questions about solar wiring,,, shunts & fuses etc!

[LonerGlide]

Hi Everybody!,, ive been lurking here for 18 months or so and finally joined
there is so much great info on here but some how have overlooked a discription and/or schematics of a solar systems design with all componets labeled such as shunts, fuses, emergency shut off etc!,,,
im going to be using atleast 2-230watt panels,45-60amp mppt controller,6-208ah 6v gc batteries and a 1000-1500watt pure sein inverter,, and might add one more panel if I have enough room,,,ive read n worried so much about this my brain is starting to rattle,
ive read that fuses are sometimes placed on the neg side in the system which I dont understand!
SO!,, #1 what size shunts and located where in system?
#2 what sized fuses and located where
#3 do I need more than one shutoff switch
#4 charging!,, other than the solar I do have a 3500watt generator so should I install an rv converter or a quality 3 stage battery charger that I can run off the gen?
I was just planning to wire up an old 30amp cable off old rv into a breaker/fuse box.
my breaker/fuse box is out of 79 coachman mh and has a converter with generator disconect in it but figured the charger in it wasnt even close to todays standards,, so by using the breaker box part of it to control the 110/12v system ,,, which would be best for the $,, a new charger I can wire into a seperate circuit or a new rv converter?,, I might add im not going to be doing much,, if any camping in a normal camp site but boondocking for weeks at a time!
my ct isnt a new fancy one I was lucky enough to buy from factory but for $1000.00 my 12x7 tandom axle in just the size I wanted and it'll do anything a new one will do and I dont have to worry about that first scratch,, lol,, its been pulled thru the woods plenty !
I thank u guys in advance and feel fortunate to have found this wonderful site!
thX again!

[MtnDon]

shunt... depends on what it is for. Shunts are at the battery as a rule. Things like trimetric meters come with suggested sizes for different capacity systems. You can have a well running PV system w/o shunts.
~~~~~
fuses... in a neg ground system fuses are in the + line.

A type T fuse right at the battery protects the system against catastrophic short circuit. Size depends on what level of current will be passed for normal uses.

A DC rated breaker can often be used as an emergency disconnect. Or you can use disconnects designed for DC. Check to see if the breaker is rated for use as a switch. I go - battery - type T fuse - breaker/disconnect - loads.

Loads like inverters should have a properly sized fuse or breaker in the + DC input line. Other loads should be fused or breaked as well. Where? As close to the battery or the positive buss as possible.

~~~~

An old V converter is not worth wasting time on, IMO. Anything that does a three stage charge and is sized for the amperage best for the battery capacity will do a great job off shore power or generator power. A good inverter / charger combination unit can do the job for you. Some are made for mobile use and have transfer switches built in; makes it an easy hookup. Then you don't need a stand alone charger.

[MtnDon]

schematics of a solar systems design

FWIW...




325 feet between the PV array and the charge controller. If the equipment was all closer together then everything would be grounded to the same ground buss and same two ground rods. For a mobile installation there would be no ground rods in the earth; hard to move a trailer/vehicle that way.

[LonerGlide]

shunt... depends on what it is for. Shunts are at the battery as a rule. Things like trimetric meters come with suggested sizes for different capacity systems. You can have a well running PV system w/o shunts.
~~~~~
fuses... in a neg ground system fuses are in the + line.

A type T fuse right at the battery protects the system against catastrophic short circuit. Size depends on what level of current will be passed for normal uses.

A DC rated breaker can often be used as an emergency disconnect. Or you can use disconnects designed for DC. Check to see if the breaker is rated for use as a switch. I go - battery - type T fuse - breaker/disconnect - loads.

Loads like inverters should have a properly sized fuse or breaker in the + DC input line. Other loads should be fused or breaked as well. Where? As close to the battery or the positive buss as possible.

~~~~

An old V converter is not worth wasting time on, IMO. Anything that does a three stage charge and is sized for the amperage best for the battery capacity will do a great job off shore power or generator power. A good inverter / charger combination unit can do the job for you. Some are made for mobile use and have transfer switches built in; makes it an easy hookup. Then you don't need a stand alone charger.

ok, ive seen where others had hooked up their meters to the shunt to measure the load, amount of power being used?
I know the old converter isnt worth using but thought I could use the breaker box out of the old mh, hopefully ?,, gotta have a way to control both ac/dc an figured the old box would work without the converter.
so money wish which is the best cost effective way?,, an inverter w/charger or a three stage charger?,, I know a quality mppt controller is expensive as it is an more so with built in charger, I guess I need to price a good charger for cheapest way to go.
im thinking the amount of solar ill have will be enough to keep system charged but want a good backup
thx so much for such a quick response!

[LonerGlide]

schematics of a solar systems design

FWIW...




325 feet between the PV array and the charge controller. If the equipment was all closer together then everything would be grounded to the same ground buss and same two ground rods. For a mobile installation there would be no ground rods in the earth; hard to move a trailer/vehicle that way.

thX for the schematic, best one ive seen yet!
would wiring it up as a 24v system have benefits over a 12v system?
with the short wire runs ill have along with the larger cabeling im using I didnt know if it would matter?
also I see that inverter is wired directly into the ac panel,, can I still wire in my 30amp shorepower cord into the ac panel?,, ill mainly plug it into 30amp outlet on gen if I run out of sun and need to charge batteries,,,,, geezzz!,, think ill call it a night,, err morning,, lol,, will check back later,, thx again guys!

[OverTheTopCargoTrailer]

So 460 watts of solar to 624 AH in batteries is that a new overkill record for a CT



MtDon

Didn't I read somewhere if your system is under 48 volts you don't need all that grounding ?

[Shadow Catcher]

With an RV there is no real advantage in having 24V as everything is 12V and voltage drop because of the short distances is not a serious problem. Having high voltage panels however does have a benefit with an MPPT controller, works better in low light. 24V means you have to buck everything down to 12V to be usable for everything from lights to fan and water pump...
In my humble, or not so, fuzes are easier to use and a circuit breaker unnecessary as if it all works well it will never trip. In my case I used Anderson Power Poles for many of the make and brake connections, and they can be hot plugged.

[OverTheTopCargoTrailer]

ShadowCatcher

I'm using Anderson powerpoles also - mainly for quick disconnect should I ever see lightning storm.

[LonerGlide]

So 460 watts of solar to 624 AH in batteries is that a new overkill record for a CT



MtDon

Didn't I read somewhere if your system is under 48 volts you don't need all that grounding ?

well I did say I was thinking about adding another 230watt panel if I had room!,, depending on which direction I go with my air,, either a roof air,, which I already have or a 5000btu,, I understand that 460w with 600+ah is overkill,, lol,, only have 4 of the 6v now so could go either way.
im just trying to setup for as long of boondocking trips as I can without spending anymore than I have to!,,,,,, maybe having a wind generator will seem overkill to some but for me,, having wind power while im down on the gulf during winter will be perfect!

[LonerGlide]

With an RV there is no real advantage in having 24V as everything is 12V and voltage drop because of the short distances is not a serious problem. Having high voltage panels however does have a benefit with an MPPT controller, works better in low light. 24V means you have to buck everything down to 12V to be usable for everything from lights to fan and water pump...
In my humble, or not so, fuzes are easier to use and a circuit breaker unnecessary as if it all works well it will never trip. In my case I used Anderson Power Poles for many of the make and brake connections, and they can be hot plugged.

well I tell ya im learning it fast, lol,, and not always the easy way,, I bought my panels off ebay and wasnt told ,, even after explaing what I was needing I still wasnt warned about the high output pv so after getting them and then talking to sales rep at coleman air and was instructed to buy a pwm controller which wont work if I end up with 690watts in pv,,so resold controller and will buy an outback or triametic 60amp mppt,,,
so I guess im heading in the right direction,,, now!,, will wire for 12v,, have about the same amount of watts=AH,, a controller I can add panels to,, and a good inverter that'll run sat tv, laptop and acouple others
ive never heard of the power poles but will google em and find out

[MtnDon]

would wiring it up as a 24v system have benefits over a 12v system?

My reasons for going to 24 volts...

1. 24 volts permitted me to have fewer batteries in parallel. Better for the batteries.

2. 24 volts gets more power through the charge controller. If the CC is used with a 12 volt battery system the PV input wattage is one half what could be used with a 24 volt battery system.

In an RV most folks will not have enough panels for the watt limit to be an issue. And yes, an RV does not 24 volts for the accessories unless they are all 120 VAC. Then the 24 volts does not matter as the power is being processed through an inverter.

The schematic shown was for a stationary cabin.

Gotta go work; back later

[MtnDon]

thX for the schematic, best one ive seen yet!

that version does not show the type T fuse at the pos buss bar where the wire then goes to the inverter breaker.
~~~~

[MtnDon]

So 460 watts of solar to 624 AH in batteries is that a new overkill record for a CT



MtDon

Didn't I read somewhere if your system is under 48 volts you don't need all that grounding ?

The NEC evolves from where it never even used to address alternative power to where it has changed a lot between today's versions. Sometimes it varies with the local inspector and their interpretation. As far as I know 12 volt system have no mandate for grounding; not sure on the latest NEC and what it may say about 24 volts. Sometimes the NEC needs interpreting. I put grounding in as it seemed like a good idea and could not hurt if done right.

[MtnDon]

Andersen Power Pole connectors are great and come in many sizes. As for their ability to be hot plugged that can vary. High amperage DC can cause some very impressive flame arcing and can be downright dangerous. The same does not occur as readily with AC. YMMV.

[eamarquardt]

Andersen Power Pole connectors are great and come in many sizes. As for their ability to be hot plugged that can vary. High amperage DC can cause some very impressive flame arcing and can be downright dangerous. The same does not occur as readily with AC. YMMV.

For those that don't understand why AC and DC are different animals when it comes to switches and connections: Starting a spark is more difficult than allowing a spark to continue when the gap between the two conductors is getting bigger. IE a DC spark will continue even if you widen the the distance from the maximum you can get a spark to start with. That's because the voltage/current is always present and the spark, once started, can cross a bigger distance. With AC current the voltage and current starts and stops sixty times a second. So, as soon as the gap grows to the point that the voltage isn't enough to generate a spark to jump the gap between contacts the spark (which is actually 60 different sparks a second) won't restart with the change in polarity/current and all sparking (along with the burning of the contacts) stops. So, DC sparks last longer than AC sparks and are harder on contacts. Switches and connectors usually have both an DC rating and an AC rating. The AC rating is usually higher than the DC rating.

Hope this helps.

Cheers,

Gus