triplethreat
Solar Enthusiast
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And there ya go ^^^^^^
How to wire a DC breaker?
- Thread starter pda1
- Start date
Uh oh.
Now, take a look at Will's page that I was trying to model my system after. Take a look at the 50 Amp breaker. Looks like I had the wrong idea....but correct if I'm wrong....please.
Take a look here-
Breaker
acdoctor
Solar Enthusiast
If that is your intention is to use it between solar charge controller and battery buss that is single direction current and the breaker in the original post will work.
Pierre
Somewhere down South
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I agree that conventional wisdom has it that the source comes in at the top and load out at the bottom. Sometimes for convenience / practical purposes it is easier the other way round. In my case the battery bank is located lower than the inverter and to create a neater and and shorter wire run layout , I fed the battery in at the bottom and inverter at the top
— nice straight runs.
So far nothing has burnt up or malfunctioned , yet. The CB also acts as an isolator when working on the system.
Therefor my original post begs for more comments.
— nice straight runs.
So far nothing has burnt up or malfunctioned , yet. The CB also acts as an isolator when working on the system.
Therefor my original post begs for more comments.
Most dc circuit breakers are directional. I'm sure there are some that are not directional. Looking at the one referenced in the OP, I would wire that directionally. I am not sure about the one shown in Will's old plan. The source, battery, must feed the, as in photo, the top terminals labeled positive and negative. I would not use that on a charging circuit, but if used the battery must connect to the top terminals. I would test to see if charging current flowed reverse through the breaker. Circuit protection is meant to protect wires from the large power surge available from a battery in case of short circuiting. The charger doesn't have the surplus power as in a battery. Just Use a Fuse.
If the breaker is for this location then it makes no sense whatsoever to use a two-pole breaker. You only need a breaker on the positive wire.
Also keep in mind that the charge controller will also draw some current from the battery to keep itself powered when there is no power from the solar panels. So it's not really a single direction either.
The breaker shown in the OP doesn't give you a choice. It's a polarized breaker. You must not wire it wrong or it becomes dangerous. It's FAR less convenient to burn down your house/trailer/RV/whatever than it is to correctly wire a polarized breaker.
The breaker you linked in your original post is not at all the correct breaker to use. You want one of these (Blue Sea Systems 285 series):
Blue Sea 7183 50 Amp Circuit Breaker Surface Mount 285 Series: Amazon.com: Tools & Home Improvement
Blue Sea 7183 50 Amp Circuit Breaker Surface Mount 285 Series: Amazon.com: Tools & Home Improvement
www.amazon.com
Hedges
I See Electromagnetic Fields!
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If a circuit breaker is used between scc and battery, it normally carries current from PV panels to scc to battery.
In the event of a short circuit in wiring or scc, battery dumps massive current into that, and breaker has to interrupt the current. So a polarize breaker maybe should be wired "backwards", with its "+" terminal connected to battery "+"?
If scc FETs fail shorted, PV array Voc gets applied to battery and current flows. If breaker is opened under those conditions, it has to interrupt current (about Imp) flowing from PV panel to scc to battery. With polarized breaker connected "backwards" for short-circuit protection, it is now trying to interrupt current flowing the wrong direction. It may arc and not interrupt. Voltage across breaker will be up to (Voc - Vbat), which could be fairly high depending on PV string configuration.
Best to use a non-polarized breaker for SCC. And to use polarized breakers only for loads.
Hedges
I See Electromagnetic Fields!
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Although I don't see the word "polarized", the picture shows one terminal labeled "BAT" and the other "AUX"
So I question whether these are entirely appropriate for any bidirectional application, including scc to battery (which is bidirectional in case of a fault).
They probably work without failure under most conditions. When first closed, scc isn't producing any current. If opened during scc normal operation, voltage output from scc close to Vbat, not much to interrupt. How high does SCC output kick? It has an inductor, but any output capacitors would snub voltage. Total energy stored in inductor fairly small, limits tie of current flow.
Probably only if scc FET switch fails shorted, so high Voc input from PV array to be interrupted, could exceed what this breaker can handle in reverse direction. Note that (Voc - Vbat) likely exceed rating of breaker even in forward direction. (rated 48V, much less than the one shown by OP, so only good for 24V or 36V battery circuit.)
"Do not use as a switch where high inrush currents are expected" so probably smaller caps in scc are OK, larger caps in inverter might burn contacts.
285-Series Circuit Breaker - Surface Mount 50A - Blue Sea Systems
Thermal circuit breakers provides medium duty circuit protection for 25 to 150 Amp loads when switching and circuit protection are both required.
www.bluesea.com
Except that the Blue Seas breaker is only rated to 48v and the original one posted by the OP is rated to 1000v.
Blue Seas should be great for a 12 or 24v system.
The OP referenced Will's 24V schematic so there doesn't seem to be a need for a breaker over 48V.
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I have the actual Bussman branded version of this breaker between my SCC and battery. I talked with the very reputable vendor I purchased it from and they stated they have done tests and have found no issues wiring the breaker in either orientation. We did verify that the "BAT" and "AUX" would be clearer if labeled "SOURCE" and "LOAD" respectively. This means that when used between the SCC and battery, the "BAT" terminal should technically be connected to the SCC since it is normally the source and the "AUX" terminal goes to the battery since it is normally the load.
Besides protecting the wire, I also use the breaker as a disconnect if I ever need to isolate the SCC from the rest of the system. I first open my PV disconnect breaker and then I open this SCC breaker. I've only done this twice since my system was initially wired up.
Yeah, I'm using a fuse for my inverter combined with one of the big red Blue Sea master switches and a precharge resistor.
I'm with @rmaddy on his recommendation of the Blue Sea 285 series. That's what I'm using on the output side of my solar charge controller.
I do use a dual pole circuit breaker between the PV and the solar charge controller.
The ad for the breaker in the original post is a bit wishy washy.
So is it polarized or not? It seems like the above is saying to wire the positive cable to the + breaker, just to follow the documented value on the breaker.
If the breaker explicitly says that it is "Polarized" then you need to be very careful with how you wire it up. If this is at all confusing, consider buying breakers that are listed as "Non-Polarized". Midnite Solar sells both types and they're good at calling out which type of breaker it is.
I do use a dual pole circuit breaker between the PV and the solar charge controller.
The ad for the breaker in the original post is a bit wishy washy.
So is it polarized or not? It seems like the above is saying to wire the positive cable to the + breaker, just to follow the documented value on the breaker.
If the breaker explicitly says that it is "Polarized" then you need to be very careful with how you wire it up. If this is at all confusing, consider buying breakers that are listed as "Non-Polarized". Midnite Solar sells both types and they're good at calling out which type of breaker it is.
I would love a link to one of Midnite Solar's non-polarized PV breakers. They are shown on their breaker poster but I can't find them anywhere. I can only find their polarized PV breakers on their site.
I've been on that page many times. There are no non-polarized PV breakers listed.
Ah, I see now that you're looking specifically for PV breakers. A polarized PV breaker shouldn't be a big deal for that. If power flows back towards the PV from the solar charge controller then something is really wrong.
Hedges
I See Electromagnetic Fields!
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If power flows back toward one string of PV from the other strings of PV, that's just a bit wrong. Like a short, or failed bypass diodes.
I say the breaker needs to interrupt the current in that direction.
If all the breakers are ganged together (metal rod inserted through holes in handles), the one getting excess current in reverse direction trips, and it turns off the others which stop the current flow.
I wasn't looking at it from the perspective of a breaker between parallel strings. I have my small PV system blinders on and didn't think beyond my simple series string.
