bathroom RCD requirements

[helix]

hi all,

I'm a bit confused (as usual ). Under regs:

1. Do low voltage (i.e. 12v) downlights in a bathroom need RCD protection?
2. Does a 240v extractor fan in a bathroom require RCD protection?
3. does a SELV extrator fan in a bathroom require RCD protection?

Also, I would like dimming lights, but the extractor fan to be controlled via the lights being turned on. The dimmer will be located outside the bathroom. Is this at all possible? Would the fan turn on ok if the dimmer was only turned half way for example?

Thanks,
Alex

 

[bernardgreen]

Some fans with over run timers will turn on and run normally when the switched live is from a dimmer provided the permanent live is permanent.

But not all types.

In those that do any "activity" on the switched live triggers the timer to connect the motor to the permanent live for the set period. In other the fan runs on the switched live until it is removed and the timer then connects the motor to the permanent live.

Bad news is that some dimmers even when OFF allow a little bit of energy to leak through onto the switched live. This may be enough trigger the fan into occasionally running.

Some dimmers have a switched but not dimmed output as well as their dimmed output. The un dimmed output being the switched live to the fan.

 

[Zambezi]

1. Yes
2. Yes
3. Yes

 

[helix]

thanks.

Sounds like the dimmer with extra undimmed switch would be the best solution. Where can these be purchased?

If relying on the fan however, if I understand correctly, fans can operate as either:

1. the fan runs on the switched live, until the lights are turned off, then it runs from the permanent live for a period of time. Would this mean that the reduced voltage of the dimmer may cause issues with the fan motor or may just not work at all when running on switched live via dimmer?

2. the fan effectively runs the motor off the permanent live, and is just triggered to come on when activity is detected on the switched live. Do these fans initiate the timed period at the point of turning on, and therefore the timer may switch the fan off before you are finished in the bathroom, or do the run until the lights are switched off, and then initiate the timer?

hope that makes sense

 

[helix]

1. Yes
2. Yes
3. Yes

thanks, makes sense.

 

[bernardgreen]

thanks.

Sounds like the dimmer with extra undimmed switch would be the best solution. Where can these be purchased?

Yes, anyone help with where to buy them

1. the fan runs on the switched live, until the lights are turned off, then it runs from the permanent live for a period of time. Would this mean that the reduced voltage of the dimmer may cause issues with the fan motor or may just not work at all when running on switched live via dimmer?

The fan motor is not going to run at all well when the light are dimmed. It may run noisily when the lights are almost fully on.

or do the run until the lights are switched off, and then initiate the timer?

The timer starts when the lights are switch off in both types.

 

[Taylortwocities]

Yes, anyone help with where to buy them

Best solution is to get a double dimmer, take one dimmer module out and replace it with one of these to be the fan switch: http://www.tlc-direct.co.uk/Products/VLSM.html

 

[ban-all-sheds]

1. Do low voltage (i.e. 12v) downlights in a bathroom need RCD protection?
2. Does a 240v extractor fan in a bathroom require RCD protection?
3. does a SELV extrator fan in a bathroom require RCD protection?

1. Depends when they were installed, and whether it was a new circuit.
2. Depends when it was installed, and whether it was a new circuit.
3. Depends when it was installed, and whether it was a new circuit.

1. How do you RCD protect a SELV circuit?
3. How do you RCD protect a SELV circuit?

1. //www.diynot.com/wiki/electrics:voltage-bands

 

[helix]

1. Do low voltage (i.e. 12v) downlights in a bathroom need RCD protection?
2. Does a 240v extractor fan in a bathroom require RCD protection?
3. does a SELV extrator fan in a bathroom require RCD protection?

1. Depends when they were installed, and whether it was a new circuit.
2. Depends when it was installed, and whether it was a new circuit.
3. Depends when it was installed, and whether it was a new circuit.

1. How do you RCD protect a SELV circuit?
3. How do you RCD protect a SELV circuit?

1. //www.diynot.com/wiki/electrics:voltage-bands[/QUOTE]

thanks for the education re low voltage, very interesting.

All installations are to be done in coming days with new wiring.

I assume then that 12v downlights and SELV fans cannot be protected by RCD?

Otherwise I am confused as you hint that you cannot protect an SELV circuit, yet for my question re the SELV fan, you also say that RCD protection depends on when the installation was done and whether it is a new curcuit.

 

[Zambezi]

Well done BAS
New circuits will require RCD protection as I said in my first post.
You normally protect the whole circuit (in the CU) that feeds the lights and fan in the bathroom, which may include SELV gear, basically you are protecting the circuit up to the SELV gear.

 

[ban-all-sheds]

Well done BAS
New circuits will require RCD protection as I said in my first post.

This was your first post:

1. Yes
2. Yes
3. Yes

I see nothing there qualifying your answers in relation to new circuits.

You normally protect the whole circuit (in the CU) that feeds the lights and fan in the bathroom, which may include SELV gear, basically you are protecting the circuit up to the SELV gear.

But what if you're installing a circuit that only supplies SELV lighting and ventilation, the SELV sources for which are outside the bathroom?

 

[ban-all-sheds]

I assume then that 12v downlights and SELV fans cannot be protected by RCD?

Because of the "S" part there's no way that an RCD could possibly work on the SELV side.

Otherwise I am confused as you hint that you cannot protect an SELV circuit, yet for my question re the SELV fan, you also say that RCD protection depends on when the installation was done and whether it is a new curcuit.

Sorry - it also depends on there the SELV source is, and where the LV switching takes place.

 

[Gteuk]

SELV can't really be RCD protected however the transformer can but transformers can leak a lot.

Any mains electrical curcuit needs to be protected by RCD unless it is under exception under BS7671:2008 but there are only a few circuits such as smoke alarms, etc. Anything that is there for emergency usage does not need RCD protection.

Low voltage <50v does not need RCD protection as 12 V is not life threatening however it may require a thermal protection device.

BS7671:2008 section 411 Protection against electric shock

 

[Spark123]

If it is separated then the upstream RCD isn't going to protect diddly squat downstream of the transormer.

Not all mains circuits need RCD protection under BS7671:2008, there are installation methods which allow circuits to remain non-RCD protected such as lighting circuits. If the smoke detectors are to be non-RCD protected then one of these installation methods should be followed.

BS7671:2008 requires all circuits of the location in a bathroom to be RCD protected, it doesn't exclude SELV in this which IMO is daft but hey ho - I didn't write the regs and did point this out to the IET in the draft for public comment when it was issued.
If took the regs to the extreme you'll probably find yourself RCD protecting all cables concealed less than 50mm below the surface (with the exception of a few such as pyro, SWA and some aluminium tubed cables), but doesn't exclude things such as PEBs nor SELV.

I still believe there is a requirement to install an RCD to any circuit you are adding to/altering in a bathroom, even if this is an existing circuit, to satisfy the 17th edn regs.

 

[ban-all-sheds]

I still believe there is a requirement to install an RCD to any circuit you are adding to/altering in a bathroom, even if this is an existing circuit, to satisfy the 17th edn regs.

And I still believe there is not.