I need help with understanding wiring

austin21jal · December 2019

Hello guys, I am super new to forums and you were my first choice hopefully you can help. I am wiring 2 solar panels to my batteries, I understand all that. However i am wiring my batteries and shore power to an inverter charger (2500w in ac in and out). I will attach a diagram of what i am wiring, although instead of shower power to inverter through i a fuse i am using the original breaker box as a “pass through” ( I believe is how to say it. And the AC out will go to a subpannel. And ALL outlets and lights will be powered through subpannel so that i can boondock or camp at a park. Im concerned on how to wire the sub pannel, i don’t fully understand the basic of where to put the G,N,L wires and if it needs its own dedicated nuetral and ground like the makn break does. Please help!! Here are some pics:

please excuse my

ROUGH DRAFT Diagram, and the 2 wires in main breaker, it originally had all lights wired to a circuit breaker. I am going to rewire lights to the subpannel.

BB. · December 2019

Welcome to the forum Austin,

Boy--This is jumping right into the fire (no frying pan middle step).

Just an FYI--A 2,500 Watt AC inverter is very big for an RV with only two solar panels (and what voltage @ Amp*hour battery bank). As a very rough rule of thumb for sizing, you would want a solar array Wattage to be something near the AC inverter wattage (i.e., 2,500 Watts of solar panels for 2,500 Watt AC inverter). Also, for a >~1,800 Watt AC inverter, you should be looking at a 24 volt battery bank and ~500 AH (at 24 volt) battery bank minimum to run a 2,500 Watt inverter at full load...

Anyway, to your question. Grounding. It is a complex subject for RV (and boats, etc.) 120 VAC power systems. For the RV, the Neutral/Ground bond is done in the shore power panel (in the USA). And when you are on the road, you have the option of running "floating" 120 VAC power, or grounded to your chassis 120 VAC neutral (if you are using a pure sine wave inverter--MSW inverters cannot have a grounded 120 VAC neutral--They will typically smoke).

Some AC inverters (and inverter-chargers) will do the ground/neutral switching for you... Others you will have to do that externally. Or, choose to let the 120 VAC float (and use GFI outlets to protect against shocks). This will work fine for most appliances. Ones that could have issues include some fluorescent tube fixtures and auto-spark ignition systems (they need neutral bonded to ground for the flourescent tubes to light reliably, and for spark flame detection to work properly).

If you do the Ground/Neutral bonding "wrong" (say you are on shore power, and have ground+neutral bond in your RV panel), it will trip the Ground Fault Breaker/receptacle on the shore power system (current is flowing both through the neutral return wire and the green wire safety ground).

I will stop typing here for the moment... We really do not have enough information yet to "give you an answer"... And, from what little I have seen here, I am concerned that your system components are not "balanced" design (too big AC inverter, too small solar array, too small battery bank)...

Anyway, just some guesses.

Further information and thoughts from you?

-Bill

mike95490 · December 2019

I'm not even going to touch this.

austin21jal · December 2019

BB. said:

Welcome to the forum Austin,

Boy--This is jumping right into the fire (no frying pan middle step).

Just an FYI--A 2,500 Watt AC inverter is very big for an RV with only two solar panels (and what voltage @ Amp*hour battery bank). As a very rough rule of thumb for sizing, you would want a solar array Wattage to be something near the AC inverter wattage (i.e., 2,500 Watts of solar panels for 2,500 Watt AC inverter). Also, for a >~1,800 Watt AC inverter, you should be looking at a 24 volt battery bank and ~500 AH (at 24 volt) battery bank minimum to run a 2,500 Watt inverter at full load...

Anyway, to your question. Grounding. It is a complex subject for RV (and boats, etc.) 120 VAC power systems. For the RV, the Neutral/Ground bond is done in the shore power panel (in the USA). And when you are on the road, you have the option of running "floating" 120 VAC power, or grounded to your chassis 120 VAC neutral (if you are using a pure sine wave inverter--MSW inverters cannot have a grounded 120 VAC neutral--They will typically smoke).

Some AC inverters (and inverter-chargers) will do the ground/neutral switching for you... Others you will have to do that externally. Or, choose to let the 120 VAC float (and use GFI outlets to protect against shocks). This will work fine for most appliances. Ones that could have issues include some fluorescent tube fixtures and auto-spark ignition systems (they need neutral bonded to ground for the flourescent tubes to light reliably, and for spark flame detection to work properly).

If you do the Ground/Neutral bonding "wrong" (say you are on shore power, and have ground+neutral bond in your RV panel), it will trip the Ground Fault Breaker/receptacle on the shore power system (current is flowing both through the neutral return wire and the green wire safety ground).

I will stop typing here for the moment... We really do not have enough information yet to "give you an answer"... And, from what little I have seen here, I am concerned that your system components are not "balanced" design (too big AC inverter, too small solar array, too small battery bank)...

Anyway, just some guesses.

Further information and thoughts from you?

-Bill

Hello, i deeply apologize for the delayed response i was never notified of the reply.

Lets start with some basic info, I am familiar with automotive electronics not familiar with the house side ( 120v system ).

i am wiring this 66’ travel trailer for my bosses wife.

The system will be run off of 2 ( maybe 3 or 4 ) 6v golf batteries ( in series ) to make it a 12v system. I am installing 2 100w solar panels, one roof mounted one a brief case panel. Into the inverter i will be running shore power as well, as a secondary charge method.

Inside the trailer was 5 lights, and 2 outlets. I have added a porch light to a switch/outlet combo and added an additional two outlets.

On one dedicated outlet will be here fridge and a microwave ( a camping world installer said for a microwave we need at minimum a 1500W inverter ) so we found a killer sale on black friday for a 2500w inverter charger. ::: https://theinverterstore.com/product/2500-watt-pure-sine-inverter-charger/

the current setup i have wired ( while im not 100% sure on what amps to use because many sites say different things )

shore power > circuit breaker > inverter
solar > batteries > inverter

inverter > sub panel > all outlets and lights

hopefully this is enough information to help further. I have most everything wired except the sub panel and fuses/circuit breakers. Because i am confused on the sizes to use.

As for the sub panel i went out and bought a second bus for ground. [ the current one over the black plastic is where i have my neutral wired ( from inverter AC OUT ) the new bus is where the small metal bar was, and my ground is wired there. And my live is wired to the large screw closest to the circuit breaker location. I do not have any dedicated lines run to the sub panel, the only three wires in it came from the inverter AC OUT. The only thing grounded is shore power. ( i do not have batteries yet so i havent grounded that end of things )

i will keep a much much closer eye on this thread, thank you so much for your time and i look forward to your response.

BB. · December 2019

Hi Austin,

No problem on the late reply... We all have lives in "real space" too and sometimes it takes a while to get back here.

And the reason you may not have received an email, is your "notification" options did not include email notifications for replies to my discussions (threads) (I am a moderator here, so I can see your profile settings). You (and anyone else here), can use this link to setup your various notification options:

https://forum.solar-electric.com/profile/preferences

And for others here, this is the AC inverter manual link:

https://www.aimscorp.net/documents/PICOGLF12W-25W12V120V%20071218.pdf

I will make a second post now to talk about your installation... I will probably start by asking a few questions first.

-Bill

BB. · December 2019

OK... Is this RV intended to operate for days on solar/battery only, or mostly from shore power and/or genset?

Is the Microwave intended to only be operated with shore power/genset power, or intended to run from solar/battery bank?

And what kind of refrigerator? A standard 120 VAC refrigerator, or a propane/DC (possibly / AC too) powered refrigerator?

For lighting, are you planning on 120 VAC wiring for lighting (inside lights, porch light, etc.)... Or will those lights be 12 volt (LED suggested) lights?

The 2.5 kW 12 volt PSW AIMS inverter manual is a bit confusing on some of the information.

Defining the loads is pretty much the first step to designing your power system. Once you understand your power requirements (12 volts @ xx Amps and YY hours per day, similar for your 120 VAC power), then we can define the size of the battery bank and supporting solar array (and things like battery charging current).

A reason you are a bit lost for wiring/battery sizing is because you don't have a good handle on the power requirements yet (I think).

The basic wiring for the 120 VAC power system:

30 Amp Shore power in => AC inverter/charger AC input => AC mains panel (30 Amp wiring input) => two or more 15 amp branch circuits (15 amps to microwave, 15 amp to AC refrigerator/120 VAC outlets/etc., 15 amps => 120 VAC lighting--If present).

Note: I suggest that lighting circuits have their own breaker/fuse... You do not want to trip a breaker (microwave/AC outlets) and have the lights turn off at the same time--2nd Breaker for lights can keep them on until other issues are resolved).

Inverter Green Wire Grounding is not clear how it is wired internally... However, the instructions simply say connect Ground/Line/Neutral to inverter input, and Ground/Line/Neutral output to yoru breaker panel. No connection of Ground/Neutral bonding is mentioned (and should be safe for a starting point).

If you follow NEC, typically 10 AWG cable for 30 Amp service. And 14 AWG for 15 amp circuits.

For the battery bank... It really depends on how much power you actually intend to pull... Say really use 2,500 Watts, the Battery bus to inverter would need a fuse/breaker/wiring (DC rated) for a minimum of:

2,500 Watts * 1/0.85 AC inverter eff * 1/10.5 volts low battery alarm = 280 Amps (AIMS inverter says 1/0 Minimum cable--Eh... No comment)

For the solar power it would be:

12 volt battery bus => Breaker/fuse => Solar charge controller => solar panels (panels only need fusing if 3 or more are in parallel).

The current from 2x 100 Watt solar panels would be (approximatly):

100 Watt panel * 1/17.5 volts typical Vmp (voltage max power) = 5.71 Amps Vmp per panel
5.71 * 1.25 NEC solar derating = 7.1 amps approximate Isc
2x 7.1 amps = 14.2 volts => 15 amp minimum solar circuit breaker to battery bus

Your drawing is a bit confused... The Shore power is 120 VAC @ 30 Amps (not 300 Amps)--And you would (typically) carry 30 amp wiring from the shore power to inverter input. From inverter output to your 120 VAC distribution panel. And use breakers/wiring to your various AC wiring points as needed.

The DC wiring... The battery bank is the "heart" of your system. There should be a battery bus +/- common point that carries all of the 12 VDC current. And it is sized to your "worst case" DC loading (your ~280 Amp AC inverter's DC input). So a 300 Amp fuse/breaker from battery bus to DC inverter input is appropriate, very heavy/short DC wiring (not the 40 amp fuse you had in your drawing).

Your solar charger (as currently spec'ed) does not handle very much current--So 15 or 20 Amp wiring/breaker/fusing is appropriate for ~200 Watts of solar power.

One thing that can confuse people working with 120 VAC and 12 VDC power... They did not really follow the power equation:

Power = Voltage * Current
Current = Power / Voltage
Voltage = Power / Current
There are more equations, but this is enough for the moment

If you have a 1,200 Watt Microwave load... At 120 VAC the current is:

1,200 Watt load / 120 VAC voltage = 10 amps

But that same 1,200 Watt load at 12 VDC:

1,200 Watts / 12 volts = 100 Amps

The above "simplified" equations do not account for inverter losses, low battery voltage, etc. But is here to help understand that 12 VDC wiring has to be much heavier than the same Wattage load at 120 VAC (I.e., 14 AWG wire and 15 amps or ~1,800 Watts @ 120 VAC, or the same 1,800 Watts at 12 VDC is 150 Amps and something like 1/0 cable--If following NEC).

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

I have answered your questions (I think) about wiring and breakers for 12 volt and 120 volt circuits...

However, I believe you are still in the middle of the campfire. These "wiring" questions usually come at the end of the design process... I suggest that:

Loads define battery bank
Battery bank defines charging (solar panels, AC charger, etc.)
And Loads also define solar array (as well as hours of sun per day/where camping/etc.).

Even if I did everything "exactly" correct in defining wire/breaker/fuse requirements (which is not actually true--Temperature, insulation type, etc. are part of the NEC rules for safe wiring design--And I skipped that).

I fear that your system (battery bank, AC inverter/charger, solar array) will not give the owner of the RV the power they expect to use...

For example (in very rough numbers) run the 1,500 Watt microwave on 2x 6 volt @ 200 AH battery bank:

1,500 Watts * 1/0.85 AC inverter eff * 1/10.5 battery low voltage alarm = 168 Amps (sort of worst case)
2x 6 volt @ 200 AH Golf Cart batteries in series = 12 volts @ 200 AH capacity
200 AH capacity / 168 Amps = 1.2 hours to dead battery bank (microwave use)

And the above is not rally true... Flooded Cell Lead Acid batteries (FLA) have much less apparent capacity at heavy loads... And at that load, those batteries would go below 10 volts if hit with that load for more that a few seconds.

A 200 AH FLA battery bank would typically supply 25 to maybe 40 amps continuously... And 80 amps maximum for a few seconds or minutes at a time... Not even close to the ~168 Amp @ 12 volts microwave load.

Second, normally suggest that a typical battery bank should not be taken below ~50 State of Charge for longer battery life (i.e., only 100 AH of "suggested" energy usage).

Anyway... I highly suggest to stop for a moment, define your loads (volts/amps/watts/hours of use per day/where the camping will be taking place, seasons--summer/winter, etc.) the owner expects to use when "dry camping" (solar/genset power), and do some paper designs first. The above starting point is not really going to work (at least as I understand it so far).

The expected loads need to be a lot less (no microwave, use propane refrigerator, LED lighting, laptop computer, cell phone charger, etc.)--Or design a much larger system (roof full of solar panels--1,000 to 3,000 Watts or so, and a very large battery bank) if these loads are the true requirements (and/or plan on a nice genset to supply the heavier 120 VAC loads).

-Bill

littleharbor2 · December 2019

Quick 2 cents worth here.
Once you get your loads figured out and subsequently your battery bank sizing calculated, you can figure out your solar needs. I'm going to wager a guess that it will be substantially more than the present 200 watts of panels. Start looking for good pricing on some, (not one), 250 -300 watt 60 cell panels and a decent 40 - 60 amp MPPT controller. This forum's host Northern Arizona Wind and Sun is a great place to start although you might find better pricing on local solar panel sources that would eliminate shipping cost. Think Craigslist, Facebook Marketplace, etc.

austin21jal · December 2019

BB. said:

OK... Is this RV intended to operate for days on solar/battery only, or mostly from shore power and/or genset?

Is the Microwave intended to only be operated with shore power/genset power, or intended to run from solar/battery bank?

And what kind of refrigerator? A standard 120 VAC refrigerator, or a propane/DC (possibly / AC too) powered refrigerator?

For lighting, are you planning on 120 VAC wiring for lighting (inside lights, porch light, etc.)... Or will those lights be 12 volt (LED suggested) lights?

The 2.5 kW 12 volt PSW AIMS inverter manual is a bit confusing on some of the information.

Defining the loads is pretty much the first step to designing your power system. Once you understand your power requirements (12 volts @ xx Amps and YY hours per day, similar for your 120 VAC power), then we can define the size of the battery bank and supporting solar array (and things like battery charging current).

A reason you are a bit lost for wiring/battery sizing is because you don't have a good handle on the power requirements yet (I think).

The basic wiring for the 120 VAC power system:

30 Amp Shore power in => AC inverter/charger AC input => AC mains panel (30 Amp wiring input) => two or more 15 amp branch circuits (15 amps to microwave, 15 amp to AC refrigerator/120 VAC outlets/etc., 15 amps => 120 VAC lighting--If present).

Note: I suggest that lighting circuits have their own breaker/fuse... You do not want to trip a breaker (microwave/AC outlets) and have the lights turn off at the same time--2nd Breaker for lights can keep them on until other issues are resolved).

Inverter Green Wire Grounding is not clear how it is wired internally... However, the instructions simply say connect Ground/Line/Neutral to inverter input, and Ground/Line/Neutral output to yoru breaker panel. No connection of Ground/Neutral bonding is mentioned (and should be safe for a starting point).

If you follow NEC, typically 10 AWG cable for 30 Amp service. And 14 AWG for 15 amp circuits.

For the battery bank... It really depends on how much power you actually intend to pull... Say really use 2,500 Watts, the Battery bus to inverter would need a fuse/breaker/wiring (DC rated) for a minimum of:
2,500 Watts * 1/0.85 AC inverter eff * 1/10.5 volts low battery alarm = 280 Amps (AIMS inverter says 1/0 Minimum cable--Eh... No comment)
For the solar power it would be:

12 volt battery bus => Breaker/fuse => Solar charge controller => solar panels (panels only need fusing if 3 or more are in parallel).

The current from 2x 100 Watt solar panels would be (approximatly):
100 Watt panel * 1/17.5 volts typical Vmp (voltage max power) = 5.71 Amps Vmp per panel
5.71 * 1.25 NEC solar derating = 7.1 amps approximate Isc
2x 7.1 amps = 14.2 volts => 15 amp minimum solar circuit breaker to battery bus
Your drawing is a bit confused... The Shore power is 120 VAC @ 30 Amps (not 300 Amps)--And you would (typically) carry 30 amp wiring from the shore power to inverter input. From inverter output to your 120 VAC distribution panel. And use breakers/wiring to your various AC wiring points as needed.

The DC wiring... The battery bank is the "heart" of your system. There should be a battery bus +/- common point that carries all of the 12 VDC current. And it is sized to your "worst case" DC loading (your ~280 Amp AC inverter's DC input). So a 300 Amp fuse/breaker from battery bus to DC inverter input is appropriate, very heavy/short DC wiring (not the 40 amp fuse you had in your drawing).

Your solar charger (as currently spec'ed) does not handle very much current--So 15 or 20 Amp wiring/breaker/fusing is appropriate for ~200 Watts of solar power.

One thing that can confuse people working with 120 VAC and 12 VDC power... They did not really follow the power equation:
Power = Voltage * Current
Current = Power / Voltage
Voltage = Power / Current
There are more equations, but this is enough for the moment
If you have a 1,200 Watt Microwave load... At 120 VAC the current is:
1,200 Watt load / 120 VAC voltage = 10 amps
But that same 1,200 Watt load at 12 VDC:
1,200 Watts / 12 volts = 100 Amps
The above "simplified" equations do not account for inverter losses, low battery voltage, etc. But is here to help understand that 12 VDC wiring has to be much heavier than the same Wattage load at 120 VAC (I.e., 14 AWG wire and 15 amps or ~1,800 Watts @ 120 VAC, or the same 1,800 Watts at 12 VDC is 150 Amps and something like 1/0 cable--If following NEC).

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

I have answered your questions (I think) about wiring and breakers for 12 volt and 120 volt circuits...

However, I believe you are still in the middle of the campfire. These "wiring" questions usually come at the end of the design process... I suggest that:

Loads define battery bank
Battery bank defines charging (solar panels, AC charger, etc.)
And Loads also define solar array (as well as hours of sun per day/where camping/etc.).

Even if I did everything "exactly" correct in defining wire/breaker/fuse requirements (which is not actually true--Temperature, insulation type, etc. are part of the NEC rules for safe wiring design--And I skipped that).

I fear that your system (battery bank, AC inverter/charger, solar array) will not give the owner of the RV the power they expect to use...

For example (in very rough numbers) run the 1,500 Watt microwave on 2x 6 volt @ 200 AH battery bank:
1,500 Watts * 1/0.85 AC inverter eff * 1/10.5 battery low voltage alarm = 168 Amps (sort of worst case)
2x 6 volt @ 200 AH Golf Cart batteries in series = 12 volts @ 200 AH capacity
200 AH capacity / 168 Amps = 1.2 hours to dead battery bank (microwave use)
And the above is not rally true... Flooded Cell Lead Acid batteries (FLA) have much less apparent capacity at heavy loads... And at that load, those batteries would go below 10 volts if hit with that load for more that a few seconds.

A 200 AH FLA battery bank would typically supply 25 to maybe 40 amps continuously... And 80 amps maximum for a few seconds or minutes at a time... Not even close to the ~168 Amp @ 12 volts microwave load.

Second, normally suggest that a typical battery bank should not be taken below ~50 State of Charge for longer battery life (i.e., only 100 AH of "suggested" energy usage).

Anyway... I highly suggest to stop for a moment, define your loads (volts/amps/watts/hours of use per day/where the camping will be taking place, seasons--summer/winter, etc.) the owner expects to use when "dry camping" (solar/genset power), and do some paper designs first. The above starting point is not really going to work (at least as I understand it so far).

The expected loads need to be a lot less (no microwave, use propane refrigerator, LED lighting, laptop computer, cell phone charger, etc.)--Or design a much larger system (roof full of solar panels--1,000 to 3,000 Watts or so, and a very large battery bank) if these loads are the true requirements (and/or plan on a nice genset to supply the heavier 120 VAC loads).

-Bill

Wow, this is a lot of amazing information and i thank you greatly. I will go over this in more detail with her shortly, as a response to answer your questions to hopefully keep this chain alive in the moment.

From what I understand she primarily plans to boondock, but the shore power will alllow her to top off on full batteries quicker, and also give her the option to have everything run on either if she ever does plan to be at a campsite.

my current wire setup is:
all lights + 1 outlet wired to a 15a -subpanel
porch light + 2 outlets to a 15a - subpanel
Outlet for micro and fridge to 20a - subpanel

she claims she wont be using much power, aside from she always wants the fridge on, and the microwave just incase she needs it. Im not 100% sure of the draw on these devices off the top of my head but i can get them when i go back over later today. They are both lowest rated watt setting she could find. I have explained the solar panels are a low w output for the system she is running but she says she wont be using the power alot.

i had a general understanding of the circuit breakers for subpanel but then a guy i spoke with over the phone said all subpanel breakers should be 30a and i got really confused. But by what you say it sounds like i was right initially.

my second point of confusion is with the wire from inverter to batteries according to:
https://www.altestore.com/howto/recommended-inverter-cables-sizing-and-breakers-or-fuses-a62/

i should be using 4/0 cable. This seems overkill. But if thats what we need we bought it.

However the fuse we bought was a 300a solo circuit breaker:
ANJOSHI 300Amp Circuit Breaker:
https://www.google.com/aclk?sa=L&ai=DChcSEwiWj6XBv6vmAhUW0mQKHUT_CTkYABASGgJwag&sig=AOD64_2JzLlmaNXqUcOz_fGXGHRCWitSkA&ctype=5&q=&ved=2ahUKEwjG3pvBv6vmAhVWtZ4KHQwiBIMQwg96BAgKEBM&adurl=

The wire seems way to big for me to (safely) wire this.

you are recommending a 1/0 cable?
will this circuit breaker work?

for our solar panel we have a 30a fuse special built for “plug and play” to the controller,

and a 30a fuse from controller to battery ( i wasnt clear why we need a double fuse system here )

now my last confused thought was the actual circuit breaker in the main panel. I believe its refered to as a “pass through” for shore power?

i believe i am supposed to use a 250a or 400a breaker but seeing as we have an old shore power plug ( I am quiet sure its only the 15a plug up ) i do not understand why we would need such a high rated breaker. Also if we do need that all the breaker i could find that large were double poles. Seeing my lesser of knowledge with 120v system i am not sure how to wire a double pole to a single line.

with all that said everything has been wired and run across the trailer i just simply need to put breakers in subpanel, and fuses in lines.

Was waiting for clarity before I started the final task, if you will.

I hope this helped clear up your missing information to an extent.

Its hard to clearly make a power draw estimate as we do not fully know how much she plans to use yet.

EDIT: EVERYTHING will be wired from the sub-panel. All lights, outlets, and appliances are 120v units. And the microwave pulls 700w rather than the normal 1200W

austin21jal · December 2019

littleharbor2 said:

Quick 2 cents worth here.
Once you get your loads figured out and subsequently your battery bank sizing calculated, you can figure out your solar needs. I'm going to wager a guess that it will be substantially more than the present 200 watts of panels. Start looking for good pricing on some, (not one), 250 -300 watt 60 cell panels and a decent 40 - 60 amp MPPT controller. This forum's host Northern Arizona Wind and Sun is a great place to start although you might find better pricing on local solar panel sources that would eliminate shipping cost. Think Craigslist, Facebook Marketplace, etc.

I appreciate all information anyone has to share and i will let her know your thoughts as well, thank you!

austin21jal · December 2019

BB. said:
OK... Is this RV intended to operate for days on solar/battery only, or mostly from shore power and/or genset?

Is the Microwave intended to only be operated with shore power/genset power, or intended to run from solar/battery bank?

And what kind of refrigerator? A standard 120 VAC refrigerator, or a propane/DC (possibly / AC too) powered refrigerator?

For lighting, are you planning on 120 VAC wiring for lighting (inside lights, porch light, etc.)... Or will those lights be 12 volt (LED suggested) lights?

The 2.5 kW 12 volt PSW AIMS inverter manual is a bit confusing on some of the information.

Defining the loads is pretty much the first step to designing your power system. Once you understand your power requirements (12 volts @ xx Amps and YY hours per day, similar for your 120 VAC power), then we can define the size of the battery bank and supporting solar array (and things like battery charging current).

A reason you are a bit lost for wiring/battery sizing is because you don't have a good handle on the power requirements yet (I think).

The basic wiring for the 120 VAC power system:

30 Amp Shore power in => AC inverter/charger AC input => AC mains panel (30 Amp wiring input) => two or more 15 amp branch circuits (15 amps to microwave, 15 amp to AC refrigerator/120 VAC outlets/etc., 15 amps => 120 VAC lighting--If present).

Note: I suggest that lighting circuits have their own breaker/fuse... You do not want to trip a breaker (microwave/AC outlets) and have the lights turn off at the same time--2nd Breaker for lights can keep them on until other issues are resolved).

Inverter Green Wire Grounding is not clear how it is wired internally... However, the instructions simply say connect Ground/Line/Neutral to inverter input, and Ground/Line/Neutral output to yoru breaker panel. No connection of Ground/Neutral bonding is mentioned (and should be safe for a starting point).

If you follow NEC, typically 10 AWG cable for 30 Amp service. And 14 AWG for 15 amp circuits.

For the battery bank... It really depends on how much power you actually intend to pull... Say really use 2,500 Watts, the Battery bus to inverter would need a fuse/breaker/wiring (DC rated) for a minimum of:
2,500 Watts * 1/0.85 AC inverter eff * 1/10.5 volts low battery alarm = 280 Amps (AIMS inverter says 1/0 Minimum cable--Eh... No comment)
For the solar power it would be:

12 volt battery bus => Breaker/fuse => Solar charge controller => solar panels (panels only need fusing if 3 or more are in parallel).

The current from 2x 100 Watt solar panels would be (approximatly):
100 Watt panel * 1/17.5 volts typical Vmp (voltage max power) = 5.71 Amps Vmp per panel
5.71 * 1.25 NEC solar derating = 7.1 amps approximate Isc
2x 7.1 amps = 14.2 volts => 15 amp minimum solar circuit breaker to battery bus
Your drawing is a bitlights + 1 outlet wired to a 15a -subpanel

porch light + 2 outlets to a 15a - subpanel

Outlet for micro and fridge to 20a - subpanel

she claims she wont be using much power, aside from

she always wants the fridge on, and the microwave just incase she needs it. Im not 100% sure of the draw on these devices off the top of my head but i can get them when i go back over later today. They are both lowest rated watt setting she could find. I have explained the solar panels are a low w output for the system she is running but she says she wont be using the power alot.

i had a general understanding of the circuit breakers for subpanel but then a guy i spoke with over the phone said all subpanel breakers should be 30a and i got really confused. But by what you say it sounds like i was right initially.

my second point of confusion is with the wire from inverter to batteries according to:

https://www.altestore.com/howto/recommended-inverter-cables-sizing-and-breakers-or-fuses-a62/

i should be using 4/0 cable. This seems overkill. But if thats what we need we bought it.

However the fuse we bought was a 300a solo circuit breaker:

ANJOSHI 300Amp Circuit Breaker:

https://www.google.com/aclk?sa=L&ai=DChcSEwiWj6XBv6vmAhUW0mQKHUT_CTkYABASGgJwag&sig=AOD64_2JzLlmaNXqUcOz_fGXGHRCWitSkA&ctype=5&q=&ved=2ahUKEwjG3pvBv6vmAhVWtZ4KHQwiBIMQwg96BAgKEBM&adurl=

The wire seems way to big for me to (safely) wire this.

you are recommending a 1/0 cable?

will this circuit breaker work?

for our solar panel we have a 30a fuse special built for “plug and play” to the controller,

and a 30a fuse from controller to battery ( i wasnt clear why we need a double fuse system here )

now my last confused thought was the actual circuit breaker in the main panel. I believe its refered to as a “pass through” for shore power?

i believe i am supposed to use a 250a or 400a breaker but seeing as we have an old shore power plug ( I am quiet sure its only the 15a plug up ) i do not understand why we would need such a high rated breaker. Also if we do need that all the breaker i could find that large were double poles. Seeing my lesser of knowledge with 120v system i am not sure how to wire a double pole to a single line.

with all that said everything has been wired and run across the trailer i just simply need to put breakers in subpanel, and fuses in lines.

Was waiting for clarity before I started the final task, if you will.

I hope this helped clear up your missing information to an extent.

Its hard to clearly make a power draw estimate as we do not fully know how much she plans to use yet.

EDIT: EVERYTHING will be wired from the sub-panel. All lights, outlets, and appliances are 120v system. The microwave is 700W as opposed to the conventional 1200w.

all lights inside are standard old lights, the patio light is led.

you also mentioned which i missed the first time over, 300a fuse for battery to inverter ( i am just not sure if it works with the 4/0 cable )

The fridge is ___w

lastly, i only need a fuse from controller to batteries ( manual recommends 30a ) not a fuse in between panels and breaker?

BB. · December 2019

Austin,

You do not need to quote replies, unless there is a specific paragraph that you want to address.

I will read the rest later when I am on a computer.

Bill

Estragon · December 2019

The shore power AC breaker should be sized for your input wiring. If it's 15a (14awg?), that's your breaker size. AFAIK, there's no such thing as multiple 100s amp shore power. I'd recommend using panel with a wrong polarity indicator, or at least carry a duplex circuit tester to catch bad shore power.

The inverter doesn't say if the neutral is switched (to use shore neutral/ground bond when on shore power, and lift otherwise). It usually is switched in mobile specific inverters, but my guess is it isn't in this case.

I think Bill's 1/0 inverter to battery wire size is from the inverter manual, not his recommendation. 2500w/10v low battery cut-off = 250a. Ampacity for 1/0 is ~130a. Your 250a breaker should be ok for 4/0, which isn't too big given the potential amps. 4/0 ampacity is ~230-260a.

An AC fridge will typically use ~1000-1500wh/day (~100ah), plus inverter losses. The standby current for the inverter is unclear to me. It says <50 "When Power Saver On". Anyway, 50w for 24hrs is another 1200wh/day to keep the inverter lit. At that rate, your 200ah bank is dead in less than a day.

You don't really need a breaker from pv to controller unless there are >2 parallel connected panels/strings. If used, the max size should be in panel spec (often 12-15a).

BB. · December 2019

Note that Estragon is using Watt*Hours for the 120 VAC energy (and can be used for 12 volt energy too)... The 100/200/etc. AH are referencing 12 volt battery/DC Bus only... You can talk about AH at 120 VAC... But talking about a "mixed" system (120 VAC/12 VDC)--it gets really confusing really quickly (remember that 10 amps of 120 VAC is 100 Amps @ 12 VDC--Both are the same 1,200 Watts).

A good tool to measure the 120 VAC loads is a Kill-a-Watt type meter... It is cheap and gives you "good enough" information to understand your appliances and estimate your daily power needs:

https://www.amazon.com/s?k=kill+a+watt+meter

Looking at energy usage and battery banks--It is like looking a gas tank... A 1 gallon gas tank will work for a lawnmower or small motorcycle. For a car/pickup, perhaps 15-20 gallons. And for a tractor trailer, 50-200 Gallon saddle tanks.

Solar/Battery power is very expensive... It is almost always cheaper to conserve energy than to generate it...

Just to give you some idea of scale--You pay something like $0.20 per kWH for power to your home... The "all in" costs for solar+battery bank power is something like $1.00 to $2.00+ per kWH... Or something like 5-10x the cost of utility power (and for weekend/summer trailers, solar power can cost even more--Solar power is generated all year round (not much during stormy weather)... A weekend/summer RV only uses a few months of power--The rest of the time (no camping), the solar power is "lost" (unused).

I can give you "numbers" for a 3,300 WH per day system (100 kWH per month)--Because, roughly that is where is sounds like this system is heading (something like a 650 AH @ 24 VDC battery bank, and a 2,500 Watt solar array, with a ~2,000 Watt AC inverter--Something probably more efficient than the AIMS inverter-charger). The location for camping, seasons (amount of sun), and details about appliances and energy usage.

Regarding how much current a cable can carry... There is the NEC table, which is a bit on the conservative side:

https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

And there is the Marine wiring guides, which are a bit on the aggressive side:

https://baymarinesupply.com/bosns_corner_wire_sizes

Using the above tables, 1/0 can range from 125 amps max (or even less) to 285 Amps max (less if you bundle wires together).

If you use NEC tables, I like to derate wiring by 1.25x (or 1/1.25)... A 15 amp load * 1.25 NEC derate = 18.75 Amp mininum rated wiring and fuse/breaker (more reliable wiring system).

And then there is the voltage drop... All wire has resistance, and at higher current, the voltage drop is much higher, so you need heavier wiring to get the resistance down (Voltage Drop = Current * Resistance).

So, besides sizing the wire heavy enough so that it does not overheat, you also have to size so that the maximum current flow and maximum voltage drop from battery to load is not excessive. You can play with a simple voltage drop calcuator (note that this one uses one way wire run length, not round trip like some others):

https://www.calculator.net/voltage-drop-calculator.html

For example, a FLA battery draws down to ~11.5 volts, allow 0.5 volt wiring drop = 11.0 volts at load.

And most AC inverters will support 2x current surge... That would be 11.5 volts - 1.0 volt (current surge) = 10.5 volts at load (battery cutoff voltage).

-Bill

I need help with understanding wiring

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