230 Volts But No Power

JOHNPT · 23-09-2011 4:14pm #1

Hello All

I was fitting a sensor light today (customer bought it in BnQ) - now although there was 230 volts going to the lampholder it still wouldnt light the bulb. Now a similar problem happened to me about a year ago with a socket - although there was 230 volts at socket and in the pins in the socket ( i checked with my meter) it still wouldnt work when a small heater plugged in or even a socket tester wouldnt work when plugged in.
My question is - is it possible that there is 230 volts but still not enough current flow to work even a small appliance like a socket testers or bulb - has anybody come across a problem like this before?

Thanks

mazthespark · 23-09-2011 4:21pm

ya likely to be a loose connection somewhere or maybe try tripping the mcb associated with the circuit a few times mite be a faulty mcb

JOHNPT · 23-09-2011 4:26pm

Its not a loose connection - i have 230 volts between live and neutral all the time but it still dosent work when plugged in socket tester or today when using bulb.

mazthespark · 23-09-2011 4:34pm

did u try phase to earth?? neutral to earth?? is it only one particular socket or a circuit??? have u replaced socket????

JOHNPT · 23-09-2011 4:37pm

230 phase to earth. Only on that circuit. I replaced with another socket but still didnt work. Is it possible to have 230 volts at two terminals but still not enough current flow to light a light bulb - has anybody come across a similar situation

brightspark · 23-09-2011 5:10pm

What is the voltage across L-N when the load is attached?

brightspark · 23-09-2011 5:11pm

What is the voltage across L-N when the load is attached?

rob w · 23-09-2011 5:42pm

Not trying to be smart.....but did you check the if the bulb is working in a different fitting?

mazthespark · 23-09-2011 6:17pm

has it always been the case or did the fault develop lately?? could still be loose connection at fuseboard/ mcb had same problem with a shower before loose connection at board also had to replace the rcbo as a result of the loose connection

JOHNPT · 23-09-2011 6:29pm

It was a new sensor light i was fitting. I tried bulb it ok. I even got a pendant light and connected it into the live in neutral in terminals - bulb worked fine then connected it in to the live out and neutral terminal but it wouldnt light - however there was 230 volts on the live out and neutral terminal. Brightspark i not sure i didnt measure the voltage when load attached. It seems to me like there was a voltage in the live out terminal but not enough to light the bulb - strange i know.

brightspark · 23-09-2011 6:52pm

JOHNPT wrote: »

It was a new sensor light i was fitting. I tried bulb it ok. I even got a pendant light and connected it into the live in neutral in terminals - bulb worked fine then connected it in to the live out and neutral terminal but it wouldnt light - however there was 230 volts on the live out and neutral terminal. Brightspark i not sure i didnt measure the voltage when load attached. It seems to me like there was a voltage in the live out terminal but not enough to light the bulb - strange i know.

As the pendant lit when connected to the input wiring it's not a problem with the wires feeding the sensor light.

I'm guessing it's one of the following

1, the sensor has an internal fault such as a loose connection or bad contacts on it's relay.

2, the sensor has a 'solid state relay' which isn't activating due to faulty circuitry or just not being triggered. (solid state relays usually have a small current leakage through them hence the voltage appearing on open circuit measurements)

3, the bulb isn't making contact properly in the holder (surprisingly easily done when fitting tubular halogens) Just reread and saw that you connected the pendant to the output terminals so its not the bulb contact

Ronin247 · 23-09-2011 7:34pm

Some sensor lights only work with regular light bulbs and not CFL which may also cause this problem.Dont know why this is but it happened to me,Something to do with the sensors electronics.

Bruthal · 23-09-2011 8:10pm

JOHNPT wrote: »

Its not a loose connection - i have 230 volts between live and neutral all the time but it still dosent work when plugged in socket tester or today when using bulb.

230v showing on an enormously high impedence device such as a digital multimeter does not in any way show there is no loose connection.

Try putting a 100 kilo-ohm resistor in series with the digital multimeter. It will still show 230v. Now try connecting a 100 watt light bulb to the same connections you just measured, it wont light at all, yet the meter will show 230v.

Another way to view it is, a bad connection with no load might show 230v. But put any sort of load on, and it is a non connection sometimes.

Im not saying this is the problem, as in a loose connection, but the true readings of multimeters in certain situations at times seems a mystery to many.

M cebee · 23-09-2011 8:12pm

sure how would you know:D

Bruthal · 23-09-2011 8:14pm

M cebee wrote: »

sure how would you know:D

From all my lunatic experiments down the years:eek:, and its very simple anyway. Drawn in a diagram its simple even for many a layperson to grasp.

JOHNPT · 23-09-2011 8:21pm

Robbie so your saying you could have 230 volts at a terminal and there still a loose connection. So the only way to test for certain is to put a load on the circuit and then test if 230 volts? Is this the only way?

Bruthal · 23-09-2011 8:26pm

JOHNPT wrote: »

Robbie so your saying you could have 230 volts at a terminal and there still a loose connection. So the only way to test for certain is to put a load on the circuit and then test if 230 volts? Is this the only way?

Yea with a digital multimeter, testing the voltage with a load on the terminals is the most accurate way to determine there is 230v and good connections. I think brightspark mentioned that, and its correct.

If a load is put onto a circuit with bad connections, the voltmeter reading across the load would drop to zero or close to it, so in this case you would want to measure voltage at the bulb when its fitted, if possible, to see what the voltage is then.

Did you check the bulb is ok? Check that with the ohms meter.

JOHNPT · 23-09-2011 8:29pm

I didnt know that thanks brightspark and Robbie.

JOHNPT · 23-09-2011 8:36pm

The bulb is fine - the light actually works ok when you cover the sensor for few seconds but it still didnt explain to me why i was getting 230 volts (with sensor not covered) on the live out terminal and the bulb still not lighting - i also checked where the bulb screws in and was getting 230 volts. I think brightspark pointed out that in solid state relay there is a small leakage current so possibly this was the reason?. Thanks for the advice - I guess I should have screwed in the bulb and then checked voltage on live out terminal

Bruthal · 23-09-2011 8:47pm

JOHNPT wrote: »

The bulb is fine - the light actually works ok when you cover the sensor for few seconds but it still didnt explain to me why i was getting 230 volts (with sensor not covered) on the live out terminal and the bulb still not lighting - i also checked where the bulb screws in and was getting 230 volts. I think brightspark pointed out that in solid state relay there is a small leakage current so possibly this was the reason?. Thanks for the advice - I guess I should have screwed in the bulb and then checked voltage on live out terminal

Yea it could well be a solid state relay alright which uses a triac as the switching device, this would have a very high impedence output when in the off state, high enough to be off for a bulb, but not high enough to appear as 0v on a digital multimeter.

JOHNPT · 23-09-2011 8:54pm

Thanks - I just have one more question - every time i put in sensor lights i buy them in an electrical wholesaler and they all have an override facility ie when u turn off the switch and turn it back on within 2 seconds the light stays on permanently. However this lady bought the lights in B n Q and they dont seem to work like this - they just work in sensor mode. Is it just certain sensor lights that have the option of having them on permanently or in sensor mode?

Bruthal · 23-09-2011 9:01pm

I dont think they all have that sensor bypass mode in them., but couldnt say for certain.

Bruthal · 24-09-2011 11:09am

Ronin247 wrote: »

Some sensor lights only work with regular light bulbs and not CFL which may also cause this problem.Dont know why this is but it happened to me,Something to do with the sensors electronics.

This happens on lights switched by triacs, which need a certain amount of current to flow through the load for the triac gate to bring the triac to the on state. If the load is too high an impedence (low wattage), not enough current will flow through the triac to switch it on.

Id say maybe nothing is wrong with the OP fitting, they just seen 230v on the multimeter even when the light was not actually on, and found it strange.

230 Volts But No Power

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