What type RCD for energy saving lights?

[ericmark]

Be it fluorescent, LED or any other lamp, I as the user don't know if it produces a DC component or not, this house one year ago did not have any energy saving lights, today most are energy saving, and the lighting supply is from 3 x 6A tripping curve B type AC 30 mA within 40 mS RCBO's do they need changing, or should I go back to tungsten lighting as I have loads of the old bulbs?

It may seem daft, but I really don't know how to work out if the appliances on a circuit have a DC component, and my old RCD tester I have used with everything switched off, so the test is really null and void as not tested under working conditions, may as well put it in the bin, but what replaces it? Pushing test button shows it trips at 30 mA, but not how long it takes, so are there now new testers that generate a DC component to test if type A or AC?

Is the oscilloscope now standard electricians test gear? OK not really that worried in my own house, I am not going to take me to court because wrong RCD fitted, but what about when working in other peoples home, how do you know if you can use type AC or not?

 

[JohnW2]

It may seem daft, but I really don't know how to work out if the appliances on a circuit have a DC component, and my old RCD tester I have used with everything switched off, so the test is really null and void as not tested under working conditions, may as well put it in the bin, but what replaces it? Pushing test button shows it trips at 30 mA, but not how long it takes, so are there now new testers that generate a DC component to test if type A or AC?

I clearly need to do some thinking/reading, since I've never really understood this business.

Regardless of the waveform (including any DC component) of the current flowing into the connected load under normal operation, the current flowing through an L-E fault (including through a human body) will presumably be sinusoidal AC, with no DC component - and, at first sight, I would have thought that the resulting AC L-N imbalance component of the current flowing through the RCD would result in in operating 'as expected'.

Mind you, I also do not understand what (mechanistically) is the difference between RCDs of the different types, so maybe understanding that would help me.

Finally, maybe I'm wrong, but I rather doubt that pressing the test button on an RCD of any type does anything other than create an AC imbalance (with no DC component).

Can anyone help me understand any of this - or point me toewards something which can?

Kind Regards, John

 

[FrodoOne]

Be it fluorescent, LED or any other lamp, I as the user don't know if it produces a DC component or not, this house one year ago did not have any energy saving lights, today most are energy saving, and the lighting supply is from 3 x 6A tripping curve B type AC 30 mA within 40 mS RCBO's do they need changing, or should I go back to tungsten lighting as I have loads of the old bulbs?

It may seem daft, but I really don't know how to work out if the appliances on a circuit have a DC component, and my old RCD tester I have used with everything switched off, so the test is really null and void as not tested under working conditions, may as well put it in the bin, but what replaces it? Pushing test button shows it trips at 30 mA, but not how long it takes, so are there now new testers that generate a DC component to test if type A or AC?

Is the oscilloscope now standard electricians test gear? OK not really that worried in my own house, I am not going to take me to court because wrong RCD fitted, but what about when working in other peoples home, how do you know if you can use type AC or not?

I really wonder of what you are speaking.
With an AC supply to any premises there is the possibility of providing "Half Wave" or "Full Wave" rectification for any "appliance" which is connected to any such supply.
While I do not know concerning the "Regulations" in the UK, any device which provides only "Half Wave" rectification is not allowed to be connected to the "mains" in Australia.

If any device produces a DC output - on the" Secondary" side from a "Full Wave" rectifier, there will be no DC component in the "Mains".

However, if the Rectifier is only "Half Wave", the Mains supply will be "loaded" at only every "half cycle". (Power supply authorities do not like this - for rather obvious reasons.)

 

[ericmark]

This is Hager on subject seems AC, A, B and F, and although I can see why, and that an electric car needs a special RCD, how do we know if that LED bulb needs a type AC or type A, likely no problem with one bulb, but what when there are 50? As to full or half wave rectified, how would I know? I don't reverse engineer a bulb to find out.

 

[JohnW2]

I really wonder of what you are speaking.....

As you will probably realise from my response, I am also a little uncertain.

However, do you not, in Australia, have Type AC, A, B & F RCDs and, if you do, when (if ever!) would you consider it necessary to use something other than AC?

Kind Regards, John

 

[ericmark]

From what I read the type AC RCD can fail to operate within the tripping times if there is too much DC component on the supply, it is clearly better than not having a RCD and before the change of consumer units and fuse boxes I think only two circuits out of 14 were RCD protected and that RCD was also type AC, so all in all an improvement.

However since I simply don't know as @JohnW2 has said, I don't know if using LED bulbs will or will not cause a problem, the same applies to any equipment which has a pulse width modulated or switched mode power supply there is no label saying 0.2 mA DC component is generated with this appliance, so you can't simply add them up. And even if it did, the type AC is AC only there is no limit quoted.

We are told 6 mA is difference between type A and type B, but it would seem there is very little type AC can be used for, yet type AC is the most common found, and my CU does have option for type A at 6 amp, but all other sizes are type AC only so would need to change whole board to change to type AC and it is less than 1 year old.

So if there is a problem then easy way is return to tungsten lights, at least until CP (Electric) Limited from Kilmarnock release a type A in other current ratings. But there must be 1000's of people with type AC RCD fitted, so there must be a way to test if the RCD works when powering a switch mode device, there must be a RCD tester which produces the DC component to test the RCD and also a device to measure the DC component so you know if it will work or not, and every practising electrician should have them in the same way as they have a loop impedance tester.

But I have yet to see one, maybe some one can direct me to the devices?

 

[JohnW2]

From what I read the type AC RCD can fail to operate within the tripping times if there is too much DC component on the supply ...

That is also my understanding of what is said - but, as I said, I don't really understand 'why', nor how the other 'types' of RCD avoid this issue.

However since I simply don't know as @JohnW2 has said, I don't know if using LED bulbs will or will not cause a problem, the same applies to any equipment which has a pulse width modulated or switched mode power supply there is no label saying 0.2 mA DC component is generated with this appliance, so you can't simply add them up. And even if it did, the type AC is AC only there is no limit quoted.

As FrodoOne implied, I would have thought that there would be a prohibition of any equipment which resulted in significant DC components of current flowing in the supply network - but I haven't got a clue as to whether that is true. Quite apart from the disruption of the network, I would doubt that DC components of current would get metered, either!

Kind Regards, John

 

[ericmark]

Unless using a rotary inverter to turn AC to DC it tends to use the peak part so will distort the wave form. Be it a capacitor or battery they tend to not drop to zero between each wave, so it will flatten off the peak. But this is not really a DC injection, I know some stone processing plants used DC injection and to be frank it was a long time ago that I worked in the Falklands on the plant and I can't remember what it did, even with the TV aerial lead we use DC and AC with the DC powering the mast head amp, but I really fail to see why any inverter would put DC on the power line, the only thing I can think of which may inject DC is those silly units for sending LAN signals on the sockets, I would not use one, as told they produce interference, however I am told SkyQ has it built in, so seems they have sneaked into my house.

 

[JohnW2]

Unless using a rotary inverter to turn AC to DC it tends to use the peak part so will distort the wave form. Be it a capacitor or battery they tend to not drop to zero between each wave, so it will flatten off the peak. But this is not really a DC injection, ...

It's not 'DC injection' at all, so long as the waveform remains symmetrical around zero.

Kind Regards, John

 

[winston1]

any device which provides only "Half Wave" rectification is not allowed to be connected to the "mains" in Australia.

Interesting. Is this a recent rule? During the valve radio and TV days much of this equipment got their HT by half wave rectifying the mains. In fact even early colour TVs did this. Sets such as Philips G8, Thorn 3000 etc. I understood these sets were used in Australia as well.

 

[JohnW2]

Interesting. Is this a recent rule? During the valve radio and TV days much of this equipment got their HT by half wave rectifying the mains. In fact even early colour TVs did this. Sets such as Philips G8, Thorn 3000 etc. I understood these sets were used in Australia as well.

A lot had mains transformers.

 

[FrodoOne]

A lot had mains transformers.

As far as I am aware, all (Cathode Ray Tube) CRT TVs sold in Australia had a "mains" transformer.
The "high voltage" secondary of these transformers was "centre-tapped" and the DC was obtained via a "full wave" rectifier, such as a 5Y3GT.
(Yes, I do know that anything less than 1000 V AC is "low" voltage, according to IEC definitions.)

Of course, later designs (and, probably, all colour TVs) utilised solid state components, including "Full Wave" (Bridge Rectifiers) but these always included a "mains" (isolation) transformer - for "safety" reasons - and the transformer was required to provide the "heater" voltage for the CRT.

(This post has sent me back looking at books and manuals which I still have from the 1970s and before.
e.g. "Miniwatt Technical Data" 1958 and
"The MAZDA Book of Pal Receiver Servicing" 1971.)

 

[bernardgreen]

was required to provide the "heater" voltage for the CRT.

I recall early TV sets had the heaters connected in series and then to a resistive core voltage dropper in the mains lead. When valves aged and cathode emissions dropped a "trick" was to shorten the mains lead by an inch or so thus increasing the current through the heaters.

Maybe this method of heater supply was outlawed in Australia,

 

[winston1]

I recall early TV sets had the heaters connected in series and then to a resistive core voltage dropper in the mains lead. When valves aged and cathode emissions dropped a "trick" was to shorten the mains lead by an inch or so thus increasing the current through the heaters.

Maybe this method of heater supply was outlawed in Australia,

No TVs used that method as far as I know, but it was common on some radios. TVs had a big “mains dropper” resistor inside.

 

[winston1]

- and the transformer was required to provide the "heater" voltage for the CRT.

(This post has sent me back looking at books and manuals which I still have from the 1970s and before.
e.g. "Miniwatt Technical Data" 1958 and
"The MAZDA Book of Pal Receiver Servicing" 1971.)

Not really. Many sets got the CRT heater supply from an extra winding on the line output transformer (flyback transformer).

I’m pleased to learn that sets in Australia did not use the live chassis techniques used in Europe. A great safety bonus but at a cost and weight penalty.