upon correction factors for earth fault loop impedance. I know that the vales of zs in bs 7671 are if the conductors are running at max temp ie worst case scenario , am I right in believing that if you get a measured result you apply 0.8 to it?
I might be COMPLETELY wrong.... but I have recently finished my level 3 in college and I'm sure I was told that if a Zs value is higher than the max reading in BS7671 it's okay if it's protected by a 30mA RCD, so it passes. I sort of remember writing 'satisfactory' on the test form next to Zs...
BS7671 tables only go to certain size fuses eg how can I find max ZS of 400 amp BS88 - 2 on niceic test sheets they ask for a max value out of regs table I have only managed to find a busman fuse chart which differs been told by employer to use these values on sheets any input would help thanks
Hi guys had a conversation with the boss in the office after work today about a zs I got on a 32A c type rcbo bs 61009, the earthing system is TN-C-S, he said he wasn't worried I got a zs reading of 0.90 even though a type c 32A rcbo has a max zs of 0.72 his words were "it's just like a TT...
I have old style Wylex push button breakers at CU, and these are labelled as BS 3871, Type B and are 5 & 30 amps. I can not find any ZS values in the regs for these, but see these labelled as N/A. Any help apprecriated.
After advice doing EICR report on a welfare set up on a building site I am after advice on my coding
welfare set up is on a tn-s protected by 100ma main rcd tripping out at 42.3ms at x1 I have some covector heating circuits on a c16 mcb but zs is to high for the c16 what code would...
The building has its own supply and forms part of a 230 v TT System. Ze and PFC have not been measured. All circuits are wired in 70 degree Celsius thermoplastic single core cables, with copper conductors, in surface mounted, galvanized steel trunking and conduit. All accessories...
As we know, for switches/cables/isolators etc, you need to multiply your Voc values by 1.15 and Isc values by 1.25 to calculate the relevant max values for suitable protection. However, does this apply to MPPT or Max DC voltage/current input values on inverters? Any thoughts?
Hello i havent done much testing before so i am trying to brush up on my Testing skills before i join Elecsa, i have a couple of questions about R2 testing please.
I understand how to carry out R1 R2 tests using method 1 and that we do them to calculate the Zs of our circuit Zs=Ze+R1+R2
Why is it when you cross connect the conductors at each leg and then test continuity, the result is one quarter of the combined resistances of the legs? I am usually pretty good at seeing how/why calculations work out, but just cannot in this case get my head around why the value measured is a...
Just had a PIR done for a house we were hoping to buy.
The house - victorian/edwardian terrace - has 8 circuits and the wiring is approx 20yrs old according to the PIR.
The report gives the same reading for ALL circuits. Live-Live is 1.01 Mohms and Live-E is 0.17 Mohms. Continuity Polarity...
A client of ours are having an 800kva optimiser installed presently.
So its got me thinking, as being as its basically another transformer (dare i say an isolating transformer? although i stand to be corrected!), will this effect the existing Zs values throughtout the installation? Rather like...
In amendment 1 of BS 7671 the BS1361 cartridge fuse is being replaced with the new BS88-3 fuse as part of over 700 changes. Another change is the replacement of the PIR form with the EICR form. My question is that after 1st January 2012 on the new EICR what version of BS7671 would have to be...
Does anyone have any experience in recording values of EFLI on circuits fed through a DB supplied via a UPS please? The meter shows the above scale arrow.
I understand that there will be no reference to the external earth due to the inverter inside the UPS but what will happen to the UPS...
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...
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...