A 50A MCB suitable for DC...?

[MtB]

I'm just pressing my recently purchased Sunshine 600w inverter into service powering my new cheapo 230Vac fridge. It works ok but the two 35A fuses (presumably in parallel) in the inverter don't protect the fixed wiring so I'm thinking an MCB would be a good idea for that circuit. How do I specify/find MCBs suitable for DC? Results from Googling for such a thing are overwhelmed with AC MCBs.

 

The existing fridge circuit has cables plenty fat enough (16mm2, looks like) but are let down by high resistance in the 20 year old rather flimsy "switch and circuit breaker" panel dropping the start-up surge voltage to 10.4v, so to test the inverter and fridge together I've bypassed it on the fridge circuit. So now I need to install a more robust circuit protection. IS a DIN rail DC MCB a Good Idea or is there something better to use? 

 

Thanks...

[Eeyore]

Something like https://www.solar-wind.co.uk/off-grid-power-electrical-accessories/12v-24v-48v-dc-rated-mcbs-circuit-breakers-enclosures/jtec-single-pole-mcb-circuit-breaker-6a-to-63a-10ka#/38-mcb_value-50_a  mounted in a single module din enclosure.

[Chewbacka]

Circuit breakers are good for quick resetting or isolating a circuit.

For circuits that don’t suffer nuisance trips then I prefer a simple fuse. 
something like this midi fuse

https://www.ebay.co.uk/itm/132373294247

 

 

 

 

[Tracy D'arth]

Schneider ( ne Merlin Gerin ) MCBs are considered suitable for DC, used extensively in 'phone exchanges.

[cuthound]

2 minutes ago, Chewbacka said:

Circuit breakers are good for quick resetting or isolating a circuit.

For circuits that don’t suffer nuisance trips then I prefer a simple fuse. 
something like this midi fuse

https://www.ebay.co.uk/itm/132373294247

 

 

 

 

 

Fuses typically provide closer protection (twice fuse rating before blowing) than miniature circuit breakers (3-5 times rating before tripping).

 

However they do age and can fail without  warning, but there again mcb's often suffer nuisance tripping.

[cuthound]

4 minutes ago, Tracy D'arth said:

Schneider ( ne Merlin Gerin ) MCBs are considered suitable for DC, used extensively in 'phone exchanges.

 

Schneider make single and double pole circuit breakers specifically for DC as well.

 

https://www.se.com/ww/en/product/A9N61518/miniature-circuit-breaker-c60h-1-pole-50-a-c-curve/

 

https://www.se.com/ww/en/product/A9N61538/miniature-circuit-breaker-c60h-2-poles-50-a-c-curve/

[ditchcrawler]

Keep away from these things

[MtB]

On 04/09/2022 at 13:46, Eeyore said:

Something like https://www.solar-wind.co.uk/off-grid-power-electrical-accessories/12v-24v-48v-dc-rated-mcbs-circuit-breakers-enclosures/jtec-single-pole-mcb-circuit-breaker-6a-to-63a-10ka#/38-mcb_value-50_a  mounted in a single module din enclosure.

 

 

Hmmm thanks for the link but proving difficult to buy. They 'may' have any in stock according to the web page and no reply (yet) to my enquiry.

 

 

 

On 04/09/2022 at 13:57, cuthound said:

 

Schneider make single and double pole circuit breakers specifically for DC as well.

 

https://www.se.com/ww/en/product/A9N61518/miniature-circuit-breaker-c60h-1-pole-50-a-c-curve/

 

https://www.se.com/ww/en/product/A9N61538/miniature-circuit-breaker-c60h-2-poles-50-a-c-curve/

 

 

Thanks for links but again, no-one has any in stock that I can find from Goggling. 

 

Do you know of a UK stockist perhaps? 

 

I've been Goggling the part number for the 63A version.... A9N61519

[David Mack]

For my solar install I used a Tomzn mcb. These used to be supplied by Bimble. Something like this.

 https://www.ebay.co.uk/itm/194165174128

 

[rusty69]

Just now, David Mack said:

For my solar install I used a Tomzn mcb. These used to be supplied by Bimble. Something like this.

 https://www.ebay.co.uk/itm/194165174128

 

 

 

I got some like that , purchased on e bay. They replaced the schneider AC ones I previously had

[MtB]

12 minutes ago, David Mack said:

For my solar install I used a Tomzn mcb. These used to be supplied by Bimble. Something like this.

 https://www.ebay.co.uk/itm/194165174128

 

 

 

Brilliant, thanks. Just ordered one.

 

Worryingly cheap though, at six quid-ish! 

 

 

[cuthound]

1 hour ago, MtB said:

 

 

Hmmm thanks for the link but proving difficult to buy. They 'may' have any in stock according to the web page and no reply (yet) to my enquiry.

 

 

 

 

 

Thanks for links but again, no-one has any in stock that I can find from Goggling. 

 

Do you know of a UK stockist perhaps? 

 

I've been Goggling the part number for the 63A version.... A9N61519

 

Sorry, I have used them in the past but they were supposed to me by sub-contractors.

 

Perhaps try RS Components?

[George and Dragon]

6 hours ago, MtB said:

Hmmm thanks for the link but proving difficult to buy. They 'may' have any in stock according to the web page and no reply (yet) to my enquiry.

Thanks for links but again, no-one has any in stock that I can find from Goggling. 

 

Do you know of a UK stockist perhaps? 

 

I've been Goggling the part number for the 63A version.... A9N61519

Farnell. https://uk.farnell.com/w/c/circuit-protection/circuit-breakers/thermal-magnetic-circuit-breakers?st=mcb&cb=700000006151%2C700000006272&ost=mcb

[matty40s]

The main problems occuring in using AC switches for DC applications only happen when the switches are used a lot. For something that is permanently on such as a fridge, the burn out will not happen.

[Tracy D'arth]

On my present boat the between battery bank switch is a 70A Merlin Gerin AC MCB Just so that I have a means of livening up the engine battery if needs be.

It gets switched on when I am on a shore line so that the battery charger charges the engine battery too. I never bother switching it off when I start so it trips out with the starter current. Its been like this for donkeys years and never burnt out or failed.

Edited September 6, 2022 by Tracy D'arth

[ditchcrawler]

4 hours ago, Tracy D'arth said:

On my present boat the between battery bank switch is a 70A Merlin Gerin AC MCB Just so that I have a means of livening up the engine battery if needs be.

It gets switched on when I am on a shore line so that the battery charger charges the engine battery too. I never bother switching it off when I start so it trips out with the starter current. Its been like this for donkeys years and never burnt out or failed.

Theory v Practical experience

[matty40s]

I have seen quite a few Aqualines develop problems with their amazingly tidy and over complicated electrical systems due to their reliance on a massive and impressive looking AC breaker system for all the electrics. 

Lots of regularly switching light/shower/bilge switches, under gunnel LED lighting and other stuff leads to these AC breakers either failing, or leading to failures in other parts of the electrical system such as the not now available dual isolator panels.

[GUMPY]

In my world I keep it simple:

AC = MCBs

DC = Fuses

 

 

Having said that the Wylex fuse boxes and rewirable fuses are getting harder to source.