Inrush currents and solutions......

[Dobes_88]

Good evening!

Wanting to pick the brains of people more experienced in this field, approaching 2nd fix stage of an ongoing rewire where the client wants a shed load of lights throughout.

What particularly worries me is the hallway and kitchen grid switches where there’s around 10-12 lights operated by numerous switches in each area… And he may want a couple more lights added to it!

The plan is to fit fixed Enlite E8 downlights throughout but worried about the dreaded inrush currents, have emailed Enlite to see what sort of figures I should be expecting per unit but no reply as of yet…

Would a better plan to fit LED GU10’s to limit the inrush?

It’s all wired in 1.5mm, clipped direct with switch drops in oval conduit so will be able to get away with a C10 (if Zs in limits), but with the shear volume of lights (around 25-30 x per lighting circuit) I’ve read about these inrush current limiters that could be the solution - but I haven't or know of anyone that has installed them.

Any guidance would be greatly appreciated!

 

[Pete999]

What do your circuit calculations tell you?

 

[Spoon]

I'm not domestic mate but I'm interested in the outcome to this.
A mate at work who had more wattage in his kitchen than I had in my entire house, GU10's, and never had a problem with inrush.
Would there be significant inrush if they are "operated by numerous switches"?

 

[westward10]

I would stick with the Enlites not GU10 and over order for some spares for future failure. That is a lot of lighting points for one circuit LED or not.

 

[Octopus]

Fwiw JCC have recommendations on the limits of numbers of their LEDs per circuit etc

Hopefully Enlite have similar guidance

 

[Dobes_88]

Yeah waiting to hear back from Enlite and have asked those exact questions.

Taken this job over from a mate (cheers!) and the client is fully aware there could be some alteration work to be done, wondering if people have installed one of these limiters or alike -

Inrush Limiter for LED lighting - https://uk.eaton.com/content/gb/en/products/product-catalog/lighting-controls-inrush-limiter-eaton.html

 

[PEG]

Yep,interesting,but does this device go before or after the switching?

A quick scan describes after,the circuit breaker.

 

[Leesparkykent]

I can't see it being a problem. It's not like there going to walk in and palm the switch bank so all the switches close at the same time.

 

[westward10]

I agree the in rush can be limited by division of lighting points across the switches.

 

[Madocks]

Have you considered a type c mcb?

 

[Pete999]

Have you considered a type c mcb?

Think the OP already has a C10 cb

 

[Dobes_88]

Haven't fitted anything yet, Consumer unit to be installed early part of next week and hopefully have the lights up and running towards the end of the week.

Initial thoughts is certainly a C6 or C10, will have to see what the Zs is first.

Just looking into possible solutions should the C type MCB not work, rather than flicking everything on and hoping for the best!

 

[Pete999]

Bang testing at it's best then?

 

[The Ghost]

You can buy inrush current limiters. However I think it is overhyped the problem with inrush currents. I have fitted LED panels in numbers that suggest very large inrush currents and the 10a mcb (type B) has been fine. I watched a great vid on this and they simulated the process of inrush on a specialised test rig. What it showed is the distance between the lights causes the inrush to be staggered as we are talking a peak inrush current for 500 ms only. Hence the problem is ameliorated. It is very much to do with the controller so you can look at the Inrush current for most controllers on the manufacturers site. If you do fit a limiter it should be before the switch and the switch should be rated as high as you can as it is the sacrificial part of currents. There have been cases of switches and contactor/relays welding together in these situations. So it is something to be aware of. But the LED panels I put in have been going for five years without any problems.

 

[Toneyz]

Fwiw JCC have recommendations on the limits of numbers of their LEDs per circuit etc

Hopefully Enlite have similar guidance

I would echo what Murdoch above posted (BTW apologies for spelling your name wrong in a previous post-Murdoch) It does also seem to be a lot of lights on one circuit.

 

[davesparks]

What do your circuit calculations tell you?

How can he calculate this when the manufacturers haven’t supplied the required information?

 

[Octopus]

The guides and regs don't help .... As far as I know they still suggest we should allow 100w per light fitting .....

We all know that this is very out if date...

How many light fittings in total are there on this circuit?

 

[sam400]

I keep telling people installing LEDs is a dark art but no one believes me! Lol
I have fitted quite a few enlites on b curve breakers and not had a problem.
But got caught out once by 3 JCC under unit lights that I had to put on a C10 to stop it tripping.
I recently contacted JCC about some LED panels I was fitting and they said they pull 36A per fitting on start up!
(Only for 20 uS tho)

 

[1Justin]

I'd be surprised if you can get a figure from Enlite, but if you do, then let us know! With domestic lights I don't think you will have a problem though.
I have had issues only once, but that was fitting 11 off 30W floods with Meanwell drivers. I eventually needed to fit a C16 breaker and only just got away with the cable installation I'd already done, phew..

 

[ImpededLoop]

12x E8's shouldn't cause you any issues on a B6 (even on one switch). I've seen it done a few times recently.

If Enlite do supply any data, please share it with us as it would be interesting to look at.

 

[davesparks]

I think one fundamental issue here is that LED lighting is still being installed and controlled by a method designed for incandescent lamps.
Switching and/or dimming the supply to the electronic driver circuitry is never going to give the best results for inrush, lifespan or dimming performance.
Electronics like this performs much better with a constant supply and a separate control input.

New technology needs to have a new approach to the way it is installed and controlled otherwise these problems are never going to go away.

 

[Pete999]

How can he calculate this when the manufacturers haven’t supplied the required information?

Hi Dave I was in a hurry and was going to suggest to the OP that he calculate the circuit parameters to see if he could use a different type of CB

 

[Midwest]

I concur the advice re JCC, so Enlite might be of same assistance.

Although I recently fitted some JCC Hybrid 9's, where there is no such advice on maximum no's on B or C mcb's in the installation instructions. So I rung their technical, who said they don't provide that default info anymore. They did say to ring the local rep, who might provide more detailed information. Looks like their testing has taken some cutbacks.

 

[Octopus]

Initial thoughts is certainly a C6 or C10, will have to see what the Zs is first.

Another interesting strategy ................ if you 1st fixed it you should have a VERY good idea what the Zs is likely to be.................

 

[Dobes_88]

Another interesting strategy ................ if you 1st fixed it you should have a VERY good idea what the Zs is likely to be.................

As in #6 post I've taken over the job from a friend (family bereavement) and client wants some lighting on by end of next week, first time on site yesterday having a nose around and just preparing for worst case scenarios.

Kitchen lighting has around 25 fittings, couple of switches operating 10-12 lights.

Upstairs and downstairs lighting around 35 fittings with hall switch operating around 14 lights.

Upstairs lighting around 35 fittings with landing switches operating around 12 lights, rest of rooms have around 4-8 lights with single switch.

 

[Pete999]

I f as you say did the 1st fix, does he have any proposed Zs calculations from the circuit designs

 

[Dobes_88]

Not that I'm aware of! It's not a massive house so the cable runs aren't too long, will look like Terminal 5 when up and running though!

 

[Octopus]

As in #6 post I've taken over the job from a friend (family bereavement) and client wants some lighting on by end of next week, first time on site yesterday having a nose around and just preparing for worst case scenarios.

Kitchen lighting has around 25 fittings, couple of switches operating 10-12 lights.

Upstairs and downstairs lighting around 35 fittings with hall switch operating around 14 lights.

Upstairs lighting around 35 fittings with landing switches operating around 12 lights, rest of rooms have around 4-8 lights with single switch.

Are ALL these lights on 1 circuit?

 

[Dobes_88]

Are ALL these lights on 1 circuit?

Thankfully not, 3 x separate circuits -

1 - Kitchen lighting
2 - Ground floor lighting
3 - !st floor lighting

 

[Midwest]

As others have said, it would be the switching which might cause the issue. Consider splitting up the luminaires across more switches.

 

[redbarnman]

One cycle of mains current takes 1/50th second or 20milli seconds. In-rush currents may be very high but last for well under a milli second - that is much less than one mains cycle. There is very little power in a transient and heating effects can be ignored as far as cables are concerned so there should be no need to change any cabling. Traditional Z calc's don't work with transient currents because the effective frequency of the transient is 1000's of Hz so that is not much help and as electricity travels along wires at around 0.8 the speed of light or a quarter of a million kilometers per second the length of cable is not going to have much impact either. You also have to remember that tungsten, halogen and fluorescent lamps also have higher inrush currents - smaller peak but over a longer time. As LED lamps always need a driver (built in or external), it is the driver circuit that will determine the inrush current and these driver circuits contain far more sensitive components than a mains switch. Unless someone comes up with real measured transient data I don't see why you wouldn't work on the basis of 20 off 10W LED's per MCB circuit. By the time you have then broken down to 6 to 10 lamps per final switched circuit there is no problem. Changing from a B curve to C curve will only provide a factor of 2.5 over current capability. You would be better running off dimmers. I'm sure if LED's were a real problem they would be in scope for the 18th edition.

 

[Octopus]

Thankfully not, 3 x separate circuits -

1 - Kitchen lighting
2 - Ground floor lighting
3 - !st floor lighting

Then I would suggest that you have nothing to worry about .......... but based on the assumption you have low Zs readings then use of Type C breakers from install may prevent the possible call back later .....

 

[Dobes_88]

Just a little update, lights all up and running on a C10 MCB's (highest Zs being 1.1 Ohms) with no issues when turning multiple switches on at the same time.

Also had a response from Enlite for those interested -

"The inrush on the EN-DE8 is 0.6A PK measured in 100ms. We have tested 2-10 fittings on our AU-DPS400X dimmer module".

Thanks to all for your input!

 

[1Justin]

Good. - & just FYI to help understand the range of these figures and how the method of measurement greatly affects to answer.. The 30W LED drivers which I mentioned in a previous post (Meanwell) where I had fitted eleven into one circuit, are individually specified at 55 Amps /500us. Hence since Meanwell use 1/200th of the time slot specified by Enlite and come out with a peak current nearly 100 times that you got from Enlite. (OK, a more powerful driver, but not by that extent). It illustrates the potential for problems though.

 

[alasdairp]

My putting the cat amongst the pigeons again...
The IET have a 200 A4 page Code of Practice for the Application of LED Lighting Systems (2014).
They also have a CoP - wait for it - for Low and Extra Low Voltage Direct Current Power Distribution in Buildings (2015) (only 60 A4 pages) that predicts we will all soon be distributing LV DC for lighting and electronics alongside normal 230 mains for high power devices and appliances - compliant with BS7671 subject to suitable sleeving and labeling - installing a second DC CU alongside the normal one.
Should be fun, eh?
One advantage its that it would get rid of the in-rush current problem for LEDs.

 

[davesparks]

My putting the cat amongst the pigeons again...
The IET have a 200 A4 page Code of Practice for the Application of LED Lighting Systems (2014).
They also have a CoP - wait for it - for Low and Extra Low Voltage Direct Current Power Distribution in Buildings (2015) (only 60 A4 pages) that predicts we will all soon be distributing LV DC for lighting and electronics alongside normal 230 mains for high power devices and appliances - compliant with BS7671 subject to suitable sleeving and labeling - installing a second DC CU alongside the normal one.
Should be fun, eh?
One advantage its that it would get rid of the in-rush current problem for LEDs.

Using a driver which has a permanent feed and a control input will get rid of the inrush problem, without the need for an entire DC distribution.

 

[alasdairp]

Using a driver which has a permanent feed and a control input will get rid of the inrush problem, without the need for an entire DC distribution.

I agree, that would be much better. However, 20 or 30 mains-voltage switch-mode power supplies located in ceiling voids must be more of a fire hazard and reliability issue than having one high quality DC supply for LEDs and electronic devices in the house. I am not push for this, just pointing out the way IET thinking seems to be going.
Many LED 'bulbs' have inbuilt 230 V AC conversters built inside them and they are by far the main cause of failure. The LEDs themselves now very rarely fail (some early high power ones did - and the higher the power the more they still fail).

 

[davesparks]

I agree, that would be much better. However, 20 or 30 mains-voltage switch-mode power supplies located in ceiling voids must be more of a fire hazard and reliability issue than having one high quality DC supply for LEDs and electronic devices in the house.

I suspect you would still require an electronic power supply of some sort for each light fitting to drive the LEDs correctly as they will almost certainly need constant current rather than constant voltage supplies.