Halogen downlights

[Observer]

I have quite a large number of SELV halogen downlighters in kitchen (50 altogether) and other areas, mostly on individual transformers. I' avoid using dimmers to vary light levels so I use several different switch configurations and lamp wattages to achieve a range of lighting levels - thus: 1 circuit for 50W lamps over worktops; another for under cupboard 20W, another for glass front cabinets 20W, another for dining area 20W and so on.

It all works pretty well and I'm not unhappy with the result. But I was wondering if the power consumption of a single transformer (~0.3A on the primary side) varies with the lighting load on the secondary side. Can anybody enlighten me?

 

[stardelta]

there`s nothing free in this world the more you want from something the more you have to put in. i assume the 0.3a rating on the primary side of the transformer was the maximum current loading for that model which means fully loaded it would give an output of approx.70 watts (assuming its a 240/12volt transformer)at 6 amps.if you put in a 50 watt lamp you will draw 4.16 amps(approx)on the 12volt side,and 0.2amps approx.on the primary side

so yes it does vary, the more you want out the more you have to put in.
.hope this helps.

 

[Observer]

A bit but not fully. The transformer is rated at 0.3A with max. output load 60W. On the primary side that's equivalent to 69W - correct? So if I apply a 20W lamp on the secondary side, does it follow that the transformer is drawing only 0.1A, equivalent to a 23W load at mains voltage? Or is the load on the primary side the same 0.3A (or thereabouts) regardless of the load on the secondary side, with some internal energy wastage in the transformer?

 

[ban-all-sheds]

The former.

 

[Observer]

Thanks BAS - and if you read this why in this post do you suggest 15A unswitched sockets (which I think are round pin)? Wouldn't 13A standard unswitched sockets (rectangular pin)be as good and no need to change plug on appliance? What am I missing?

 

[ban-all-sheds]

There is a fuse in 13A plugs - the idea is to make sure the fuse is somewhere accessible, not under a worktop behind an appliance. 15A roundpin plugs are unfused.

 

[Observer]

Of course. So can use a standard FCU above instead of an unfused DP switch, which seem to start at 20A. Cheers.

 

[Adam_151]

There is a fuse in 13A plugs - the idea is to make sure the fuse is somewhere accessible, not under a worktop behind an appliance. 15A roundpin plugs are unfused.

Though chances are that if the fuse blows, you are going to have to pull the appliance out anyway, to repair it, kitchen appliances in my experience don't have much of a penchant for blowing 13A BS1362 fuses for no good reason

 

[ban-all-sheds]

Don't tell me that you don't do what everyone else does when a fuse blows - replace it and see if it happens again before embarking in any repair process?

And sometimes, it doesn't blow again....?