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Help and Clarification on Trailer Solar Install


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I've gone through everything I can find in this forum and other forums on solar on travel trailers. Head is swimming. Although we are seasoned RVs we have stayed mostly in RV parks over the years; however, now that we are retired and the travel budget is less we have decided to mostly boondock. We travel generally 7-9 months out of the year so we are almost full timers. I hate running our little generator (2000 watt) to charge the batteries so am going to solar. Need some advice on the switch over.

Here is my situation: I have three 100ah SLA VRLA AGM Deep Cycle RV batteries wired in parallel in my battery bank, planning on two REC Alpha 340 watt panels or two REC N-Peak 330 watt panels depending on which I can get wired in series, Victron 100/50 charge controller, 250 volt circuit disconnect between the panels and charge controller, 100 volt 60 amp circuit breaker between the charge controller and battery bank, and 2000 watt pass through inverter. Currently I can run everything except the A/C, including the frig and microwave, off the battery bank for a couple of days before recharging. I'm also considering installing a SmartStartRV in the A/C unit.

Now for my dilemma: Am I better off keeping the battery bank in parallel and 12 volts or rewire it in series to 36 volts? Some indicate that if I rewire than the bank will charge fast even under less than ideal sunlight. Also, if the batteries are wired in series and the inverter input is 12 volt will I damage the inverter? Some advice on installing the SmartStartRV in the A/C would also be appreciated, do you think I will be able to run the A/C after the SmartStartRV is installed? The A/C and microwave are pretty close in watts and amperage.

Thanks in advance for any council you can provide. I've also attached a schematic of the planned system.

Schematic of Solar Install.docx

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36 volt is a very uncommon voltage for an RV solar system.  Some people will go 24 volt or 48 volt, but rarely have I ever seen or heard of a 36 volt RV system.  There are other issues with going to a higher voltage battery bank.  Everything else in your trailer is 12 volt, so you have to have a way to get back to 12 volt to run those things (lights, RV fridge, jacks, slides, heater, water heater, etc.). This means some kind of DC to DC converter.  You cannot use a 12 volt inverter on a 36 volt battery bank, so your existing inverter (if you have one) will have to be replaced as well.  In addition, 36 volt inverters are not common, so it may be difficult to find one to meet your needs.  With the size system you are talking about, I can think of no advantage to running your batteries in series at 36 volt.  There are some advantages to higher voltage systems, but they don’t really come into play on smaller systems like yours.

You will find that running an air conditioner with the system you are describing will not be feasible.  Running an air conditioner requires more battery capacity than you have and also is not suited to AGM or lead acid battery banks because of their power output curves.  Running high draw items like air conditioners is better suited to a lithium battery bank.  Lithium batteries have a power output which is much more linear than AGM or lead acid. Lithium batteries can produce the same constant power through most of their charge cycle.  AGM and lead acid batteries cannot maintain the same power output as their state of charge decreases.  This means less power is available for high draw appliances as the battery state of charge decreases.

The micro air easy starts are great devices and are relatively easy to install. They come with very good instructions for DIYers and they sell installation kits that provide all the bits and pieces you may need to install one.  I have installed a handful of them and have never had any issues with various model air conditioners.  This being said, you will find it difficult to run any air conditioner of significant size (even with an easy start) from a 2000 watt inverter (assuming you had the battery capacity available).  You are better off using the generator for the AC with the easy start.

I have done a number of solar/battery/inverter installations and have helped many more do their own installations.  You can check out my website in my signature for more information if you would like.  There is a lot of information about batteries, inverters and solar under the Learn page.

In reviewing your diagram, their are some issues.  As I stated above, I see no advantages to going to 36 volts for your proposed system.  As I also stated, you will need to add components to get your system back to 12 volt for the rest of the trailer and you cannot use a 12 volt inverter charger with a 36 volt battery bank.

I do have one other concern in that you stated your batteries are 12 volt deep cycle RV batteries, but you didn’t state what brand they are.  Most RV branded batteries are hybrid batteries and are not true deep cycle batteries, but I can’t say this is true for sure in your case without more information.

Let me know if you have any specific questions I can help you with.

Edited by Chad Heiser
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Ken, I don't have any specs or data on your (or one you may choose) charge controller or Inverter but my SHORT ANSWER is:  (FWIW looks like Chad and I as typical basically agree yayyyyyyyyy lol)

                               I would keep the system you proposed at 12 versus 36 volt.

 That's ONLY my opinion, given the ONLY options being 12 or 36 volts.  Its YOUR money YOUR choice and you have the equipment and specs to make an informed decision which I don't

1) I cant say from here if your batteries will charge any faster?? They would get the same charging amps in series while if left in parallel their voltage would be clamped in balance

2) Is your charge controller (or one you can purchase) suitable for charging a 36 volt battery bank ???? More typical systems Ive seen are 12 or 24 or 48 volts, but your system isn't all that big to possibly gain the advantages higher voltage affords. My MPPT charge controller has settings for flooded lead acid orrrrrrrrrr AGM, I suggest one that has that...

3) Similar is your Inverter suitable for a 36 volt battery bank???? 

4) If you go with 36 volts you need a DC to DC converter to power all the RV 12 volt loads, which is another loss in efficiency plus expense 

5) I like and use a solar disconnect as you show in a convenient location. I like your choice of series solar panels to send higher voltage at less current down to your controller

6) For proper protection the battery cables that lead to the charge controller (you show a 60 amp breaker) need to be protected at or very near the batteries. Likewise the HUGE cables that feed your Inverter need protected at or near the batteries.  Of course the closer the better.

7) Im not going to take the time  to size all your cables (is 6 Gauge adequate??) and compute the line voltage drops, but when I practiced power distribution (pursuant to the latest NEC at the time) I sized sized the cables to have a minimum ampacity of 125% of the maximum continuous current and then if line voltage drop was excessive I upgraded. The I sized the overcurrent protection to protect the wiring

😎 Sure an AC soft start is a good idea REGARDLESS but your system isnt one that suits any AC use for long plus a 3000 Watt Inverter is more typically used for AC (I just use my genset if needed for AC).  As you know 300 AH of AGM shouldn't be discharged deeper then 50% so you ONLY have 150 AH available. FWIW and as an example only, I (small Class C moderate energy user) likewise run ALL EXCEPT AC using 520 AH of Deep Cycle AGM, 1080 Solar Watts, straight 12 Volt system, and don't run out of battery energy or discharge much over 30% 50% max, UNLESS it rains or there's no sun a few days on end grrrrrrr 

    Looks like given the size of your system sticking with the more standard 12 volt versus 36 is much easier simpler and likely cheaper, but its your equipment and your choice, it can be made to work at 36 if the equipment allows I guess ??? Best be checking your specs prior to going 36 volts  

Best wishes, congratulations on doing your homework FIRST. Im a retired electrical engineer who designs his own systems but Im NOT any solar expert, so see what THEY have to say

John T

 

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6 hours ago, Chad Heiser said:

Let me know if you have any specific questions I can help you with.

Ken, welcome to the Escapee forums!

I have been part of these forums for a very long time and am also retired from an electrical career as well as having owned and maintained RVs since the 70's. I am not into solar and off grid camping for extended periods but I have followed the progress of solar installations in RVs and Chad is one of the best informed and most reliable sources of solar information on any of the RV forums that I follow. Chad has been involved for a long time and has stayed current with the improvements that have come. Be very careful about whose advice you take as while I am no solar expert, I do know electricity and enough about solar to know that there are some who should not be relied upon on the RV forums. 

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2 hours ago, Kirk W said:

Be very careful about whose advice you take as while I am no solar expert, I do know electricity and enough about solar to know that there are some who should not be relied upon on the RV forums.

   AMEN Kirk I agree, spot on good advice.  Looks like were on the same page on this one yayyyyyyyyyy.   As an RV owner of 49 years and electrical engineer I have observed plenty of potentially hazardous MIS information out there. Where fire (especially in an RV) and life safety are concerned,  I advise people (if technically challenged) to seek out trained professional advice and don't hang ones hat on, take a risk, or rely solely on anything posted as you say by "some" .....  "on the RV forums" or also for that matter You Tube lol..........

  One potential rookie hazard I often see is people who fail to provide proper Overcurrent Protection (back in my power distribution design days I had to take day long NEC seminars on that topic alone whewwwwwww it got deep and very technical) for the huge high current capacity (perhaps 1000 or more short circuit extreme high temp amps) battery cables at or near the source, which is why I posted my Para 6 and 7 information above, hope it helps !!!!!!!!

 Hope all is back to normal down your way, best wishes and God Bless...

 John T  Also NOT any solar expert

  

Edited by oldjohnt
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Thanks to all that have replied. As pointed out there are too many opinions on how to install solar correctly. I looked up Chads website and profile so feel I can rely on his council. Additionally, our trailer is small, 25 ft Dutchmen Kodiak (201QB) new last year. The system I started with was a kit from Northern Arizona Wind and Sun than I started modifying the parts to fit my perceived needs. 

I will be sticking with 12 volt as recommended. The batteries are Weize which from my reading reviews indicate that they are true deep cycle and have a good reputation; but again I'm relying on sites that I know little about. I was not able to find the Weize manufacturer site so had to rely on the reviews. In my limited knowledge and going with my gut feeling I settled on 6 AWG, which may be larger than I need, to reduce loss and less heat build up. Again, thanks for all your advice.

Edited by Ken Larson
small update
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15 hours ago, Ken Larson said:

I will be sticking with 12 volt as recommended.

 Ken, thanks for the feedback and CONGRATULATIONS on going with our recommendations above, there's also universal agreement  "there are too many opinions on how to install solar correctly" lol. When allllllllll posters agree it must be correct Ya think ???   Hey no harm in oversizing conductors to reduce loss and heat, you did good...Of course use DC rated circuit breakers (on those DC circuits) but I'm sure you already know that.

  Don't forget to provide Overcurrent Protection for big Inverter cables (see my Par 6 and 7 above) those batteries could produce one HUGE amount of current plus extreme heat and/or an explosion if a short in their cables occurred. I bet all here would agree on the proper use of overcurrent protection !!!!!!!!!! It was one of the most important parts of the NEC. 

PS I suggest use of a Master Battery Disconnect Switch (Fused disconnects/switchable breakers  are an option) I don't think your diagram showed one ?? I incorporated such in my designs and bet all here would agree that's a good idea ??? Check out Blue Sea for quality high power DC components.

PS there shall be ONLY one Neutral Ground Bond and your RV panel should have separate insulated and isolated Neutral and Ground Busses, I'm unsure how your Inverter is configured. There could be some transfer issues HOWEVER your Pass Through Inverter may take care of what's needed making it simpler.

PS if you install a shunt based battery monitor that requires a single common battery negative to and through the shunt with all your - load cables on the shunts other side. One design to incorporate all the PS above would be to have a master disconnect (or combo overcurrent protection and disconnect) that feeds a Master + Buss to which your Inverter and charge controller etc are all connected via a breaker sized to match and protect the cables feeding individual loads. 

 Hey I'm NOT trying to be bossy, you asked for help so here's my advice, its still YOUR choice. There are too many variables and unknowns to try and design a system over the net, see what any Solar Experts have to say !!!!!!!!!!

 Best wishes and God Bless

John T  Long retired and rusty electrical engineer so NO warranty, but believe my post above is accurate............ 

Edited by oldjohnt
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I also made the choice today to upgrade the Victron 100/50 charge controller (700 watts max) to the Victron 150/70 (1000 watt max) which will allow me to add an additional panel (330 watt) should I want to in the future. 

Also, I ran across what appears to be a good explanation of calculating the charging parameters for a solar system. It can be found at: http://support.rollsbattery.com/support/solutions/articles/237882-calculating-proper-charge-settings-for-rolls-flooded-lead-acid-batteries

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11 hours ago, Ken Larson said:

Also, I ran across what appears to be a good explanation of calculating the charging parameters for a solar system. It can be found

Ken, I thought you were using AGM batteries, the info you posted is for Rolls brand flooded lead acid. However, it's still good information for those flooded lead acid battery users, I'm sure will be appreciated.  BOTH your solar charge controller and Charger need to be matched to suit your chosen battery chemistry, I'm sure you chose accordingly. 

John T

Edited by oldjohnt
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John, thanks for the reply. My post really was to provide some information about battery charging and the things to think of regardless of the type of battery. Yes, the article was directed to flooded batteries but the concepts and considerations are the same.

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1 hour ago, Ken Larson said:

John, thanks for the reply. My post really was to provide some information about battery charging and the things to think of regardless of the type of battery

  Hey Ken, you're sure welcome and hopefully that good info will help someone in the future. I considered purchasing Rolls Surette batteries back when I used FLA batteries as they seem to be good quality (were pricey as I recall). I also looked at Crown and Interstate and the cheaper ones sold at Sam's Club (some were less money but also less Amp Hours) before choosing the classic Trojan T-105's this last time which performed fine. I think you will like your AGM's I do mine even though I'm considering upgrading to Lithium now as we do more and more boondocking.

 Its wise to do your homework as you're now doing BEFORE jumping in and spending big bucks. There are a lot of fine knowledgeable gentlemen on here all willing to help, gotta love this forum !!!!!!

 Its been nice chatting with you, isn't if fun building up a solar system !!

 Best wishes, John T

Edited by oldjohnt
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On 3/6/2021 at 5:14 AM, Kirk W said:

Chad is one of the best informed and most reliable sources of solar information on any of the RV forums that I follow. Chad has been involved for a long time and has stayed current with the improvements that have come. 

Kirk, thank you for the kind words.  I appreciate it.

 

On 3/6/2021 at 12:51 PM, Ken Larson said:

Thanks to all that have replied. As pointed out there are too many opinions on how to install solar correctly. I looked up Chads website and profile so feel I can rely on his council.

Ken, I am happy to help.  Let me know if there is anything specific you need or I can do.

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Chad,

I appreciate the extensive discussion you provided to my question. Now, I need a little advice on specifics. Like you our current travel trailer was an impulse buy but have grown to love it. The TT is a 25 foot that I have been modifying and upgrading ever since we bought it. The TT is the typical 30 amps. I immediately installed three Weize 100 ah SLA VRLA AGM batteries and an AIMs 2000 watt inverter. I replaced the shore power 10 AWG wiring with 8 AWG because of the distance from the shore power plug to the battey bank. Disconnected the WFCO converter and wired so it only comes on when on shore power as I did not want it running when on battery power. This system has worked well; we can run the microwave, TV, DVD player, A/C fan, coffee maker, toaster and Frig off the batteries along with my CPAP at night, I use a iPower portable generator (2000 watt start/1600 watt running) to recharge the batteries; but want to get away from the noise of the generator.

Based upon my research and question answers I gotten over the last couple of days I have upgraded the solar system I want to install; I've attached an updated schematic of it. I believe I need to install additional circuit breakers but not sure just where and size; like in the 12 Vdc line from the batteries to the control panel and/or batteries to inverter. Would I need a circuit breaker between the shore power plug and the inverter or inverter to power panel?  Also, as is shown on the schematic I thought I should use 6 AWG wire but an wondering if 8 AWG would be more appropriate? The run from the solar panels to the electronic "bay" is about 12.5 feet in cable length. The distance between components will be less than 3 feet as everything is close together, only have about a 3x3 foot space to install the new components. The ground wires are one from the control panel and one from the battery bank to chassi ground.

Components: WFCO 8955 control panel, AIMs 2000 watt inverter, REC 330 watt solar panels (Vmpp=34.6, Impp=9.55, Voc=41.0, Isc=10.33, Pmax=-0.350C. Voc=-0.270C), batteries are Weize 100 ah SLA VRLA AGM's

I would appreciate any council you care to share. 

Solar Schematic Updated.docx

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Ken,

Running all three of your panels in series adds all the voltage and keeps the amperge the same (as I'm sure you know).  That puts the max voltage at approximately 120 volts and max amperage at approximately 10 amps.  This can easily be carried on 10 AWG wire.  Over a distance of 15 feet there will only be a 0.25% voltage drop on 10 AWG wire with the rated output of your panels.   Going up to 8 AWG drops that to 0.16% voltage drop and sticking with 6 AWG wire drops it to 0.10% voltage drop.  Most systems shoot for anything under 3%.  I personally like to keep it around 1% or less.  You are well under that with any of those wire choices. 

You have the correct sized Victron charge controller for that set up and have an in line disconnect shown between the panels and the controller which is good.  I would use at least 6 AWG wire out of the controller to the batteries, but would prefer 4 AWG wire there.  There is a much higher amperage potential on that wire run than on the wire coming from the solar panels.  At approximately 3 feet of run with 70 amps at 12 volt, there is 0.87% voltage drop with 4 AWG wire and 1.38% voltage drop with 6 AWG wire.  (All of these calculations come from the calculator.net voltage drop calculator I have linked on the resource page of my website.)

The breaker you have in your drawing between the charge controller and the batteries states 100 volt/60 amp.  That breaker should be a 12 volt breaker at 70 amp for your system and the selected charge controller.  The charge controller will be outputting 12 volt power at up to 70 amps, so the circuit breaker should be at least rated for that.  I prefer Blue Sea System DC circuit breakers.

Going back to talking about wire size, I would also use 4 AWG wire from your WFCO 8955 to the batteries and from your battery charger to the batteries rather than the 6 AWG wire you indicate.  Most all OEM's use 4 AWG wire between the converter and batteries/12 volt panels in RV's and there is good reason for that at the amperage potential they can produce.

The wire size you have shown for your battery interconnections and the connections to your inverter are also too small.  2 AWG is not sufficient for a bank that size.  You will have 2 to 3 feet of wire minimum making those connections between batteries.  With a 300 amp potential at 12 volts, the voltage drop on 2 AWG wire over that distance is 2.34%.  Even at 2/0 wire, the voltage drop is 1.17%.  I would use a minimum of 2/0 cable for that size bank.  I prefer to make all of my battery interconnect cables out of 4/0 (0.74% voltage drop in your system), but I tend to over engineer things.  2/0 will work and is a little bit easier to work with than 4/0.  I also recommend good quality welding cable for all the DC wiring to the batteries.  It is much more pliable and easy to work with in cramped quarters (like an RV) than standard stranded wire. 

Direct from the AIMS 2000 watt manual, at 12 volt they recommend a minimum of 1/0 wire.  Again, making everything out of 2/0 will work better.

You also need a catastrophe fuse between your inverter and the battery bank.  A quick scan of the Aims manual did not show what size is required, but it does indicate some type of overcurrent protection is needed between it and the battery bank.  It will typically be in the 300 amp range for a 2000 watt inverter.  I prefer Class T fuses for this protection.

You have a lot of connections going off to different components on the DC side of your system.  To simplify things, I like to add DC bus bars to make all those connections.  This way you only have one positive and one negative connection coming from your battery bank and all the other connections go to the buss bars (one positive and one negative).  I like Blue Sea or BEP Pro high amperage DC bus bars.

I would also consider adding a high amperage shut off switch between the battery bank and all your DC loads to be able to isolate the batteries for servicing/maintenance and storage.  This is much easier if you have bus bars in the system as the switch can be between the batteries and the positive bus bar.  Blue Sea Systems makes some very nice high amperage DC on/off switches for this purpose.

Finally, you do not indicate you have any type of battery monitoring in your system.  Anytime you have high draw loads on a battery bank, it is a good idea to add battery monitoring so you know the state of that battery bank.  I personally like the Victron BMV 712.  It is a very good battery monitor and will tell you a lot of information about your batteries.  The shunt for the battery monitor needs to be in the negative cable between your batteries and all DC loads and chargers.  Again, much easier to do if you have a negative bus bar where all the negative DC connections go and just one cable between it and the battery bank.  The shunt would go on that cable.

You asked if you needed a breaker before the inverter on the 120 volt side.  Assuming that connection is your trailers power cord, there will always be a breaker involved when you plug into a power pedestal.  You do not need to add another one, but you could if it made you feel better.  The 8 AWG ac wire you indicate in this connection is plenty big.  Typically 30 amp AC loads are carried on 10 AWG wire, but distance will be a factor and it never hurts to have more capacity than you need.

I think that addresses everything, but this is a fairly quick review of your system (and it is my anniversary today so I had some other things going on 😁).

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15 hours ago, Ken Larson said:

I believe I need to install additional circuit breakers but not sure just where and size; like in the 12 Vdc line from the batteries to the control panel and/or batteries to inverter. Would I need a circuit breaker between the shore power plug and the inverter or inverter to power panel?  Also, as is shown on the schematic I thought I should use 6 AWG wire but an wondering if 8 AWG would be more appropriate? The run from the solar panels to the electronic "bay" is about 12.5 feet in cable length. The distance between components will be less than 3 feet as everything is close together, only have about a 3x3 foot space to install the new components. The ground wires are one from the control panel and one from the battery bank to chassi ground.

  Congratulations Ken for doing your homework excellent advice above to which I will add a few power distribution engineers comments based on the NEC when I last practiced, but no warranty things may have changed since. WHERE FIRE AND LIFE SAFETY ARE CONCERNED CONSULT PROFESSIONALS AND THE NEC don't risk a fire or your life ONLY on what's posted (mine included) on a Forum  .

1) I believe I need to install additional circuit breakers but not sure just where and size; like in the 12 Vdc line from the batteries to the control panel and/or batteries to inverter.

   Overcurrent Protection to protect the "cables" needs to be placed at the energy source that delivers current into them NOT SOMEWHERE DOWNLINE because if so (placed later downstream)  the cable FROM the battery TO a short circuit BEFORE the overcurrent protection IS NOTTTTT PROTECTED. So to answer your good question PLACE THEM AT THE SOURCE/BATTERY not somewhere downstream.

2) " but not sure just where and size"

      Once you properly size the conductors to

a) what the manufacturer recommends   AND

b) to have a MINUMUM ampacity of 125% of the "Maximum Continuous Current" (I strongly advise using the bigger of the two above if they differ, no harm if the wire is a bit oversized) YOU SIZE THE BREAKER TO PROTECT THE WIRES AMPACITY IE if its say 60 amp rated wire don't use over a 60 amp breaker WELL DUH lol  

 2b)  "or inverter to power panel?"

      1) Consult manufacturers recommendation if they say use one USE IT

       2) Often such a device has its own overcurrent protection (does yours ???) so the output cable FROM Inverter TO the load is already protected (depends on Inverter and its design and circuitry, I cant say)  HOWEVER no harm in placing an external auxiliary protection device (for extra safety and/or convenience) if you so choose. 

 2c)  "and/or batteries to inverter."

   I STRONGLY ADVISE YOU TO ABSOLUTELY provide protection (at the batteries NOT way downstream) for the huge high current capable (in case of a short) cables leading FROM the battery TO the the Inverter !!!!!!!!!!!!!!!!!!!! If those were to short out and there was no protection you could draw hundreds to thousands (depends on battery bank capacity) of amps and heat causing a fire or explosion !!!!!!!!!!!!! See if any Solar Experts or others agree or not ??????????

      3) In the event the device DOES NOT have a means to protect the output  (sorta doubt it) THE WIRE AT LEAST (hopefully the manufacturer protected the output) NEEDS TO BE PROTECTED so sure add overcurrent protection if you like, Im not here to stop you.

3) Engineering comment: A Thermal Magnetic Circuit Breaker (in the event thats what you have, I cant say from here) can trip the thermal at currents EVEN LESS then its rating IE a long term current even if just under the rating can cause a trip. However if you follow the design guidelines I was taught under the NEC and sized the conductors to have a minimum ampacity of 125% of the MCC with an appropriate breaker THE BREAKER WILL BE OPERATING AT ONLY 80% OF IT RATING SO WILL NOTTTTTTTTTTTTTT TRIP THE THERMAL  Thats how I was taught and practiced.

4)   "Would I need a circuit breaker between the shore power plug and the inverter or inverter to power panel?" EXCELLENT QUESTION based on what I was taught and the NEC here is my engineer's answer

 NO you do not "need" a circuit breaker between the shore power cord and the Inverter, HERES WHY: The pedestal where you plug the power cord has (should at least) Overcurrent Protection to protect that cable already HOWEVER if you want for added safety or convenience OR THE MANUFACTURER SAYS  a disconnect and/or fused disconnect there FINE THATS YOUR CHOICE NO HARM DONE... 

5) WIRE SIZE without digging into wire sizes I will only repeat a) Size the wire to have a MINUMUM ampacity of 125% of the MCC b) Compute Line Voltage Drop and if excessive (3% MAX for sure I prefer much less) increase the wire size.  

6) OTHER ENGINEERS INPUTS even to questions NOT asked lol but believe it to be good advice 

    Most all designs Ive seen and my own thoughts and preferences for BOTH safety and convenience  would be TO USE A MASTER BATTERY DISCONNECT (or a combination device, fused disconnect). It will "work" without it  and its YOUR choice not any of ours, do as you wish.

FINAL COMMENTS I am NOT any Solar Expert, consult and trust the manufacturer and them over me. I am a retired Electrical Power Distribution Design Engineer who spent much of his career working with and studying the NEC who has designed and installed his own systems and been an RV owner for 49 years.

QUESTION does perhaps Chad or any others agree or disagree with any of the above ?? I'm never too old to learn so if the above is wrong PLEASE EDUCATE ME !!!!!!!!!!!!!!!!!!!!!!!! I love sparky chat and helping others anytime I can soooooooooooo if what I posted in wrong PLEASE PLEASE CORRECT ME we don't what to give Ken bad advice or see him or his RV hurt !!!!!!!  

We all agree be cautious as there can be INCORRECT info out there on the Forums grrrrrrrrrrrr

PS Yessssss I know this is an RV and some of the NEC may or may not apply HOWEVER when it comes to wire size and the location and sizing of circuit breakers I say no harm is erring on the side of safety even where above and beyond any codes .....Using bigger wire reduces line voltage drop, wires should be properly protected at the source of current, no harm in safety or convenience battery disconnects THATS MY STORY N IMA STICKIN TO IT unless corrected by a Solar Expert or the manufacturer says otherwise !!!!!!!!1

Hope this helps, that's my intention, best wishes be safe and God Bless all here.   Let me know your thoughts and any follow up questions and I and others will be glad to help

John T

 

Edited by oldjohnt
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10 hours ago, Chad Heiser said:

I think that addresses everything, but this is a fairly quick review of your system (and it is my anniversary today so I had some other things going on 😁).

CONGRATULATIONS Chad, best wishes. Our daughter got married this summer ON OUR FIFTIETH ANNIVERSARY what a treat and thrill it was

 Take care and as always its fun and a pleasure sparky chatting with you (seems we usually agree), thanks for the help you provide here.

 John T  NOT a Solar Expert but like to help anytime I can  

Edited by oldjohnt
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Based upon the information both of you have provided I plan on making the following changes:

I’ll use 8 AWG from the panels to the disconnect to the chrg/cntlr as it will be easier to work with.

The Victron chrg/cntlr manual says to use 2 AWG, I tried larger size cables and the connections on the chrg/cntlr will accept a max of 2 AWG, larger will not fit. Therefore, I’m stuck with 2 AWG between the chrg/cntlr and the batteries. I’ll connect the positive output of the chrg/cntlr to a 12 Vdc 70-amp fuse (ANL type OK?) than on to the battery bank. The negative output will be connected directly to the battery bank.

Then use 2/0 to parallel connect the batteries connecting the positive leg to a 300-amp fuse (ANL type OK?) to the positive input of the inverter. I’ll use 2/0 to connect directly to the negative side of the inverter.

The WFCO 8955 has a built-in converter/charger (called the Main Board Assembly or MBA) to provide battery charging and supply the 12 Vdc to the power panel. All 12 Vdc devices get their power through the Power Panel and are fused in the power panel. To provide the charge current to the battery bank the TT manufacturer used 6 AWG wire with a 15-amp breaker.

I disconnected the MBA from the 120 Vac bus in the power panel to prevent using battery power to charge the batteries via the inverter, want the solar to charge the battery bank. I than spliced a wire into the shore power positive leg prior to it being connected to the inverter. With no shore power provided the inverter auto switches to battery power, disconnecting from the shore power. This new leg was than connected to a newly installed standalone 15-amp circuit breaker to power the MBA only when connected to shore power.

The 6 AWG that was originally used to provide charging power is now only used to provide 12Vdc to the power panel. The total amps used by the 12Vdc appliances is 105 based upon the 12Vdc fuses (7 circuits with 15amp fuses) in the power panel. Do you think I need a fuse in the 12Vdc leg from the battery bank to the power panel? If so, would a 12Vdc 150-amp circuit breaker be appropriate?

The current set-up has been working fine, no problems. I can power all the 120 Vac appliances except the A/C and all 12 Vdc devices off the current battery bank. Based upon your advice it appears I need to increase the wire size from the chrg/cntlr to the battery bank to the inverter using 2/0 AWG wire due to the high current expected. Also, install the circuit breakers or fuses as you have suggested.

Now, last issue: There is a 6 AWG wire from the power panel to the trailer frame and a 6 AWG wire from the battery bank to the frame for grounding. Should I replace those wires? The power panel lug might not take a larger wire is the only problem. 

Thanks again for all you advice in this DIY project.

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Hi Ken, Sorry I dont have time to answer allllllll your questions in detail, maybe Chad does so for now I will only provide a bit of information hoping it helps, best I have to offer for now………

  

I’ll use 8 AWG from the panels to the disconnect to the chrg/cntlr as it will be easier to work with.

You Have approximately 1000 Solar Watts of 3 panels in series. Are they so called 12 or 24 volt panels ??? Vmp is higher (My 24 volt panels operate around 36 volts)  If they were “operating” at lets for now use 18 volts each in series  1000/54 = 18 Amps panels to controller,,,,,,If operating at lets use 36 Volts 1000/108 = 9 amps, therefore 8 gauge will suffice UNLESS you want to reduce line voltage drop even further, and it depends if they are 12 or 24 volt panels !!!!! ALSO I have NEVER seen 100% out of my panels, I doubt you will ever realize 1000 watts, maybe 700 to 800 which makes 8 Gauge look even better, or use bigger to reduce voltage drop is okay YOUR CALL. HOWEVER if operating at say ONLY 12 Volts (I doubt that but had to say), 1000 / 36 (3 in series) = 28 amps in which case 8 gauge will still suffice if the VD isn’t more then you’re willing to accept

 

1)    I’ll connect the positive output of the chrg/cntlr to a 12 Vdc 70-amp fuse (ANL type OK?) than on to the battery bank. The negative output will be connected directly to the battery bank.

 I take it youre NOT using any shunt based battery monitor which is fine and YOUR choice

          Lets for now just use 13.6 as your charging voltage, it may vary from 14.4 to 13.2 subject to your controller ??? Even ifffffffff you had 1000 watts (not likely) 1000/13.6 = 73 Amps so I see a 70 amp fuse as okay

          DONT FORGET to ALSO provide overcurrent protection for the cable FROM the battery TO the controller at or near the battery bank. This is different from whatever fuse you speak of above Im assuming is at the Controllers output. Cables hoked to the battery need protected PERIOD and a fuse up at the controller on its output DOES NOT protect the cables FROM battery TO controller  

   

2)    Then use 2/0 to parallel connect the batteries connecting the positive leg to a 300-amp fuse (ANL type OK?) to the positive input of the inverter. I’ll use 2/0 to connect directly to the negative side of the inverter.

 Sorry, I just dont have the time to design the whole thing over the net (Im in the middle of closing three estates for some legal clients back home) and look up all the cable ampacity charts, maybe Chad has them handy and the time, but 300 sounds a bit high. YES you need overcurrent protection there and Id use at least a master battery disconnect switch myself or one could use a circuit breaker there rated for switching or a fused disconnect to satisfy BOTH protection PLUS a disconnect means

 3)     

To provide the charge current to the battery bank the TT manufacturer used 6 AWG wire with a 15-amp breaker.

    WOW that must not have been a very high current rated charger. I would expect a 15 amp 120 volt input breaker but for charging current ????????? the wire and breaker should be at least 125% higher then the rated charging amps

 4)    The 6 AWG that was originally used to provide charging power is now only used to provide 12Vdc to the power panel. The total amps used by the 12Vdc appliances is 105 based upon the 12Vdc fuses (7 circuits with 15amp fuses) in the power panel. Do you think I need a fuse in the 12Vdc leg from the battery bank to the power panel? If so, would a 12Vdc 150-amp circuit breaker be appropriate?

 a)    I seriously doubt that 105 amps !!!!!!!! The sum of all the fuses is NOT the total typical total amps being supplied

b)    YESSSSSSSSSSS yessssssssss   yes         you need a fuse from the battery bank to the 12 VDC panel, those wires need protected at or near the battery SEE ALL MY POSTS ABOVE EXPLAINING THAT. Wire size and fuse needs to be computed  

 5)    Based upon your advice it appears I need to increase the wire size from the chrg/cntlr to the battery bank to the inverter using 2/0 AWG wire due to the high current expected. Also, install the circuit breakers or fuses as you have suggested.

If the Inverter is 2000 Watt, 2000 / 12 = 167 Amps not taking inefficiency into account sooooooooo the minimum ampacity of wire I would use is 167 x 1.25 = 208 Amps with overcurrent protection at the batteries remember NOTE the ampacity of single conductors in FREE AIR is much higher then if in a jacket or enclosed, you have to look it up.

  Hope this helps Ken sorry I can’t design the whole thing over the net, I don’t have the time or all the necessary information, but still glad to offer this small amount of assistance

  John T NOT a solar expert (maybe they can help more)  just and old retired power engineer and semi retired attorney……

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56 minutes ago, Ken Larson said:

John T, thanks a lot for what you have been able to do.

You're most welcome, sorry I don't have time to look up all the cable sizes but that will be easy for you. I did give the amperage requirements (like the 208 amps above) and recommendations for where to place breakers and other NEC necessary (as I best recall) overcurrent protection requirements and their locations.

 You're on top of this congratulations, as I get more time I may add more info. See what any solar experts have to say also............

 John T  

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19 hours ago, oldjohnt said:

QUESTION does perhaps Chad or any others agree or disagree with any of the above ?? I'm never too old to learn so if the above is wrong PLEASE EDUCATE ME !!!!!!!!!!!!!!!!!!!!!!!! I love sparky chat and helping others anytime I can soooooooooooo if what I posted in wrong PLEASE PLEASE CORRECT ME we don't what to give Ken bad advice or see him or his RV hurt !!!!!!!  

There is nothing I disagree with in what John said.  I don't have the electrical education or experience he does.  My experience is more practical and comes from working with my dad (a master electrician) when I was growing up and then applying what I learned from him to wiring projects I have done over the years - to include houses, shops, RV's and various other projects.  Had I not gone into law enforcement, I would most likely be running the family electrician business today.  Now that I am getting ready top retire from law enforcement, I am in the process of starting an RV electrical business to give me something to do and to formalize what I have already been doing for several years on the side anyway.

Edited by Chad Heiser
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9 hours ago, Ken Larson said:

I’ll use 8 AWG from the panels to the disconnect to the chrg/cntlr as it will be easier to work with.

This will be sufficient for your system.  I just wired four 310 watt panels in series on a Grand Design over the weekend and used the OEM 10 AWG solar wiring already in place.  Based on all calculations, that was sufficient for the project.  8 AWG wire will be fine for your three 330 watt panels in series.

 

9 hours ago, Ken Larson said:

The Victron chrg/cntlr manual says to use 2 AWG, I tried larger size cables and the connections on the chrg/cntlr will accept a max of 2 AWG, larger will not fit. Therefore, I’m stuck with 2 AWG between the chrg/cntlr and the batteries. I’ll connect the positive output of the chrg/cntlr to a 12 Vdc 70-amp fuse (ANL type OK?) than on to the battery bank. The negative output will be connected directly to the battery bank.

The Victron charge controller will take a maximum of 2 AWG wire.  That does not necessarily mean you need 2 AWG wire.  As I indicated above, 4 AWG would be fine but it never hurts to go larger.  I prefer DC circuit breakers like Blue Sea systems makes rather than fuses between the battery and the charge controller.  They play a double role in my systems.  They are first and foremost circuit protection for the equipment and wiring and should be placed close to the batteries for that protection.  They also can act as a shut off switch for maintenance or servicing the system.  Simply open the breaker and the batteries are isolated from the charge controller as needed.

9 hours ago, Ken Larson said:

Then use 2/0 to parallel connect the batteries connecting the positive leg to a 300-amp fuse (ANL type OK?) to the positive input of the inverter. I’ll use 2/0 to connect directly to the negative side of the inverter.

I would use a minimum of 2/0, if it were me.  I have scanned the manual for the AIMS inverter several times and can find no reference to the size or type of circuit protection they recommend between the inverter and the batteries.  The only reference I can find is they recommend there be overcurrent protection in the form of a DC breaker or fuse.  I have no personal experience with an AIMS inverter.  I have consulted on a DIY installation of an AIMS inverter recently and that was a result of the owner using too small of wire on his installation and almost burning his coach down.  He asked my advice on how to fix the problem and I gave him the same recommendations I gave you, 4/0 cables and a Class T fuse (400 amp for his inverter - a 3000 watt AIMS). 

Personally, if I were you  I would call AIMS directly and ask what their specific recommendation is on the type of over current protection they recommend.  I always use Class T fuses, unless using a Lynx Distributor in a Victron system.  In that case I will use CNN and Mega fuses as they recommend for the Lynx distributor.

As always, put the over current protection close to the battery.

I would also highly recommend a battery monitor with a shunt to monitor the state of your batteries.

9 hours ago, Ken Larson said:

The WFCO 8955 has a built-in converter/charger (called the Main Board Assembly or MBA) to provide battery charging and supply the 12 Vdc to the power panel. All 12 Vdc devices get their power through the Power Panel and are fused in the power panel. To provide the charge current to the battery bank the TT manufacturer used 6 AWG wire with a 15-amp breaker.

If that wire is OEM, then it should be sufficient to leave in place.  It wouldn't hurt to upgrade it to 4 AWG but shouldn't cause problems to leave it as is.

9 hours ago, Ken Larson said:

I disconnected the MBA from the 120 Vac bus in the power panel to prevent using battery power to charge the batteries via the inverter, want the solar to charge the battery bank. I than spliced a wire into the shore power positive leg prior to it being connected to the inverter. With no shore power provided the inverter auto switches to battery power, disconnecting from the shore power. This new leg was than connected to a newly installed standalone 15-amp circuit breaker to power the MBA only when connected to shore power.

The 6 AWG that was originally used to provide charging power is now only used to provide 12Vdc to the power panel. The total amps used by the 12Vdc appliances is 105 based upon the 12Vdc fuses (7 circuits with 15amp fuses) in the power panel. Do you think I need a fuse in the 12Vdc leg from the battery bank to the power panel? If so, would a 12Vdc 150-amp circuit breaker be appropriate?

Again, if the 6 AWG wire was OEM and the converter you are using is still the OEM converter, just connected in a different spot, then I see no issue with leaving it sized as the OEM did.  This is assuming the OEM sized it properly to begin with.  As John stated, you will never see 105 amps in that panel on the DC side.  OEMs typically install some type of resettable breaker near the batteries in the positive line feeding the DC power panel.  These come in different form factors.  You may have one in your system nd not realize it.  If you don't, I would add one.  The sizing would depend on the ampacity of the wiring and the draw the panel may require.  For a travel trailer with OEM 6 AWG wire that is going to only require a 55 to 75 amp breaker.  Look for a small rectangular device with two connection posts on it.  That is a common RV style resettable breaker for that application.

9 hours ago, Ken Larson said:

The current set-up has been working fine, no problems. I can power all the 120 Vac appliances except the A/C and all 12 Vdc devices off the current battery bank. Based upon your advice it appears I need to increase the wire size from the chrg/cntlr to the battery bank to the inverter using 2/0 AWG wire due to the high current expected. Also, install the circuit breakers or fuses as you have suggested.

The charge controller does not need 2/0 wire, but the battery interconnections and the connections between the battery and the inverter should be at least that size.

9 hours ago, Ken Larson said:

Now, last issue: There is a 6 AWG wire from the power panel to the trailer frame and a 6 AWG wire from the battery bank to the frame for grounding. Should I replace those wires? The power panel lug might not take a larger wire is the only problem. 

The 6 AWG wire from the DC distribution panel to frame ground will be fine based on the other 6 AWG wire OEM runs.  I personally would make the battery ground wire the same size as the battery cables (in this case 2/0).

Don't forget to also ground the inverter.  The AIMS manual recommends 8 AWG (bare copper) from the inverter chassis ground (not the DC negative stud).  There should be a ground stud on the AIMS inverter to connect this wire to and then run it to a frame point on the trailer for grounding.

Edited by Chad Heiser
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