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Johny London

DC circuit breakers

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Wanting to upgrade my solar connections now that I have a few panels and couple controllers or so, adding breakers would be good and I saw a few options, the neatest of which would appear to be consumer unit style ones https://www.ebay.co.uk/itm/63A-DC-Circuit-Breaker-MCB-Solar-Fuse-125v-Single-Pole-1P-Ebike-TOB1Z-63-C63/271990741484?epid=2098495247&hash=item3f53e959ec:g:URUAAOSw3YNXYTfc with a little consumer unit say: https://www.ebay.co.uk/itm/weatherproof-consumer-unit-modular-enclosure-RCD-MCB-contactor-switch-IP65-box/112896821422?hash=item1a492cc8ae:m:mrh8pMhkNMZE25CiEMGti_Q as I wouldn't necessarily need to include the master double pole switch, just four breakers. Or could get an eight way and include master.

Is there a better way to do this? I see a lot of chinese looking stuff that I want to avoid!

 

could maybe wire it so that breakers are between panels and mppt controllers and then the combined outputs go through the master switch?

Edited by Johny London

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Most AC domestic breakers, MCBs, are not advised for DC use. They have not the engineering to cope with the sustained arc on break that occurs with DC.

Schneider, was Merlin Gerin, are used on DC supplies in telephone exchanges etc. and are used on my boats. They have been good for over 20 years.

 

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Yeh I know about the different requirements for DC breakers, the one I linked to is for DC, the consumer unit is just bog standard. Not sure about compatibility though. I'll take a look at the Merlin Gerins.

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48 minutes ago, Johny London said:

could maybe wire it so that breakers are between panels and mppt controllers and then the combined outputs go through the master switch?

Yes. Those breakers appear fine up to 125V D.C. so will have no problem handling your panel outputs. Where you might have difficulty if you then wanted to wire the controller outputs through a breaker is getting more than a single cable into that ‘master’ switch. It would be a neat solution if it’s possible. Don’t forget to use ferrules on the cable ends. 

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25 minutes ago, Boater Sam said:

Most AC domestic breakers, MCBs, are not advised for DC use. They have not the engineering to cope with the sustained arc on break that occurs with DC.

Schneider, was Merlin Gerin, are used on DC supplies in telephone exchanges etc. and are used on my boats. They have been good for over 20 years.

 

 

Unless the practice has changed recently, BT use fuses rather than breakers to protect DC circuits in their exchanges, because they provide much quicker protection.

 

Fuses also provide much better discrimination, rupturing at twice the rated current rather than the 3-5 times rated current that MCB's open at. 

 

 

Edited by cuthound
To unmangle the effects of autocorrect.

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6 minutes ago, cuthound said:

 

Unless the practice has changed recently, BT use fuses rather than breakers to protect DC circuits in their exchanges, because they provide much quicker protection.

 

Fuses also provide much better discrimination, rupturing at twice the rated current rather than the 3-5 times rated current that MCB's open at. 

 

 

My experience is with modern exchanges and switching centers, Cable & Wireless ( Mercury ) We installed thousands of M-G MCBs, replacing fuses in new disboards often.

They always specified rotary switches too, better arc gaps.

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24 minutes ago, Boater Sam said:

My experience is with modern exchanges and switching centers, Cable & Wireless ( Mercury ) We installed thousands of M-G MCBs, replacing fuses in new disboards often.

They always specified rotary switches too, better arc gaps.

 

Modern exchanges are VOIP (voice over internet protocol).

But I thought you knew that already ?

 

https://availability.samknows.com/broadband/exchanges/21cn_overview

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I have been using those in your first link for a couple of years. I also have some Merlin Gerin ones as BoaterSam suggests as I  read they were good for DC applications. 

 

ETA. Mine are fitted in a couple of garage consumer units. 

Edited by rusty69

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Great - sounds like this could be the way forward for me. I'm uncertain about compatibility of different manufacturers breakers/consumer units. From my limited dealings think different breakers are physically different?

63a is perfect, a bit more than I get off any one array and I want a breaker on each array.

The purpose is two fold - one to give me a good place to bring all the connections together, two to allow me to isolate the panels if/when I'm mucking around.

So I would have each array connected into it's own breaker. the breaker outs to each controller (one per array) then controller outs commoned back to the master switch, then off to the batts. If the busing in the consumer unit allows things oeseparately hooked up - again I cant remember - seem to think there is common live rail but it can be split up?

 

Ps: Been meaning to get into using ferrules, what do I need to get started?

Edited by Johny London

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15 minutes ago, peterboat said:

Or in my case solder ? I did because I knew that aroundtuit would never happen so figured that solder would work as well

 

Theoretically soldering can lead to broken wires, particularly if they are subject to vibration, because the transition from flexible to solid cabling is very sudden. 

 

The crimp s designed to support the cables to minimise the chance of this happening.

 

That said 20 years ago soldering was a pretty common practice.

  • Greenie 1

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2 minutes ago, cuthound said:

 

Theoretically soldering can lead to broken wires, particularly if they are subject to vibration, because the transition from flexible to solid cabling is very sudden. 

 

The crimp s designed to support the cables to minimise the chance of this happening.

 

That said 20 years ago soldering was a pretty common practice.

No vibration on my boat as its a super smooth electric motor, I did talk to the panel builders opposite to the garage and they said it would be ok and again they said they did it in the olden days?

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3 minutes ago, cuthound said:

 

Theoretically soldering can lead to broken wires, particularly if they are subject to vibration, because the transition from flexible to solid cabling is very sudden. 

It'll be fine ... it's not like @peterboat has any unusually high powered electrical systems on his boats! :icecream:

  • Haha 1

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6 hours ago, Boater Sam said:

Most AC domestic breakers, MCBs, are not advised for DC use. They have not the engineering to cope with the sustained arc on break that occurs with DC.

Schneider, was Merlin Gerin, are used on DC supplies in telephone exchanges etc. and are used on my boats. They have been good for over 20 years.

 

Hager in mine. They are certified for 12V dc too.

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11 hours ago, Richard10002 said:

BEAMA Guide to Low Voltage Circuit-breakers Standards in accordance with BS EN 60898-1, BS EN 60898-2 and BS EN 60947-2: 

 

That points to a pdf on your C drive. I don’t have access to your pc ;)

Edited by NB Lola

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