Advice needed on RCD requirements.

[allan.vaughan4]

Hi All,

I am new to this site and will introduce myself as a time served qualified sparks. I have just started a new job, been in it one week and have some questions about RCD'S.

My questions are about private sewage pumping stations that are being taken over by my employer ( about 2000 of them). some are TT supplies which I believe require a 100 A 100 mA type S RCD as a main isolator and a 30 mA RCBO covering the single S/O on the control panel can anyone give advice on this?. 

Also for TN systems do I require the same or do I replace the main incomer with a normal 100 A isolator and a 30 mA RCBO for the single S/O?

As said previously I am new to the water industry and because it is the start of two years worth of work want to get it right at the start, I do not have a contact number of anyone in a position to help at my new job yet and when asking one of the electricians and an electrical supervisor who have been on the firm a while both said you do not require RCD'S  in either scenario. I have read the 17th edition and disagree, am I right to be considering RCD'S in these installations??

Your help is very much appreciated.

Cheers All,

Allan.

 

[Essex1]

Hi All,

I am new to this site and will introduce myself as a time served qualified sparks. I have just started a new job, been in it one week and have some questions about RCD'S.

My questions are about private sewage pumping stations that are being taken over by my employer ( about 2000 of them). some are TT supplies which I believe require a 100 A 100 mA type S RCD as a main isolator and a 30 mA RCBO covering the single S/O on the control panel can anyone give advice on this?. 

Also for TN systems do I require the same or do I replace the main incomer with a normal 100 A isolator and a 30 mA RCBO for the single S/O?

As said previously I am new to the water industry and because it is the start of two years worth of work want to get it right at the start, I do not have a contact number of anyone in a position to help at my new job yet and when asking one of the electricians and an electrical supervisor who have been on the firm a while both said you do not require RCD'S  in either scenario. I have read the 17th edition and disagree, am I right to be considering RCD'S in these installations??

Your help is very much appreciated.

Cheers All,

Allan.

Welcome Allan,

On the face of it your TT thoughts are about right. 

Again, sounds correct on the TN system also. 

What are the sockets for and where are they located?

 

[Sidewinder]

Just remember that BS7671 is not retrospective.

Also, just because it's TT, does not mean that it must have an RCD.

BS7671 is ok, but, correctly engineered solutions can give the same or better levels of safety than those proposed in BS7671.

However, as has been suggested, in general RCD's would be required.

Just realise that you often can't just stick a "normal" 30mA RCD on a pump inverter and expect it to work.

It is all really down to the design risk assessment, and how this translates into the functional design specification.

Whilst BS7671 will have an input into this, there, may, be times when BS7671 is irrelevant, as the equipment is covered under other standards.

 

[allan.vaughan4]

Hi All,

Well thanks very much for the information guys you have been very helpful. I will have to see the panel schematics to see if the pumps are protected by 30 mA rcbo's or mcb's if I do put in a 100mA main switch after the service head and and before the panel then all of the equipment fed via the control panel will be covered by 100 mA That just leaves the 3 pin socket outlet mounted on the panel which theoretically could be used to plug in any 230 volt equipment although primarily designed for the telemetry guys to plug in their laptops. This I believe should have a 30 mA rcbo covering it.

I have taken canoeboy's post and read with interest as his set up sounds to be very much like what I am encountering at the moment, with regard to damaging the motors and shocking any passers by I have read the regs and although it does not state that RCD'S are a requirement I do think that they are a good idea!!

Thank you all very much.

 

[Sidewinder]

You need to be careful with the devices you retrofit.

Whilst the current version of BS7671 may suggest that these are needed, you need to be sure that you fit the right ones, or you could come unstuck.