Overloads

[sparkymalarky]

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Any of you ever come across overloads protective devices failing? Was testing a installation yesterday with water pumps and the pumps were wired in 1.5 HO7 RNF on a 40 Amp BS88-2 however the start and run windings of the pump motor were both protected by 6Amp overloads.

 

[stef]

Anything can fail. Overload relay protects the device, not the wiring, so 40A is a bit too high in my opinion.

 

[sparkymalarky]

Agreed. The high rating of the fuses has been used only for fault protection so that a small disconnection time is achieved. As the pumps were drawing such a small current I recorded it as a C2 with further investigation required.

 

[ruston]

Any of you ever come across overloads protective devices failing? Was testing a installation yesterday with water pumps and the pumps were wired in 1.5 HO7 RNF on a 40 Amp BS88-2 however the start and run windings of the pump motor were both protected by 6Amp overloads.

Tried to red your avitar , what does it say lol?

 

[sparkymalarky]

such a failed attempt at an avatar lol,

 

[ruston]

Just me lol, mind in the gutter again:17:

 

[Marvo]

however the start and run windings of the pump motor were both protected by 6Amp overloads.

If you mean there was an overload for each winding I've never seen an arrangement like that. Usually the same overload would protect both windings. It is possible for overload relays to fail, short circuit damage and even insects inside them could cause it.

The 40A fuse with the 1.5mm cable is oversized even for neoprene I might suggest 20A would be more suitable.

 

[sparkymalarky]

Sorry marvo you are correct one overload for both sets of conductors for both windings!What a difference an 's' makes. It's just that it would be a pretty bad scenario that if the overload were to fail and the contactor was to be welded shut, if the pump were to pull a greater current because of a rag stuck in its motor, then the conductors are left under rated. Personally I would recommend the 20A as well to achieve suitable fault current protection.