Which consumer unit and RCBOs?

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TTbangbang

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Hello all,

I'm looking to buy one or two new consumer units to fill with RCBOs. Which brand would you recommend? I prefer the solid looking metal ones but since the installation is TT, have to go for plastic. Are there any caveats with the RCBO price differences? Contactum do them for

 
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Contactum RCBO'S are a job to get in consumer unit. How many ways are needed. I tend to go for MK as they do have a bit more room at top. If you shop around you can get MK for about

 
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Hello all, I'm looking to buy one or two new consumer units to fill with RCBOs. Which brand would you recommend? I prefer the solid looking metal ones but since the installation is TT, have to go for plastic. Are there any caveats with the RCBO price differences? Contactum do them for
 
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I use TLC at last count they didn't seem to have MK 6a and 32a had to be transferred so took a few days to come in. 6 AMP Rcbo's seem to be the main shortage. Must be because having to put Rcd protection on Bathroom circuits. I can't believe Mk can't get more manufactured until December. Seems crazy to me.

Batty

:|

 
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I use TLC at last count they didn't seem to have MK 6a and 32a had to be transferred so took a few days to come in. 6 AMP Rcbo's seem to be the main shortage. Must be because having to put Rcd protection on Bathroom circuits. I can't believe Mk can't get more manufactured until December. Seems crazy to me.Batty

:|
Spose it also depends on which wholesalers / retail outlets have the greatest clout the get the supplies from MK when they are available?? ?:| :(

On a lighter note...

its good news for Spam lovers..

Tescos, Sainsbury's & Occado home delivery can do a 340g tin for

 

TTbangbang

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Thank you for your replies and the in-depth market analysis :D

I'm sure I saw Crabtree's RCBOs at

 

steptoe

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Hello all, I'm looking to buy one or two new consumer units to fill with RCBOs. Which brand would you recommend? I prefer the solid looking metal ones but since the installation is TT, have to go for plastic. Are there any caveats with the RCBO price differences? Contactum do them for
 
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Evening Mr S

I thought that you could no longer use a time delayed Rcd as a main switch but if you look in the on site guide it has a consumer unit with time delayed main switch on a TT system. So there is no reason why you could not put a time delayed Rcd in an enclosure before consumer unit. My only thought is with this if you have a fault on lighting you would lose all electrics. I thought their was a regulation that said you could not do this. It is a bit late to look it up.

Batty

 

steptoe

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Evening Mr S I thought that you could no longer use a time delayed Rcd as a main switch but if you look in the on site guide it has a consumer unit with time delayed main switch on a TT system. So there is no reason why you could not put a time delayed Rcd in an enclosure before consumer unit. My only thought is with this if you have a fault on lighting you would lose all electrics. I thought their was a regulation that said you could not do this. It is a bit late to look it up.

Batty
I get your point batty, but this is in addition to your split board with RCBOs, and your dual RCDs, if your go that far for discrimination.

your RCBO should trip before a time delay RCD in any case I would have thought.

Ive never had any problem in this area,(nuisance tripping) was just wondering if maybe 17th made it wrong now to use a MC CU even with RCD upstream protection,

it was AFAIK fine on 16th and deffo OK on 15th. !

 
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I was looking at diagram on page 24 which shows TT installation with circuits ie lighting going into earthed metal conduit sytems. The problem with this is if there is a fault on lighting main switch will trip out. I have used metal consumer units on TT system but use nylon bush for tails for protection.

Batty

 

steptoe

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I was looking at diagram on page 24 which shows TT installation with circuits ie lighting going into earthed metal conduit sytems. The problem with this is if there is a fault on lighting main switch will trip out. I have used metal consumer units on TT system but use nylon bush for tails for protection.Batty
get you, mechanical protection so no RCD/RCBO protection required.

good point batty, tho I dont think that would be much of an issue on a domestic.

would always do as you say and use good non conductive bush myself, normally simply a plastic bush and lock ring TBH.

 
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I know of absolutely no reason why you can't use metal CU on any system, as long as the casing is suitable earthed, its suitable for the environment etc etc.

Grommeting holes is simple good practice on any metal enclosure.

 

TTbangbang

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OSG p.24 states: 'The enclosures of RCDs or consumer units incorporating RCDs in TT installations should have an all-insulated or Class II construction, or additional precautions recommended by the manufacturer need to be taken to prevent faults to earth on the supply side of the 100mA RCD.'

Unfortunately it doesn't give the 'why' and what such precautions are. :-( I've assumed that the why is because of possible faults occurring inside the consumer unit itself.

 
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OSG p.24 states: 'The enclosures of RCDs or consumer units incorporating RCDs in TT installations should have an all-insulated or Class II construction, or additional precautions recommended by the manufacturer need to be taken to prevent faults to earth on the supply side of the 100mA RCD.'Unfortunately it doesn't give the 'why' and what such precautions are. :-( I've assumed that the why is because of possible faults occurring inside the consumer unit itself.
The Why bit is if the live supply tail makes contact to a non earthed metal enclosure I think?

e.g. fault BEFORE the RCD!!!

 

TTbangbang

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Thank you Special Location. Wouldn't metal CUs be earthed as a matter of fact?

If a live-earth fault occurred, would it be sufficiently large to blow the supplier's fuse? From the red book a BS1361 60A fuse blows in 5s with a fault current of 330A. R= Zs = V/I = 230/330 = 0.7ohms which is not very likely in a TT system?? Is this where I've done a big foot in the mouth?! BlushingBlushingBlushing

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:_| :_| :_|

 

steptoe

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Thank you Special Location. Wouldn't metal CUs be earthed as a matter of fact?If a live-earth fault occurred, would it be sufficiently large to blow the supplier's fuse? From the red book a BS1361 60A fuse blows in 5s with a fault current of 330A. R= Zs = V/I = 230/330 = 0.7ohms which is not very likely in a TT system?? Is this where I've done a big foot in the mouth?! BlushingBlushingBlushing

...

...

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...

:_| :_| :_|
:^O

not a big foot in mouth, but thats basically what its all about, short from tail to MC CU before internal RCD,

thats why I would use an external (s)RCD in a plastic enclosure prior to the CU in TT systems.

only as youve seen many more people are more eloquent at presenting these kind of facts than I am. :p

 
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