Never seen one of these before, under what circumstances would this need to be used in a H and V panel
K type mcb
- Thread starter 333rocky333
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Interesting so old type 1 now type Z and type K simular to type D but tighter range so less loop impedance required.
Never seen one, one it seems is always learning thank you both.
Never seen one, one it seems is always learning thank you both.
The drawings were a bit vague, but seemed to be doing some of the control circuit within a panel, its gone off twice recently and there was reports of slight fluctuations on the supply at the same time it went off causing the lights to momentary flicker.
It causes a lot of grief when it goes off resulting in todays xmas day call out.
At first i thought some sort of anti surge device, but it does seem to be a 2 amp mcb listed on the ABB site.
Just intriqued by the choice, wonder if it does transformers in the panel as the BMS display goes off with it.
Sunray I believe builds panels wonder if he will know
It causes a lot of grief when it goes off resulting in todays xmas day call out.
At first i thought some sort of anti surge device, but it does seem to be a 2 amp mcb listed on the ABB site.
Just intriqued by the choice, wonder if it does transformers in the panel as the BMS display goes off with it.
Sunray I believe builds panels wonder if he will know
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Or an integral switch mode power supply in an intergrated BMS display. Had an issue last christmas where a 63A feed to a BMS panel had tripped, someone has reset it but one of two controllers on the front of the panel was off, opened the panel and there were two tripped breakers, a C2 (found to be the controller that was off) and a C16 (found to be one of the immersion heaters in a DHW tank), what had happened was the element had failed, and due to lack of discrimination between MCBs also tripped the supply to the panel, once this got reset the C2 on the controller had tripped due to inrush (which it seemed to do at least 50% of the time after power being restored). This was a panel with an interlcoked isolator and there were two of these displays, it took a good few goes of reseting the breaker in order to shut it up and have both stay on!. I Imagine the K type is a little bit more forgiving of this, but it was felt that a D type would be overkill
As Eric summised it's a little less forgiving than type D, I tend to look on them as between types C & D although in reality they sit within the D curve.
The inrush on panel transformers is high, especially if the secondary is loaded. For transformers I will normally install a:
25VA C2
50/75VA C4 or D2
75/100VA C6 or D4 however up to D8 or even D10 if the load consists of lots of half wave rectified electronic devices like 4DIX/2RM modules.
400VA D16 or D20 despite the 'on load' current <2A
Sadly the Primary MCB [as I've been describing] quite often ends up being the same size or bigger than the 24V secondary MCB.
IME the type K is usually 'special order' and therefore tends to be more expensive. Only one of the companies I have worked for hold them as a stock item but TBH the workshop foreman [and generally the only person working in the workshop] seems to favour them and they often have to be changed in the field. He is a bit of an idiot and has some crazy ideas and practices as an example he insists a 100VA transformer only need a K1 where MI's show the inrush far far exceeding a D2. The workshop 1500VA 110V transformer has a C6 in the dist board and he insists it's the correct device despite having to climb a ladder everytime it gets powered to keep resetting it.
The inrush on panel transformers is high, especially if the secondary is loaded. For transformers I will normally install a:
25VA C2
50/75VA C4 or D2
75/100VA C6 or D4 however up to D8 or even D10 if the load consists of lots of half wave rectified electronic devices like 4DIX/2RM modules.
400VA D16 or D20 despite the 'on load' current <2A
Sadly the Primary MCB [as I've been describing] quite often ends up being the same size or bigger than the 24V secondary MCB.
IME the type K is usually 'special order' and therefore tends to be more expensive. Only one of the companies I have worked for hold them as a stock item but TBH the workshop foreman [and generally the only person working in the workshop] seems to favour them and they often have to be changed in the field. He is a bit of an idiot and has some crazy ideas and practices as an example he insists a 100VA transformer only need a K1 where MI's show the inrush far far exceeding a D2. The workshop 1500VA 110V transformer has a C6 in the dist board and he insists it's the correct device despite having to climb a ladder everytime it gets powered to keep resetting it.
I think this was caused by a momentary supply power outage, according to the security, I too wondered too how im gonna shut the door, but luckily it stayed on and the display stayed lit.
600 resident student accommodation apparently had no heating or Hot water
Thanks sunray, hopefully there maintenance and the HV contracters have the sence to sort it out, though according to the manager, they said they would after it happened last time.
I am not too hot with trip curves too be honest, i understand Efli, i hope, but why do they use such low amp breakers, if the Efli would allow for something bigger in the first place, is it to try to protect the electronics.
Appreciate the advice.
Possibly, but electronics tend to die in microseconds/milliseconds, so I somewhat doubt that any LV OPD, no matter how low their rating, would 'save' the electronics.
Don't forget about the chicken and eggs - it is probably the 'dying' of the electronics that usually causes high currents which may trip and OPD, not the other way around. If/when that happens, the tripping is obviously 'too late' to achieve anything.
Kind Regards, John
I recall you saying similar in the past, though I cannot fathom out, why Mcb something as low as 2 amp, when surely they can use higher ratings or something more foolproof.
I recall most panels back in the day would have HRC fuses when i opened them up.
We have similar issues with Dataracks and Tills tripping Mcbs, for some reason they put the socket circuits on C16 mcbs, whenever they restart after power loss, they often trip, sometimes losing tens of thousands of pounds in trading.
I cannot answer that question and my comment did not attempt to, but ...
As I implied. I doubt that any over-current protection would be useful, let alone 'foolproof', in terms of protecting the electronics, no matter how low the rating of the \OPD - since, as I said, it's usually the electronics dying which causes 'excessive' (even if fairly modest) currents to flow (i.e. 'high current means already too late to do any 'protecting').
Kind Regards, John
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