FCU with Integral RCD

[stem]

At my place of work (Built 2005) we have a wet room with an electric towel warmer in it. A recent PIR recommended that this towel rail be protected by an RCD.

There are no RCD's anywhere in the electrical distribution system, which is comprised of offices upstairs and engineering workshop downstairs. So, we are considering replacing the existing FCU with one that contains an integral RCD. However, the existing FCU is used as the main operating switch to turn the towel warmer on and off.

I was wondering if operating an RCD so frequently was a good idea, but after looking at a Powerbreaker unit, it actually says on it "test before use" so using the RCD as the regular on/off switch would make sure that this was done, however, if for any reason the RCD failed to trip when tested, then it would not be possible to turn off the appliance, which sounds a bit dangerous. Is this right?

The FCU is connected to a 32A ring supplying sockets in an upstairs office / server room.

 

[stillp]

if for any reason the RCD failed to trip when tested, then it would not be possible to turn off the appliance

But you'd then know the RCD was faulty, and could avoid use of the towel warmer. Is there an MCB upstream of the FCU that could be used to turn it off if the RCD failed??

 

[EFLImpudence]

It must be more than 1.2m from the water outlet but also - suitable for the environment ???

But to answer your question: You can take out the fuse.

To be pragmatic, if the RCD failed, as you suggest, the situation would be the same as it is now but at least you would know the RCD was faulty.

 

[stem]

Is there an MCB upstream of the FCU that could be used to turn it off if the RCD failed??

Yes, but it supplies the sockets in the server room and according to our IT manager must not be turned off under threat of death!

 

[stem]

It must be more than 1.2m from the water outlet

The FCU is outside of the door, the flex outlet is 1.4m from the drain, but it does get splashed. Someone has 'siliconed' the top and sides, but it was like that when we moved in and the building was new.

the situation would be the same as it is now

Not really, because we can turn it off using the isolator on the FCU.

 

[stillp]

If the RCD failed, you could take the fuse out of the FCU and padlock the fuse carrier. Powerbreaker are not the most respected maker of RCDs though.

Yes, but it supplies the server room and according to our IT manager must not be turned off under threat of death!

He won't be happy if the towel warmer develops a short and trips that breaker then!

 

[stem]

He won't be happy if the towel warmer develops a short and trips that breaker then!

Suppose not. Perhaps he hopes the 3A fuse in the FCU will blow before the 32A MCB trips.

 

[EFLImpudence]

The FCU is outside of the door, the flex outlet is 1.4m from the drain, but it does get splashed.

That's alright then.

Not really, because we can turn it off using the isolator on the FCU.

Yes, I meant safety-wise.
I assume it will be replaced if faulty.

 

[EFLImpudence]

Suppose not. Perhaps he hopes the 3A fuse in the FCU will blow before the 32A MCB trips.

Yes, it may not but that is the same as now.

 

[stem]

I assume it will be replaced if faulty.

Indeed, but it would take awhile to replace it, and meanwhile the towel warmer remains on permanently.

Seems odd to me that a device that's there for safety, in the event of a malfunction could prevent an appliance being isolated. Whatever happened to 'fail safe'?

 

[stillp]

Perhaps he hopes the 3A fuse in the FCU will blow before the 32A MCB trips.

That will largely depend on the load connected in the server room.

 

[stillp]

Seems odd to me that a device that's there for safety could prevent an appliance being isolated.

Could you not still operate it manually if the trip failed? It should still switch off.

 

[EFLImpudence]

I assume it will be replaced if faulty.

Indeed, but it would take awhile to replace it, and meanwhile the towel warmer remains on permanently.

Or off - if you remove the fuse.

Seems odd to me that a device that's there for safety, in the event of a malfunction could prevent an appliance being isolated. Whatever happened to 'fail safe'?

Can't argue with that.

 

[stem]

Could you not still operate it manually if the trip failed? It should still switch off.

I don't think so, there is only the test switch that simulates an earth fault.

 

[EFLImpudence]

Seems odd to me that a device that's there for safety could prevent an appliance being isolated.

Could you not still operate it manually if the trip failed? It should still switch off.

No. They only have the test button.