Chris Pearson:

Nano Brewery:

Chris Pearson:

Could you not have an RCD incomer in the DB?

Cheers Chris.  I was hoping to keep all elements on separate circuits, and also have RCDs on all circuits, just so if one develops a fault the other 3 will continue to operate, and any fault will be quicker and easier to detect?

No, I wouldn't look at it that way. Each element will have its own MCB/fuse. A short circuit would trip the MCB, but not the RCD. A fault (i.e. to earth) might trip both. Ok, that is a bit of a bother if the whole lot goes off. I am not sure how that affects your business, but if it slows down a batch, is that an issue? If it occurred, you can still isolate the faulty element by its MCB.

Cheers Chris.  With this in mind, maybe the option of an RCD to MCB (or an RCBO) in the Distribution Board, then feeding out to the Control Panel would be the way to go?  It would then just be the Control Panel (Elements) that would go out in the event of an Earth fault and not the whole place? 


...Would I even require an MCB in the Distribution Board for the Control Panel feed, or could I just feed direct from the RCD?  At present the Control Panel has 6 individual circuits, with Rail Mounted Cartridge Fuses and Contactors installed on each.

mapj1:

IF there are no plugs and sockets, then the RCDs are not required by regulation, so long as the loop impedance is low enough (the fault current would be high enough)  to operate whatever MCB or fuse is protecting.

Having said that, where liquids and electrics meet RCDs are a very nice thing to have, even if the RCD covers more than one immersion heater.

(https://www.tlc-direct.co.uk/Products/WYWRS32slash4.html) sort of sized object.

Cheers.  I was hoping to keep all elements on separate circuits, so if one develops a fault the other 3 will continue to operate, and any fault will be easier to detect.  At present the Control Panel has 6 individual circuits, with Rail Mounted Cartridge Fuses and Contactors installed on each.  I understand that the Control Panel can be fed either via a Henley Block or from the 3-Phase Distribution Board?  Wondering if an enclosure with RCD would be an option?... https://www.cef.co.uk/catalogue/products/1051602-3-module-insulated-ip65-enclosure

Nano Brewery:

Chris Pearson:

Nano Brewery:

Chris Pearson:

Could you not have an RCD incomer in the DB?

Cheers Chris.  I was hoping to keep all elements on separate circuits, and also have RCDs on all circuits, just so if one develops a fault the other 3 will continue to operate, and any fault will be quicker and easier to detect?

No, I wouldn't look at it that way. Each element will have its own MCB/fuse. A short circuit would trip the MCB, but not the RCD. A fault (i.e. to earth) might trip both. Ok, that is a bit of a bother if the whole lot goes off. I am not sure how that affects your business, but if it slows down a batch, is that an issue? If it occurred, you can still isolate the faulty element by its MCB.

Cheers Chris.  With this in mind, maybe the option of an RCD >to> MCB (or an RCBO) in the Distribution Board, then feeding out to the Control Panel would be the way to go?  It would then just be the Control Panel (Elements) that would go out in the event of an Earth fault and not the whole place? 


...Would I even require an MCB in the Distribution Board for the Control Panel feed?  Or could I just feed direct from an RCD?  At present the Control Panel has 6 individual circuits, with Rail Mounted Cartridge Fuses and Contactors installed on each.

Any more thoughts on this Chris?  Cheers!

 

Nano Brewery:

Nano Brewery:

Chris Pearson:

Nano Brewery:

Chris Pearson:

Could you not have an RCD incomer in the DB?

Cheers Chris.  I was hoping to keep all elements on separate circuits, and also have RCDs on all circuits, just so if one develops a fault the other 3 will continue to operate, and any fault will be quicker and easier to detect?

No, I wouldn't look at it that way. Each element will have its own MCB/fuse. A short circuit would trip the MCB, but not the RCD. A fault (i.e. to earth) might trip both. Ok, that is a bit of a bother if the whole lot goes off. I am not sure how that affects your business, but if it slows down a batch, is that an issue? If it occurred, you can still isolate the faulty element by its MCB.

Cheers Chris.  With this in mind, maybe the option of an RCD >to> MCB (or an RCBO) in the Distribution Board, then feeding out to the Control Panel would be the way to go?  It would then just be the Control Panel (Elements) that would go out in the event of an Earth fault and not the whole place? 


...Would I even require an MCB in the Distribution Board for the Control Panel feed?  Or could I just feed direct from an RCD?  At present the Control Panel has 6 individual circuits, with Rail Mounted Cartridge Fuses and Contactors installed on each.

Any more thoughts on this Chris?  Cheers!

This getting to be a bit like remote design, but without enough information. We also have two threads running on the same installation.


I don't know what is in your control panel, but it sounds rather like a distribution board - i.e. 6 circuits (but you mentioned only 4 elements, so what do the other 2 do?), each with its own fuse and presumably, a switching mechanism - you mention contactors. Perhaps the thermostats also act on the contactors. I see no place for RCDs in there.


Then there is the DB. Is it the only one? What else does it serve? I assume that there must be some lights. Apart from re-lamping, I don't really see how they would present a shock risk that needs additional (RCD) protection - it is mandated only in domestic settings. There are, presumably, some 13 A sockets. They must have additional protection, but that is easily achieved by fitting RCBOs. The outgoing device in the DB will be either an MCB or an RCBO, you cannot do away with the MCB and just have an RCD.


What you cannot do in a three-phase board is to split it as in a domestic consumer unit - usually with 2 RCDs split so that upstairs lights and downstairs sockets are on one side and downstairs lights and upstairs sockets are on the other. That way if the lights trip, you can still use a table lamp and vice-versa. So you have to decide whether an RCD incomer is acceptable or not. The benefit is (much) lower cost; the disadvantage is that if it trips, everything goes off. That is it goes off until you have identified the faulty circuit. The alternative is RCBOs for circuits which need them. If you feel that your heaters need them, then you put an RCBO in the DB. Yes, if it trips, all your heaters go off until you have identified the faulty circuit.


I fear that this brings us full circle. Do you need to protect the elements with RCDs? As far as I can ascertain, BS 7671 does not require them.


The only other question that I have is why do you expect your equipment to develop faults?

Chris Pearson:

Nano Brewery:

Nano Brewery:

Chris Pearson:

Nano Brewery:

Chris Pearson:

Could you not have an RCD incomer in the DB?

Cheers Chris.  I was hoping to keep all elements on separate circuits, and also have RCDs on all circuits, just so if one develops a fault the other 3 will continue to operate, and any fault will be quicker and easier to detect?

No, I wouldn't look at it that way. Each element will have its own MCB/fuse. A short circuit would trip the MCB, but not the RCD. A fault (i.e. to earth) might trip both. Ok, that is a bit of a bother if the whole lot goes off. I am not sure how that affects your business, but if it slows down a batch, is that an issue? If it occurred, you can still isolate the faulty element by its MCB.

Cheers Chris.  With this in mind, maybe the option of an RCD >to> MCB (or an RCBO) in the Distribution Board, then feeding out to the Control Panel would be the way to go?  It would then just be the Control Panel (Elements) that would go out in the event of an Earth fault and not the whole place? 


...Would I even require an MCB in the Distribution Board for the Control Panel feed?  Or could I just feed direct from an RCD?  At present the Control Panel has 6 individual circuits, with Rail Mounted Cartridge Fuses and Contactors installed on each.

Any more thoughts on this Chris?  Cheers!

This getting to be a bit like remote design, but without enough information. We also have two threads running on the same installation.


I don't know what is in your control panel, but it sounds rather like a distribution board - i.e. 6 circuits (but you mentioned only 4 elements, so what do the other 2 do?), each with its own fuse and presumably, a switching mechanism - you mention contactors. Perhaps the thermostats also act on the contactors. I see no place for RCDs in there.


Then there is the DB. Is it the only one? What else does it serve? I assume that there must be some lights. Apart from re-lamping, I don't really see how they would present a shock risk that needs additional (RCD) protection - it is mandated only in domestic settings. There are, presumably, some 13 A sockets. They must have additional protection, but that is easily achieved by fitting RCBOs. The outgoing device in the DB will be either an MCB or an RCBO, you cannot do away with the MCB and just have an RCD.


What you cannot do in a three-phase board is to split it as in a domestic consumer unit - usually with 2 RCDs split so that upstairs lights and downstairs sockets are on one side and downstairs lights and upstairs sockets are on the other. That way if the lights trip, you can still use a table lamp and vice-versa. So you have to decide whether an RCD incomer is acceptable or not. The benefit is (much) lower cost; the disadvantage is that if it trips, everything goes off. That is it goes off until you have identified the faulty circuit. The alternative is RCBOs for circuits which need them. If you feel that your heaters need them, then you put an RCBO in the DB. Yes, if it trips, all your heaters go off until you have identified the faulty circuit.


I fear that this brings us full circle. Do you need to protect the elements with RCDs? As far as I can ascertain, BS 7671 does not require them.


The only other question that I have is why do you expect your equipment to develop faults?

Thanks for you feedback Chris!


To clarify the Control Panel has 6 Three-phase circuits.  Each circuit has Rail Mounted Cartridge Fuses, Contactors, On/Off Rotary Switches and Pilot Lights.  At present I will only be using 4 of these circuits to switch each of the immersion elements when required.  2 of the 4 circuits being used will be switched via PID for temperature control.


The Control Panel does not have any RCD protection installed so I was wondering if I could take a direct feed from an RCD which would be installed in the Three-phase Distribution Board?  Would this be allowed/possible?  Just thinking about the extra protection as there will obviously be liquid involved. 


At present the 3-phase Distribution Board will be feeding everything else in the building, mostly Single-phase stuff apart from a Three-phase 27kW Instant Water Heater.


Maybe I'm worrying too much about incorporating RCDs!?

 

switched via PID for temperature control