# disconnection

1. ### Disconnection Time Requirements?

Why do circuits 32 amps and under require a 0.4 second disconnection time at 230 volts, but circuits over 32 amps are legally allowed 5 seconds? 115 volts for 5 seconds is enough to cause injury to the human body.
2. ### Disconnection Times Again! Fig 3A4

Looking at Fig 3A4 Type B 60898 unless I'm getting it wrong once we In*5 our device there is no way of telling if our disconnection is 10s or 0.1s unless im missing something although this seems quite important??? as our Disconnection time needs to be at least 0.4 seconds and for doing our...
3. ### 18th edition RCD max disconnection times!!

Hi all. I am seeing different figures here all over the net, table3a (p363) states a 30ma RCD has a trip time of 300ms max. So at 5x is the maximum 60ms? I seem to recall 200ms and 40ms for a 30ma and these are the figures I am seeing over the net... Please I just want the correct figures for...
4. ### Maximum Disconnection Times

What is the reasoning behind having a 0.8 disconnection time for up to 120 volts Uo, but it then jumps to 0.4 seconds as soon as you go over it? Wouldn't it be better 0.8 seconds for 150 volts Uo and under, 0.4 seconds 150 volts and over Uo?
5. ### Disconnection times, some clarification

Evening, just revising for 18th update course and wondered if someone can just clarify something. (I might just be confusing myself, too long staring at the BBB) Reg 411.3.2.2 ii) does that also include luminaries? I understand 411.3.4 applies. Do notes 1 & 2 of 411.4.4 mean that the use of an...
6. ### Short circuit disconnection times

Could someone shed some light on the following please? 411.3.2.1 implies that the 5s / 0.4s disconnection times only apply to earth faults. I've not found anything else in the regs that suggests they apply to short circuits. 435.5.2 says faults should be disconnected before the fault current...
7. ### RCD disconnection times on 2018 forms

Evening all, happy Friday! On the new forms there is only one column for RCD disconnection times. I understood you would just record the highest of the 5x readings but on looking around to confirm I found this article on Professional-Electrician: "The model forms in Appendix 6 have been...
8. ### Domestic Changes to the requirements on recording RCD disconnection times

Hi everyone, long term visitor to the forum but first time posting a question... be gentle This question is with regards to the changes to the 18th edition certificates, which only require one disconnection time recorded. When recording the highest value taken when carry out RCD tests, Reg...
9. ### Disconnection time of a 32Amp Cooker circuit with a panel socket?

Hi, What would be the Maximum disconnection time for a 40Amp domestic Cooker circuit in a TNCS system be, where it has a 13A socket outlet on the panel/isolator faceplate? Obviously a final circuit >32A would be 5 secs but I was just interested as to whether the presence of a 13A socket outlet...
10. ### looking through previous certificate and have a question about disconnection time.

On a domestic inspection and testing certificate or conditional reports, I always put maximum disconnection time permitted by BS7671 as 0.4 sec. I've been given a testing job for an HMO property and on the previous conditional report, the maximum disconnection time of 0.4 sec is only given for...
11. ### Automatic disconnection of supply

Can the above method alone be classed as basic protection according to 131.2.1 it can. Based on that regulation you can leave live terminals exposed if supplied by a 30mA RCD
12. ### Disconnection times for finals

Just received a completed test sheet from an installer on a TN system with the max permitted disconnection time column filled in for the lighting circuit and 20A heater circuit as 5secs, surely 0.4
13. ### Disconnection times help

Hi all just a little bit of advice at the company i work has just had a condition report done and they have marked down excessive zs for a 63a type d breaker but they have put it at 0.4 disconnection time it is a permanent fixed compressor I thought this would have been 5 sec it also has a b.s...
14. ### I'm confused about Type C Breaker Disconnection Times

Hi All, When I consult Table 41.3 for a Type C Breaker rated 16A I see s max Zs of 1.37 Ohms. However this value is defined for both a 0.4s AND 5s disconnection time. This is obviously correct so I am missing something. Fig 3A5 also shows the table 0.1s to 5s. Can anyone explain please...
15. ### Deadly Disconnection here in Minorca!

Presently on holiday in Cala Blanca, Minorca and came across this situation. The meter box is built into a wall outside a now disused restaurant along the pavement, the door is completely missing and the clear plastic cover over the 4 wire cut out has been broken and removed. It would appear...
16. ### NIC QS Assessment charge

Not long had my Approved NIC/EIC assessment and had to be QS assessed.This took an extra half a day(on top of the other half a day for the yearly assessment).Just got the bill for the half day charge.......£366!:eek::mad::( Feel ripped off or what. Have any of you guys had to pay this fee?
17. ### Homework help

I'm looking for the section in my on-site guide that covers disconnect times for circuits over 32a. In my regs class my homework features a circuit with a type B 45a RCD. EDIT: oops never mind I now see it says anything exceeding 32a must not be more than 1 second. I thought there was a more...
18. ### Would you replace this RCD?

This is a new RCD, came in the CU. The max disconnection time I need to comply with is 400ms (Table 41.1 TN ac 230V). From a new RCD I'd expect something roughly in the region of 30ms (for a 30mA fault test). What I'm getting is 234ms (x0.5 there's no disconnection and x5 it's a 13ms...
19. ### Table 41.3 Max earth fault loop impedence (Zs)

The heading of table 41.3 says it shows " max earth fault loop impedance Zs for Circuits Breakers..... giving compliance with 0.4s disconnnect time of 411.3.2.2 and 5s disconnnect time of 411.3.2.3." 411.3.2.2 is for final circuits not exceeding 32A. 411.3.2.3 is for distribution circuits and...
20. M

### NICEIC Certification Scheme help filling in niceic test certs please

The test cert is for a transportable building I have fill in a test not done it since college, i dont know what to put in the max disconnection time for Bs60898 MCBs protected by a 63A 30ma RCD main switch, no circuit exceeds 32A is it 0.4s for a TN system is it 0.2s for a TT system or 300ms...
21. ### RCD test

hello every one can some body help me please in this particular question?When tested at Idn time 5 , a 30nmA RCD protecting a 230 V a cooker circuit incorporating a socket outlet in its control unit must trip within : time please
22. D

### DISONECTION TIMES- Circuit Ratings

Stupid question that i need answering. How do what your circuit is rated at? I know that if its above or below 32A there are different disconnection times depending on the type of earthing system
23. S

### trouble with 2394/2395 revision queston

hey guys.... ive downloaded some revision questions for my 2394/95 course i have booked for august and ive come across a question im a little unsure about......even when i have used the regs and GN3 to help. a little help would be greatly appreciated as there is no answer sheet for the...
24. ### TT distribution circuit

Hi, a bit of advice required. I need to install another d.b to a garage, the tails are to be split. The earthing system is TT, the cable is armoured, clipped to the side of the building & over to the garage on a small cantenary wire. As it is TT would the distribution cable need to have rcd...
25. M

### Cable size for single phase motor control panel

Hi all, Your help would be appreciated. We are mainly domestic sparx so I havn't much experience with cable sizing for motors. On site, we need to supply a motor control panel which operates the sewage pump. There are in fact two pumps but I think they switch between periodically to prolong...
26. S

### Zs on rcbo

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...
27. R

### Notification of a disconnected circuit

Do I need to notify the disconnection of a shower circuit? I have disconnected and made safe at the consumer unit and confirmed at the business end that the circuit is de-energised. If I do need to notify, on what basis am I doing so? Alteration in a special location? Sage advice/experience...
28. ### 2392 Question: Maximum earth loop impedance for 20A BS88 (gG) fuse

What is the maximum earth loop impedance to BS7671:2008 for a circuit protected by a 20A BS88 (gG) fuse giving a 5 second disconnection time is: A: 7.42 B: 2.91 C: 1.84 D: 1.35 The green book says the ln for this type of fuse is 78A p299, that doesnt give you the right answer though. :confused5:
29. ### s type rcd

Hi all, looking some advice on s type rcds. Basically can you use them on tt installations for earth fault protection on circuits that don't require additional protection? Know that on a tt installation disconnection times of either 0.2 sec or 1sec must be achieved depending on circuit, but with...
30. ### RCD tripping times, 0.4 or <200 etc.....

I always been told that an 30m/A RCD should trip within 200m/s (x1) and 40m/s (x5). But something iv never taken much notice of before is on test sheet the maximum disconnection time of a circuit less than 32A is 0.4. So....which is it? within 0.4 or within 200m/s????
31. W

### TT Max ZS loop reading for circuits over 32A

HI all anyone know the above, i put 1667 ohms in the box normally for all TT circuits but noticed the other day it is only for circuits upto 32A Anyone enlighten me, i need it for a 50A and 40A circuit?? thanks
32. ### "just bang it on an RCBO!"......... TABLE 41.3

this slightly confuses me; whenever a Zs reading comes up too high, e.g on a particularly long run, to get around the problem if you cant change the MCB rating, I get told to change it for an RCBO. Table 41.3 of the regs gives max Zs values for both MCB and RCBO protection. If our Zs value...
33. S

### PIR on property with disconnected supply

Hi folks, client has requested PIR on a property with disconnected supply (not sure how disconnection has been effected). Property has been empty for a long time and potential buyer (retired electrician - no pressure) wants to know as much as possible to see if price can be negotiated down...
34. ### disconnection times v voltage bands

Guys BS 7671 table 41.1 shows that a disconnection time of 0.4 secs for 120<volts to <inc 230 volts, and a disconnection time of 0.2 at 230< to < inc 400v. (TN systems). My query is with a 10%+/- tolerance which could possibly increase 230 volts to 253 volts hence taking your 230v 0.4s disc...
35. W

### TT System and 30mA RCD tripping times

Help! Sorry having a bad day. I understand the concept behind touch contact of 50v and the above 1666 ohms. But when physically testing with 17th ed dilog and testing a TT system 30mA RCD. At 1x and 5X what reading would you see on your meter? or would you just test the mechanical aspect...
36. ### PIR Question

My uncle wants his property tested as theres a new tennant going to be moving in and just by looking at it i can see its only his sockets that have rcd protection, shower etc don't. What code does this go down as on test sheet and do they have to be changed so that all circuits are rcd...
37. O

### Help with PIR

Hi Needing help with a PIR. 1. Old wylex type 2 CBs what BS is this an what Ka rating does it have. 2. MEM Memway 3 phase DB with rewireable fuses i take it they are a BS3036 3.The Memway is fed via an 60A TPN switch fuse Oterail make would this have a BS No 4. Method of protection on PIR...
38. ### Is there any point testing earth loop impedance

In a tt system? The earth spike is Reading greater than 50 ohms so clearly the mcbs won't make their rated disconnection times. Waste of time?
39. ### 315amp fuse max Zs

does any one know the max Zs permitted for a 315Amp BS88 fuse got brain freeze know on page 45 of periodic report :mad:
40. ### 16th Edition and RCDs?

Can anyone give me a quick answer on whether or not the 16th Edition permitted the non-use of RCDs for additional protection? I've just had a call from a woman buying a house and she's described the consumer unit as having one rcd protecting cooker, shower and two socket circuits, but three...