rcd, rcbo query

[Rockomuir]

Been working on my local campsite and the client has mentioned that he is having a problem with his caravan hook ups. Basically there are 5 hook ups protected by a type c16amp rcd. Each of these hook ups are supplied from buried armoured cable from a type b20 rcbo. the client is complaning that the rcbo trips before the rcd. A few of the rcds seems to not work properly and need replacing but i think this problem has exsisted for a while. I was just after some advice on likely solutions and whether it has anything to do the type b and type c rcbo and rcd.

Many Thanks

 

[shanky887614]

Been working on my local campsite and the client has mentioned that he is having a problem with his caravan hook ups. Basically there are 5 hook ups protected by a type c16amp rcd. Each of these hook ups are supplied from buried armoured cable from a type b20 rcbo. the client is complaning that the rcbo trips before the rcd. A few of the rcds seems to not work properly and need replacing but i think this problem has exsisted for a while. I was just after some advice on likely solutions and whether it has anything to do the type b and type c rcbo and rcd.

Many Thanks

a b type should trip before a c type.

 

[babylonsBurning]

Not entirely sure of your set up but i would have thought that the rcbos protecting the SWA should have been time delayed RCDs. Also when you say type c16amp rcd, doesnt this mean an RCBO as well? The set up sounds a little strange or im misunderstanding your post.

 

[Geoffsd]

If they are both 30mA then there's no telling which one, if not both, will trip first with an earth fault.


I am puzzled why you call one a c16amp rcd and the other a b20 rcbo.
Are they not both rcbos?

 

[babylonsBurning]

Also is it "tripping" from overcurrent or earth leakage?

 

[babylonsBurning]

My thinking the same as yours geoff, i think there is 2 x 30mA rcds in series

 

[babylonsBurning]

Think the upstream should be s type, but not entirely sure of the set up.

 

[Geoffsd]

Just to be clear.

There are five 20As aren't there?

 

[snowhead]

I read it as 1x20amp b type Rcbo supplying 5x16amp c type RCD, ??

 

[dan86]

I am puzzled why you call one a c16amp rcd and the other a b20 rcbo.
Are they not both rcbos?

he's perplexed us all

 

[Geoffsd]

That's how I read it first.

Tripping hardly a surprise then.

 

[shanky887614]

delete

 

[Richard Burns]

Been working on my local campsite and the client has mentioned that he is having a problem with his caravan hook ups. Basically there are 5 hook ups protected by a type c16amp rcd. Each of these hook ups are supplied from buried armoured cable from a type b20 rcbo. the client is complaning that the rcbo trips before the rcd. A few of the rcds seems to not work properly and need replacing but i think this problem has exsisted for a while. I was just after some advice on likely solutions and whether it has anything to do the type b and type c rcbo and rcd.

Many Thanks

An RCD cannot be type C as this is applicable to MCBs/RCBO, so there is confusion there.
I assume both the 20A RCBO and the 16A RCD are 30mA rated.

If the "type C" 16 A RCD is an RCBO then this does not really change things unless you are considering over current trips.
For over current (considering the MCB parts only, if they are present) a type B will trip before a type C in general at those levels of current rating (20A and 16A) there is no true discrimination between them. Using a type C 32A breaker at the origin would probably just about provide discrimination, however this would need you to consider the size and CCC of the supply cable.

If you are looking at earth leakage tripping then having two 30mA RCDs (of any type) in series it is a moot point which will go first, although the upstream one will experience more leakage current as it will cover all the sub feeds, however differences in tripping time and current could mean either will trip first.
To resolve this the upstream RCBO should be replaced with a 100mA time delayed version.

 

[ian.settle1]

Been working on my local campsite and the client has mentioned that he is having a problem with his caravan hook ups. Basically there are 5 hook ups protected by a type c16amp rcd. Each of these hook ups are supplied from buried armoured cable from a type b20 rcbo. the client is complaning that the rcbo trips before the rcd. A few of the rcds seems to not work properly and need replacing but i think this problem has exsisted for a while. I was just after some advice on likely solutions and whether it has anything to do the type b and type c rcbo and rcd.

Many Thanks

20A Type B RCBO supplying 5 x 16A RCDs which each supplies a caravan, wasn't at the front of the queue when the brain cells was handed out

 

[Rockomuir]

sorry about the late replys , the joys of bt home hub being out of action for 2 days. Thank you for the replys. Yes they are two rcbos was not thinking when typing. I not sure yet if the tripping is overcurrent or earth leakage as i am not due back on site till monday. I have got a feeling it will be overcurrent though. To clear a few things up there are 5 type b20 amp rcbos. Each one individually supplys a caravan hook up where there are 2 type c 16 amp rcbo, both rcbo are 30ma Should i change the 20 amp Rcbo to time delay?