Author Topic: Xantrex DC disconnect/Overcurrent Module breakers with Classic MPPT controller??  (Read 557 times)

showme

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I've got a Xantrex dual SW5548 system I'm setting up, and I'm wondering about the compatibility of the existing breaker/disconnects with MS Classic 150's. This set up will include the Xantrex DC disconnect and it's 250 main battery/inverter disconnect, and also what looks like CD60DC switch for the array disconnect switch. This system previously used a single Xantrex C40 PWM and I'm just wondering if these switches will work with my dual inverter set up that will be 8kw of panels, brought in through two arrays (4k each) into (2) Classic 150's which will be run through individual SW5548's. I'm going to need two of each since the system I bought used was a single inverter and array system. (I have two new old stock, in box, SW5548's that I'll use, and two new classic 150's along with the 8kw LG's and MS combiner boxes). The used SW5548 will be back up, the 3 C40's will be stored or sold. The T240 Autotransformer will get new breakers, too. And the Xantrex AC Disconnect has just gotten two 'new' (good used) disconnect breakers from Littleharbor2 (thanks, Mike!), but since this and the T240 are on the outgoing side of the inverter and charge controller, this isn't part of the question.

I'm wiring the first array right now, with the other one being erected and wired once the shed for the power wall is built. It occurred to me that since the mppt's will handle a much higher voltage, do I need to upgrade the breakers handling what is being fed through the classics? I'm using LG Neon 320w panels in (4) series of (3) panels on each array. I've been advised that the 150's should be fine with this configuration. But what about the disconnect amperage? 

 My question here is, can anybody tell me if the breakers that were used in the original format that originally worked fine with the C40's will work with the Classics, or do I need to reassess these disconnect switch sizes before firing it up? Thanks for any comments and experience on this. Lee

« Last Edit: February 18, 2022, 04:53:22 PM by showme »

ClassicCrazy

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You need to know what the current draw will be on your system .
That will give you the wire size you need also considering any voltage drops for distance.
There are voltage drop calculators online.
The higher you go in voltage the lower the amps are going to be compared to a lower voltage .
Your existing breakers should have the ratings on them somewhere. If the voltage is in specs with what you want to use you should be okay.  You size the breakers for the maximum current capacity of the wires you are using.  You can go with a smaller amp  breaker  than max on a higher rated capacity wire if it will fit in the breaker.
So for example in household wiring commonly use 15 amp breakers on 14 gauge wire  and 20 amp breakers on 12 gauge wire.
You could use a 15 amp breaker on 12 gauge wire because the max current rating for 12 gauge is 20 amps and you can put on a smaller breaker.
Use the Midnite Solar String calculator for your PV and what the Classic can handle.
https://www.midnitesolar.com/sizingTool/
You will need a combiner box with breakers for your PV arrays before you get into  your other boxes inside where the main PV input breaker will be .
Larry
« Last Edit: February 17, 2022, 08:09:41 PM by ClassicCrazy »
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , Jakiper 48v LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batteries

showme

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Thanks, Larry. I've got MS6 combiner boxes with 4 series running through 15a breakers each through 10g pv wire. I'm using 6g wire from the box to the dc disconnect/charge controllers, which at present will be about 30' from combiner box to cc.  The original systems battery cables that came with the system are heavy duty but I can't remember right off hand what gauge they are (they've been waiting in storage for time to use them).

I will add that everything but the combiner boxes will move to the house we're building this summer, which will be a 260' run. I'm thinking of using welding lead for that run. Or the heaviest, low loss copper I can find.  (Retired Ironworker and welder, here :)

I've been on the string calculator many times. That's where I got my calculations (there and the smart fellers on these forums). But for right now my main concern is the disconnect breakers in the DC box. I'm building the "Power Shed!", (aka, my wife's garden shed), to mount the power panel in now. I have one array up and wired to the combiner box. As of now, the panels are left plugged into themselves. I have the +, -, and 6g ground wired fished through liquid tight conduit, and I'm ready to install it in the combiner box, then trench and bury it, then it's time to know what I'm doing. I'm hooking up one side (one array, cc and inverter) for a test run while I'm building my other rack (MT Solar top of pole 12), placing the modules and getting it hooked up. I'm slow, but consistent. And as I've always said, The first one's the worst one!

ClassicCrazy

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With that long of run to the new house you may want to explore some of the new charge controllers coming on the market by Midnite and others that will take a much higher PV voltage like up to 600v I think.  Not sure though if your pv panels are rated for that high of series voltage ?  That would certainly help on your long wire run.

Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , Jakiper 48v LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batteries