Earth Leakage

Although it's hard to make a blanket recommendation based on a short question, I'll try. In most cases you will want to use the RCCB<30A on individual circuits. There are several fundamental reasons:

(1) They will sometimes go bad (That's why you test them every month) and it's cheaper to replace a 30A unit than it is to replace a 300A unit.

(2) Some circuits have the nasty habit of tripping RCCBs and you don't want to knock out the whole house every time this happens. I frequently use extension cords outside and sometimes they get wet (Don't comment on my lack of intelligence for doing this) and trip the breaker (we call them GFIs). I then know to just fish the cord out of the puddle that it's in and reset the breaker.

(3) If there is a trip, it's much easier to find when you have only one circuit to look at rather than the whole house.

(4) I don't know the specs on a <300A unit, but I think the sensitivity might be better on a 30A unit. Is this true?

Thanks for your reply,

In this case we have to replace all the appliences resepticals with RCDs, and also this will coast a lot of money for materials and manhours.

Is one main RCCD is better? and if we use it, what about the safety rate for humanbeing should no more than 30mA while the main RCCD is about 300mA

One thing about RCB receptacles (I know them as GFCIs) is that you usually only need one per circuit. You wire the RCB receptacle up to the start of your string of receptacles and feed the rest of the receptacles through the RCB and all of your receptacles are protected. I have personal experience with the efficacy of this set up (don't ask). Suffice to say they work very well.

Thank you for these information, but if you increse the current of the RCB that means you also increasing the earth leakage current which should be no more than 30mA.

Two critical things should be taking care with it:1. the earth leakage current <30mA.

2. The time should be no more than 40ms.

Regards,

No. If you use a branch circuit protector, you have the same leakage trip no matter how many feeder receptacles you have down the line. In my case, that's 5 mA not 30 mA. I have some that are actual duplex receptacles and some that are breakers. Both are OK; the duplex receptacles are a little cheaper to buy. Do you have an electrician there? He would know how to do this without too much work.

What is your application? In some cases earth leakage is required at the main breaker in addition to individual subcircuits (hospitals etc.) This is an IEC guideline.

Outside of a domestic application I would not recommend the use of a 'bulk-RCD' as we call it over here, that is, one large RCD at the power-distribution level.

Individuals are not protected against the 30 mA. I have seen this done at the final distribution level (i.e. a relatively large RCD in each DB) but these arrangements are either useless or subject to nuisance tripping.

TVP-45 what is a branch circuit protector?

I have also seen a serious problem with the one circuit breaker for the whole thing scenario. I was at a job investigating a person that got seriously shocked. It turns out there WAS GFCI protection on that circuit. It was at the main breaker.... it never tripped. The next day the electricians at the site were installing receptacle GFCIs.

I'm sorry. I used generic terminology when I should have been more specific. We (US) use GFCI (Ground Fault Circuit Interrupters). Since I don't want to misuse your terminology, I'll keep using GFCI. Typical residential GFCIs trip at 5 mA. There are two ways to install them:

You can put one at each receptacle. This is easy to do and is sometimes done in existing wiring to protect one location that has a potential hazard. Cost is about $10 US for each receptacle and a few minutes to replace.

On new wiring, where the wiring path is known, you can put a GFCI in the first receptacle and wire it so that everything further down the circuit is also protected. This requires knowing the order of receptacles in a circuit. You also are subject to adding up all the residual leakages of the whole circuit and you might get nuisance trips. Since this uses the same GFCI unit as the previous instance, the cost is still about $10 but you have to know what you're doing. This is what I called a branch circuit protector.

If you don't know the order of wiring in old wiring, you can use a GFCI breaker for the whole branch circuit back at the breaker box. It's easy to install, but costs about $30 US. This protects the whole branch circuit. Oh, to Shawn V, nobody ever bothers checking the ones in the breaker boxes, so you never know when they go bad. So, they're not nearly as good in my estimation.

Thanks man

TVP45&MB,

Gentelmen,

Thanks a lot, both gave me good information.

Appriciate,

the function of earth leakage protection (e/l )is to facilitate isolation for a circuit that feeds portable appliances, the local code for wiring of premises may vary (check this first ), this is mainly due to the fact that portable appliances may loose their effective earth continuity due to handling or due to improper installation by the end user. (the end user is allowed to replace a plug on an appliance).

hence if protection against leakage is limited to only socket outlets then the other fixed parts of the installation such as lighting, fixed cooking etc. would not need to be on the e/l. this is mainly to prevent nuisance tripping especially with discharge lamps etc. this would mean that (e/l) may only be installed downstream and not for the entire incomer especially if the main incomer feeds several end users.