In line fuse and wire size

Hi, first post here. I have ben browsing the forum for some time.
Niel and Mike 90045 have been helpful in responding to a thread I posted elsewhere.
I am installing a solar system on my 24 foot motorhome.
Will start with around 100 W and be using a Morningstar MPPT controller with RTS. My wire run from controller to Batteries is 3 feet. I am using # 10 Ancor boat wire. I am striving for as little line loss as possible. The charts I have consulted would indicate that at full rated output of the controller (15A ) that this should be fine. Am I correct in assuming this? Also, I am trying to find an in line fuse arrangement that will attach to the #10 wire I am using. Or as an aternative one that comes with #10 or larger leads that I could solder into my Pos. Line. Does it matter if I use the blade type fuse as opposed to the traditional glass automotive type? Suggestions for a source? Am I being too critical about staying with #10 wire in the fuse leads? In my mind I visualize a bottleneck if I go to #12 or higher in the fuse install.
System may eventually go to 200 watts in series to the controller. Run from the panels to controller will be about 15 feet with a break in the line for a connection. ( Panels will be portable and carried in storage compartment when traveling ). I have purchased some Ancor boat wire in #14 for the panel to controller. I was planning on #12 but it was was not available. Any comments on this wire size/use is appreciated.
Lastly, can anyone suggest a quality two lead connector to place in the panel to controller line? Of course I am still looking to keep line loss at a Minimum.
Thank you,
DD
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Comments

  • banjorenebanjorene Solar Expert Posts: 36
    Re: In line fuse and wire size

    I think a 30 amp automotive fuse holder has #10 gauge wire I use blade type on my system and connect it close to the Panel and leave it inside the box on the panel where it's nice and dry
    Rene
  • banjorenebanjorene Solar Expert Posts: 36
    Re: In line fuse and wire size

    Any auto store,or Bennys,Sears,Walmart
  • BB.BB. Super Moderators, Administrators Posts: 32,804 admin
    Re: In line fuse and wire size

    Also, remember the voltage drop is based on length of wire... Fusing is based on gauge of wire (plus insulation type, enclosed or not, fill factor, temperature, etc.)...

    12 awg 6" pigtail is going to add much less resistance vs 100' of 10 awg wire... Just calculate the voltage drop/resistance of the two segments and go on.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Banjorene,
    Thanks for your reply.
    I just got back from visiting 3 Auto parts stores, 2 hardware stores and an electrical supply place. Largest any had or showed avaialble was 30Amp but only #12 AWG wire.
    I did buy for $5.00 a fuse holder with 30A 32V Buss HFB embossed on the outside of it. Bought at NAPA, P/N 782-3101. It is rather nice, and weather tight. Problem is it will only accept wire up to #12 AWG. I like it because I can take it apart and solder the connections. I may try to pry open the ends where the wire inserts to get my # 10 AWG to fit, then solder.
    Or, if the concensus from those on this forum is that I am being too fussy, I could solder short pieces of #12 wire into the fuse holder and then make two more solder connections. Those would connect my #10 AWG to the # 12 AWG on the fuse holder.
    I'll wait to get the opinions of those more experienced than I before I start modifying the fuse holder.

    banjorene wrote: »
    Any auto store,or Bennys,Sears,Walmart
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Thanks BB,
    I think what you are telling me is that I should not worry about 6 inches of #12AWG in a run of #10 AWG that is only 3 feet in total lenght.
    Correct?

    BB. wrote: »
    Also, remember the voltage drop is based on length of wire... Fusing is based on gauge of wire (plus insulation type, enclosed or not, fill factor, temperature, etc.)...

    12 awg 6" pigtail is going to add much less resistance vs 100' of 10 awg wire... Just calculate the voltage drop/resistance of the two segments and go on.

    -Bill
  • wxh3wxh3 Solar Expert Posts: 70 ✭✭✭✭
    Re: In line fuse and wire size

    Northern Tool has inline automotive fuse holder with 10 gauge wire.
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Thanks Wxh3,
    I was hoping to find one local so I could finish this stage of the project before heading to Arizona in a couple of weeks.
    I did go to Northern Tool's site. Doing a search I could not find any fuse holders. I will keep trying.
    wxh3 wrote: »
    Northern Tool has inline automotive fuse holder with 10 gauge wire.
  • wxh3wxh3 Solar Expert Posts: 70 ✭✭✭✭
    Re: In line fuse and wire size

    I found them at a NT store, not online. Cheap too, something like 2 bucks.

    Edit: There were actually two different ones in different parts of the store. I think one was 12AWG and one 10AWG. The 10AWG one was actually cheaper.
    Thanks Wxh3,
    I was hoping to find one local so I could finish this stage of the project before heading to Arizona in a couple of weeks.
    I did go to Northern Tool's site. Doing a search I could not find any fuse holders. I will keep trying.
  • BB.BB. Super Moderators, Administrators Posts: 32,804 admin
    Re: In line fuse and wire size

    Technically, I would worry more about the solder connections than the 12 awg wire with a 30 amp fuse (assuming normal temperatures and open wiring--not a hot, enclosed space).

    Solder with high currents (like during a short circuit) can easily melt and cause the wire(s) to unsolder and fall out (and cause secondary shorts). For holding current carrying wires--they need some sort of mechanical holding (crimp, binding post, screw, etc.)... Solder is not really safe (plus there are problems with work hardening where the solder stops in the strands/braid, etc.). If this is a sub-fused curcuit off of a larger fused circuit--soldering would probably work... If this is the first fuse off of battery--be really careful. Make sure that if the solder melts, that the wires cannot fall out of the holder and short to something else nearby.

    I looked around but did not find it--there was a post here on using fuse blocks built for car audio guys that looked very spiffy. Some examples (don't know anything about the products or companies):

    Hifi sound connection
    Skycraft surplus

    Not to sound all paranoid--what you want to do will probably work fine--crimp vs solder is the stuff that all of the safety/UL/NRTL/etc. is all about.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: In line fuse and wire size

    You say you are getting a MPPT controller. When you expand to more than your 100W, if you can insure panels will not be partially shaded, I would suggest series wire the panels, if they are still within the MPPT controller's input voltage limit. That will save you on line loss.
    Inside, after the controller, and to the battery, 200W @ 14V = 14A, so use wire with at least that capacity, so you don't have to rewire in the future.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: In line fuse and wire size

    you should be able to find something at even an auto parts store or radio shack as well as many car audio places. as a general guide some say they are rated for different amps of service like 20a or 30a. 20a is #12 gauge and 30a is #10 gauge.(of course it doesn't mean they can always physically connect that wire gauge, though it should) you can place a fuse up to the service rating and it can be less like 10a or 15a to better suit our solar applications while keeping wiring large for low voltage drops.
    using a small pigtail of #12 won't hurt much in the big scheme of things, but even the fuse itself will offer up some resistance so i can understand your quest to keep resistances down by trying to obtain the proper #10. if you have a good dmm you can check the voltage before and after the fuse to see the drop it creates.
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Well, gues I am getting my eyes opened here. Thats great as getting educated on these matters is hat I am seeking.
    I was soldering all connections because I thought that was the best way to proceed. I have always been a gearhead and cannot even begin to count the number of times I have encountered loose, green corroded crimp on fittings. Both in autos, motorcycles and boats in particular. Even some aircraft I have worked on. All of my soldered connections are heat shrink wrapped and well insulated. As far as amperage, 15 AMP max. out of the Sun Saver MPPT controller. Fuse will not be 30A. More likely 10A for 100W of panel to start. So, I hope I have done the correct thing as I have spent a good deal of time putting together a neat and tidy harness to connect my controller to the batteries. I will look at ways to mechanically fasten the wires so that they cannot move out of the connector should the solder melt.
    I am just trying to keep effeciency as high as possible.

    BB. wrote: »
    Technically, I would worry more about the solder connections than the 12 awg wire with a 30 amp fuse (assuming normal temperatures and open wiring--not a hot, enclosed space).

    Solder with high currents (like during a short circuit) can easily melt and cause the wire(s) to unsolder and fall out (and cause secondary shorts). For holding current carrying wires--they need some sort of mechanical holding (crimp, binding post, screw, etc.)... Solder is not really safe (plus there are problems with work hardening where the solder stops in the strands/braid, etc.). If this is a sub-fused curcuit off of a larger fused circuit--soldering would probably work... If this is the first fuse off of battery--be really careful. Make sure that if the solder melts, that the wires cannot fall out of the holder and short to something else nearby.
  • BB.BB. Super Moderators, Administrators Posts: 32,804 admin
    Re: In line fuse and wire size

    Remember the fuse to the charge controller is protecting the wiring (and the charge controller) from high currents available from the battery feeding into a down stream short (or charge controller internal short).

    Go ahead and use as 20 amp fuse placed as close as practical to the "high current source" (presumably battery/battery bus), assuming the wiring supports using a 20 amp fuse. (NEC recommends that the wiring be rated, at least, 1.25x the planned current. And fuses/breakers should also be rated 1.25 or more times the expected maximum continuous current flow).

    You will not really be protecting anything better with a smaller fuse (and you will have more voltage drop across the smaller fuse--so a larger fuse is more efficient too)... If a short occurs, the 20 amp fuse will still pop--and if the controller shorts internally, a smaller fuse is really not going to save anything.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Controller is already installed at a location right next to the batteries. Sun Saver MPPT controller. You say use wire with at least the capacity of use.
    i.e. 15A. Thats what I am trying to get reassurance on. I have used #10AWG fine strand Ancor boat wire between the controller and the Batteries.
    Will be using #14AWG Ancor fine strand boat wire between the panel and the controler. 15 foot run.
    I am considering another panl in series. Well within the Voltage limit of the controller. However in researching other threads on this forum, I am seeing the opinion that for the length of my wire run it may not make a big difference.
    I am open to comments on that.
    mike90045 wrote: »
    You say you are getting a MPPT controller. When you expand to more than your 100W, if you can insure panels will not be partially shaded, I would suggest series wire the panels, if they are still within the MPPT controller's input voltage limit. That will save you on line loss.
    Inside, after the controller, and to the battery, 200W @ 14V = 14A, so use wire with at least that capacity, so you don't have to rewire in the future.
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Thanks Niel,
    I thought I would just go out and buy wha I wanted with no problems. I have been in a bunch of places and no go. And I don't live in the boonies, believe me. Nothing at radio Shack and nothing at 3 auto parts stores. Just the fuse holder I described earlier in the thread, and I am reluctant to solder in # 12 AWG pigtails now to make it work as that doubles my solder connections. The fuse holder I bought at NAPA is rated for 30A, but states right on the literature it will only accept up to #12AWG wire. I have tried and the #10AWG does not even come close to fitting. I realize that thecontroller will only put 15A through the circuit.
    The reason I have been so anal about llosses is the cumulative effect. Like putting weight in an airplane. If you just say ,"oh the hell with it. Its just a few pounds", pretty soon weight and balance goes out the window. With the solarI was trying to avoid that scenario and get the most effeciency that I can by be mindful of a little loss here and a little loss there.
    Thats why I was asking about a quality connector to use in the panel to controller line to allow for portability.
    Maybe I am being too fussy and will do more harm than good. i.e. soldering my connections instead of just crimping them on.



    niel wrote: »
    you should be able to find something at even an auto parts store or radio shack as well as many car audio places. as a general guide some say they are rated for different amps of service like 20a or 30a. 20a is #12 gauge and 30a is #10 gauge.(of course it doesn't mean they can always physically connect that wire gauge, though it should) you can place a fuse up to the service rating and it can be less like 10a or 15a to better suit our solar applications while keeping wiring large for low voltage drops.
    using a small pigtail of #12 won't hurt much in the big scheme of things, but even the fuse itself will offer up some resistance so i can understand your quest to keep resistances down by trying to obtain the proper #10. if you have a good dmm you can check the voltage before and after the fuse to see the drop it creates.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: In line fuse and wire size

    i've just noticed you mentioned the use of #14 between the pv and controller. why did you choose that gauge there and #10 between the battery and controller? with #14 copper wire going on a 15ft run (30ft of wire) creates a voltage drop on that wire segment over 4.1%. this is too high even though it will still work less efficiently. using #12 for that run would still be over 2.6% for that segment and that must be added to the run from the controller to the battery too for the overall system drop adding that the overall should be under 3% with some recommending, like from outback, to keep that under 2%. if you made the wire run #10, it would bring that voltage drop percentage on that part of the system to just over 1.6% and would be very acceptable on the overall system for voltage drop percentage.
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Thanks BB,
    The fuse will be 2-4 inches from the Pos. terminal of #2 battery. Neg. lead is to the Neg. terminal of #1 battery. Batteries are in parallel. Group 24 DEKA AGM's totalling about 160 AH.
    Max current from the controller is 15A 15x1.25=18.75. Thus was my decesion on a 20A fuse. Thats with 200W of panel. I will be starting with 100W of panel.
    Where do I find the information in regards to whether or not my wiring supports a 20A fuse? I know what happens when you ass u me, however I would think the cable that I bought in #10AWG, approved for marine use would qualify. It is Fine multi strand, two leads inside a protective out cover.
    States on the outside, Ancor Marine grade 2 cond 10AWG (UL) Boat Cable
    600V 105 degree C dry (75 degree C wet) oil resistant BC5W2 E67078
    LL22035 CSA AWM II A/B
    With all of that information and considering what it cost per foot it must be able to withstand a direct nuclear blast!!!



    BB. wrote: »
    Remember the fuse to the charge controller is protecting the wiring (and the charge controller) from high currents available from the battery feeding into a down stream short (or charge controller internal short).

    Go ahead and use as 20 amp fuse placed as close as practical to the "high current source" (presumably battery/battery bus), assuming the wiring supports using a 20 amp fuse. (NEC recommends that the wiring be rated, at least, 1.25x the planned current. And fuses/breakers should also be rated 1.25 or more times the expected maximum continuous current flow).

    You will not really be protecting anything better with a smaller fuse (and you will have more voltage drop across the smaller fuse--so a larger fuse is more efficient too)... If a short occurs, the 20 amp fuse will still pop--and if the controller shorts internally, a smaller fuse is really not going to save anything.

    -Bill
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Actually I tried to get #12AWG for the panel to controller run. I was under the impression from what I have ben reading that it would be plenty. The place where I bought the wire was out of #12AWG. The #10 AWG was over $5.00 per foot. I thought that I could handle that for 3 feet of it. However, I as not too eager to pay over $75.00 for 15 feet of wire. Again I thought that I have seen people using much smaller wire in much longer runs. i.e. speaker cable, landscape wire. The 15 feet of #14AWG was over $30.00.
    I thought I had gone way overboard with my research, but I guess I may have goofed big time between my soldering connections and my choice of wire.
    Also, I consulted the wire guage chart in the Morningstar mnual prior to commiting to the #14AWG. ( once it is cut off the spool I own it ) According to that chart I was still at overkill with the gauge wire I brought home from the supplier.
    Probably if I had just thrown this system together without regard for all my concerns it would have functioned just fine for mny years. Seems to work for so many people I come across. I am always told I am way to particular and worry too much about the details.
    Well, I am committed to the #10AWG from the controller to the battery. Perhaps I can search for some #10AWG wire to use for the panel to controller.
    I'll have to frame my 15 Ft. of expensive wire.
    What do you guys with residential applications use? Some of you must have runs much longer that 15Ft. Where do you source it from?

    On Edit: In looking again at the Morningstar manual I see it was the #12AWG that was listed as appropriate for a 15 Ft. run at 15 A.
    I had #12 on the brain when I went to buy. It was my error when I substituted the #14 for the unavailable #12. I was visualizing the #14 in the position on the chart that is occupied by the #12. They list everything as 3% loss. I thought that this was a standard loss that was the best one could achieve. I did not realize that I could improve over what was listed.
    I will start looking for some resonably priced 2strand #10AWG wire. I wasn't having much luck before at the local building supply stores. That just one of the reasons that I bought the boat cable when I found it locally.

    Thanks to everyone for your input and suggestions.

    niel wrote: »
    i've just noticed you mentioned the use of #14 between the pv and controller. why did you choose that gauge there and #10 between the battery and controller? with #14 copper wire going on a 15ft run (30ft of wire) creates a voltage drop on that wire segment over 4.1%. this is too high even though it will still work less efficiently. using #12 for that run would still be over 2.6% for that segment and that must be added to the run from the controller to the battery too for the overall system drop adding that the overall should be under 3% with some recommending, like from outback, to keep that under 2%. if you made the wire run #10, it would bring that voltage drop percentage on that part of the system to just over 1.6% and would be very acceptable on the overall system for voltage drop percentage.
  • mike95490mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: In line fuse and wire size
    What do you guys with residential applications use? Some of you must have runs much longer that 15Ft. Where do you source it from?

    We don't use marine grade wire ? The spools of household wire, are much less, as miles get made, and price goes down to nearly material cost. Fancy wire = Fancy cost.


    One more note, be sure you get a battery temperature sensor for the Charge Controller. Because of the power going thru the charge controller, it warms up, and it's internal temperature sensor gets fooled, and your batteries get shortchanged on a full charge.

    Mike

    PS look up "Anderson Connectors" for good rugged disconnects. Housing and pins come separate, and must be bought separately.
    http://store.solar-electric.com/anpo15to45am.html
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Mike,

    Rather than tell me what You don't use, perhaps someone could tell me what they do use. And, more importantly where to purchase it.
    All I am looking for is some direct advice as to what I need from people that I look to as having far more expertise than I. Household wire is solid. After about 4 weeks of reading this and other forums I was under the belief that for 12V use multistrand was preferable. The finer the better. I also thought that I came away from my reading learning that I should be concerned with exposure to the elements, durability, managability etc. Hence my choice of the fine stranded marine cable. Just trying to do the right thing here.


    Reference my first post in regards to my controller and RTS.

    Thank you for the connector lead. I noticed that "for multistrand wire" and "solder contacts" were mentioned in some of the description.
    I will be going through Arizona in a few weeks. Perhaps I could stop and buy what I need on site. I was planning on buying my PV panel when I arrived in the Southwest. I was just trying to get started on the install before I left. Thus, my attempt to get materials locally.
    I see wire listed on the NAWS site. I will see what they have.
    mike90045 wrote: »
    We don't use marine grade wire ? The spools of household wire, are much less, as miles get made, and price goes down to nearly material cost. Fancy wire = Fancy cost.




    One more note, be sure you get a battery temperature sensor for the Charge Controller. Because of the power going thru the charge controller, it warms up, and it's internal temperature sensor gets fooled, and your batteries get shortchanged on a full charge.

    Mike



    PS look up "Anderson Connectors" for good rugged disconnects. Housing and pins come separate, and must be bought separately.
    http://store.solar-electric.com/anpo15to45am.html
  • BB.BB. Super Moderators, Administrators Posts: 32,804 admin
    Re: In line fuse and wire size

    Should be OK with the wiring... You will loose an extra 2% over heavier (and costly) wire to the panels--but that is ~2 watts you have lost... Not the end of the world.

    In general, for home type wiring, solid or stranded work OK electrically... It is only at high frequencies that the "skin effect" take hold--where most of the current is on the outside "skin" of the wire. DC has no skin effect. For radio frequencies--stranded does work better.

    Regarding fine vs course vs solid wire--Copper wire work hardens as you bend it... The smaller the diameter, the tighter/more it can bend... So, you fine very fine stranded cables on locomotives, arc welding equipment, and such.

    For home use, solid wire is usually installed because there is no flexing after installation.

    There are a couple difficulties with using fine stranded wire... One is that is it difficult to fit XX awg fine strand wire into connectors that are designed for solid/course strand wire (fine stranded wire has more air gaps and is larger diameter). So--it can be difficult to properly terminate (without solder).

    The other issue I have is that solder, flux, and other contamination wick up through the hollow spaces in fine braid--so things like battery acid go up the cable core and corrodes the cable up to a few inches from the "lug" under the insulation.

    That you have the heavy/short leads from the controller to the battery is good... That gives the controller the most accurate voltage measurement of the battery during charging (less voltage drop at high current).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: In line fuse and wire size

    i use romex house wiring for mine without any armor, conduit, or any other protections as my system isn't big or grid-tied. (note that the weather will often destroy the insulation if not protected) the stranded wire is good when one needs to move the wire often as it is less likely to break, but is a pain to work with when making connections and costs more. i use #10 stranded up to the pvs and makes adjustments for different pv angles easier for me and less likely to break the wire. it is not inconceivable to use heavy speaker wire too if the price is right. see disclaimer in the next paragraph. for a long lasting install or one that's connected to the grid it should be done just as house wiring would be done with conduit for protection and per nec specs. you don't have to use the stranded either if you don't want to.

    if you wish to utilize the wire you have and upgrade the voltage drop specs and aren't worried about the nec or long lasting permanent installs then take the 2 #14 wires for your dc from the pvs to your controller and combine them to only one of the polarities. btw, do not hold me responcible if you elect to do some of this stuff being it is in noncompliance with the nec and all is upon you as a disclaimer for myself. when that is done the other polarity would be needing a wire and you can then buy some 15ft of #10 wire for it. an example to be clear might be you combine (acting as 1 wire) the 2 15ft lengths of wire and attach it to the + of the pv and run it to the + of the controller pv input. the - now needs to be a 15ft length of the new #10 wire and you connect this to the - of the pvs and the - of the controller pv input thus completing the circuit. the combined #14 wires would be equivalent to 1 #11 wire 15ft long. this does make the calculations a bit more complex for the voltage drop, but it can be figured for the individual wires and individual sections and then added all together for the final voltage drop total and its percentage. that total will be roughly .265v dropped for a percentage at 12v of 2.2%. this is close to halving what your loss is now.

    i am glad you had read in the forum, but you misconstrued and misread a few things that would've made it advisable for you to ask us our opinions to double check what you were proposing to do and with what. as i mentioned it is doable as is, but will represent a slight loss higher than normal. in the future with any additional pvs to be added i would like for you to plan on replacing that wire and it may be advisable to double check with us before actually doing it.
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Bill,
    Thank you, Thank you!!!
    Your explanation and educating me on the wiring is very helpful. I can now see that where I thought I was doing the absolute best for my application, I in fact made some less than optimal choices. Though apparently not fatal.
    I am currently looking for some #10AWG wire for the panel to controller. I am sure that someday I will find a place to use the 15 Feet of #14 AWG wire that I purchased. My disappointment last evening has been replaced with an attitude of learn by your mistakes.
    One thing though that may be another factor in all of this.
    The panels that I am looking at have a Voc of 27V, and Vpm of 21.5V. These voltages should work to my advantage if I did stay with the AWG#14. Correct?
    Should I add a second panel in series, voltage loss would be even more negligable. Am I wrong with this understanding. The voltage capability of the MS Sunsaver is one of the reasons I chose it in combination with the higher voltage panels. OR, did I goof again?
    Thanks again for your help.


    BB. wrote: »
    Should be OK with the wiring... You will loose an extra 2% over heavier (and costly) wire to the panels--but that is ~2 watts you have lost... Not the end of the world.

    In general, for home type wiring, solid or stranded work OK electrically... It is only at high frequencies that the "skin effect" take hold--where most of the current is on the outside "skin" of the wire. DC has no skin effect. For radio frequencies--stranded does work better.

    Regarding fine vs course vs solid wire--Copper wire work hardens as you bend it... The smaller the diameter, the tighter/more it can bend... So, you fine very fine stranded cables on locomotives, arc welding equipment, and such.

    For home use, solid wire is usually installed because there is no flexing after installation.

    There are a couple difficulties with using fine stranded wire... One is that is it difficult to fit XX awg fine strand wire into connectors that are designed for solid/course strand wire (fine stranded wire has more air gaps and is larger diameter). So--it can be difficult to properly terminate (without solder).

    The other issue I have is that solder, flux, and other contamination wick up through the hollow spaces in fine braid--so things like battery acid go up the cable core and corrodes the cable up to a few inches from the "lug" under the insulation.

    That you have the heavy/short leads from the controller to the battery is good... That gives the controller the most accurate voltage measurement of the battery during charging (less voltage drop at high current).

    -Bill
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Thank you Niel,
    Another informative and understandable suggestion.
    As I stated in a response to BB, I will put my AWG#14 on the shelf for use on another day. I will find some acceptable #10AWG and use it right from the start. I see that NAWS has some. I may just wait and get some from them when I arrive in AZ in a few weeks.
    Please note my panel voltages. They do work to my advantage . Correct? At least in regards to line loss. I understand that a watt is a watt, regardless of what combination of A X V you use to arrive at it.
    Well, at least my decision to use multistrand is warranted, as the panels will be used in a portable fashion. Wire will bo moved about quite a bit.
    I will inspect my solder connections on a regular basis.
    By the way, I visited 4 more places today. No fuse receptacles for #10 wire.
    I followed a link that BB supplied and see the audio folks apparently have them. There are two audio installer facilities in my area. Guess where I am going tomorrow?


    niel wrote: »
    i use romex house wiring for mine without any armor, conduit, or any other protections as my system isn't big or grid-tied. (note that the weather will often destroy the insulation if not protected) the stranded wire is good when one needs to move the wire often as it is less likely to break, but is a pain to work with when making connections and costs more. i use #10 stranded up to the pvs and makes adjustments for different pv angles easier for me and less likely to break the wire. it is not inconceivable to use heavy speaker wire too if the price is right. see disclaimer in the next paragraph. for a long lasting install or one that's connected to the grid it should be done just as house wiring would be done with conduit for protection and per nec specs. you don't have to use the stranded either if you don't want to.

    if you wish to utilize the wire you have and upgrade the voltage drop specs and aren't worried about the nec or long lasting permanent installs then take the 2 #14 wires for your dc from the pvs to your controller and combine them to only one of the polarities. btw, do not hold me responcible if you elect to do some of this stuff being it is in noncompliance with the nec and all is upon you as a disclaimer for myself. when that is done the other polarity would be needing a wire and you can then buy some 15ft of #10 wire for it. an example to be clear might be you combine (acting as 1 wire) the 2 15ft lengths of wire and attach it to the + of the pv and run it to the + of the controller pv input. the - now needs to be a 15ft length of the new #10 wire and you connect this to the - of the pvs and the - of the controller pv input thus completing the circuit. the combined #14 wires would be equivalent to 1 #11 wire 15ft long. this does make the calculations a bit more complex for the voltage drop, but it can be figured for the individual wires and individual sections and then added all together for the final voltage drop total and its percentage. that total will be roughly .265v dropped for a percentage at 12v of 2.2%. this is close to halving what your loss is now.

    i am glad you had read in the forum, but you misconstrued and misread a few things that would've made it advisable for you to ask us our opinions to double check what you were proposing to do and with what. as i mentioned it is doable as is, but will represent a slight loss higher than normal. in the future with any additional pvs to be added i would like for you to plan on replacing that wire and it may be advisable to double check with us before actually doing it.
  • BB.BB. Super Moderators, Administrators Posts: 32,804 admin
    Re: In line fuse and wire size
    One thing though that may be another factor in all of this.
    The panels that I am looking at have a Voc of 27V, and Vpm of 21.5V. These voltages should work to my advantage if I did stay with the AWG#14. Correct?

    As always, read the manual for the details--but from the MorningStar SunSaver Web Page:
    Maximum Open Circuit Voltage = 75 V
    Two Voc=2x27 volts = 48 VDC

    Well under the Voc-max=75V of the controller.

    Current wise, assuming these are two 100 watt panels with Vmp=21.5V then:

    200 watts / 2*21.5v = 4.65 amps (well below the 15+ amps max current allowed in 14 AWG wire--assuming panels are installed in series)

    Using the voltage drop calculator for 15' of wire (x2 for round trip=30' of 14 awg, Vmp=43volts) gives 0.82% drop--more than acceptable (assuming I have all of the information correct).

    For one 100 watt panel:

    100 watts / 1*21.5v = 4.65 amps

    Voltage Drop for 14 awg wire is 1.65% max. Still fine.

    And to finish up for the controller to battery drop. 10 awg, 14 volt battery charging (approx 15 amps), 2*3' foot run gives ~0.62% drop...

    Unless I missed something--you should be fine.
    Should I add a second panel in series, voltage loss would be even more negligable. Am I wrong with this understanding. The voltage capability of the MS Sunsaver is one of the reasons I chose it in combination with the higher voltage panels. OR, did I goof again?
    Thanks again for your help.
    If you add the second panel in series, the current remains the same, the Vmp doubles, so the percentage voltage (wiring loss) drop is 1/2 of the 100 watt single panel system. If you add the 2nd panel in parallel--the current doubles, so the percentage voltage drop of two panels in parallel is 2x worse (vs 1 panel in series).

    So--everything is going your way... By all means though--read the MPPT manual (from the MorningStar Link I supplied above). I have skimmed through it before--but you are the one responsible for your installation. ;)

    -Bill

    PS: Don't feel bad if you have to trim a few of the strands off of your wiring to get it to fit the wire connection point... It will not affect anything in your system (voltage drop or safety). As always, make sure the wires are well tied off to prevent strain on the fuse blocks...
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • FreeBrrdFreeBrrd Solar Expert Posts: 116 ✭✭✭✭
    Re: In line fuse and wire size

    Wiringproducts.com has an inline with 10 awg. I've ordered a few things from them. Fast shipping.

    Their site doesn't work for linking to a particular product so go to the site and search for "78335" product number. That will take you to the page, second one down is "Inline Watertight ATO/ATC Fuse Holder" for $3.91. Shows three sizes - 35 Amp 10 Ga. (78335)
    http://www.wiringproducts.com/index1.html
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Thanks BB,
    The controller is already mounted right next to the batteries. I have read the manual several times. However, as Niel mentioned in regards to my time researching the forum, perhaps there are times whn I am misinterpreting what I am reading. I have never had a comprehension problem in the past, but I am not getting any younger. I will be less timid in the future in asking questions prior to acting. Just a comment on that matter. One of the reasons that I researched for so long before posting. I have often seen on forums (including this one) where someone is chastised for NOT using the search feature prior to asking. I guess I was just trying to be a good new forum member.
    M.S. suggests using a 25A fuse which I am intending to do. I will ensure that all my wire is mechanically secured, particularly near the ends where the connections occur. I try to be diligent about inspecting things on a regular basis. I will add the solar wiring to the list.
    Thank you for the computations. They are quite helpful.
    Giving credit where it is due, I have seen these figures before from Niel. I thank the both of you.

    I was thinking of removing some of the strands of wire to get it to fit the fuse holder. Frankly, I was afraid to ask if it would be acceptable.
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    Thanks freebrrd,
    I am on my way to wiringproducts right now.
    FreeBrrd wrote: »
    Wiringproducts.com has an inline with 10 awg. I've ordered a few things from them. Fast shipping.

    Their site doesn't work for linking to a particular product so go to the site and search for "78335" product number. That will take you to the page, second one down is "Inline Watertight ATO/ATC Fuse Holder" for $3.91. Shows three sizes - 35 Amp 10 Ga. (78335)
    http://www.wiringproducts.com/index1.html
  • BB.BB. Super Moderators, Administrators Posts: 32,804 admin
    Re: In line fuse and wire size

    DD,

    I used to think my reading comprehension was OK until I started dealing with regulatory while doing engineering design...

    Regulatory is the worst combinations of Engineering and Law... And, quite a few times, I would run up against wording (must, shall, should, recommended) and argue that they have different meanings--and find out there is a whole back story on how things are really done--sort of like Law--you think you can read the Constitution and then find out there are 200 years of precedent that say almost exactly the opposite of what the "plain wording" of the Constitution seems to state.

    Arguments long into the night over the use of 70C rated wire vs 90C rated wire (for example, 70C was perfectly OK for my application--but 90C was cheaper and available off the shelf--the regulatory argument was since I was using 90C rated wire, I had to derate the current capacity, conduit fill/size, box fill/size, get 90C hardware, etc.--just using a higher rated component in my 70C system).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Different DrummerDifferent Drummer Solar Expert Posts: 26
    Re: In line fuse and wire size

    OK,
    Lets see if I can open up another can of worms.
    First let me ask. When the formula's and calculations are placed before me I have no problems understanding them or the related math. But tell me, where would I go to arm myself with this information? Is there a reference where I can find a formula for calculating such things as voltage drop over x ft of x AWG wire at X temp. with X humidity. Is all of this stuff listed in the NEC?
    Now for the can of worms. I noticed that BB doubled my 3 foot run of #10AWG wire when doing the calculation for the wiring between the Controller and the batteries. I have two batteries mounted next to each other end to end. Looking at the batteries from the side, the controller is mounted to the left of the left hand battery. It is within 4 inches of the battery. Looking at the batteries again from the side the first (L) battery is mounted with the negative terminal closest to the controller. So the 4 terminals for the two batteries are positioned as follows left to right.
    Neg. _Pos._Neg._Pos The Neg. lead from the controller is connected to the battery right next to it. The Pos. lead is connected to battery farthest from the controller. I guess the best way to describe my reasoning is to say that I thought this would give me a more linear flow of electrons through the batteries. So some one go ahead and tell me it doesn't make any difference how I connect them. Second can of worms issue is going back to BB doubling my approx 3 foot run. I am guessing that is to account for the negative lead. However my negative lead is only about 5 inches long! So, I am waiting to hear a reason why both leads should be the same length!
    Go ahead, fire away!! I thought that shorter would be better.

    Edit: BB, your numbers are right on for the panels.
    Also, when I made up the harness for the controller to battery. I carefully placed an opening in the outer covering where I wanted the Neg. lead to exit. I then pulled the Neg l. lead from the remainder of the outer covering and cut off the excess Neg. lead (wire). My plan is to attach the RTS to the same terminal as the Pos. lead from the controller. I have run the wire from the sensor back through the space available inside the outer sheath that was left vacant by removing the Neg lead. This makes for a nice neat, integrated wiring harness. So, for my final can of worms. Any problem running the RTS lead right along side the Pos. lead inside the original covering of the electrical cable? Interference from the Pos. leads current with the Temp sensor?
    I think paranoia is setting in!!
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