Robbob2112 Answer thread

[robbob2112]

Just putting this thread together as a place for me to post answers to common questions I see over and over.

Whatever you read below is my opinion - read at your own risk -

I found all the answers in the cellar at the end of the hall in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying 'Beware of the leopard.'

If you are new and reading this and have question - please post a new thread.
If you are more experinced and have a correction or disagree with what I have here - post and I'll make the correction if it makes sense.

Rules to live by -

1. If it seems to good to be true, it is..people lie to make a buck
2. There can be only one - this is when talking about grounding - one rod - one grounding system - one ground potential for all equipment
3. Never stack lugs - You can get away with a lug and a ring terminal on top, but never stack larger lugs
4. You can do it right, or you can do it over, once it burns down
5. Buy cheap, buy twice, or three times depending on how long it takes you to learn
6. Fuse EVERY live positive wire
7. Use the right type and amperage of fuse
8. Class T fuses are expensive but if sized right they only blow when they save your butt.
9. Buy the voltage battery you need, don't try and string them together for higher, it causes problems
10. Trying to reuse your old equipment in your new design will cost you in the end - money or efficiency
11. If you didn't listen to #10 & #11 use an active equalizer/balancer to keep them in balance.
12. Use a MRBF fuse with holder on each battery post at 12v with 4 or less
13. Use bus bars with more than two batteries or if you can't land all the large lugs without stacking
14. Use a class T between the bus bar and inverter
15. Do use rubber boots to insulate the cable ends and bolts they are on.
16. All wires and fuses are sized 1.25% higher than max expected current.
17. Try to use pure copper bus bars verse brass. Ensure you know the metal then you can do the math to figure the capacity
18. Carefully read and understand any ad selling things - you usually get exactly what you order - and it is on you if you don't vet the ad.

Last one - Everyone has an opinion - the hard part is deciding which one is worth listening to

Post in thread 'Robbob2112 Answer thread'

Jan 14, 2025

Standard Blurb

Don't spend any money, until you have planned out the entire system. An eraser is cheap, but returns can be costly.

Planning

1. Energy Audit - what do you have to power?
2. Size the inverter for your maximum instantaneous demand (including surges).
3. Size the battery for how long you want power, when the sun isn't shining.
4. Size the PV to cover the loads and recharge the battery, when the sun is shining for your area - most in the US use 4hrs or 5 hours a day of sun
5. Trying to use old equipment you already have usually costs more in design compromises than just...

• robbob2112

• 

Links in this thread

#1 - how to decide battery voltage and also figure how many panels you need.

#2 - Sample system - off grid cabin - 24v - 4 panels - bougerv mppt -

#3 - My CPAP backup unit

#4 - Sample system - 4 x 12v parallel off grid - don't use

#5 - Tools - Things I have and use - YMMV

#6 - Ferrule usage

#7 - Do you need an equalizer/active balancer with series strings of batteries

It is ALWAYS better to have the correct voltage of battery, it will save you trouble in the end. If you don't and have a series string see below​

​

Running strings of 2 and 4 batteries - do you need an equalizer - it depends - if you charge discharge the same amount day after day you need an equalizer - if you run totally random patterns that are from 20 to 80% usage every day you don't. BUT, very few actually run a totally random pattern day after day. The sun rises and sets, the ac cycles on and off, etc. So random in the day will delay the batteries but they will get out of sync and require being put in parallel or disassembly and charging individually.​

​

Do I need an Active balancer for two 12.8v 100ah in series?

Easy to add later if an issue develops. Not a permanent skip feature on a large component.

diysolarforum.com

Do I need an Active balancer for two 12.8v 100ah in series?

Easy to add later if an issue develops. Not a permanent skip feature on a large component.

diysolarforum.com

#8 - How to choose system voltage

#9 - What are common types or wire and usage

#10 - Buried conduit - NEC and rules

#11 - Wires on a rooftop

#12 - Fuses, disconnects/isolators, and breakers on PV lines

#13 - Attaching the battery negative to ground

#14 Batteries for perfect balance without the math - a practical example

#15 24v UPS - outputs 240 split-phase


#16 - Link to my 4 panel trial build thread
Trial build thread

#17

• Labeling requirements
• EGC sizing guide

#18 - Some info on SPD
SPD information and recommendation

#19 - PV wire in or on a building
PV wire in conduit


More on EGC and grounding

Good links to read not by me

opening 12v batteries without damage

Grounding Requirements for Portable Generators | JADE Learning

Portable generators are useful for when temporary or remote power is needed. Knowing when to ground a generator is critical for operator safety.

www.jadelearning.com

Hooking multiple batteries in parallel and where on the bus bar to place the uplink cables.

Gasses released by LiFePO4 batteries during a cell vent. I have this one as a PDF, but it is to large to post -- just in case it disappears

Probably the neatest DIY Battery rack I have ever seen

Shading, bypass diodes, and optimizers


External links I want to remember -

Raw copper bus bar material

Custom bent/cut/punched/plated busbar assemblies

No-OX-id Special A grease - use it on all contact surfaces

EM radiation song - very funny


Topics to master:
Wire - what is good and bad. CCA vs pure copper, Temperature
Wire - sizes, strand count, sheath materials, ampacity and voltage
Tools. - list of essential tools for crimping, torquing, striping, etc
Tools - general torque specs for bolts and connectors
Lugs - material, plating, good and bad brands, what to look for
Fuses - DC arc breaking, sizes, types, where needed type to use
Switches - dc disconnect, ???
Inverters - how sized? Good brands? What to look for?
MPPT. - what to look for ?
Solar panels - ???
Battery options- rack mount vs home built vs ?
Balancers - what they do and what to look for
BMC - how to use them to control the battery charge states?
Conduit - what goes where and how to pull cables
Bus bars - what to look for, what works




SME list - These guys can answer any question - they parse through the listings and pick what they want that is general or in their area.

This is by no means comprehensive, it just covers the folks I see all the time.

@Hedges - 3 phase - sunny island inverters - transformers and the like
@timselectric - Mr Grounded - i.e. all things grounding - all things electrical as well
@sunshine_eggo - Grand Pa smurf - all things Victron
@Brucey - his blood runs blue as well
@Rednecktek - has a different take on doing things on the cheap verse
@12VoltInstalls - lower voltage stuff
@Mattb4 - Generalist - low voltage stuff
@BentleyJ - Schneider expert
@BKY2003 - Schneider expert
@400bird - Schneider expert
@GRMRC - Schneider expert
@Daddy Tanuki - we keep him around for the crude comments and sense of humor
@FilterGuy - expert at most things - DIY batteries especially


Sellers and vendors
@EG4TechSolutionsTeam - anything EG4 related
@SignatureSolarJess - Anything related to signature solar
@HighTechLab - Current connected owner

 

[robbob2112]

#1 - how to decide battery voltage and also figure how many panels you need.


From this thread

Plug and play kit - shed

Hi anyone have recommendations for a mostly plug and play kit - for a shed. to support the normal ....... lighting / low amp led but mostly power tools ...... direct and chargers for battery chargers. So its possible to have 2x 15A circuits dedicated on at a time plus lights. (eg Fan and...

diysolarforum.com

Question was how do I decide battery voltage - I also answered on how to determine solar panels needed.


The main decision on battery voltage comes down to how many amps are drawn from the battery - Most of us are of the opinion that 3000w is the highest practical wattage for a 12v system. 5000w for a 24v system. Then 48v for anything beyond.


Watts drawn by your tools/etc multiplied by the number of hours in a day you want to use them. This give you watt hours. Batteries are rated in amp hours and can be crossed into watt hours by mulitplying by voltage.

i.e. 12.8v * 100ah = 1280wh
With LFP batteries you don't want to draw below 10% ever and 20% is used as the floor by many.
1280wh * 80% = 1024 usable wh


If your tool draws 330 watts to run (110v * 3 amps) and you run divide your usable battery watt hours by that to find out how long the battery will run it.

1024wh / 330w = 3.1 hours of constant run time.

So if you assume you want 10 amps at 110v for 8 hours a day of continuous usage you are looking at 8800wh needed.

a 51.2v battery rated at 100ah can do
51.2 * 100 = 5120wh * 0.8 = 4096wh usable

4096wh * 2 = 8192wh

So you would need two of those larger batteries to run for 8 hours roughly. Or you would need 8 of the 12.8v batteries.


For solar panels you need to lookup your address and see how many hours of sunlight you get a day - i.e. Washington state will be less than Florida.

Now - for panel size - if you have full sun on a 300w panel for 5 hours you will get 1500wh out of it.

8192wh / 1500wh = 5.4 panels

Now, you won't get 100% efficent on the panels and the SCC (solar charge controller) and the sun won't shine for your house location as much as the average lists everyday. So you can figure you will need at least 20% more than you think just to break even.

5.4 * 1.2 = 6.5 panels - so call it 7 panels.

300 watt panels are fairly large (65" x 30") and they make up to 550w panels which are a bit larger than a 4' x 8' sheet of plywood. So where you are going to mount things comes into play.

Panel Rules -
Each string of panels - all panels in a string MUST face the same direction - So if you don't have room to install panels into the same plane you need to have multiple strings. i.e. some face east, some face west.

Each strings needs its own MPPT Correction - see below
You can have multiple strings on a single MPPT - but all the panels in a string need to face in the same direction so they have similar power out

Output current will be limited by the charge controller, and thus some people over-panel (despite the max possible panel current exceeding the MPPT output rating). That will just result in some clipping at solar noon on perfect days.




Strings can be in series and parallel or a combo - Series voltage adds and current stays the same. Parallel current adds and voltage stays the same. It is pretty common to have series/parallel combos to get optimal current/voltage

You may NEVER exceed the voltage of your MPPT - even a few volts over will damage it. Panel voltage is measured in a lab at 25c. As heat increases voltage decreases and as it gets colder the voltage increases. So when figuring the max voltage leave at least a 10% buffer or more if you get really cold winters.

If you have more than 2 strings you need a combiner box with breakers that disconnect both poles of the panels.

Grounding - repeat this - 'there can be only one' - Your service entrance from the utility will have a ground rod - ALL other points in the electrical system MUST be tied to that one rod. If you have a independant system in your shed it will need an independant ground rod and the panel frames and the other pieces of equipment will be tied to it. If you later decide to connect to the house power you MUST disconnect the local ground rod..... When removing this rod you must remove the neutral/ground screw 'there can be only one'

The panels should have their frames connected to a grounding system. The shell of the inverter, the power panel, any other equipment with a ground screw will be connected.




Go here to get the estimate for your hours per day of usage

PVWatts

Estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations

pvwatts.nrel.gov

plug in 1k for the panel amount and it will tell you what watts to expect

One thing on energy audit - most tools don't run constantly... I would be willing to guess unless it is a sander it runs only 20% or less of the time depending on the tool

You can use that as a scaling factor to figure out the required number of panels. - here is my result - basically I can expect 4hrs in winter an 6 hours in summer of sun....

 

[Mattb4]

...

Each strings needs its own MPPT

...

...

Pardon me but I disagree with this usage. Every SCC (MPPT or PWM) has its own Array. An Array can consist of several strings of panels typically referred to with the shorthand like 3S2P to symbolize 3 panels in series (a string) connected parallel to another 3 panels in series.

I know that folks/companies have jumped whole hog onto calling a SCC with MPPT just a MPPT. This should be discouraged in my opinion.

 

[Texas-Mark]

Each strings needs its own MPPT

I disagree with this too. I have one string facing East and one facing West. They are connected to the same MPPT controller and it works perfectly.

Also, not sure if I see the use of this thread as it will be tiresome for someone to wade through trying to find an answer that would be best served with a dedicated thread or using the search. Just my $.02

 

[robbob2112]

sigh, the point was for me to be able to post links to my personal thread verse typing out the same answer repeatedly


Please explain what you mean - So you are saying you can have 3 strings - one east, one south - one west - ... all connected to the same MPPT - given that your don't exceed its voltage and doing the conversion math voltage/current to battery voltage/current and don't exceed the output current?

 

[Texas-Mark]

So you are saying you can have 3 strings - one east, one south - one west - ... all connected to the same MPPT - given that your don't exceed its voltage and doing the conversion math voltage/current to battery voltage/current and don't exceed the output current?

Yep. Except I would also add that the output current will be limited by the charge controller, and thus some people over-panel (despite the max possible panel current exceeding the MPPT output rating). That will just result in some clipping at solar noon on perfect days.

 

[Texas-Mark]

sigh, the point was for me to be able to post links to my personal thread verse typing out the same answer repeatedly

Ok, I did not realize it would just be mainly for you to link to vice people going to it as some sort of FAQ.

 

[Brucey]

You can have two strings, one facing east, one west. The east string will capture the morning sun, and the west string will capture the afternoon sun. Instead of a classic solar curve it won't peak as high but it will spread the production for more hours of the day. This can help if you don't have a ton of battery capacity. The voltage wont be an issue as they are paralleled, and neither will amperage as both strings will never be at max output.

 

[Texas-Mark]

This can help if you don't have a ton of battery capacity. The voltage wont be an issue as they are paralleled, and neither will amperage as both strings will never be at max output.

It also helps if you have a roof that faces east and west (like one of my sheds). Here where I am in TX, the sun is nearly overhead at noon this time of year, so I actually get more output from these E/W strings, than my tilted south facing array of the same size. Note: that south array (with two strings) does have it's own controller because all three would be too much for just one controller.

 

[Brucey]

Yes not sure how successfully east/west strings would be when sun is lower on the horizon in winter. Mine are all on the ground so will just move them all south for winter.

 

[Mattb4]

sigh, the point was for me to be able to post links to my personal thread verse typing out the same answer repeatedly


...

Many years back when I was participating on a Linux Forum I made up a list of common answers I made that I could just copy from a file on my computer and paste into a question post. I have thought about doing such a thing here but for some reason it has not bothered me yet to simply type out a response.

 

[Texas-Mark]

Yes not sure how successfully east/west strings would be when sun is lower on the horizon in winter.

I will find out this winter since I just put these up a couple of months ago. But here, the sun is not really that low even in the winter. At least not as much as people up north.

 

[robbob2112]

Ok, I did not realize it would just be mainly for you to link to vice people going to it as some sort of FAQ.

It still works for that even with the discussion - I intend to link at the top the answers I compile - so I can send people to the FAQ and they can consume the conversation only if they want to

Seems I just answer the same things over and over and over... and sometimes I do really detailed explanations ... so I am copy/pasting those into this thread and linking on post #1

 

[robbob2112]

#2 - Sample system - off grid cabin - 24v - 4 panels - bougerv mppt -


Taken from this thread -

Review my system please

Alright I'm a decent fellow. But I'm not good at everything. Well, I suck at solar power. This is my third attempt to build a solar power for my cabin. My first two attempts busted and I couldn't figure out how to fix it. I figure after these two attempts and the subsequent attempts at repair...

diysolarforum.com

Ideally the OP would have used a single 24v battery, but he already had 2 x 12v batteries so this is how to use them in series with an equalizer.

I attached the drawio file and picture in a zip if you want to download and modify (either of you)

I changed some of the links to be more appropriate wire and I added a main disconnect switch and an active equalizer to keep the batteries in sync.
Don't skimp on the switch - I picked one of a brand I know is good, this is one place the cheap knock-offs are pleantiful and not nearly so good. You can get a cheaper version, just make sure you know what you are getting. If you pay less than $15 it is very likely junk.

Also changed the breaker to 16amp dual pole since it was talked about being for disconnecting the PV wires verse being inline with the inverter.

I don't have one of the battery monitors you linked so I have no idea what size the shunt bolts are.

@platinumphoenix - You will need to figure out what the correct lug sizes are when you order cables - they have to be right.
I linked the windy nation pre-made battery wires on Amazon - they are good stuff and you can't go wrong.

Note - I may have missed a link from prior posts - so ask if you have questions

Did I miss anything?

View attachment 216581



You have batteries - 12v 200ah - connected in series to get 24v

Equalizer - connects to the batteries to keep them in balance - required

Amazon.com

Wire between batteries and to hookup to inverter and breaker are 4 AWG - pure copper with lugs - these are the 2ft version
Need to know what size the screws on your batteries are and bolts on the shunt

Amazon.com

Wire between the solar panels and the MPPT and splitter

Amazon.com

Amazon.com

MPPT - Charge controller - bougerv 40amp

Amazon.com

Battery Monitor - @Rednecktek - what size are the bolts on the shunt? 3/8 or 5/16?
https://www.amazon.com/gp/product/B07FGFFHC6

Fuse, holder, cap
https://www.mouser.com/ProductDetail/Bussmann-Eaton/MRBF-150?qs=r5DSvlrkXmKYtJ1cVnWOqw==
https://www.mouser.com/ProductDetail/Bussmann-Eaton/CFBAR1-250SP?qs=r5DSvlrkXmKMfmwp3Zb/Bw==
https://www.mouser.com/ProductDetail/Bussmann-Eaton/CFCOVER-1R?qs=zijbFIqa2JEOjMDsOT7upA==

Ground wire

Amazon.com

Ground rod

https://www.amazon.com/GOUNENGNAIL-Ground-Electrical-Grounding-Lightning-Industrial/dp/B08N5YZM4V

Breaker - changed to 2-pole (if you are using to disconnect solar panels you have to do both poles - NOTE the breaker is polarized - so have to get the pos and neg in the right place.

Amazon.com

Battery disconnect - this is your on/off switch - 3/8" screws/lugs

Amazon.com

Get a tub of this and use it on all mating contact surfaces. Just a thin coating. It will prevent corrosion and it has zinc particles in it to cut through any aluminum oxide already present

https://www.amazon.com/NO-OX-ID-Special-Electrical-Contact-Corrosion/dp/B00HDF9EXE

 

[robbob2112]

#3 - My CPAP backup unit

Use this at your own risk just as an idea

This is my cpap backup. Add in a MPPT and a couple of panels for solar charging.

Have to figure the panel count to go from 20% to 100% in 4 hours sun. 4 x 200watt would probably do it.

Fits in a sewing box.

Total probably come in around $1100, basic box is $500

Downside, it will never grow beyond a small system.

I have a Resmed Aircurve 10 ASV unit - when using with heated humidifier and heated hose it consumes 250ish watt hours in 10 hours. With those turned off it consumes around 70wh.

So I have basically 4 nights of use without a recharge, maybe 3 depending.

I have the 20amp LiTime charger plugged into a wall timer so it recharges the battery each day starting around noon. I could also plug a MPPT and some solar panels into the charger plug and recharge that way.

The inverter is not needed for the build - but I have it in case we have a power outage - it will run my full sized fridge for 15hours.

 

[robbob2112]

#4 - Sample system - 4 x 12v parallel off grid - don't use

The OP had this built into an entertainment center in the bedroom - I highly suggested that he should put it into something non-flamable and NOT in any living space.

After several other threads I would probably switch the MRBF to class T fuses. The MRBF have similar response times to the class T but they don't have the AIC.

 

[robbob2112]

#5 - Tools

Everyone will have different ideas on tools - these are the ones I have to work on solar


Temco - TH0005 hydraulic crimper - cheaper from Temco directly
https://www.amazon.com/gp/product/B00HJXG3KM

Temco - TH0004 hydraulic knockout punch kit - when installing I kept needing it and the little Greenlee set dad bought 50 years ago still works but not good enough or big enough since it is 1/2, 3/4, and 1in.

2 inch Hydraulic Knockout Punch - Electrical Conduit Hole Cutter Tool Set

The TEMCo TH0004 Hydraulic Knockout Punch has a powerful 9 US TRUE TON punching capacity and produces perfect, uniform holes every time. Its compact design is especially designed for field use on construction sites and maintenance jobs. Quick, effortless and simple to operate. Punches more than...

temcoindustrial.com

Southwire cable cutter (large cables)
https://www.amazon.com/gp/product/B00EZ378HQ

Cable cutter - medium size
https://www.amazon.com/gp/product/B0000302X1/

Greenlee cable striper
https://www.amazon.com/gp/product/B0042VIHE4/

Torque wrench
https://www.amazon.com/gp/product/B09F652KV9/

Husky torque screwdriver

Husky 8-40 in./lbs. 1/4 in. Drive Electronic Torque Screwdriver H4DETSD - The Home Depot

Husky offers this durable Hex Torque Driver for technicians working with aluminum to copper connector. Eliminates slippage or dropping in tight spaces.

www.homedepot.com

Clamp meter with inrush (replaces the Fluke above for most things)
https://www.amazon.com/Hioki-CM4375-90-Clamp-Wireless-Adapter/dp/B09ND6VQK8/

4 wire YR1035 battery internal resistance meter - use for measuring internal battery resistance or mΩ values through fuses or connections
https://www.amazon.com/dp/B07S7NKZ45

Megger meter for testing insulation

Amazon.com

Solar panel watt meter

https://www.aliexpress.us/item/3256806499413854.html

Beyond that are your basic hand tools for working on cars - the additions to that are insulated tools so you don't accidently short something out. Example would be screwdrivers with heatshrink on all the metal parts except the tips, insulated wrenches for tightening bolt, etc.



There are cheaper clamp meters than the one I linked. There is a $100 version that works almost as well.

Some like it some say it is wildly inaccurate
https://www.amazon.com/AstroAI-Multimeter-Auto-ranging-Resistance-Capacitance/dp/B08MTCMWLB/
Accurate and has most features
https://www.amazon.com/UNI-T-Resistance-Capacitance-Temperature-Continuity/dp/B0987B1ZZ8
Dunno about the quality but it is cheap for the features

https://www.amazon.com/ANENG-Multimeter-Capacitance-Resistance-Continuity/dp/B0BKVVFP21/

This one is recommended by @Hedges

CM1000A 1000A T-RMS AC/DC Clamp Meter

Amazing deals on this 1000A T-Rms Ac/Dc Clamp Meter at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

I have one of these because I love scope meters

https://www.aliexpress.us/item/3256806293694932.html

And this is the best of all worlds if you are going to only have one meter

https://www.aliexpress.us/item/3256808296116940.html

 

[robbob2112]

#6 - Ferrule usage

When to use ferrules and when not to use them. This is sometimes hotly debated depending on the type of terminal block

Use them when -

• The screw terminal just has the screw directly contacting the wire and the wire is fine stranded.
• When the mfg calls for them

When not to use them -

• On stranded THHN when the screw pushes on the wires directly unless the mfg calls for it
• When the mfg says NO - like the victron MPPT Changed 8/24 - see wiring unlimited.
• In any sort of spring push connection like wego unless they are called for
• On solid wire.

Optional -

• When the screw pushes down a plate that is cupped so that it gathers the stranded wire together - like the victron MPPT
• When the screw pushes down a plate that is flat and the wires are not fine stranded (like thhn)
• When the hole is a hex shape and cups the wires top and bottom

Ferrules are like everything these days - mfg in china - all of them for the most part.

Good ferrules are:

• thin enough to deform with the crimper but NOT become crooked like a snake.
• When they are crimped they are straight.
• Long enough to bottom out on your socket

Bad ones are:

• thin and when you crimp them they tear at any point
• Not long enough to bottom out in the connection you are using them in - touching plastic is not bottoming out.
• So thick they are super hard to crimp and they don't make a nice shape

What to crimp with

• Ferrule crimper - hex, square, w-shaped
• Hydraulic hex crimper for lugs
• Hex crimper for lugs

Whatnot to crimp with

• Pin crimper for lugs
• Regular pliers of any sort
• Hammer
• Anything that doesn't compress the ferrul and wire into a solid mass

How to crimp

• Strip the wire long enough to go all the way to the end of the ferrule and extend a bit out.
• Have the wire sheath inside the ferrule plastic
• Push it all the way through
• Use the correct crimper - 4, 5 ,6 and 8 sided ones exist.
• For electrical stuff it will be the 4 or 6 sided typically. This depends on if the socket is a flat plate/screw or if it is the hex shapped socket.
• Do NOT twist the wire before inserting - you want a cold weld type bond and twisting will cut strands.
• it is permissable to double the wire back on itself, but discouraged.
• And there are non-insulating ferrules that don't have the plastic bit. These are typically larger awg

It shouldn't deform the wire into a snake.
It shouldn't tear the metal of the ferrule
it should fill the ferrule completly before you crimp if it doesn't you will get a snake
If it doesn't fill the ferrule completely you can double the wire back on itself and cut the excess after
The finished product should be a cold weld of the wire and the ferrule just like a regular lug.

Ferrules come in sizes like AWG and they are also in mm in metric. Just like crimpers they can be mismarked.

A good reliable source of ferrules is - you get what you pay for.

Ferrules Direct​

Insulated Ferrules, Non-Insulated Ferrules, Terminals, Wire Ducts, Crimping Tools, Cable Accessories, Terminal Blocks, Push Buttons, Heat Shrink, Compression Lugs, Automotive Products, Wire Cutters, Wire Strippers

www.ferrulesdirect.com

 

[robbob2112]

#7 - my UPS for the Media server and computers

ExpertPower 2000w 12v Inverter
2 x 330w Qcell panels
Victron 150/35 smartsolar
Victron Smartshunt
LiTime 12v 200AH battery
MRBF fuse on the terminal - 200a
Windy Nation #2 wire 105c - good to 205amps

I expect the max amps I will see is 166. In reality it pulls a lot less than that.

 

[robbob2112]

Which Voltage should I choose for my system


Answer the questions - Is it mobile like a trailer, stationary like a house or cabin, or a UPS/solar generator?


General rule of thumb is

• 12v for 2000w or less
• 24v for 3000w or less
• 48v for anything over 3000w
• You can use 48v for all the small stuff to if you want to upgrade later or now

Mobile - (low power system)

• Is it a motorhome/travel trailer/van?
• Are all your appliances lights and everything else 12v or AC?
• Is your power usage 2000w or less normally with 3000w surge once in a while?
• Do you never plan to upgrade to more power

If all are yes then 12v will work for you - if you plan to upgrade to higher power read on.

Stationary cabin - (medium power system)

• Is it off-grid or on-grid?
• Is your power requirement below 3000w with surge over that to 6000w?
• Are your appliances 12v and AC?
• Do you never plan to upgrade to more power?

If the answers are yes then 12v or 24v will work for you - if you plan an upgrade read on

House -

• The simple answer is go with 48v.
• Nothing else makes sense in a house install because of the power requirements.
• If you are planing a smaller system with an eye towards upgrade later, just bite the bullet and go with 48v now and add more panels, batteries, SCC, and inverters later.
• If you can afford it get the larger bus bars you will need and any other component you will have to upgrade.

Whichever you choose - buy your batteries in that voltage - try not to string them together in series. And if you do strng in series use an active equalizer/balancer to keep them in sync verse letting them drift.

 

[robbob2112]

What are the types of wire and their common usage

House wire is typically THHN -

• course stranded and not very bendable
• Sheath is typically vinyl
• Most times it is pure copper but aluminum is available.
• Usually rated at 90c or less.

Automotive wire -

• It is about twice as fine as THHN and more bendable
• Sheath is a mix of vinyl and other coatings to resist chemicals
• Good ones are made from copper strands that are tinned then combined into the wire.
• Most are just copper strands and the really cheap ones are CCA (copper clad aluminum.
• Usually 105 or higher because of where it is used.

Battery wire -

• much finer than Automotive battery wire easy to bend
• Always pure copper
• In marine use each strand is tinned before combining into the final wire.
• Usually 105c but can be 90c up to several hundred degrees C
• Sheath - chemical resistant and varies with application

Welding wire - NOTE: most welding wire is NOT UL listed.
DLO wire is similar but with a different sheath and is UL listed.

• Super fine wire and very bendable, even tha large stuff
• sheath is typically a rubberized coating that resists damage when you walk on it or drag it across and around a shop floor.
• Always pure copper
• never tinned inside it
• Always rated at 105c or higher

PV wire -

• fine stranded and super bendable
• Sheath is UV resistant
• Typically in 14 to 10 AWG
• should be pure copper

There are MANY types of wire - for our purposes most people recommend welding wire because of the bendability and the higher temperature rating.

Higher temp rating allows for more current without overheating
All wire we use in the US will be rated at least 600v

For current carrying capacity all the matters is the cross-section area of the wire - 1 strand or 3000 strands and higher it all amounts to the same capacity when naked.

The sheath insulated and prevents arcing along with protecting the wire itself. It will have a temperature rating on it and many times other ratings for special use like under water, direct burial, etc.

Temperature ratings are in free air where the heat can bleed off while the air circulates. You put it in conduit, bury it, enclose it in a building, use it on a roof or attached to the side of a building where it is in the sun you have to de-rate it for the conditions.

The longer the distance the less current it can carry because of resistance in wire.

Conduit - in the US - to protect the wire and structure

• DC wires must be in metal conduit when in a dwelling, on a roof, attached to a dwelling.
• When outside and not attached to a building the conduit can be PVC.
• When pulling wires in conduit it MUST be all done at once - no adding another strand later without pulling the whole bundle and repulling it.
• You can't mix AC and DC wires in the same raceway or conduit - MUST be separated.

Common usage -

• Welding wire (also battery wire) - between the battery and the inverter or SCC (solar charge controller)
• THHN - between the inverter and the electrical panel and in the house, also between combiner box and SCC
• PV wire - between panes and SCC or combiner box.

Pretty much automotive wire is not used unless you can't get the other. Not that it can't be, just isn't common practice. If you use it you can't listen to their stated ampacity, instead you have to look at the temperature and AWG to get a current carrying capacity.

 

[robbob2112]

EM radiation song

 

[robbob2112]

Sample hardware either I own or that others have recommended

Rednecktek

Amazon.com

 

[robbob2112]

NEC regarding burried conduit and EGC

According to the 2023 National Electrical Code (NEC) Table 300.5, the minimum cover requirements for conduits under a driveway are as follows:

- For Rigid Metal Conduit (RMC) and Intermediate Metal Conduit (IMC): 6 inches (150 mm)
- For Rigid Nonmetallic Conduit (PVC): 18 inches (450 mm)
- For Direct Buried Cables or Conductors: 24 inches (600 mm)

These depths are measured from the top of the conduit or cable to the finished grade, surface of the ground, or surface of the concrete. Always check with local authorities for any additional requirements or amendments to the NEC.


**250.120 Equipment Grounding Conductor Installation.**
- (A) General. All equipment grounding conductors shall be installed in accordance with the requirements of this section.
- (B) Continuity and Attachment. The continuity of the equipment grounding conductors shall be ensured by one of the following methods:
1. An equipment grounding conductor run with the circuit conductors.
2. An equipment grounding conductor run in the same raceway, cable, or trench as the circuit conductors.

**690.43 Equipment Grounding and Bonding.**
- (A) Photovoltaic Systems. Exposed non–current-carrying metal parts of PV module frames, electrical equipment, and conductor enclosures shall be grounded in accordance with 250.134 or 250.136(A), regardless of voltage.
- (B) Equipment Grounding Conductors. Equipment grounding conductors for photovoltaic source and output circuits shall be contained within the same raceway, cable, or trench with the PV source and output conductors.

**300.3 Conductors.**
- (B) Conductors of the Same Circuit. All conductors of the same circuit, including the neutral and equipment grounding conductors and other conductors that are intended to carry fault currents, shall be contained within the same raceway, trench, cable, or cord.


The burial depth of EMT (Electrical Metallic Tubing) when buried is primarily affected by the following factors according to the 2023 NEC:

1. **Voltage of the Circuit**:
- For circuits rated up to 120V, the minimum cover requirement is 18 inches (45.7 cm) for general underground installations.

2. **Type of Installation Location**:
- **Under Buildings**: EMT can have zero cover if buried under a building.
- **Under Driveways and Parking Areas**: Special considerations may apply, with the depth generally being 18 inches (45.7 cm) for one- and two-family dwellings driveways and parking areas.

3. **Additional Protection Requirements**:
- **Concrete Encapsulation**: When EMT is installed under a concrete slab with no vehicular traffic, the depth can be reduced to 4 inches (10.2 cm).
- **Physical Damage Considerations**: In areas where EMT might be subject to physical damage, additional protective measures such as encasement in concrete may be required.

4. **General Locations Not Specified Elsewhere**:
- For general underground installations not covered by specific conditions, the depth requirement is 24 inches (61 cm) for circuits above 120V but not specified for 120V, indicating a standardized depth for safety.

### Summary of Minimum Burial Depths from NEC Table 300.5(A):

- **Under Building**: 0 inches
- **Under 2-inch Concrete Slab with No Traffic**: 4 inches
- **Under 4-inch Concrete Slab with No Traffic**: 4 inches
- **Under One- and Two-Family Dwellings Driveways**: 18 inches
- **General Underground Installations (Up to 120V)**: 18 inches
- **General Underground Installations (Above 120V)**: 24 inches



### How to Bury EMT with AC Wire

For burying EMT (Electrical Metallic Tubing) with AC wire, especially for 240VAC 200-amp service or 120VAC 10-amp circuits, the following steps and requirements should be followed based on the 2023 NEC:

1. **Select Appropriate Fittings**:
- Use fittings that are specifically identified for direct burial applications. These fittings are designed to withstand moisture and soil conditions and are essential for ensuring the integrity of the installation【12†source】【13†source】.

2. **Corrosion Protection**:
- EMT installed in direct contact with the earth must be protected against corrosion. This may involve using galvanized or stainless steel EMT. In areas with severe corrosive influences, additional protective measures such as coating or wrapping may be required【12†source】【13†source】.

3. **Minimum Burial Depth**:
- **120VAC, 10-amp circuit**: Minimum cover requirement is 18 inches (45.7 cm).
- **240VAC, 200-amp service**: Minimum cover requirement is 24 inches (61 cm) for general installations【12†source】【13†source】.
- Specific conditions such as under concrete slabs or driveways may alter these depths (e.g., 4 inches under a 4-inch concrete slab with no vehicular traffic).

4. **Physical Damage Protection**:
- In areas where the EMT may be subject to physical damage, additional protective measures are required. This can include encasing the conduit in concrete or using other mechanical protection methods to prevent damage from physical impacts【11†source】【12†source】.

5. **Compliance with Local Codes**:
- Always check with local codes and regulations, as they may have additional requirements or restrictions. Some jurisdictions may still prohibit the use of EMT for direct burial despite the NEC provisions【13†source】.

6. **Installation Procedure**:
- Excavate the trench to the required depth.
- Install the EMT with the direct burial fittings.
- Ensure corrosion protection measures are in place if necessary.
- Lay the conduit in the trench, ensuring it is straight and level.
- Backfill the trench with soil, ensuring there are no sharp objects that could damage the conduit.
- Compact the soil to prevent settling and protect the conduit from physical damage.

 

[robbob2112]

Wires on a rooftop

According to the 2023 National Electrical Code (NEC), when running photovoltaic (PV) wire across a roof in Electrical Metallic Tubing (EMT), there are specific requirements for the distance the conduit must be above the roof surface.

Per NEC Article 690.31(C)(1), the conduit should be supported at intervals not exceeding 4.5 feet (1.37 meters) and secured within 3 feet (0.91 meters) of each enclosure or fitting.

Additionally, for conduits installed on rooftops, NEC 310.15(B)(3)(c) specifies that conduits installed above rooftops must be installed at least 7/8 inch (22 mm) above the roof surface to allow for proper cooling and to account for temperature adjustments in ampacity calculations.

This is the flexible metal conduit - Titan 2 - good to 105c on the roof.

Titan®2 Type UL Liquidtight Flexible Metal Conduit | Southwire

Keep your electrical systems safe with Titan®2 Type UL Liquidtight Flexible Metal Conduit.

www.southwire.com

E

Thread 'Emt or rigid conduit for PV on outside of house?'

Jul 10, 2024

I have 400 volt dc solar coming from a ground array, wires buried in the ground, and then the solar wire will be coming up the side of a house. I know the code book mentions that on the outside or the inside of the house the high voltage DC needs to be enclosed in metal.... but I couldn't find the code reference to use EMT or rigid conduit as it goes up the side on the house.
I have PVC in the ground and when it comes up on the side of the house I will go into a junction box and then switch to metal as it goes up the side of the house.
For the metal pipe on the outside of...

• ElkPicture
• Replies: 109
• Forum: DIY Solar General Discussion