PLZ Help Me to NOT burn the cabin down. Question regarding Panel-to-Ecoflow wire size....

[farmhand]

Good day all, hope to get some replies here:

My panels on the chicken coop are 120' from the Ecoflow Max 2k.
The Eco MPPT pulls in 800w.
My 24 100w panels are in (6) strings of (4) panels.
All strings fused, dioded, surged, 15A DIN breaker - then to a Siemens fused disconnect with 15a FRS fuses. Then>>>

First leg 50ft: (From coop to outhouse) is (4) #12THHN.
Second leg 60ft: (From outhouse to cabin utility room) 12/2RX

By all calculations, and using several different sites, I feel the 7-8 amp draw from the ECO will be no issue for heat on the line. Yet not being to much in-the-know on residential DC.... do you agree this wire size for the distance is safe with DC?

Thanks all, I don't post much but stock the forum often & enjoy the threads on here

Here's a pic during the build last summer*

 

[Wakintx]

Something don't add up to me ... 24 panels of 100 watts. But mppt only accepts 800 watts?

 

[zanydroid]

You can use direct burial or conduit. Direct burial (with appropriate depth and protection where it comes up) is likely used all the time for commercial solar farms that are at higher voltage than your system.

AFAIK where you’ll get into trouble is where the conductors pop up. Physical protection, arc and ground fault protection (the former to prevent burning something and the latter to prevent shocking), correct type of splice hardware, and having disconnects in the appropriate places to properly service the long cable run.

 

[rhino]

Do you have link to the charge controller you are using?

 

[Bud Martin]

Good day all, hope to get some replies here:

My panels on the chicken coop are 120' from the Ecoflow Max 2k.
The Eco MPPT pulls in 800w.
My 24 100w panels are in (6) strings of (4) panels.
All strings fused, dioded, surged, 15A DIN breaker - then to a Siemens fused disconnect with 15a FRS fuses. Then>>>

First leg 50ft: (From coop to outhouse) is (4) #12THHN.
Second leg 60ft: (From outhouse to cabin utility room) 12/2RX

By all calculations, and using several different sites, I feel the 7-8 amp draw from the ECO will be no issue for heat on the line. Yet not being to much in-the-know on residential DC.... do you agree this wire size for the distance is safe with DC?

Thanks all, I don't post much but stock the forum often & enjoy the threads on here

Here's a pic during the build last summer*

1) What is the max PV input Voltage of this Ecoflow Max?
2) What is the max input current limit of this Ecoflow Max? 15A? 20A?
3) So you have the panels setup to be 4s6p, correct? since typical 100W panel will have Imp of about 5.55A, so 6 strings in parallel = 33.30A.

 

[DarrylG]

@Bud Martin Ecoflow Max 2000 has a Solar Charge Input: 800W 11-100V 10A max.
But I don't understand the setup exactly.

 

[Bud Martin]

@Bud Martin Ecoflow Max 2000 has a Solar Charge Input: 800W 11-100V 10A max.
But I don't understand the setup exactly.

OP is using 4s6p for the twenty-four 100W panel, which is way over panel.
100W panel will have Vmp of around 18V, Imp of around 5.55A, Voc around 22V.
So 4s will have total Vmp of around 18V x 4 = 72V (Voc will be about 22 x 4 = 88V, so about 12V headroom for cold temperature), even though the 4s6p can deliver 33A but the Ecoflow limits the input current to 10A by design so it will pull 10A max from the panels, so 72V x 10A = 720W of power even though the panels OP has can deliver more.
OP should arrange the strings to face many directions so it will collect the power for a longer period of the day.
BTW, when having more than two strings in parallel, each string should have fuse.

 

[farmhand]

1) What is the max PV input Voltage of this Ecoflow Max?
2) What is the max input current limit of this Ecoflow Max? 15A? 20A?
3) So you have the panels setup to be 4s6p, correct? since typical 100W panel will have Imp of about 5.55A, so 6 strings in parallel = 33.30A.

Hi Bud, thanks for replying.
1)The Max voltage input is 100v
2)The Max amperage input is 10a
4s6p Correct. Yes, 33amps max.

Each string can be easily disconnected at the combiner box by opening fuse holder (but never under any load). 3 strings are HQST Poly, 3 strings are HWST Mono.

My understanding is you can overpanel an MPPT as it pulls what current it needs, and that a higher potential amperage does not affect them.

My main concern is running 7-8amp of DC power on 12awg romex. Haven't been able to find much research on using this for DC in a residential structure.

The (+) and (-) are both fused at 15A in a Siemens disconnect right after the combiner box.

 

[farmhand]

OP is using 4s6p for the twenty-four 100W panel, which is way over panel.
100W panel will have Vmp of around 18V, Imp of around 5.55A, Voc around 22V.
So 4s will have total Vmp of around 18V x 4 = 72V (Voc will be about 22 x 4 = 88V, so about 12V headroom for cold temperature), even though the 4s6p can deliver 33A but the Ecoflow limits the input current to 10A by design so it will pull 10A max from the panels, so 72V x 10A = 720W of power even though the panels OP has can deliver more.
OP should arrange the strings to face many directions so it will collect the power for a longer period of the day.
BTW, when having more than two strings in parallel, each string should have fuse.

Thanks again Bud!

Yes, each string has a 5amp fuse in the combiner box, and they all have reversing diodes.

Sadly to move 4 strings to tilt east & west would be a LOT of work! My racking is all unistrut (thought I'd save $$$), then the inspector noted by using unistrut I had to run a single piece of #8 to every panel, and tag the rack in a few places, all back to the combiner box, not one splice allowed. This was quite a task, thank God I could use THHN!!! So that is a good idea to scratch my head around... but re-bonding would be complex along with buying a longer run of wire (more $$$).

 

[zanydroid]

You still need to protect the MPPT against Isc, which your disconnect OCPD does. I believe you are using paralleled small conductors, and using that size OCPD will guard against undetected failures of that config.

What are your concerns about heating? The NEC charts are for DC and AC. And physics wise DC will behave the same heating wise at the same current. % voltage drop will be the same, DC you can straight apply ohm's law and AC requires the power factor to be 1.0 to directly apply ohm's law.

 

[farmhand]

Based on the information provided, the wire sizes you have selected are appropriate for the distance and current consumption. The #12 THHN wire used for the first leg has a maximum amperage of 20A and the 12/2RX wire used for the second leg also has a maximum amperage of 20A. Since your Ecoflow Max 2k can only handle 7-8 amps, you shouldn't have any problems with the line heating up.

Thanks Pinkie!

Pinkie & Bud, here are some current pictures to get a better idea:

Note: I am splitting the panel bus accordingly to have all 120v up top which the Eco can surely handle (many breakers but very little load). The 240 Mini-split, backup wall-pack heater, and original unused baseboard heaters will all be kept on utility. A rotator switch will allow switching from the ECO to Utility for the upper sub-section of the panel for the 120v. I will have pictures once the parts get in & installed.

 

[farmhand]

You still need to protect the MPPT against Isc, which your disconnect OCPD does. I believe you are using paralleled small conductors, and using that size OCPD will guard against undetected failures of that config.

What are your concerns about heating? The NEC charts are for DC and AC. And physics wise DC will behave the same heating wise at the same current. % voltage drop will be the same, DC you can straight apply ohm's law and AC requires the power factor to be 1.0 to directly apply ohm's law.

]Thanks for the reply Zany!

The first leg of the DC run is paralleled 12thhn, the second leg is single conductor 12solid (Romex).

I guess I'm just concerned about safety so much here as.... well I've been watching & reading of what can go wrong with DC so a second opinion never hurts Residential DC just kinda freaks me out now, a major reason the panels are on the coop, better the chickens than us :D Everything is from china... and I don't want to solely bet on such quality standards.

 

[zanydroid]

Yes it is good to be careful and you look like you’ve done a lot of due diligence already on your project.

With paralleled conductors there is risk of one breaking or one path having higher resistance and unbalancing the current split away from 50/50. If you keep the current under that supported by a single conductor then it is probably a strict upside efficiency wise.

I think your DC system voltage and current is on the tame side. Solar panels don’t push as much current as batteries (EG one 48V battery is enough to cause bad news, solar panels are bounded by their Isc)

Make sure you understand what happens when DC GFP is tripped. I believe DC GFP are focused on telling you there’s a problem (EG by turning off your MPPT output) but will still leave things that shouldn’t be energized at high voltage, but I’m still wrapping my head around it.

 

[farmhand]

Yes it is good to be careful and you look like you’ve done a lot of due diligence already on your project.

With paralleled conductors there is risk of one breaking or one path having higher resistance and unbalancing the current split away from 50/50. If you keep the current under that supported by a single conductor then it is probably a strict upside efficiency wise.

I think your DC system voltage and current is on the tame side. Solar panels don’t push as much current as batteries (EG one 48V battery is enough to cause bad news, solar panels are bounded by their Isc)

Make sure you understand what happens when DC GFP is tripped. I believe DC GFP are focused on telling you there’s a problem (EG by turning off your MPPT output) but will still leave things that shouldn’t be energized at high voltage, but I’m still wrapping my head around it.

Zany, thanks again for the info!

My PV combiner box does not have GFP... Guess I simply haven't thought of that. Should I install one in place of the 2-pole din mount breaker in the combiner box, or is the Eco's built in well enough?

After hearing from you all today I finished the DC side!!! WooHoo!!!
Have the "bad weather disconnect in the closet, SEA port is mounted and for such a cloudy day it's showing 80vdc (no load, but heavy overcast).

Will she pull 800w (30%) in overcast or shade I wonder.......... Will find out soon enough, the Eco shows up tomorrow :D

 

[zanydroid]

I’ll defer to others to provide GFP advice. Maybe there’s a thread you can read on that or glom onto.

It’s possible that your system voltage and max Isc is low enough to be more YOLO. However I’m pretty sure your voltage is above touch safety level and your Isc might exceed the ampacity of the ground conductors (yours are #8, so maybe not).

 

[farmhand]

WooHoo! It's here! 2years in the making! It's a shame I just started my work week (4 10's) so I am not here for a lick of daylight till Sunday
And the AC hookup isn't done quite yet, but this weekend!!! The app is great!