Door Bell Transformer

[John]

I have just received a home energy monitor and spend a while trying to track down where my last 2p of electricity was being used.

I found that isolating the door-bell circuit breaker made a difference. This circuit feeds an adjacent Freidland transformer (house built in 1988) which feeds a satisfyingly loud buzzer and an illuminated button.

I wondered if there is a more modern equivalent to the iron transformer that is suitable for this purpose as I recall reading that switched mode power supplies do not have a resistive load.

Please don't shoot me down for being tight - but this thing is on continuously and if there is a simple alternative then I would like to consider it - but I quite like the illuminated button and the loud buzzer which is only the size of a cotton bobbin. Most bing bongs look naff IMHO.

[Richard Russell]

Is your energy monitor the kind that actually measures current, not power (e.g. it clamps around the incoming cable)? If so the actual power consumption of the bell transformer is probably a lot less than it indicates, because it will be largely 'wattless' (inductive) current.

Richard.

[Dave Liquorice]

How warm is the transformer? If it's taking any significant power it'll be warm if not hot. TBH I'd be surprised that one of the energy monitors can reliably see just a bell transformer, I'd be looking for something else on the same circuit.

They are more effcient and don't waste as much when idle.

Small 24/7 loads soon add up. At 10p/unit 1W 24/7 costs 87.6p/year. If your bell transformer is wasting (ie as heat not powering that little bulb in the push) 5W thats just over =A34/year. A small SMPSU, if you can find a suitable one, is going to be =A310 to =A320.

What is the rating of the bulb in the push? You can probably make more savings by changing that to a modern LED. Best would be modern LED and SMPSU. In fact with a modern high effciency LED it might be practical to go to batteries, but the buzzer may not buzz if it relies on the AC from the mains.

[Frank Erskine]

Most of that consumption (unless you have an awful lot of callers) is probably being eaten up by the bulb in the pushbutton.

[John]

Is your energy monitor the kind that actually measures current, not power (e.g. it clamps around the incoming cable)? If so the actual power consumption of the bell transformer is probably a lot less than it indicates, because it will be largely 'wattless' (inductive) current.

Richard.

- It clamps around the incoming main cable from the meter.

[John]

How warm is the transformer? If it's taking any significant power it'll be warm if not hot. TBH I'd be surprised that one of the energy monitors can reliably see just a bell transformer, I'd be looking for something else on the same circuit.

They are more effcient and don't waste as much when idle.

Small 24/7 loads soon add up. At 10p/unit 1W 24/7 costs 87.6p/year. If your bell transformer is wasting (ie as heat not powering that little bulb in the push) 5W thats just over £4/year. A small SMPSU, if you can find a suitable one, is going to be £10 to £20.

What is the rating of the bulb in the push? You can probably make more savings by changing that to a modern LED. Best would be modern LED and SMPSU. In fact with a modern high effciency LED it might be practical to go to batteries, but the buzzer may not buzz if it relies on the AC from the mains.

[Andy Dingley]

Now there's an idea. If I connect a few more bell transformers in the cupboard under the stairs, a couple of watts of heating in there will help to keep it dry. I'd spend money and energy to do that!

[cynic]

If you believe what the typical "energy monitor" (which it isn't) tells you you are deluding yourself

[dom]

[Tabby]

It might be wasting a couple of watts, total cost =A31.70-=A32 a year. The lightbulb might be wasting another watt, maybe another 85p a year. I cant see it being worth doing anything about, there are marginally more energy efficient supplies available but they come with their own issues, and I'd sooner stick with an iron one myself.

NT

[Tabby]

[Harry Bloomfield]

on 26/11/2010, Frank Erskine supposed :

Budget around half a watt or so for that. You could reduce it by replacing it with a suitable white LED.