Wiring layout challenge :) Help needed!

[Stepandwolf]

Attempting to install the solar into my TT. The components are being mounted under the bed. At the back of the compartment will be 4X 100A 12V batteries wired 2S2P for 24V. In front of the batteries is a 16"X46" sheet of plywood to mount the solar components on. Not a lot of space, but I hope enough. I do intend to mount the 300A T fuse on the back side of the sheet of plywood with the batteries. The AC in, AC to existing fuse panel, PV in, and DC to existing fuse panel all come through the floor between the batteries. probably makes sense for all those connections to come in through holes in the plywood where they are needed.

I laid these components out of the sheet of plywood and moved them around like doing a jig saw puzzle and couldn't find something I was satisfed with. This is my first time doing a layout like this and was tired of banging my head on the wall.

If someone who has a knack for this can move around the pieces in their optimum location, that would be great. I would like to leave about 3" on the far right and left size.

I am also attaching the original design which was using individual cells vs. the 12V bats so ignore that side of the drawing.

 

[robbob2112]

I would not use an ANL for anything - they run hot and can be a shower of sparks if they blow from major overcurrent

Breaker listed as #7 can be a really bad choice - they tend to run hot and have the handles break off or burst into flames if they ever flip with current through them... Use a MCCB instead -- Dihool, midnite solar or TOMNZ are good, the random ones are not... they are large but will work and can be used repeatedly even with power

You can do the arrangement with drawio or there are some 3d model things that are free for arranging rooms that work well...

 

[Stepandwolf]

I would not use an ANL for anything - they run hot and can be a shower of sparks if they blow from major overcurrent

Breaker listed as #7 can be a really bad choice - they tend to run hot and have the handles break off or burst into flames if they ever flip with current through them... Use a MCCB instead -- Dihool, midnite solar or TOMNZ are good, the random ones are not... they are large but will work and can be used repeatedly even with power

You can do the arrangement with drawio or there are some 3d model things that are free for arranging rooms that work well...

The configuration I listed and the parts I showed were reviewed by dozens of people 2 years ago and nothing negative was said at that time. Is this all news to the community? In fact, the drawing is version M as it included a lot of input on the configuration. I have the parts and will use them. When I go up in flames I will remember your advice and wish I had taken it. Thanks!

 

[robbob2112]

Shrug, your choices your consequences...

There has been a change in attitude in the last year concerning fuses combined with LFP batteries -- specifically their ability to break an arc - the AIC rating -

The ANL typically has an AIC of only 2ka if there is an arc .. it has higher resistance than other similar fuses so it produces more heat and wastes more power at a given current... and they are often faked or mislabeled where they don't blow at 10 x the rated amps... Basically the current consensus is they are fine for car audio, leave them there ...

There have been a number of new things with the up-in-smoke where Mega fuses recommended by victron 4 years ago are not sufficient anymore and Victron has increased the working voltage of them and switched to ceramic bodies. Even then mega fuses of the new type only have an AIC of 3500amps ...

The breakers of that type unless they are the bussman or blue sea (relabeled bussman) are pretty notorious... search a bit... nobody will recommend them... I am surprised if you have been through that many iterations up until now you haven't had it pointed out.

 

[Stepandwolf]

Shrug, your choices your consequences...

There has been a change in attitude in the last year concerning fuses combined with LFP batteries -- specifically their ability to break an arc - the AIC rating -

The ANL typically has an AIC of only 2ka if there is an arc .. it has higher resistance than other similar fuses so it produces more heat and wastes more power at a given current... and they are often faked or mislabeled where they don't blow at 10 x the rated amps... Basically the current consensus is they are fine for car audio, leave them there ...

There have been a number of new things with the up-in-smoke where Mega fuses recommended by victron 4 years ago are not sufficient anymore and Victron has increased the working voltage of them and switched to ceramic bodies. Even then mega fuses of the new type only have an AIC of 3500amps ...

The breakers of that type unless they are the bussman or blue sea (relabeled bussman) are pretty notorious... search a bit... nobody will recommend them... I am surprised if you have been through that many iterations up until now you haven't had it pointed out.

I am kind of like a sponge, absorbing all I can on a subject before proceeding, knowing I will likely make a mistake or two, but hopefully not deadly. I certainly wasn't aware about the change in preferences or dangers since the time I did that design. Based on your reply, I can tell you are a guru of this stuff and would appreciate your opinion. The ANL was off the battery bank. The battery bank will be 4X12V 100A batteries, 2S2P. Would you have a suggestion in product or rating for the replacement, another MCCB? Switch 7 is the 60A break off the 100/30 charge controller that you suggested would be a MCCB. Would I look for the same 60A rating? Thanks

 

[robbob2112]

I would put a MRBF fuse on the lead battery positive post of each string ... rated 125% of the bms continuous output.... 150a bms * 1.25 = 187a so use 200amp fuses instead of 300amp. The wire can be sized for 200amps as well.

This would be suitable.. or a midnite brand similar style.... I picked 2-pole because you want to break both positive and negative with one switch.

https://www.amazon.com/DIHOOL-Circuit-Breaker-Disconnect-Switch/dp/B0C4359JB3/

Instead of the 2p 32a breaker i would use a dc isolator... it snaps and will break a very large arc... where the small breakers like i linked will only do 6k to 10k aic if they are dc rated.... the imo brand disconnect is quite a lot higher and it breaks both poles in 100ms when it is flipped...

This in line with the inverter positive and negative would cut the power instead of the switch to turn on and off the inverter lines... I don't think the switch you show is rated 300amps...at least unless you get the heavy duty version of it..like the first link.

https://www.amazon.com/dp/B0BQL11HBW

https://www.amazon.com/Heschen-Circuit-Breaker-HSM3DC-320-Photovoltaic/dp/B0CM3J7BKL

 

[Stepandwolf]

OK, to summarize, you are suggesting the MRBF fuses on each string, two total where I had none before the T1.
You are suggesting the Dihool 60A breaker vs. the one pictured (#7), a 60 circuit breaker for the charge controller to bus bar.

The switch I showed is intended for marine and is rated at 275A.

I didn't get what the last link was for, the Heschen, to replace what part of my design?

Thanks

 

[robbob2112]

Is this a mobile install or a house... some things differ... and I see you are grounding the negative bus bar which would only be correct in a mobile install.

Assuming a mobile install I would do the mccb breaker where it would cut off the batteries... both poles from everything else ... the only wires to leave connected would be the shunt and shunt power...

Did you do your drawing in drawio or something else? If it is drawio you can upload it and I could make a few tweaks.

This is my 24v design

Post in thread 'Robbob2112 Answer thread'

Oct 22, 2024

24volt UPS

Schneider Electric 865-2524 Conext SW 3,000 Watts, 24VDC Inverter/Charger for Split-phase 120/240 VAC

This inverter has been discontinued.

www.solar-electric.com

Schneider Electric RNW8651016 Conext SW DC Circuit Breaker Panel

Schneider Electric RNW8651016Conext SW DC Circuit Breaker Panel

www.solar-electric.com

Schneider Electric RNW8651017 Conext SW AC Circuit Breaker Panel for 120/240 VAC

Schneider Electric RNW8651017 Conext SW AC Circuit Breaker Panel for 120/240 VAC

www.solar-electric.com

Victron 250/100
4 - 335w Q cell panels.
Bus bars from Signature solar
Victron Smart Shunt
Class T fuse (150amp)
Class T fuse holder, ignition protected
Blue Sea systems switches for each battery bank
MRBF fuse + holder for each battery bank (also 150amp - each bank can run the inverter with the other off)
4 -...

• robbob2112

• 

I intend to use a similar mccb instead of the black switches... so i can turn off each string separately.

 

[Stepandwolf]

The first message says for install in my TT, i.e. travel trailer, so yes, mobile. I drew the image in Paint, cutting and pasting the components from someone else's drawing. Seems you are telling me something different now than what I thought I understood? I already bought all the components back in 2021 that I am not installing until now. Anything not used will be wasted and anything I have to buy new now will be additional money to spend. When I get panels from a member on here, I will be doing another build using the cells in the drawing with a 48v JK BMS with a LV6048 inverter. Thanks

 

[robbob2112]

Ok, lemme work on how I would do it with minimal changes today...using the components you have with the exception of the anl and that flip breaker....bonus, I'll upload the drawio file and you can play with it.

 

[robbob2112]

Sorry, I write novels to explain things and why I do things


This is the Victron install guide recommendation for fuse and wire size

https://www.solar-electric.com/lib/wind-sun/Victron-Service-Manual-MultiPlus-3k-120V-%28firmware-xxxx4xx%29.pdf

Which version do you have?

The size of the class T used should be 300amps or 400amps, you

Changed the breaker size from the PV panels to more closely match the MPPT - 40amp verse 60amp

Amazon.com

Fuse to the buck converter - I would switch to this type breaker verse the automotive breaker -

Amazon.com

Automotive breakers that self reset like the ones you picture can cause problem because you don't know if it is tripping and resetting - no indication ... I much prefer something I have to flip back so I know to watch for problems.

Both of these layouts require 4 bus bars to avoid stacking lugs. -- if you want to make changes - download drawio and use the two attached files ... it takes about 20 minutes on youtube to learn the basics.

Those are 200amp MRBF fuses to go onto your battery post - or you can put them at the bus bar end of things. They require a holder.. I say the bus bar end because I haven't seen a picture of the battery and if it has terminal lugs the output cables are connected to or if you are just bolting directly to the positive cell and the BMS. Terminal lugs is for sure the way to go on that.... safer and the MRBF can't hurt anything if you torque it down to spec.... I get mine from pkys.com or mouser... There are many cheap copies on amazon that don't stand up to actual use...

One thing I see that is missing is an equalizer to run on each string to keep the 2 batteries in sync - being home built and you can monitor the cells for runners that may not be an issue the typical new user with store bought batteries would need to add one.

The plastic enclosure you have on the table will hold both of the dihool black breakers

Note - on the bus bars I picked the particular stud things connect to on purpose






And here it is with the additional large MCCB instead of the switch -- gives you a single switch to turn off the batteries... a second switch to turn off the MPPT... and a third switch to kill power to the buck converter and DC panel.

The advantage of the MCCB is you can turn it off while there is a full load on it with no damage -- the standard switch in the first drawing is only meant to be turned off while there is no load. If turned off repeatedly with a load the contacts get burnt and it starts running hot.

I am assuming the AC out has a fuse or breaker built into the existing panel as does the DC panel. If they don't have that something would need to be added.

 

[time2roll]

I would tighten up the battery fuses so that I could skip the inverter fuse and switch. Increase wire size if needed.
Covered ANL fuse to branch circuits off the positive bus to the controller and DC supply.
60A fuse to a 30 amp controller seems large. 40 amp is plenty.
Use same size 40A to the DC converter to simplify spare items. That self reset breaker as shown is probably junk.
No fuse, breaker or switch from panels to controller.

Picture above seems like a lot of unneeded connections/terminals.

 

[robbob2112]

I would tighten up the battery fuses so that I could skip the inverter fuse and switch. Increase wire size if needed.
Covered ANL fuse to branch circuits off the positive bus to the controller and DC supply.
60A fuse to a 30 amp controller seems large. 40 amp is plenty.
Use same size 40A to the DC converter to simplify spare items. That self reset breaker as shown is probably junk.
No fuse, breaker or switch from panels to controller.

Picture above seems like a lot of unneeded connections/terminals.

are you talking about the original or my suggestions?

 

[time2roll]

Mostly the original to reduce and simplify as requested.
I don't think that is really accomplished with the picture just above with more connections and more components.

 

[robbob2112]

I would tighten up the battery fuses so that I could skip the inverter fuse and switch. Increase wire size if needed.

So, you are saying skip any protection on the line between the bus bar and the inverter? What if the inverter shorts?

Covered ANL fuse to branch circuits off the positive bus to the controller and DC supply.

IMO ANL bad -

60A fuse to a 30 amp controller seems large. 40 amp is plenty.

Agreed - or breaker that breaks both lines -- the breaker I showed could also go between the panels and the mppt

Use same size 40A to the DC converter to simplify spare items. That self reset breaker as shown is probably junk.

I prefer breakers to fuses - nothing to hunt in the middle of the night - no spares to carry.

No fuse, breaker or switch from panels to controller.

With only 2 parallel strings there is no need for a fuse in the PV lines - an IMO disconnect would be nice though - but a travel trailer may not matter.

IMO the extra connections and devices are all there for safety... OP will have to decide what he prefers...

 

[time2roll]

So, you are saying skip any protection on the line between the bus bar and the inverter? What if the inverter shorts?


IMO ANL bad -


Agreed - or breaker that breaks both lines -- the breaker I showed could also go between the panels and the mppt


I prefer breakers to fuses - nothing to hunt in the middle of the night - no spares to carry.


With only 2 parallel strings there is no need for a fuse in the PV lines - an IMO disconnect would be nice though - but a travel trailer may not matter.

IMO the extra connections and devices are all there for safety... OP will have to decide what he prefers...

Protection of the inverter connection would be the battery fuses and BMS protection.

ANL not so bad IMO for smaller branch circuits due to more resistance in the wire.

Breakers on both wires creates more connections. More connections is not going to help simplify the layout. Not to mention two extra bus bars.

Never a fuse has opened on my RV power system in 20+ years. Should take a real fault to open the fuse. Should be extremely rare for fixed components.

Yes a switch is nice on the panels. Saves about 60 seconds every 5 to 10 years when something needs service. Same with the inverter switch.... in the very rare case it needs service a cable can be lifted.

Either way works. Trying to stick with the simplicity side to lay out the components in limited space.

 

[robbob2112]

Mobile qualifies as a floating electrical system - i.e. it is not tied to an earth ground. For floating electrical systems you are supposed to break both conductors with a single action ...

 

[time2roll]

OK. NO RV from the factory comes with such a system.

 

[robbob2112]

shrug - guess they are doing it wrong or they assume the NEC doesn't apply... and maybe it doesn't - I never thought about it much

Key Points from NEC 690.41(B):​

• A means of disconnecting all ungrounded conductors must be provided.
• This disconnect must simultaneously open all ungrounded conductors of the PV system.
• The disconnect must be readily accessible and located in accordance with the general rules for PV disconnecting means.

There is also a requirement to have a means to disconnect the inverter, SCC, and any power equipment in 609.15

 

[time2roll]

Virtually all RVs are RVIA certified that requires compliance with NEC. All the negatives are grounded conductors in an RV. Except maybe the solar.

 

[robbob2112]

shrug - I dunno then - connecting everything to the chassis ground still leaves it on wheels - unless it is plugged into a pedestal for shore power there is no earth to reference...

If I ever buy an RV I'll deep dive the subject...

And aside from writing novels instead of answers we established in another thread I like building rube goldberg machines.

 

[Stepandwolf]

Hiya....it isn't the amount of words, it is the knowledge level assumed

Before I respond, I wanted to mention that old drawing doesn't show my change to the Siekon 12V 100A batteries that Will loves. I have 2 of them now, 2 are coming for the install, and possibly 2 more after that, so, I will either have 24V/200A or 300A.

"This is the Victron install guide recommendation for fuse and wire size"

I have the 2400/3000/70 model. My 200A system is at the bottom end of the recommended capacity but might mistakenly become 300A. They suggest a 300A fuse, so my 300 T is fine. My 2/0 battery cable is suitable too, so all boxes checked as far as that goes.

PV breaker to 40A, check

"Fuse to the buck converter - I would switch to this type breaker verse the automotive breaker -"

That link is for a 250A fuse. Is that appropriate for a 40A load?

re: MRBF...as mentioned above, I am not using the individual cells and BMSs for the battery build. I will have 4X 12V 100A bats. I was going to get these fuseblock/fuse which was what I could find that were 200A. Blue Sea only seemed to have 300A

https://www.amazon.com/gp/product/B0CHJP4G4S

"One thing I see that is missing is an equalizer to run on each string to keep the 2 batteries in sync"

The Siekon batteries are supposedly able to resolve cell issues internally and the batteries can be installed up to 4s4p. I am starting with 2S2P, possibly adding the third pair.

The web page for the Siekon product even has Will's YT video showing

https://www.siekonenergy.com/products/siekon-100ah-deep-cycle-lifepo4-lithium-12-volt-battery-classics-upgrade

"Next-Gen BMS Upgrade: Our Siekon Energy's 100Ah LiFePO4 12 Volt Battery comes equipped with an upgraded BMS featuring pulse equalization as well as low-temp protection at 0℃(32℉). It also effectively prevents overcharging, over-discharging excessive current flow, or short circuits to ensure safe use and stable performance."

"The plastic enclosure you have on the table will hold both of the dihool black breakers"

Ah....good catch. I didn't notice that they used the same DIN rail.

"And here it is with the additional large MCCB instead of the switch"

That 300A MCCB isn't cheap. I do understand what you are swaying about using the breaker vs. a switch. Honestly, I don't think I will ever use the switch. This is expected to be in use full-time, 365DY

Yes, the AC and DC panels have breakers and fuses. The TT also has it's own battery switch that I suspect will be bypassed by my wiring.

Thanks so much!

 

[Stepandwolf]

I would tighten up the battery fuses so that I could skip the inverter fuse and switch. Increase wire size if needed.
Covered ANL fuse to branch circuits off the positive bus to the controller and DC supply.
60A fuse to a 30 amp controller seems large. 40 amp is plenty.
Use same size 40A to the DC converter to simplify spare items. That self reset breaker as shown is probably junk.
No fuse, breaker or switch from panels to controller.

Picture above seems like a lot of unneeded connections/terminals.

Thanks for coming to the party....the more of you discussing the build, the better.

Most of my wiring is at or greater gauge than my original drawing. I have 2/0 for the batteries. Other than the PV wiring which is 10ga, where my diagram has 10ga, I actually have 8ga.

"Covered ANL fuse to branch circuits off the positive bus to the controller and DC supply."
Are you saying an ANL where my original drawing has a 60a breaker?

"Use same size 40A to the DC converter to simplify spare items."

Is the DC supply and DC converter the same thing?

Sorry for my confusion borne out of ignorance.

 

[Stepandwolf]

With only 2 parallel strings there is no need for a fuse in the PV lines - an IMO disconnect would be nice though - but a travel trailer may not matter.

hmmm....didn't know that... Whether or not needed, isn't that how you shut off current from the panels to work on the rest of the system?

IMO the extra connections and devices are all there for safety... OP will have to decide what he prefers...

I would rather lean in the better safe than sorry direction

 

[Stepandwolf]

Virtually all RVs are RVIA certified that requires compliance with NEC. All the negatives are grounded conductors in an RV. Except maybe the solar.

To be clear, are we talking about the factory supplied panels, wiring, etc? I showed one chassis ground in my drawing. Is there some other grounding I need to do other than that?