DIN Mount Mini Circuit Breakers?

[skidmark]

Hello all -

Anyone using DIN-rail mount mini circuit breakers in their control box? "Search" didn't want to turn up any results ...

What are your thoughts on using the "B" versus "C" curve breakers? What amp rating are you using for a 4500W element? For your pumps? Are you using fuses for the electronics?

Thanks for your thoughts!

 

[BrunDog]

Electric Brewing Supply has them and many here buy them.

-BD

 

[skidmark]

Electric Brewing Supply has them and many here buy them.

-BD

I talked to the folks from EBS at NHC2015 about their C curve breakers. They said that they sell them because, "that's what we can get from our suppliers", which doesn't really answer my question.

 

[MerlinWerks]

I use the D curve supplementary breakers from Automation Direct with success. Not sure if these are "mini" breakers though...

FWIW they have B and C curve available as well.

 

[BrunDog]

Oh... Sorry, thought I answered your first question.

-BD

 

[skidmark]

I use the D curve supplementary breakers from Automation Direct with success. Not sure if these are "mini" breakers though...

FWIW they have B and C curve available as well.

What drove you to the D curve, rather than the others?

 

[skidmark]

Oh... Sorry, thought I answered your first question.

-BD

Thanks, I can see where it was a little ambiguous. There are plenty of sources, but EBS sells Cs, Auber sells Bs, etc. I am trying to understand some of the selection criteria used to choose one for the application.

 

[nhamilto40]

http://www.studyelectrical.com/2014...breakers-mcb-types-characteristic-curves.html

 

[MerlinWerks]

What drove you to the D curve, rather than the others?

It was recommended in a thread on here, but I've also read that B curve should be sufficient for a typical home brewery HERE. To be honest, even though I generally do my research to understand the why behind certain choices, as you are doing now, this was one subject where I did not.

 

[ajdelange]

You obviously want the breaker that responds most quickly to a fault but that does not trip on inrush current. The B and C breakers are for motor starting situations or fluorescent lighting loads where hefty starting current persists for a fairly long time. With a purely resistive load like a heater there may or may not be much inrush current depending on how hot the element gets. I an incandescent light bulb the cold resistance can be less that 0.1 times the hot resistance and inrush current can thus be 10 or more times load current but the inrush current duration is much less than a second. By contrast the ratio in something like a hair blow drier is much less - not even detectable because of the presence of the motor. I expect the water heater elements are similar. They do not glow incandescent nor even dull red if operated properly. Thus inrush current can be small. It's easy enough to determine what it is by measuring the impedance with an ohm meter when disconnected. The inrush current will be 220 (or 240 or whatever you have with the heater off) divided by the ohm reading. The load current is best measured with a true rms ammeter but if that's not available calculate the operating resistance by dividing the rated voltage squared by the rated power and then divide the voltage measured at the heater terminals when it is on by the operating resistance to get an estimate of the operating current. Based on the inrush current as compared to the breaker rated current you can choose the trip curve based on published graphs of those curves.

 

[podz]

Hello all -

Anyone using DIN-rail mount mini circuit breakers in their control box? "Search" didn't want to turn up any results ...

What are your thoughts on using the "B" versus "C" curve breakers?

My entire house (about 45 circuits altogether) is running on DIN-rail mounted C-curve mini circuit breakers. Even the 3-phase circuit in my garage for brewing.

Why don't I use B-curve breakers? Because they cost 3 times as much as the C-curve breakers.

 

[sandyeggoxj]

I bought 30-amp eaton c-curve breakers from AD. I had the 25 amp EBS breakers and they started failing. So I swapped them all out. I use a 15-amp c-curve on my 115vac circuit. That way I can drop wire size for those things and run 14-gauge wire post breaker. For 4500w elements I would use 25-amp breakers. That puts your total load on the breaker just under 80%. Good place to be.

 

[podz]

I bought 30-amp eaton c-curve breakers from AD. I had the 25 amp EBS breakers and they started failing. So I swapped them all out. I use a 15-amp c-curve on my 115vac circuit. That way I can drop wire size for those things and run 14-gauge wire post breaker. For 4500w elements I would use 25-amp breakers. That puts your total load on the breaker just under 80%. Good place to be.

What do you mean started failing? I've been using MCBs since like 1992 and have only had one failure ever (it simply refused to keep the circuit closed anymore). The things are normally in use for years and years without ever flipping once.

 

[sandyeggoxj]

Same as you. Refused to stay closed. Kept tripping. No faults downstream. Only an instact heating element.

 

[podz]

Same as you. Refused to stay closed. Kept tripping. No faults downstream. Only an instact heating element.

That's one breaker. You said "they" started failing. Was it the case that only one of them failed and you just decided to replace them all, or did multiple breakers start failing at the same period of time?

 

[skidmark]

You obviously want the breaker that responds most quickly to a fault but that does not trip on inrush current. The B and C breakers are for motor starting situations or fluorescent lighting loads where hefty starting current persists for a fairly long time. With a purely resistive load like a heater there may or may not be much inrush current depending on how hot the element gets. ... /QUOTE]


Pardon me, AJ, but aren't the C and D curve breakers the ones with the extra "headroom" for high inrush currents? If I am reading the curves correctly from nhamiltons' link (Thanks - I had read that article before, which led to my questions in the first place ...), the B breakers would have the greatest limit on the energy allowed through - and the best candidate for the heater elements- while Cs might be better for the spiked inductive load of the pump motors.

That's why I was wondering whether I had missed something.

 

[ajdelange]

B, C and D are, according to the article referenced earlier in this thread, designed to withstand (if briefly) over currents of, respectively, 3-5, 5-10 and 10-20 times rating. Thus the higher the inrush current (the more difficult it is to start the load) the higher letter is selected. I could have worded it more clearly, I agree.