Rcd burning ???

[sidekick]

Have customer with elecric powered gates. The supply for the gates comes from a plug in RCD unit in a kitchen socket. Apparently it has been like this for some years but recently the plug in unit gave off very strong burning smell and eventually burnt out and stopped working, i.e would not reset and power to gates was lost.
On removing the unit and fitting ordiary 13a plug the power was restored and gates operated fine with no burning smell from plug. The sockets used are all protected on main board RCD anyway on TT system.
A replacement plug in unit was used and the 13a plug plugged into that. The burning smell returned and Rcd unit would not reset but main board rcd still not tripping.

What could the problem be ???

 

[DurhamSparky]

not sure... !!!

i would personally swap plug for a FCU with double pole switch and hard wire the gate feed in!

 

[telectrix]

overloading plug in RCD. motors have high start up currents. as you already got RCD on sockets, do away with the plug-in. preferably fit an FCU for the gates.

 

[telectrix]

Snap....

 

[sparks_114]

I would start out with testing the RCD. Ramp test should reveal if the RCD is tripping within the stated times. Just to clarify, are there 2 RCDs on the same circuit, one at the board and one incorporated in the socket (BS7288 type)?

 

[telectrix]

Not much point trying to test it now he's burnt it out.

 

[Knobhead]

Have you checked what current the gates are taking?

 

[sidekick]

The Socket used is plain switched socket protected on main board with RCD and the cable for the gate has rcd unit fitted on end of cable and plugged into socket. Its the plug in RCD which has burnt out. Understand the bit about motor start up but not sure how its lasted so long.

 

[sparks_114]

"The burning smell returned and Rcd unit would not reset" Is this the RCD at the board? If the gates are operating then the RCD must be reset! Unless you mean it won't trip upon pressing the "test" button?

 

[sparks_114]

I understand now. With motors you're looking at type "C" at the very least. It's the high starting currents I think too.

 

[sidekick]

No burning or tripping of the RCD at the board and trip tests ok at the socket. The only problem is with the plug in RCD. First one burnt out with burning smell. Then everything ok when exchanged for 13a plug. Replacement Plug in RCD then fitted and was also starting to burn out so removed. Now 13a plug in socket RCD protected at board and all works fine but no fault found to have caused problem.

 

[telectrix]

if the gates are ok on a 13A fuse, then it must be cheap chinese plug-in rcds.

 

[sidekick]

Thanks for all your advice guys. Will leave on the 13a plug for now and reccomend to customer to change to Switched FCU.
(Although its a 2g socket being used at the moment)

 

[sparks_114]

The thing with RCDs is that they don't really recognise overload and even short circuit as such, all they're concerned with is out of balance current. Not sure of the type of RCD used there but it is also possible for it to eventually burn out from fatigue. It would also depend on how much usage the electric gates see and in what space of time. Loose connection can also be a factor. Inclined to think the RCD in question is the "cheap chinese" stuff!

 

[sidekick]

Not sure - may be chinese but first lasted few years and replacement was identicle and yet would not operate at first fit so would suggest problem occurred elsewhere.

 

[sparks_114]

IR test should reveal the condition of the cable. Tongue test can help as well in seeing starting current and earth leakage current (if any). Being a motor drive at the end of the circuit, it is very easy for an obstacle (or even kids!) making it harder for the gate to open/close which will drastically increase the current it's pulling!

 

[truckster]

Hav you checked the rear of the socket? If the RCD has been overheating it may have damaged the actual socket as well.

 

[SirKit Breaker]

Get this kind of problem a lot with people (usually DIY'ers) who force a 2.5mm flex into a plug top for things like ovens, it has to be overload in my opinion.

Cheers........Howard

 

[sidekick]

Hav you checked the rear of the socket? If the RCD has been overheating it may have damaged the actual socket as well.

Thanks Truckster. Yes have checked behind socket first thing to ensure no bad connections and no damage from RCD burning out.