Blowing Controller Output Breaker on Midnite Solar XW-E Panel

[Emerald Power]

Hi zoneblue,

This appears to be beyond my comprehension. I admit I am a bit slow. I have a controller that has a 60 amp max output, but I screwed up and only used a 63 amp breaker and should have used an 80 amp breaker to start with. Do I have this right?

EP

[Vic]

Emerald,

I am not a real Code expert,  however,  in looking at the XW SCC manual -- 975-0400-01-01,  dtd 3/09 Rev B,  the following is stated,  regarding Output circuit breaker size,

... " Battery Circuit
The NEC requires the battery circuit to be protected with a device rated for 125%
of the rating of the circuit. The DC-rated fuse or circuit breaker between the
battery and the XW SCC must be rated for 1.25 × 60 A (the maximum current
rating of the XW SCC) ... "

Also noted in this manual is the statement that the maximum wire size is #6 AWG.

So,  seems that they are saying that they believe that a 75 Amp CB would be needed.

All FWIW,      Vic

[zoneblue]

Yeah i know, i know 60 amp breaker on a 60 amp controller sounds reasonable but heres why sometimes reasonable isnt reasonable:

- you have 3500Wp into a 60A controller at 48V nom. Thats 72 Amps give or take.
- on cold clear days that could go another 20% higher, so 88amps.
- the way mppt controllers work is that they do timed sweeps and in between those sweeps some quite biggish surges are able to pass through the controller in some cases.
- And; the din rail breakers are polarised, which means that they can only be fitted in one direction.
- when fitted to a CC, they are in "backwards", positive to the battery, negative to the CC.
- this is so that in the worst case scenario, (CC blows), the battery is more positive
- if in your case you blew it by over powering the CC with your PV, so the CC is more positive, and thats not a good way to trip those breakers.
- even though they say load rated, doesnt mean i would run one at load for long periods
- with your overpanelled setup, you WILL be running that controller hard for long periods (make sure you have plenty of airflow around it.
- maybe even consider adding a computer fan if your ambient is over 25*C.
- make sure to retorque the breakers one hour after you install them. Running 60A through a loose connection will make it heat up mighty quick, and mighty hot.

Anyway youre doing the right thing, the panel mount breakers are not polarised, have better fittings, and 80A should see you right.

[dgd]

This appears to be beyond my comprehension. I admit I am a bit slow. I have a controller that has a 60 amp max output, but I screwed up and only used a 63 amp breaker and should have used an 80 amp breaker to start with. Do I have this right?

I'm no expert on breakers but I sort of agree with the logic that a 63A breaker should be good for a circuit that moves 60A. Despite the NEC requirement for larger breaker the logic of 60amps through a 63A breaker works for me.
I also seem to remember that the KID manual said something about 30A breakers since the maximum battery current it can produce is 30 amps. Nothing about a larger breaker being required

Then again when I look at the Carling surface mounted breakers used by MN and Outback they specify an FL current which is the breaker rated current, eg 30A   I'm not sure what FL means - Full Load?
Then there is a Trip current specified, in the case of 30A breaker this is 37.5A
So does this mean the 30A breaker is intended for continuous full load of 30A but will not open until the Trip current of 37.5A is reached.
Same for the DIN CDi breakers made in Lesotho, I'm looking at a 50A one with Trip current 65A.

So back to the 63A breaker, does it open at 63A or is 63A the max load rating? and does it open at a higher Trip current?
Maybe a breaker guru can explain this?

And does it mean the 100A breaker I use between my Classic 150 and battery bank is sufficient? Would that fail NEC requirements and I would need a 120A breaker?

dgd

[Halfcrazy]

In reality the breaker is to small. The Schneider regulates very slow and is capable of over 80 amps output. I have seen this personally. I would never install a XW 60 amp controller with less than a 80 amp breaker.

You see it all boils down to how fast the controller can regulate that 60 amps. Some are a LOT faster than others. I have no idea why the meter reads 53 and the breaker trips but in my mind its a non issue as the Charge controller or something is massively wrong.

Install the 80 amp breaker and a new charge controller and lets see what happens.

I do know I run our breakers continuous from time to time and have no issues so I am wondering if the ripple from a single cylinder charge controller is introducing an issue with the amp meter?

Simple Math tells us it should be closer to 70 amps not 50 so I am still suspect of the meter.

Ryan

[Emerald Power]

Hey dgd,

I am looking at one of my extra 63 amp breakers and it states max volts is 125 but MNS has relabled it for 150 vdc. The trip amps are marked 81.9. It also says "polarity sensitive do not reverse feed". Maybe ratings are different in Africa than they are here.

EP

[Emerald Power]

Hey zoneblue,

I wanted to thank you for your wordy explanation.

EP

[Vic]

Emerald,

MidNite has had these breakers ETL ( I believe it was ETL) Tested for 150 VDC,  when used in a MidNite box,  IIRC.  So they ARE good for 150 VDC.

Know that you have ordered an 80 A breaker ...   Personally would not dwell on this issue too much,  until you get the new breaker and replacement CC.   FWIW,  Vic

[zoneblue]

No worries! Too bad you dont have a classic, you wouldnt have had those problems... and, you would be able to harvest all of your array output!

Hey zoneblue,

I wanted to thank you for your wordy explanation.

EP

[Emerald Power]

Hey Ryan , Vic, All,

Thanks for all of your input. It has made me research and learn much about my system. Schneider/Xantrex has agreed to replace the controller under warranty. When it and the new breaker are all in place, I will report back here with the results.

Kind Regards,   EP

[Westbranch]

hopefully it is not a repaired unit...

[Emerald Power]

Hey All,

Just thought I would send in an update for my controller problem. 

Xantrex sent me a brand new XW MPPT60-150 controller and I installed it with the new MN 80  amp breaker and all is well. Appearenty, the controller was delivering about 30 percent more amps than it was reporting. There were also spikes that would trip the 63 amp breaker. The new unit delivers a nice constant amperage that I think would work with a 63 amp breaker, but since I have the 80, I will continue to use it. Output ramps right up to 60 and stays there. I also measured this at the battery output wire with the new clamp on ammeter, and they are within .1 of each other. Very satisfied now with my system.
Thanks for all of your input. Really made me dig into how this system works.

Kind Regards,      EP