Wiring and fuses

[Just_Askin]

Here is the spec sheet from my panels
I have connected 2 panels in series (with panel's 10 awg wire) and then the 2 strings in parallel (with 50a branch connectors and 8awg wire. I am planning on using a 500v 63a breaker as a disconnect switch between the panels and a 150v 70a SCC. Do I also need a fuse or fuses in addition to the breaker? Does what I've done seen safe so far?

 

[FilterGuy]

Please review this:

Fusing & Wire Sizing guidelines for solar panels

Jan 1, 2021

What fuses or breakers do I need on my solar panels

• FilterGuy
• Beginners' Resources

 

[Just_Askin]

So, I have read a lot and opinions seem to vary. I am trying to be safe and am asking for confirmation that what I've interpreted from various sources and how I've applied it is correct.

 

[FilterGuy]

From a safety point of view you do not need string fuses

From a safety point of view your wire sizes are fine.

I don't have enough information to say if the wires need to be larger to cover voltage drop issues.

 

[Just_Askin]

Thanks. The longest wire between the panels and the SCC is about 8'.

 

[Just_Askin]

Any thoughts on the viability of the 500v 63a breaker strictly as a solar disconnect switch in previously described system?

 

[Just_Askin]

The breaker was purchased on Amazon. https://a.co/d/3pxWYBo should I be looking for a U.S. built breaker? Any recommendations for my system? I have 4 of the above panels in 2s2p configuration.

 

[FilterGuy]

That should work fine as a disconnect.

Note: I would not have said that if it didn't have a DC rating to it.

In general, I don't like using breakers as a disconnect because breakers are not typically designed for as many life cycles as a switch.

Having said that.... Presumably, the disconnect would be used pretty rarely, and finding DC switches with the current and voltage rating needed is hard.

 

[Just_Askin]

I have 2 12v 280ah batteries that will be connected in parallel. Would you recommend connecting the batteries together and having one class t fuse coming off the bank or should I connect each battery to the busbars and have a fuse from each one? I will be using 2/0 105c wire/cable connecting the batteries together and/or to the busbars and to a https://a.co/d/7o2IrZG 2000w inverter.

 

[glandpuck]

So your Voc is 40.8 and your amps are amps are 25.6. But that is lab conditions. Figure you will get voltage of 32 and amps of 20 = 640 watts on good real world day. Each 2 panel series should have a 15 or 20 amp DC breaker rated for like 125 volts. See Midnite Solar supply for these. I would also use an inline solar fuse of 20 amps for each string. A fuse reacts quickly for an overcurrent. A breaker does not, it protects wires from overheating.
Then, combine the 2 strings in parallel and connect them to a Dc disconnect switch rated for like 40 amps and at least 100 volts. A DC disconnect switch breaks the circuit without an electrical arc. See amazon. Then into your inverter.

 

[Just_Askin]

That should work fine as a disconnect.

Note: I would not have said that if it didn't have a DC rating to it.

In general, I don't like using breakers as a disconnect because breakers are not typically designed for as many life cycles as a switch.

Having said that.... Presumably, the disconnect would be used pretty rarely, and finding DC switches with the current and voltage rating needed is hard.

There are no instructions on wiring this breaker. Nor are there markings indicating positive and negative posts. Can you tell from the diagram on the pic how it should be wired (i.e., direction and polarity)?

 

[FilterGuy]

It does not appear to be a directional breaker.

 

[Just_Askin]

So, in on the top from panels and out on the bottom to SCC? Doesn't matter if red is on the left or right just as long as they are the same top to bottom?

 

[glandpuck]

View attachment 296251
There are no instructions on wiring this breaker. Nor are there markings indicating positive and negative posts. Can you tell from the diagram on the pic how it should be wired (i.e., direction and polarity)?

This breaker should not be used on any installation in the USA. Use only breakers that are UL listed. they are easy to find. Non UL listed items may not pass any inspections if there is one and may also void any fire insurance or property damage claims and also could expose you to liability claims in the event of any personal injuries. Lastly, one of the kinds like this I tried melted and short circuited and blew up over 1K worth of transformers that I had connected to it in circuits at my own expense.

 

[Brucey]

The breaker was purchased on Amazon. https://a.co/d/3pxWYBo should I be looking for a U.S. built breaker? Any recommendations for my system? I have 4 of the above panels in 2s2p configuration.

Yeah don't use that one, grab one of these:

MidNite Solar MNEPV50-600-2PP Circuit Breaker 50A 600VDC

Shop now for MidNite Solar MNEPV50-600-2PP Circuit Breaker 50A 600VDC.

www.stellavolta.com

They have other lower ratings available.

Remove the series jumper bridge link that it ships with from the bottom terminals, bring panel + and - in from the bottom, then out from top to scc.

Enclosure could be something like an mnpv3 or perhaps an mnpv6 to give you 6 din spaces versus 3.

 

[glandpuck]

Yeah don't use that one, grab one of these:

MidNite Solar MNEPV50-600-2PP Circuit Breaker 50A 600VDC

Shop now for MidNite Solar MNEPV50-600-2PP Circuit Breaker 50A 600VDC.

www.stellavolta.com

They have other lower ratings available.

Remove the series jumper bridge link that it ships with from the bottom terminals, bring panel + and - in from the bottom, then out from top to scc.

Enclosure could be something like an mnpv3 or perhaps an mnpv6 to give you 6 din spaces versus 3.

Yes, this is correct. Midnite makes solid PV equipment. These breakers are excellent choices and last for years.