Bulb wattage versus transformer wattage

[loveandmercy]

Hi

I have a two-pronged question for the better (electrically-minded) person than me.

I posted a while back about swapping 50w for 20w MR16s in my bedroom (14 of them) and successfully did that.

However, I understand/know that the dimmer switch I successfully installed to handle that load "sees" the wattage rating on the transformers and not the bulb (unless you have transformers like this http://www.1stopelectrics.com/product/yt50l/50w_transformer_with_electrical_leads/).

My transformers are all rated at 60w, whilst their bulbs are 20w. Here are my questions:

(1) How much power are the lights actually consuming - is it 20w per light or is it actually 60w per transformer?

(2) When I turn the bedroom lights on in conjuction with a couple of other rooms with similarly crazy numbers of MR16s (20 in the kitchen and 6 in the bathroom!!!) the trip switch goes on the fuse box. Does the fuse box see the load of the bulbs, therby making it more likely to trip with 50w bulbs rather then 20w (kitchen is still full of 50w bulbs), or does it see the load of the transformer - irrespective of the rating of the bulb plugged into it.

In (2) above, if it is the former case, I can probably reduce the trip switch incidents by simply swapping the kitchen 50w bulbs for 20w bulbs. In the latter case, I may be therefore able to stop the trip switch constantly going by swapping my current 60w fixed transformers for ones like http://www.1stopelectrics.com/product/yt50l/50w_transformer_with_electrical_leads/

As ever, any help gratefully received!!!
John

 

[RF Lighting]

The transformers are rated for upto 60W

Each light point will use the amount of power which is stamped on the lamp.

 

[TicklyT]

The 'transformers' (actually switch mode power supplys) should adjust their output according to the load to maintain a constant voltage to the lamps, so their power consumption should match the load, plus a bit for losses - they aren't 100% efficient.

One problem is those SMPSs can draw large inrush currents on power-up, as do the lamps until they reach their operating temperature (hence the need to de-rate many dimmers etc used with halogen loads). The inrush current could trip a breaker that's already quite heavily loaded.

According to my sums, you have a load of about 1600 Watts, or about 7 Amps, without allowing for any startup inrush.

 

[loveandmercy]

Hey, thank you TicklyT.

So I know where I stand with my electric bills anyway...charged for lamp wattage - not transformer

So based on your answer, I think there are a couple of things to do to stop my trip switch going.

Firstly, switch my remaining 50w lamps to 20w. That should take down total power consumption and therefore load, meaining that when I do get an inrush I have more capacity (ampage?) to work with before the trip switch goes - because the lamps already on at that time are taking up less wattage. [NB across kitchen, bedroom and bathroom I have a total of 44 MR16s, of which 15 are still 50w bulbs (ther other 29 are 20w).

Secondly, if I still have the tripping issue, I wonder if switching my transformers to these
http://www.1stopelectrics.com/product/yt50l/50w_transformer_with_electrical_leads/

would stop the issue - because these transformers offer a couple of things my current ones do not ("Soft start for extended lamp life" and "For dimming, load is measured by the rating of the lamps (not by the transformer rating as with other transformers)").

Please could you kindly let me know if you agree with my plan of attack!!!

Thanks again
John

 

[1john]

you could (should) replace all of those lamps and transformers (where acceptable with the regs) for GU10 / GZ10 lamp holders and 9W CFL's or LED's, so the 14 lights in your bedroom would have gone from using -

700W @ 50W lamps (3+Amps) => 280W @ 20W lamps (1.2A) => 126W @ 9W lamps [CFL's] (0.5A) / 70W @ 5w lamps [LED] (0.3A)

With your kitchen and bathroom thrown into the mix, worst case @ 50W lamps is 40 x 50W = 2000W / 230V = 8.7A if you do with LED's then you would only be using 0.87A in total, your lighting energy running costs would be a tenth of what they are now. The CFL's would use about 1.6A in total.

 

[loveandmercy]

Is there any way to minimise the inrush current effect. i.e. is it a function of transformer "capacity" (60w in my case) for example?

I'm just looking for ways to minimise the effect.

Thanks!
John

 

[ban-all-sheds]

I posted a while back about swapping 50w for 20w MR16s in my bedroom (14 of them) and successfully did that.

Please step back for a minute, and ignore the fiddling around the edges to go from 700W of lighting (about what I use for an entire house) to 280W, or even down to 100-odd watts.

Unless your bedroom is bigger than Hugh Hefner's doesn't the fact that you need 14 of anything to light it tell you that the fundamental problem is that you're using lights not designed to light it?

 

[big-all]

Hey, thank you TicklyT.

So I know where I stand with my electric bills anyway...charged for lamp wattage - not transformer

So based on your answer, I think there are a couple of things to do to stop my trip switch going.

Firstly, switch my remaining 50w lamps to 20w. That should take down total power consumption and therefore load, meaining that when I do get an inrush I have more capacity (ampage?) to work with before the trip switch goes - because the lamps already on at that time are taking up less wattage. [NB across kitchen, bedroom and bathroom I have a total of 44 MR16s, of which 15 are still 50w bulbs (ther other 29 are 20w).

Secondly, if I still have the tripping issue, I wonder if switching my transformers to these
http://www.1stopelectrics.com/product/yt50l/50w_transformer_with_electrical_leads/

would stop the issue - because these transformers offer a couple of things my current ones do not ("Soft start for extended lamp life" and "For dimming, load is measured by the rating of the lamps (not by the transformer rating as with other transformers)").

Please could you kindly let me know if you agree with my plan of attack!!!

Thanks again
John

if you are worried about your lecky bill you should forget about "stylish " but very inefficient spots go for compact low energy bulbs
my whole house runs on less than 2 amps for lighting if all bulbs are running together 460 w will give low energy bulbs equivilent to 17 100w normal bulbs
so assuming you have 9 rooms to light with 180w of normal bulbs will be by far to bright for the average room

 

[ericmark]

BAS has given you a good answer that spot lights are designed to light a spot not a room. However all extra low voltage transformers are not the same. Mine are just transformers very old and as a result there is an in-rush when switched on which if I had too many would cause the trip to open.

However most modern types are switch mode power supplies and these normally have a soft start to stop the in-rush when switched on. And because they control the voltage so long as you don't fit any dimmer switches are more economic than the low voltage (230v GU10) type.

However the low voltage types will take cold cathode lamps where the extra low voltage (12v) will only work with halogen or LED.

With halogen lamps you should not use a dimmer as to work well the envelope temperature is very important and dimming switches reduce the life of the lamps.

The norm is to use a 1/3 and 2/3 split so 1/3 of lamps or 2/3 of lamps or all can be used. However the tiny lamps that make the room look like a planetarium will never light a room and you need to use at least 5 inch lamps to get the spread required and as you move to larger units then florescent is the norm and low voltage rather than extra low voltage.

The room does then tend to look like an office. Well of course the people who light offices are going to use lamps that don't cost too much to run and emulating an office ceiling will of course mean cheap to run lighting the guys who light offices are not daft.

As to tripping the breaker it's just a question of counting. 5A = just over 1000W so at 50W each 20 lamps. Any normal house should be able to be lit with less than 20 lamps something is very wrong if you can't.