I have a Classic 150 and bunch of 10 awg solar wire that I am planning on using. I can't swap 150 for 250, nor swap out 10 awg wire for heavier size. The solar panel are located fairly far from the point of use (Classic 150).
Looking at 400 ft one way run for farthest way modules. See attached sizing tool for details. I will not be moving the panels any closer, though I may run up to 4 sets of 10 AWG conductors to reduce the voltage drop some.
- 1 set of 10 AWG Conductors @ 400 ft, 99.6 v, 45.48 amps = Voltage Drop 36.59%
2 set of 10 AWG Conductors @ 400 ft, 99.6 v, 45.48 amps = Voltage Drop 18.29%
4 set of 10 AWG Conductors @ 400 ft, 99.6 v, 45.48 amps = Voltage Drop 9.15%
My question is will the Classic 150 be able to operate with the wiring that will result in voltage drop of 9.15%, 18.29%, or 36.59%? I will the inefficiency introduced be similar to voltage drop % (aka 9.15% drop mean array will be at 90.85% of it rating max)?
If the Classic 150 work, I will go ahead and use in. A 9% or even 37% loss is better than just letting Classic 150 sit unused in storage!
The greater the voltage drop the more you use the energy to heat up the wire along the way. The Classic will work with what is left of the power that gets to it.
Every time you double up your 10 guage wire you go to the next wire size . So two 10 will be same as 8 and four would be the same as 6 . But you better make sure they are exactly the same length and bonded together very well on either end otherwise you could have different currents running on each wire instead of them all sharing evenly.
I would think you are right that getting something working is better than nothing ! Just make sure you install the correct breakers sizes.
Larry
can you tell us more about the array(s)? Can you increase the voltage you are trying to send to the Classic?
I appreciate info guys, Thanks!
They are using Topoint 190w panel (see attached docs), bunch those panels are available for use from another grid-tied project. They using Midnite string size tool, I had original planed to have 3 PVs in series (120 voc, 99.6 VMP) and 8 of those in parallel.
I could attempt to put 4 in series w/ 160 voc, with 9.15% voltage drop should remain under hyper voc (150v). Possibly do 4 in series, 6 of those in parallel.
For this, I could use 3 set of conductor in series. @ 132 VMP, that is 8.31% voltage drop.
As a general target it is better to stay away from maxing out any electronic devices... so you do want to deliver a voltage that the Classic can handle without going into Hyper VOC...
that means you would do well to use the voltage loss to buffer the excess voltage of,say, 4 panels over that long distance and keep it well below the 150V that is its max. operable voltage.
A telephone call into MidNite would be advised.
hth
I wonder if there are any issues with heating up the wire when you have that high a loss factor - wouldn't want to melt the insulation.
When I was playing around with the wire loss calculators I noticed less amps longer distance. So would it be possible to use the Classic to limit the amount of amps to the level where that wire could handle it - that way no wire heating right ? Maybe someone else could weigh in on this .
Larry
Hello yellowstar,
The NEC Ampacity of # 10 AWG THHN type building wire is about 35 Amps, and this is for three or fewer current-carrying conductors in conduit/raceway, etc. Would suggest not using a single set (a pair -- one for PV positive, and one for the negative) of # 10 AWG conductors.
This system may not need to be inspected, but NEC is a good and conservative guide for system design, in general.
Paralleling # 10 AWG conductors is considered to be a bit of a risk, and not permitted in the Code for small conductors like # 10, if the Code is important to you.
We know almost nothing of your system details, or even your location, but would suggest NOT running strings of 4ea 72 Cell PVs on a Classic 150. ASSUME that the target system is using a 48 V battery, is this site off-grid?
So, believe that you have said that someone, perhaps you have run the MN Classic String sizer with appropriate data entered.
Did make a guess about the coldest temperature for your location, but this guess may be far off from reality, and ran some numbers on the MN Classic Sizer. It is customary to use the data for the desired PVs, from the data sheet, as requested in the Sizer data entry from. Looks like you were using NOCT Vmp, and am not quite certain which PV string current that you used. Have attached the Sizer output, based on the Topoint 190s, but a guess of --5 C as the lowest temperature for your location. IMO, it is most useful to use the data from the PV data sheet, as specified in the Sizer form.
Agree, that running power electronics at/near the maximums for hours and hours per day can take its toll on longevity and reliability. Under light loads the input voltage from the PVs to the Classic will approach 130 V. This will cause quite a lot of heating in the Classic, and cause the fans to run, perhaps without interruption for hours and hours per day. If the environmental temperatures for the location of the Classic are warm or hot, you could well see some loss of solar power production due to the Classic limiting its output current.
Just my opinions. FWIW, Vic
in some ways the nec is good, but they nit pick things to death. they frown of paralleling the wire, but you aren't going to come to harm if you do as this isn't wiring inside your home we're talking about and the single strands are more apt to be strung in free air than having an expensive raceway put in 'cause that's how they do things in the nec. also, don't worry about the wire heating to the point it melts insulation as i doubt it'll get anywhere near that point.
the system will still work even if lossy from voltage drop and the high open circuit voltages seen will NOT overheat the classic because there's so few amps flowing when it reaches the open circuit voltage area. technically, if it hits the oc voltage there's no current flowing and therefore no watts to produce heat. the current will be semi-limited by the wire loss resistances too and yes, it will be dissipated in the form of some heat, but there's too much wire present for you to worry and being free air will keep it from building.
i did try to answer you before, but i got things goofed up in my response and took it down. i basically was making a few points that paralleling the wires would improve things and getting a new classic 250 won't solve the wire issues altogether so going for the goal of about #00 or better would be best for a run like that, which is expensive. you need to charge the batteries you have and, although not being done ideally, you will give them a charge.
one other point was about the 2 #10 wires being put together. it will cut the resistance in half as was correctly stated before, but it is not equal to a #8 wire. 2 #10s is equal to a #7 wire. 4 #10s is equal to a #4 wire and so on for every doubling of the wires.
i should add that you inputted some wrong figures in your calculations. the vmp on 1 of those 190w pvs is 36.5v and 3 in series is 109.5v. not sure if you did the imp correctly or not, but each string will be at 5.2a so with 8 strings that's 5.2a x 8 = 41.6a. i get about 38.7% at 90c for an 800ft total run of #10. that's about a worst case scenario and that would drop about 42.4v, which is significant, but the classic will mppt the remaining power for your batteries. paralleling another #10 wire would cut those losses directly in half. if you're uncomfortable with the high losses you can reduce the number of strings supplying power until you get the proper wires.