Connect Neon to Live & Earth?

[DaveFix]

I have a four gang switch with no access to Neutral but would like to fit a neon indicator for one switch.

Is there a good reason why the neon should not be connected between Live & Earth, as although it doesn't trip the RCD it just doesn't feel right.

 

[bernardgreen]

The current through the neon could be as much as 5 mA which is un-likely to trip a 30mA RCD but will increase the risk of nuisance trips from other sources of Earth leakage currents

 

[Harry Bloomfield]

The current through the neon could be as much as 5 mA which on it's on is un-likely to trip a 30mA RCD but will increase the risk of nuisance trips from other sources of Earth leakage currents

Plus the risk in the wrong circumstances of someone getting an unexpected belt from an earth which is live.

 

[JohnW2]

Plus the risk in the wrong circumstances of someone getting an unexpected belt from an earth which is live.

Theoretically true (if the 'earth' got disconnected from earth) but no greater a risk that exists when there is, say, an L-E filter capacitor.

I wonder, particularly in the pre-RCD days, how many people have "never done it"?

Kind Regards, John

 

[sparkwright]

If you have a four gang switch, there are probably loads of wires, and there may be a good chance you will be able to convert one of the live wires to a neutral - perhaps.

 

[SUNRAY]

The current through the neon could be as much as 5 mA which is un-likely to trip a 30mA RCD but will increase the risk of nuisance trips from other sources of Earth leakage currents

5 or 0.5mA?
They usually include a resister of 470K 230/470mA.

Using the CPC used to be the common way to do it but I don't like it but only for the reason; 'it just doesn't feel right.'
We used to see cast iron enclosed switches with a big red lens hiding a 15W pygmy bulb and that was often wired that way.

 

[DaveFix]

I've just done a bit more testing, and discovered that the neon indicator wouldn't work properly in this situation anyway.

It's for a kitchen diner where the downlights are controlled by an occupancy sensor. At the 4-gang wall switch, one switch acts as an over-ride switch for the downlights in the diner area, so that the lights stay on even when people are sitting still at the table and the occupancy sensor turns off the lights. The problem I'm trying to get round is that most of the lighting in the house is PIR controlled so people are not used to switching off after them, and often the next morning we discover the diner area lighting had been on all night.

So, what's happened in testing is that all poles of the over-ride switch are live whenever the occupancy sensor has the lights on, so the neon stays lit regardless.

I'm not sure how to overcome this.

 

[flameport]

A neon isn't a solution to any of those problems.
People that expect lights to work automatically and don't use switches won't even look at a switch or the neon indicator, as they have no need to do so.

 

[JohnW2]

.... most of the lighting in the house is PIR controlled so people are not used to switching off after them, and often the next morning we discover the diner area lighting had been on all night.

I wonder how much all these PIRs cost, what it cost to install them, how often they will need replacing and how their (constant) energy consumption will compare (over time) with occasionally "leaving an LED light on all night".

If, as I presume, the intent all relates to perceived 'cost saving', I would not like to predict what a comprehensive cost-benefit assessment would actually show!

The effective disappearance of incandescent bulbs has changed everything, such that one now has to be very careful about what one spends in efforts to avoid LED lights being on a bit more than they need to be.

Kind Regards, John

 

[Harry Bloomfield]

If, as I presume, the intent all relates to perceived 'cost saving', I would not like to predict what a comprehensive cost-benefit assessment would actually show!

That's a difficult one - you have to factor in the cost of the wasted energy of left on, versus the PIR device and wear and tear on the lamp(s).

Another factor is that of convenience. I only have two PIR's at the moment, though I did have more outside and on higher wattage lamps. At the moment I have one built into a 20w LED, which adds extra light in the drive, mostly intended to allow the way to my garage to be illuminated and light up my bin store. The second one, turns a florescent light on in my utility room, adjacent to the kitchen and simply for convenience - often someone goes in or out of there with both hands full, so if its dark, the PIR switches the light on or off. It's not perfect, it really needs an override fitted, for when I am in there a while bottling my wine - Where I bottle is hidden from the PIR.

Oh, I forgot - I have one included in the bathroom extractor fan too, so that operates and remains on 20 minutes, even if the light is not turned on.

Where they are fitted needs to be carefully thought out. I remember one very large leased office space where each modular suspended light fitting, included it's own PIR. Anyone walking through the room, would bring lots of lights on, but with everyone busy working at their desks they would slowly find themselves working in darkness as the lights timed out. They would take it in turns to volunteer to walk round, to keep the lights on.

 

[JohnW2]

That's a difficult one - you have to factor in the cost of the wasted energy of left on, versus the PIR device and wear and tear on the lamp(s).

Indeed, those are also factors.

As I implied, it was very easy in the days of incandescent bulbs, since the 'unnecessary' energy usage of leaving one on accidentally for 24 hours (or, once in my case, for several months is a dusty corner of the house!), was so large that almost any credible amount of capital outlay (and the 'downsides' of PIR energy consumption, effect on lamp life etc.) was worthwhile in terms of potential 'cost saving'.

In the era of LEDs, it really does require a lot of perceived "unnecessary leaving on of lights" to justify the capital cost and other potential downsides of having PIRs (even with current electricity prices) - and it seems that a lot of people don't think about, and/or realise, that.

Kind Regards, John

 

[SUNRAY]

Theoretically true (if the 'earth' got disconnected from earth) but no greater a risk that exists when there is, say, an L-E filter capacitor.

I wonder, particularly in the pre-RCD days, how many people have "never done it"?

Kind Regards, John

Many years ago I added a socket to a fusebox, there were 3 Wylex boxes with a total of around 20 fuses, I removed all 3 covers to see what was spare to find the 16mm² tails looped between them...

However one box, the box containing the heater circuits had the red tail in the 'L' terminal, the black tail in the 'Earth bar' and the green wire in the 'N' terminal... Strange thought Sunray, not seen that format used before. following the grey sheathed tails back to the meter I found that well established pattern of 'black, red, red, black' all nicely sealed away with a proper identifiable DNO seal. It took several goes to see that as the grey sheath went right into the meter and the wire colours not visible.

 

[SUNRAY]

I wonder how much all these PIRs cost, what it cost to install them, how often they will need replacing and how their (constant) energy consumption will compare (over time) with occasionally "leaving an LED light on all night".

If, as I presume, the intent all relates to perceived 'cost saving', I would not like to predict what a comprehensive cost-benefit assessment would actually show!

The effective disappearance of incandescent bulbs has changed everything, such that one now has to be very careful about what one spends in efforts to avoid LED lights being on a bit more than they need to be.

Kind Regards, John

One has to be very selective these days, a few years back a 5 floor office block so 10 toilets had 3 PIR's fitted to control 4 CFL's.
It had been noted that the first person in the morning switched the lights on and the cleaners switched them off 11-12 hours later, the companies energy consultant/electricians recommended fitting the PIR's to save energy and the job was done. While working there a short time later (still doing more energy related works) we were asked if we could check to see why the toilet consumption had risen.
For 7W CFL's and 3W PIRs my calculations now comes up with approx:
OLD: 4 x 7W x 12h x 5 days x 10WC's = 16.8KWh per week
NEW: 3 x 3W x 24h x 7 days x 10WC's = 15.12KWh (edited, thank BOC) per week for sensors plus (50% of 16.8) 8.4KWh = 23.5KWh per week or 40% increase. To be fair I don't recall the increase being that dramatic.
We got the job to fit new switches and remove the PIR's.

Of course I'd not expect indoor PIR' to be 3Watts nowadays and likewise with the significant improvement of low power LED lighting it may feasibly make more sense to leave a 1W LED running 24/7 than power a PIR.

 

[JohnW2]

One has to be very selective these days .... Of course I'd not expect indoor PIR' to be 3Watts nowadays and likewise with the significant improvement of low power LED lighting it may feasibly make more sense to leave a 1W LED running 24/7 than power a PIR.

I suspect that, in many cases, 'being selective' is probably essentially a no-brainer. If the interest is in cost, and the concern relates only to low-power LEDs being occasionally left on for 'longer than necessary', then I seriously doubt that it ever makes (financial) sense to expend capital on some technology which itself consumes some power (and, in some situations, may decrease LED life). Indeed, as you say, purchase and use of the technology may not make (financial) sense even when the alternative is to leave the LEDs on continuously.

I suppose the situation could be helped a little, particularly with outdoor PIRs, if the PIR itself ran off solar-charged batteries, but that would presumably increase the capital outlay.

People contemplating 'investing in' PIRs for these reasons should perhaps reflect on the fact that at least as great 'cost savings', without any capital outlay, could probably be achieved by regularly reducing the duration of their shows by a few seconds, reducing the amount of water they boiled in their kettle by a few mL or turning their room thermostats down by a fraction of a degree etc. etc.!

Kind Regards, John

 

[boringoldcodger]

Deleted as no longer relevant.