LV shower downlights, extractor fan & transformer confus

[mace48]

I would really appreciate some help. I am fitting 3 IP65 12V 50W MR16 lights in my shower room:

these

I have bought the following transformer from Screwfix:

this

Currently, the shower room light pull operates a 60w tungsten bulb and an extractor fan.

I had planned to simply wire the transformer into the ceiling rose replacing the tungsten bulb. However, if I understand the transformer instructions correctly, I cannot wire the transformer into the same circuit as the extractor (due to something about inductive and conductive circuitry).

Can anybody please explain this, and if possible offer a solution.

Many thanks

Dave.

 

[securespark]

Hmmm

New on me. I have installed may fans & selv lighting in bathrooms over the years and nowhere on the instructions for either the fan or transformers does it say cannot mix the two. What exactly does it say?

BTW, I found it very funny - when you click on the screwfix links it says "You may also be interested in the following products.....Chainsaw, Router, Pinkgrip" !!!!!

Like, what relation do these things have to electrical gear???

Although I like the sound of pink grip.....I think I'll order some of that!

 

[breezer]

BTW, I found it very funny - when you click on the screwfix links it says "You may also be interested in the following products.....Chainsaw, Router, Pinkgrip" !!!!!

Like, what relation do these things have to electrical gear???

the chain saw is for "extra large" holes, the router is so you can finish them properly , and the pinkgrip is to stick new plaster board up when you realise the hole is too big

 

[mace48]

Thanks for your replies. Didn't need the Pinkgrip for the ceiling!

The transformer instructions read as follows:

"Electronic transformers, which is for resistive loads, must not be used in the same circuit as inductive loads (fluorescent lamps, discharge lamps, ventilating, etc). When switching inductive loads, spikes of several thousand volts may result, causing damage to the transformer. Separate load circuits must always be provided."

What does this mean?

Thanks again

Dave.

 

[breezer]

it means back emf, now thats as clear as mud isn't it?

have you ever switched off a flourescent light and watched the switch as you do it? (please say yes) you may see a saprk or hear a "crack / zap sound) that is back emf (electro motive force)

when you have something that has a coil in it such as flourescent lights do, when you disconnect it (or switch it off) you get a considerable high voltage flowing "backwards" for a split second this high voltage then goes to anything else it can find (electronic dimmer in your case) as its a very hight voltage it can literaly fry the elctronics in the transformer. Thats whay yo do not do it.

How ever the coil in a small fan shoul produce such a small voltage i would be inclined not to worry about it

 

[mace48]

Thanks Breezer. Yes, that was as 'clear as mud' until you explained it.

I'm going to be using the following fan (Xpelair DX200T), which has the follwoing spec.:

Air Flow at FID: 106 m3/h (29.4 l/s)
I.P. Rating: X5
Bathroom Zones: 1,2&3
Fan Size: 100 mm (3.9 inches)
RPM: 2400
Max Ambient Temperature: 40 °C
Power: 35 W
Colour: white
Voltage: 240V
Mounting: Wall, Window, Ceiling Mounted, Ducted
Usage: Utility, Bathroom, Shower Room, Toilet, Public Toilet, Washroom,
Hotel

Does this count as a 'small fan'? If so, then I'm going to remove the current ceiling rose, fit a 5amp junction and then wire the timer fan (using 5 amp triple + earth wiring to the junction along with the transformer).

Cheers

Dave.

 

[breezer]

small fan yes, but its the transformer that is of concern, sorry all i can suggest is try and see

 

[mace48]

So, if it works...then it works. If not, then the transformer is knackered and I replace it (and think up a new way of sorting out the problem).

I take it that there is no risk of fire or anything like that.

thanks.

 

[breezer]

it will work, not a problem, the way round it is to feed either the fan or light from differnt cable, but that defeats the object, as you would need a switch for each

 

[mace48]

Yes, a seperate switch would be a problem.

I'll give it a go (wiring fan and transforer into junction box) and see what happens.

Thanks for your help

Dave.