I need help with understanding wiring
austin21jal Registered Users Posts: 5 ✭✭
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.
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.
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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?
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
gen: http://tinyurl.com/LMR-Lister ,
i am wiring this 66’ travel trailer for my bosses wife.
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.
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.
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.
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:
And for others here, this is the AC inverter manual link:
I will make a second post now to talk about your installation... I will probably start by asking a few questions first.
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:
For the solar power it would be:
- 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)
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):
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.
- 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
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:
If you have a 1,200 Watt Microwave load... At 120 VAC the current is:
- Power = Voltage * Current
- Current = Power / Voltage
- Voltage = Power / Current
- There are more equations, but this is enough for the moment
But that same 1,200 Watt load at 12 VDC:
- 1,200 Watt load / 120 VAC voltage = 10 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).
- 1,200 Watts / 12 volts = 100 Amps
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:
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.
- 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)
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).
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.
2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.
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:
i should be using 4/0 cable. This seems overkill. But if thats what we need we bought it.
ANJOSHI 300Amp Circuit Breaker:
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.
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 )
lastly, i only need a fuse from controller to batteries ( manual recommends 30a ) not a fuse in between panels and breaker?
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).
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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:
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:
And there is the Marine wiring guides, which are a bit on the aggressive side:
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):
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).