two supplies to a relay

[markythesparky]

Question for you guys; I have wired a control panel with 230v ac supply and within the panel there is a relay which is used to control other devices outside the panel. the relay operates when a device controlled by the panel operates. i.e. when the device is on, the relay contacts are closed and when it is off, the contact are open. I connected another circuit (230v ac) to the contacts to run some other equipment, on the same phase as the panel supply but a separate circuit, and all in accordance with the manufacturers details. a guy mentioned to me that I shouldn't have done this and I should have taken a supply only from the panel feed. at the least I should have labelled the panel as having two feeds. I disagreed as the panel has only one feed, but has control wiring running into it. what do you all think?

 

[telectrix]

so you have 2 circuits, each fed by it's own OCPD, connected to common terminals on a relay. so that means you have to isolate both circuits to kill the supplies. bad. ( if i've read your OP correct).

 

[Rockingit]

I've done this before as a way to overcome RCD tripping issues where different circuits have to action a common item. Just label it accordingly, personally I can't see an issue.

 

[telectrix]

could you not use a second relay and parallel the coils so they both energise simultaneously. separate feeds to each relay contacts?

 

[HandySparks]

Given that you've got supplies on two circuits entering the same enclosure and not capable of being isolated by a single device, I'd put a suitable label on in accordance with BGB 514.11

 

[markythesparky]

so you have 2 circuits, each fed by it's own OCPD, connected to common terminals on a relay. so that means you have to isolate both circuits to kill the supplies. bad. ( if i've read your OP correct).

No, you have indeed misunderstood. there are two circuits both with OCPD. one feeds the panel with 'juice' to make it work. the other goes into the contact terminals of a relay within the panel to control other devices that are outside the panel. the circuits are not connected together in anyway.

 

[markythesparky]

given that you've got supplies on two circuits entering the same enclosure and not capable of being isolated by a single device, i'd put a suitable label on in accordance with bgb 514.11

bgb???

 

[telectrix]

so basically, you have just added an extra output circuit to the existing relay??? if so, as long as the relay is rated to take the extra load, no problem as i can see.

 

[HandySparks]

bgb???

BS 7671:2008, Amendment No.1: 2011 (big green book).

 

[Darkwood]

If you have added this yourself then maybe for future ref' you could simplify things by increasing the supply if needed and fusing down for the extra aux' supply... as it is then as other have said it requires labeling in accordance with BS7671... anyone who is within the panel should need a tool to enter it and also should be competent to be in there hence labeling is all that is necessary but a must as panel layouts and designs vary so much; confusion can be a killer, i always check ALL! cables before i work on them ...too many time ive seen bodgit additions and upgrades where remote power has been brought in for control reasons in voltages that are dangerous.

Other methods and normally the way to go is to use Selv control voltages to link independent equipment of low voltage so at most you will trip a dc power supply or operate a fuse with minimal risk to engineer.

 

[Darkwood]

OOh and for those not up to speed you can do optical signalling no electrical connection at all ... highly reliable using fibre optic plug in signal cable and jobs a good un.... but big pennies needed and not the main trend at the moment as cheaper methods still rule ....Its the future I tell thee!

 

[Robotstar5]

I usually use different coloured wiring to identify anything carrying "external voltage" not isolated by panel switch disconnector as well as warning labels.

 

[gazj82]

On a new panel I would probably put auxilary contacts on the isolator, so the second supply also is switched off with the panel isolator and mark it up as having two incoming supplies, and mark on the front the circuit references that need to be isolated.

 

[markythesparky]

BS7671 states that a label should be applied if the circuits cannot be isolated by a single device . A single device could be the Main isolator. Surely this reg is referring to properties where there is more than one source of energy and therefore the supplies CANNOT be isolated by ONE device?

 

[johnboy6083]

A control panel doesn't have to abide by BS7671.

what I do is cover any terminals that remain energised after operating the isolator with Clear PVC. This is labelled accordingly.

this is often done to comply with the form factor requirements of the clients spec.