Replacement question

[yeleek]

Hi,

We've bought a new house which has an older style fuse box. We are getting quotes for getting it changed.

Whats been suggested is a two zone RCD with MCB's. Is this a good idea? Instead of getting an RCBO? Apparently RCBO is more costly, but does if offer any protection greater than a two zone RCD with MCB's?

Thank you

 

[PrenticeBoyofDerry]

No, the protection will be same and rcbos are more costly,
but if you have rcbos on circuits when the rcbo trips you know which circuit is the problem one.
But if you have rcds protecting a number of mcb protected circuits when the rcd trips the problem circuit is not flagged up.

 

[yeleek]

So it (RCBO) aids in troubleshooting only then really?

Thanks

 

[PrenticeBoyofDerry]

So it (RCBO) aids in troubleshooting only then really?

Thanks

RCBOs are a wonderful product but I wouldn't dare say that they are only an aid but they do help.

 

[yeleek]

OK thank you

 

[Chri5]

RCBO's are the best system.

An RCD has a number of circuits on it, so if one device causes a trip of the RCD, all other circuits are taken out that share the RCD.

An RCBO is a combined MCB and RCD unit and you need 1 x per circuit.

Expect to pay £25 for each RCBO so for 10 circuits and a suitable board the raw material is £300.

For 10 circuits on a split board with 2 x RCD's and 10 x MCB's it's £120


Most blend the 2 items by getting a dual RCD board with the addition of a direct (non RCD) way.

Certain items such as mains smoke alarms, alarm systems, fridges and freezers are best not being on shared RCD rails.

Take the fridge on a shared RCD rail, a light pops the RCD on the way out the building. No one notices, you come back and everything has melted !

The smoke detection is important. A fire starts away from the smoke detection, melts wires, trips the RCD and the smoke detection won't work / raise an alarm. (although most detectors do have battery back up).

If you want the unit to be an asset, and the best way of conforming to BS7671 17th RCBO all the way. Hager are price keen.