replacing an old consumer unit...is it worth it?

[xelaris]

The consumer unit in question is an old Hager (6 ways) no RCD.
There have been no major changes in the electrical circuits in my property except for the inclusion of a new Electric Underfloor Heating cable (only 400w) which uses a dedicated RCD and a Steam Shower (3kw) also with a dedicate RCD.
Since more and more new appliances nowadays require RCD I'm thinking that maybe it would be worth considering replacing the old Hager with a new consumer unit.
Then, as I've understood, the RCD on the cheaper consumer unit acts on all circuits - (unless one is prepared to spend more for more RCD for more circuits)....if so, wouldn't be better to have dedicated remote RCD only for certain appliances and rely on the old Hager? After all is working fine and it seems that changing a CU isn't that simple....and new testing have to be done.
On the other hand, it would be neater to have the RCD (more than one) on the CU rather than having them scattered in remote corners in the house...

 

[EFLImpudence]

Appliances don't need RCDs. They are for your safety.

 

[EFLImpudence]

Appliances don't need RCDs. They are for your safety.

 

[sparkwright]

It's up to you.

The very best thing you could do is replace everything for a new consumer unit using only RCBOs. That will make it 'neat' as you mention, and a fault will only effect the circuit that it's on.

A dual RCD, to replace everything, again neat, and considerably cheaper. But the problem with a fault effecting several circuits. Then again, how often do you expect a fault?

Or, leave it as it is, if no requirement to change it. However, it won't be as safe as it could be. It won't be so tidy. Making future alterations to your wiring will be a problem if no RCD present.

If you're going to do it, save up a bit more, and get all RCBOs. And make sure there's some spare ways. That way you have the best possible set up, and should last a very long time.

Hager are a particularly good make.

 

[xelaris]

It's up to you.

The very best thing you could do is replace everything for a new consumer unit using only RCBOs. That will make it 'neat' as you mention, and a fault will only effect the circuit that it's on.

A dual RCD, to replace everything, again neat, and considerably cheaper. But the problem with a fault effecting several circuits. Then again, how often do you expect a fault?

Or, leave it as it is, if no requirement to change it. However, it won't be as safe as it could be. It won't be so tidy. Making future alterations to your wiring will be a problem if no RCD present.

If you're going to do it, save up a bit more, and get all RCBOs. And make sure there's some spare ways. That way you have the best possible set up, and should last a very long time.

Hager are a particularly good make.

I didn't even know about RCBO (I really need an update/refresh in this stuff) - the very first I noticed about RCBO is how expensive these are (wow)...
The RCD of the Underfloor cable triggered a couple of times in the past 9 months - this when I plugged a very old and dodgy hair-clipper (which I promptly chucked away once I realized this was the culprit and not the UFH). The problem was that the UFH has to share the power circuit - it is recommended to use a dedicated circuit - but that's not an option with my old Hager.
In other words....the RCD of the UFH is checking the whole circuit and while this means the rest of the house doesn't lose power unexpectedly though at least I get a warning - which is useful -....if I update the CU with a cheap model, the RCD would shut the power in the whole house that's no so good....but maybe a bit safer.

 

[sparkwright]

An RCBO, in case you don't know, is an MCB and RCD in one.

 

[xelaris]

An RCBO, in case you don't know, is an MCB and RCD in one.

thanks...googling it right now about it - while I'm starting to appreciate the benefits....do these need to be so expensive?

I've just stumbled across a very useful link:

http://www.smallinstalls.co.uk/info-ideas/blog/57-what-is-an-rcbo-2

the third option is a combination of Dual RCD and a couple of RCBO - this seems to me a useful and cheap option....

 

[sparkwright]

Yes, well done!

That is a good type of board - not too expensive, and space to put RCBOs on any particularly important circuits, where if it trips it won't effect anything else.

You catch on fast!

 

[ericmark]

Question 1 has to be what type of earth do you have? I will guess not TT or there would already be a ELCB of some type. (Earth leakage circuit breaker) but may be not part of consumer unit and you were unaware it exists.

With a TN system much easier single pole RCBO good enough.

30ma can trip for what it seems no reason and the less that is on each circuit the less likely to trip. There are also better quality RCD's like the X-pole which are claimed to trip less. So with 8 RCBO's less likely to trip than with 2 RCD's

Fitting a consumer unit we have four options.
1) Use just 2 RCD's
2) Use 1 or 2 RCD's for items not considered as sensitive but use RCBO's for sensitive circuits.
3) Use all RCBO's
4) Use special wiring exempt from RCD protection for sensitive circuits.

Since you say some circuits already RCD protected and they do trip then to combine those circuits with other circuits would be short sighted. But nothing to stop you protecting half with single RCD and other half with RCBO's.

The rules do not say you must use 2 RCD's what it says is:- "Every installation shall be divided into circuits, as necessary, to (iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation." it is considered using 2 RCD's will conform but it does depend on house. With a boat or caravan all goes through a single RCD forming just one circuit. But in a large house you may need 8 RCD's to prevent unwanted tripping.

There is nothing to stop you fitting an external RCD to protect the whole ring however what you end up with is a line of RCD's which in the end cost more than changing a consumer unit.

The major problem for electricians is most are members of a scheme which makes them follow BS7671 so they can't do half a job. And for DIY people to swap a consumer unit will cost more in LABC charges than getting an electrician to do the work.

I would say all RCBO's is best option but what I worry about is if it does trip will you know in time? All I can say is my house has two consumer units from two RCD's for last 25 years and they do trip normally in a batch may be once a week for 3 weeks the 6 months without a single trip. My mother has 4 RCBO's in kitchen and they have never tripped. So it would seem RCBO's are the way to go.

However mine are 25 years old and no electronics the newer RCD with electronic damping is less likely to trip.

Nothing says you must upgrade but it's hard to just do part of house as once changing consumer unit really it's all or nothing.

One big problem is existing faults most electricians will test before they start so are aware of any faults before they remove old consumer unit. But with a twin RCD unit there is no option to have any non protected circuits so any faults have to be found and corrected not a DIY job.

To change how many circuits are RCBO and how many are common RCD means cutting the buzz bars to length so not easy to do bit at a time.

 

[xelaris]

Wow...There's so much than just replacing a CU - the more I read about the more stuff starts popping up - e.g. it seems a couple of smaller CU are better than a single big one.....
It's getting complicate - surely it's worth taking more time and do it properly....It looks like I'd better to postpone any major change in my electric system (right now it's working fine)...later on there might be some changing in the first floor which might justify updating the CU and also rewiring and adding new power points etc.


Just a point from the previous post:
"Since you say some circuits already RCD protected and they do trip then to combine those circuits with other circuits would be short sighted. But nothing to stop you protecting half with single RCD and other half with RCBO's."

I wouldn't say the power circuit in my property is protected (just a compromise really) because the RCD of the Underfloor cable didn't close the entire circuit...only the UFH - by mistake as the problem was to be found elsewhere in the house (this old hair clipper which tripped the RCD each time it was turned on....).

 

[ekmdgrf]

That is a good type of board - not too expensive, and space to put RCBOs on any particularly important circuits, where if it trips it won't effect anything else.

I hate to be pedantic but the word is "affect" rather than "effect".