Hager 6A Type B MCB Tripping With Toroidal Transformer

[Owlsroost]

Hello

Recently installed a Low Voltage wire track lighting system in the kitchen which uses a ceiling mounted Arte 300 watt 12v toroidal transformer. Running 5 Osram 50W 12v halogens. The hager 6A Type B, MCB trips frequently (not every time) so I guess it is simply a in surge current issue and changing to a Type C will be OK.

you think this is the culprit?

I have ordered a Hager Type C based on what I have read on other posts to try. Is it a simple job to switch off the mains to the consumer unit and change the MCB for a competent DIY'er or is it time to call in the sparky!?

Thanks

 

[flameport]

Replacing the MCB is easy enough, but before that, it is essential that the circuit and supply are tested to ensure they are suitable for a type C.

Explanation here: http://www.tlc-direct.co.uk/Book/5.3.4.htm

 

[ban-all-sheds]

Running 5 Osram 50W 12v halogens.

250W for a kitchen?

Is that because it's a very large kitchen, or because the lights don't do a good job of lighting it up?

 

[Taylortwocities]

Does he need permission from the DNO for a load that big?

 

[eveares]

Replacing the 6A mcb for a type C type is OK ONLY if the Zs for the circuit is no higher than 3.06 Ohms.

Remember that: Zs = Ze + (R1 + R2)

Also to measure Zs you will either need:

1) A earth loop impedance tester capable of performing a ( A low current test if the circuit is protected by RCD/RCBO) test between the Line and Earth conductors at the furthest point on the lighting circuit.

OR

2) A earth loop impedance tester capable of measuring Ze AND a low ohm resistance meter capable of measuring R1+ R2 at the consumer unit (with Line and Earth joined together at the furthest point of the lighting circuit) where you then will at the R1/R2 reading onto your Ze reading to give you Zs

Measuring Ze: https://www.youtube.com/watch?v=PUTn3t65na4

In reality, unless you have the equipment and the required knowledge, it may be easier getting an electrician in to give you the Zs of the lighting circuit and possibly sort your issue out for you.

250W for a kitchen?

Is that because it's a very large kitchen, or because the lights don't do a good job of lighting it up?

Well at least it is not like my kitchen with 975w of lighting, soon to change though!

 

[ban-all-sheds]

I don't think I've got 975W in my entire house.

 

[eveares]

I don't think I've got 975W in my entire house.

I have a total of 2.3KW of lighting my house.

 

[ban-all-sheds]

You're barking mad.

It it because you like to walk around wearing welding goggles, or because you've decided to have lights which are so pigging useless at actually lighting up rooms that you need vast swathes of them to overcome their dreadful shortcomings?

 

[JohnW2]

Recently installed a Low Voltage wire track lighting system in the kitchen which uses a ceiling mounted Arte 300 watt 12v toroidal transformer. Running 5 Osram 50W 12v halogens. The hager 6A Type B, MCB trips frequently (not every time) so I guess it is simply a in surge current issue and changing to a Type C will be OK.
you think this is the culprit?

No-one seems to have answered the OP's question. What do people think - is it credible that the switch-on current of a 300W transformer would cause a B6 MCB to operate (presumably 'almost immediately')?

Kind Regards, John

 

[Taylortwocities]

The OP said

The hager 6A Type B, MCB trips frequently (not every time)

I have seen this before and the likelihood of it tripping when the track is switched on will also depend on how many other lights on that circuit are also energised at the same time.

So, MCB doesnt trip if there are no other lights on, switch on a few of those 50w halogens and thethreshold for the MCB changes so the surge will trip it.

 

[JohnW2]

The OP said

The hager 6A Type B, MCB trips frequently (not every time)

I have seen this before and the likelihood of it tripping when the track is switched on will also depend on how many other lights on that circuit are also energised at the same time. ... So, MCB doesnt trip if there are no other lights on, switch on a few of those 50w halogens and thethreshold for the MCB changes so the surge will trip it.

Yes, that's true. I was thinking of the transformer and 5x50Ws in isolation. Having said that, if we are talking about 'almost immediate' (on switching on) trips, even if the circuit were almost fully loaded up to 6A, it would still take a fairly substantial switch-on current to cause such a trip.

Owlsroost: Have you noticed whether the MCB trips if there are few, or no, other lights on the same circuit switched on?

Kind Regards, John

 

[eveares]

You're barking mad.

It's even wore than what I first thought, my wattage breakdown below!

Kitchen: 975w
Living room: 240w
Porch light: 60w
Loft light: 180w
My Bedroom 250w + ceiling fan motor
My Bedroom on-suite: 50w
Main bathroom: 200w
Downstairs hallway: 80w
Upstairs hallway: 20w
Front Bedroom: 120w
Spare bedroom: 160w
Mums bedroom: 160w
Mums on-suite: 150w
Mums dressing room: 100w

Total: 2.745Kw

 

[plugwash]

Whether or not it trips is also likely to depend on where in the cycle the AC waveform is at the point of switch on which for a manually triggered switch is effectively random.

As I understand it switching on at certain points (zero crossing being the worst) in the AC cycle can cause saturation of the transformer core which leads to a large current surge.

 

[JohnW2]

Whether or not it trips is also likely to depend on where in the cycle the AC waveform is at the point of switch on which for a manually triggered switch is effectively random. ... As I understand it switching on at certain points (zero crossing being the worst) in the AC cycle can cause saturation of the transformer core which leads to a large current surge.

That all makes sense, but I'm not sure it is necessarily enough to explain what is being experienced.

Maybe I'm wrong in my assumption that we are talking about 'almost immediate' trips (say, within 10 seconds). If we were, and even if the circuit were already loaded right up to 6A, we would probably be talking of a switch-on current which was something like 30 times the normal running current due to the lamps (or the rating of the transformer) - which I wouldn't really have expected, even with switching at the most unfavourable part of the cycle. However, maybe my intuition is totally wrong!

It is, of course, possible that the B6 has become 'trigger happy'.

Kind Regards, John