Working out power consuption in Amps from a transformer.

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What I want to confirm is that you work out Amps that a transformer uses the same as a non transformer item.

My power shower runs off 220-240volts input transformer, and says it outputs 100W 19V = 5.26AMPS?

The reason;
I'm fitting a separate MCB in my consumer unit for my power shower and yet to be fitted extractor. At the moment the shower is spurred off the immersion - not what I would call ideal. The final separate circuit will run in 1.5 T&E, with an MCB, and then power the shower and a suitable extractor, via a D.P pull cord switch. (possibly another D.P switch in the airing cupboard or somewhere upstairs)
Then I know what MCB rating to use and what extractor power consumption to look out for.

Thanks, Kevin.
 
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The power stays more or less the same on both sides of the transfomer.
The current then adjusts accordingly depending on the voltage.
 
I'd run a 2.5mm T/E radial from a 16amp mcb (gives scope to extend/utillise circuit) to a fcu, fuse down to 5amp at the fcu.
Supply the shower/extractor from the fcu.
 
I'd run a 2.5mm T/E radial from a 16amp mcb (gives scope to extend/utillise circuit) to a fcu, fuse down to 5amp at the fcu.
Supply the shower/extractor from the fcu.

Unfortunately I was only able to run the 1.5 T&E cable (put in while I rewired my central heating) 10amp MCB should serfice.
 
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I'd run a 2.5mm T/E radial from a 16amp mcb (gives scope to extend/utillise circuit) to a fcu, fuse down to 5amp at the fcu.
Supply the shower/extractor from the fcu.

Unfortunately I was only able to run the 1.5 T&E cable (put in while I rewired my central heating) 10amp MCB should serfice.

With the above in mind, i will fuse down at FCU and run a suitable MCB, but i still need conformation of how to work out the Amps on the transformer? 100w divided by 19v is not right if its 5.26 amps. Should be less than 1 surely in bathroom?

Can't find anywhere online etc for a method. Even an old sparky at work is not sure but says it's less than 3 amps.
As i say in an ideal world i would have run 2.5 to the FCU but with such low amps it will handle it.
Thanks.
 
Power input to primary = Power out from secondary + some small losses which can be ignored.

Amps = Watts/Volts

Primary Amps = Watts/Volts = 100/230 = 0.43
Secondary Amps = Watts/Volts = 100/19 = 5.26


"Even an old sparky at work is not sure but says it's less than 3 amps. "
Any spark who doesn't understand this elementary level stuff should retire :rolleyes:
 
You are missing what Ricicle said, the power is roughly the same on both sides of the transformer. This means for 100w on the 230v side the current will be approximately 0.43A. On the ELV side of the transformer it is 100w/19v = 5.26A.
Please note that if you live in England/Wales this work is notifiable to your LABC under part P of the building regs.

Note to myself, must type faster :LOL:
 
With the above in mind, i will fuse down at FCU and run a suitable MCB, but i still need conformation of how to work out the Amps on the transformer? 100w divided by 19v is not right if its 5.26 amps. Should be less than 1 surely in bathroom?

Please can you elaborate?
 
Power input to primary = Power out from secondary + some small losses which can be ignored.

Amps = Watts/Volts

Primary Amps = Watts/Volts = 100/230 = 0.43
Secondary Amps = Watts/Volts = 100/19 = 5.26


"Even an old sparky at work is not sure but says it's less than 3 amps. "
Any spark who doesn't understand this elementary level stuff should retire :rolleyes:

Thank you. So with the calculations in mind that means that the fuse in the FCU has to be sufficient for the Primary Amps?

As for the electrician i spoke to - i should have worded it that he said he estimated it at less than 3amps without a calculator, saying it will be less on the input.
 
You are missing what Ricicle said, the power is roughly the same on both sides of the transformer. This means for 100w on the 230v side the current will be approximately 0.43A. On the ELV side of the transformer it is 100w/19v = 5.26A.
Please note that if you live in England/Wales this work is notifiable to your LABC under part P of the building regs.

Note to myself, must type faster :LOL:

Sorry, you are right I had missed that what Ricicle had said.

Would It be ok to wire an extractor to this too? Hence why I wanted to know Amps so I don't overload anything.

What I would end up with would be: 1.5T&E from a 10AMP MCB, then a FCU (3/5Amp) then a DP pull switch controlling the shower and extractor.
Is this correct practice?

Note: At the moment (from previous owner) it is spurred off the immersion heater and HAD the heating timer spurred from this. The heating controller now is removed and has its own power. Shower to sort as above.

From what I have been reading and found wrong I wouldn't of put any money on my house passing part P when i moved in last July.
 
With the above in mind, i will fuse down at FCU and run a suitable MCB, but i still need conformation of how to work out the Amps on the transformer? 100w divided by 19v is not right if its 5.26 amps. Should be less than 1 surely in bathroom?

Please can you elaborate?

Not very clear by me - Put it another way, what is limited/reduced in bathrooms to be safe (because of water) Amps or voltage, considering that the shaver socket runs 230v that is why i said is 1Amp OK?
 
Please note that if you live in England/Wales this work is notifiable to your LABC under part P of the building regs.

I like to find out everything first before doing anything and will run it by an electrician in the family. In regards to notifying LABC, it would have to be done by or signed off by a qualified electrician?
 
With the above in mind, i will fuse down at FCU and run a suitable MCB, but i still need conformation of how to work out the Amps on the transformer? 100w divided by 19v is not right if its 5.26 amps. Should be less than 1 surely in bathroom?

Please can you elaborate?

Not very clear by me - Put it another way, what is limited/reduced in bathrooms to be safe (because of water) Amps or voltage, considering that the shaver socket runs 230v that is why i said is 1Amp OK?

A shaver socket is somewhat of a one off, they have isolating transformers in them. Protection is basically by the means of you will need to have 2 faults in order to get a shock. The circuits supplying class 1 or 2 electrical items in the zones and other metallic items which can introduce potential into the bathroom should be supplementary bonded together (take a look at the wiki) in order to minimise the potential difference which can exist to a safer level. 0.1A is enough to kill, in a bathroom the risk is increased owing to wet bodies and lack of clothing (awaits reply :LOL: )
 
Please note that if you live in England/Wales this work is notifiable to your LABC under part P of the building regs.

I like to find out everything first before doing anything and will run it by an electrician in the family. In regards to notifying LABC, it would have to be done by or signed off by a qualified electrician?

If you sparky relative is a member of a competent person scheme then see if he will do the work for you and notify it. If he isn't then the work needs to be notified to your LABC before it is carried out and their fee paid. It is then up to the LABC to oversee compliance with the building regs.
 

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