UK MK RCDs

[Jim_Mc]

Hi there,

I picked up an MK domestic CU, which comes populated with 1 x main switch, 1 x SPD and 2 x RCDs @ 100A 30mA each. I planned on replacing the MCBs with RCBOs which are also rated at 30mA.

Because both the RCBOs and RCDs are rated 30mA, it's anyones guess as to which will trip first. So I intended on replacing the RCDs with a 100mA version, is this ok for domestic installation? As I'm reading mixed information that 100mA is not suitable for domestic, but is that over-ridden by the fact I am using RCBOs behind them?

If 100mA is not suitable, would a 30mA S type or delayed be suitable and work as intended, i.e. the RCBO will trip before the inlet RCD.

Final thing, I am struggling to find an MK 100A 100mA or 30mA non-instant, I'm completely puzzled by this as they're advertising them on their website, yet every supplier I've checked with has them listed as out of stock or discontinued.

A friend of mine recommended bypassing the RCDs altogether, but the SPD doesn't accept the bus-bar on the bottom, so it would mean placing the SPD before the main switch, which I wasn't entirely comfortable with.

Any recommendations appreciated.

 

[andyb]

Ignoring the question of why buy a setup that you do not need, why not just replace the RCDs with 2 new MK incommers and label appropriately.

100A Double Pole 2 Module Switch Disconnector

Suitable for installation in Sentry consumer units and two or four module enclosures

www.cef.co.uk

 

[MrPupsi]

Sack off the RCDs and just use RCBOs.
Put the SPD first, then main switch, then RCBOs.
Not sure why you’re uncomfortable with the SPD being first. In fact, pretty sure most manufacturers do it that way.

 

[loz2754]

It's pointless buying a dual RCD split load board if you're then going to change the MCBs for RCBOs. Just keep it as it is. Or do what @MrPupsi suggested.

30mA S type RCDs don't exist as far as I know.

Do not buy 100mA RCDs as there is no reason to have them in this situation.

 

[SparkyChick]

First up, unless the surge protection device has been explicitly approved by MK for use in their boards, it will be non-compliant. The 18th edition added this requirement. To the best of my knowledge MK have never made such a device and there isn't one listed on their website in the Sentry section (or at least not that I could find).

Secondly, I wouldn't be installing a new MK board. They announced the discontinuation of their Sentry product range back in 2019 which is probably why you are finding it difficult to get hold of their devices.

I've seen their boards on numerous offers locally but have chosen to walk on by because of the risk that I won't be able to get spares in the not too distant future. In other words, I'd take it back and get a refund and go with a company like Contactum (fitted several of these and they seem like nice boards), Fusebox (get good reviews from the people who try them) or Hager.

 

[westward10]

You can get them with factory fitted SPD but why bother adapting it just leave as it is.

USE CODE ** MKYS8666SMET ** | MK_Sentry (YS8666SMET)

 

[andyb]

You can get them with factory fitted SPD but why bother adapting it just leave as it is.

USE CODE ** MKYS8666SMET ** | MK_Sentry (YS8666SMET)

I think that's what he purchased Westward and he doesn't want to move the SPD for some reason.
Although it looks like it will easily move to the left of the main switch and then just fit a MK busbar.

 

[SparkyChick]

You can get them with factory fitted SPD but why bother adapting it just leave as it is.

USE CODE ** MKYS8666SMET ** | MK_Sentry (YS8666SMET)

Have they gone back on their decision to exit the consumer unit market? I stopped looking at MK boards when they announced it back in 2019, had no idea they'd brought out an SPD, so thanks for that useful nugget

 

[Jim_Mc]

Thanks for the replies, I called up MK today to find out what they had to say about the RCD situation. The plot thickens. The chap there told me as mentioned above they have never approved any SPDs for use with their Consumer Units. The whole production of the CUs/MCBs/RCDs/RCBOs got licenced out to a company called Circpro UK Limited. So it's actually another company producing MK parts with MK branding. I've called them up this morning and am awaiting a call back from a technical chap.

Correct me if I'm wrong, but isn't it still beneficial having the inlet RCDs for neutral isolation, which the RCBOs wont offer? I also don't want to move the SPD beause it would have to run in parallel with the live inlet of the main switch, which means if it develops a fault I can't easily isolate it -- although I could purchase an additional main switch as mentioned above, appreciate that.

 

[Strima]

Take it back and get a refund. Look at a Fusebox CP DB with built in SPD and RCBOs.

FuseBox Circuit Protection - https://cpelectric.co.uk/

Has your risk assessment identified a need for SPDs?

 

[nicebutdim]

Take it back and get a refund. Look at a Fusebox CP DB with built in SPD and RCBOs.

FuseBox Circuit Protection - https://cpelectric.co.uk/

Has your risk assessment identified a need for SPDs?

The OP mentioned neutral isolation in their last post. It's worth pointing out that miniature RCBOs from CP Fusebox (RTAM range) will provide this.

Crabtree 61/M and Wylex NHXS1 ranges would also meet this requirement.

 

[pc1966]

Has your risk assessment identified a need for SPDs?

Or lack of risk assessment...default is to fit SPD unless established they are not required.

 

[goasis]

Maybe I'm reading this incorrectly, but are you suggesting fitting a split load RCD (61008) board, then populating it with RCBO's?!!

 

[westward10]

Thanks for the replies, I called up MK today to find out what they had to say about the RCD situation. The plot thickens. The chap there told me as mentioned above they have never approved any SPDs for use with their Consumer Units. The whole production of the CUs/MCBs/RCDs/RCBOs got licenced out to a company called Circpro UK Limited. So it's actually another company producing MK parts with MK branding. I've called them up this morning and am awaiting a call back from a technical chap.

Correct me if I'm wrong, but isn't it still beneficial having the inlet RCDs for neutral isolation, which the RCBOs wont offer? I also don't want to move the SPD beause it would have to run in parallel with the live inlet of the main switch, which means if it develops a fault I can't easily isolate it -- although I could purchase an additional main switch as mentioned above, appreciate that.

Seems they have approved them here.

MK-Electric

Monitor and control plug-in equipment to reduce energy consumption.

www.mkelectric.com