Newbie Looking For Advice

PrinceLH

My first post on your site and I hope you pro's can help me out.

Recently purchased my first solar panel, a 120 watt, 12v type A. I also purchased a 500 watt grid tie inverter (10.5v - 28v) and plan to also add a couple of more 120 watt panels, later this spring. Here are my questions:

What would you recommend for cable, between the panel and the inverter? The run, maybe 40 feet, from roof to basement. I am in Canada, southern Ontario, to be exact, and once I mount the panels on the roof, once winter arrives, they're there until spring. I will be using them for net metering.

Any and all advice would be helpful, as I start on my quest to become energy self sufficient.

BB.

Re: Newbie Looking For Advice

I am guessing that the Vmp of your "12 volt panel" is probably around 17.5 volts:

• 120 watts / 17.5 volts = 6.9 amps = Imp

The minimum current, using the US National Electric Code, would be around (really need Isc -- short circuit current):

• 6.9 amps * 1.25 * 1.25 = 10.8 amps circuit

So, rounding up, you should plan on a minimum 15 amp circuit (usually 14 AWG -- US size copper wire).

Now, Normally, we would want no more than 3% voltage drop (down to 1% is about as low as anyone bothers to go)--Use a voltage drop calculator. Assuming 40' wring run (this is the 1/2 way round trip wire length for the above calculators--some use full round trip length):

• 17.5 volts * 3% = 0.525 volt drop maximum
• 17.5 volts * 1% = 0.175 volt drop minimum

Using 6.9 amps, 40 feet of copper wiring with normal temperatures:

• 14 awg wire = 1.7 volt drop
• 10 awg wire = 0.7 volt drop
• 8 awg = 0.4 volt drop
• 4 awg = 0.2 volt drop

So, even for such a small installation--the low voltage of the array is really costing you a fair amount of money for just 120 watts of GT power.

For each additional 17.5 volt 120 watt panel you add, you will have to add that much more wire (either home run to inverter, or that much heavier gauge wire).

Larger GT inverters (2,000 watts and above), typically, run around 200-600 volts DC solar array input voltage... The high voltage allows low current (power=volts*amps).

For example, my 3.5 kW array for my GT system runs around 340 VDC and 10 amps maximum. If I did the same thing with a low voltage GT unit, I would need ~18x more copper ($$$) for the same sized solar array.

-Bill

niel

Re: Newbie Looking For Advice

i'm kind of curious as to what inverter you have, make and model.

PrinceLH

Re: Newbie Looking For Advice

OK, I see what you are trying to say about the low amount that I am starting with. Can I daisychain these panels, from one to the other and to the other and down to the inverter, or do I need to do a 40 foot run for each panel to the inverter?

With the cost of electricity ready to skyrocket, here in the province, I need to get moving on reducing the cost of electicity. I have also considered a small wind turbine, but I'm having second thoughts. I may stack two 500 watt grid tie inverters, by next year, and add more panels, two at a time, until I reach 4 then 8. By then, I'll try to reduce hydro costs one panel at a time. Peak hours, from 7AM to 9PM, cost 27 cents per kw\hr. Off peak hours will be 9 cents per kw\hr. We'll also experience an 8% VAT increase, July 1st, so it is imperitive that I get this up and running quickly.

PrinceLH

Re: Newbie Looking For Advice

niel wrote: »

i'm kind of curious as to what inverter you have, make and model.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330432058013&ssPageName=ADME:B:BCA:US:1123

Hope this helps.

PrinceLH

Re: Newbie Looking For Advice

niel wrote: »

i'm kind of curious as to what inverter you have, make and model.

This is the panel:

http://cgi.ebay.com/RAMSOND-120-WATT-W-120W-PV-SOLAR-PANEL-MODULE-12V-RATED-/360253874524?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item53e0cde15c

BB.

Re: Newbie Looking For Advice

OK, my numbers are close enough for now--You can re-run them with the values from the EBay site.

No, with this GT inverter, you cannot put the panels in series for a higher Vmp (array) voltage... You can only parallel them together... And to do that, you either need a single very heavy cable from the GT inverter to the Array--then parallel the each panel (behind a ~15 amp fuse/breaker to the common bus connection point).

Or, you have to run sets for wire, from each panel to the GT inverter, again connecting with fuses to each panel, then on to the inverter input.

Just the usual warning--This is not a "legal installation" and you are accepting risks from un-Listed equipment (UL/CSA for panels and inverters), and are doing the install without building permits or utility approval. And if your utility discovers the meter "running backwards"--they may tell you to disconnect the GT inverter, or they may disconnect your power service.

I would suggest that if you are planning on building out a 2kW or larger array--You should at least get a quote from a local installer as to how much they will charge...

I know that prices for solar are high in Canada, but you do have various programs to offset costs if done through the official process.

Also, have you looked at conservation (insulation, alternative fuels, CFL lighting, low power computers, turning off unused sat/digital TV receivers and DVRs, etc.)--It is almost always cheaper to conserve a watt than to generate a watt.

-Bill

PrinceLH

Re: Newbie Looking For Advice

From your expertise, looking at that box on the back of the panel, the IP65 Junction Box, with the multi contacts, there appears to be a male and female connector. In your opinion, what is the name of those connectors? Does one plug into another panel, to parallel the wattage, or are both of these required to plug into the cable heading into the inverter?

http://cgi.ebay.com/RAMSOND-120-WATT-W-120W-PV-SOLAR-PANEL-MODULE-12V-RATED-/360253874524?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item53e0cde15c

BB.

Re: Newbie Looking For Advice

Those Aapear to be MC type connectors. The specification does not say, but they are probably MC-4 type--although, older designs did have MC-3 (non-locking).

The MC-4 are required for new Grid Tied panel installs (locking connectors).

You can either:

1. purchase male/female cables, cut in 1/2, then splice to your leads and plug into the panels (see link above)
2. cut to plugs and wire up as you desire (possibly will void warranty--check with vendor for details)
3. you may be able to open the junction box and wire in your own UV rated cables.

They are just +/- connections and this is where you connect to your array's wiring.

The tooling and training required to make up your own cable assemblies with MC-x hardware is probably prohibitively expensive for a do-it-yourself install for one home ($600 or more for tooling?). Usually most people just purchase male/female cables and use those to splice into their array wiring.

If you have just one or two panels to connect in parallel, you can just get an adapter cable (above link) to parallel. If you have three or more panels to parallel, you are supposed to put one fuse/breaker in each string before they are bused together in parallel.

-Bill

Ralph Day

Re: Newbie Looking For Advice

Prince,
Why, oh why would you be looking at net metering? When you can sell your generated power for 80.2cents per kwhour it makes no sense to net meter any more. Check out the microFIT program if you haven't already.

I'm installing a 10kw microFIT system but can't net meter my domestic wind and solar...10kw per connection point, grrr.

Ralph

train82499

Re: Newbie Looking For Advice

Also in Canada where we have snow. Put your panel as close to the edge of your roof as you can and angle it at 50 degrees or so ie tilt it well up and off the roof. This will let the snow slide off onto the ground below - and not just slide to the roof, accumulate and shut down your system which will happen if you mount it near the top of your roof. That will work in parts of the USA where they don't get snow but not up here! Also, putting panel at the edge of the roof lets you get at it with a plastic snow rake, and you can easily pull off the snow and ice that builds up - especially on a nice sunny day. Good luck.

PrinceLH

Re: Newbie Looking For Advice

train82499 wrote: »

Also in Canada where we have snow. Put your panel as close to the edge of your roof as you can and angle it at 50 degrees or so ie tilt it well up and off the roof. This will let the snow slide off onto the ground below - and not just slide to the roof, accumulate and shut down your system which will happen if you mount it near the top of your roof. That will work in parts of the USA where they don't get snow but not up here! Also, putting panel at the edge of the roof lets you get at it with a plastic snow rake, and you can easily pull off the snow and ice that builds up - especially on a nice sunny day. Good luck.

I am lucky to have a good angled roof, leading from a flat roof garage on the south side. It is about a 3 foot drop, from the angled roof, to the flat garage roof. I can access it by ladder or television tower. I recently built an HD antenna array, on the west side of the building and the tower will allow me to run my power wire to the basement, in a straight run.

PrinceLH

Re: Newbie Looking For Advice

Ralph Day wrote: »

Prince,
Why, oh why would you be looking at net metering? When you can sell your generated power for 80.2cents per kwhour it makes no sense to net meter any more. Check out the microFIT program if you haven't already.

I'm installing a 10kw microFIT system but can't net meter my domestic wind and solar...10kw per connection point, grrr.

Ralph

Probably not going to have a high enough wattage system to start in year one. I'm just trying to defer the cost of the expensive cycle that the Ontario government charges, between 7AM and 9PM. Since I am at work during the day, the solar panels will allow me to save money on appliances like fridges and freezers, while I am away in the daytime. Do you have a link to the microfit program?

train82499

Re: Newbie Looking For Advice

The Ontario Government's microfit program brochure is here

http://microfit.powerauthority.on.ca/pdf/microFIT-Program-Overview.pdf

Note that on the cover of this brochure the panels are on top of the roof. A system with panels mounted as illustrated would likely not work anywhere in Ontario starting when the snow flies ie anytime December to mid April (normally!). Keep them near the edge and at a nice angle. There is a complicated formula for the angle depending where you live and etc, but 45 or 50 degrees is likely close enough for a permanent installation (unless you are good at climbing and readjusting everything several times a year).

Other info is here:
http://microfit.powerauthority.on.ca/

The program is for up to 10K rated projects, which is a good sized system, and pays well at $.80 a KWH - about 10 times what hydro costs us (before tax and other increases set for later this year).

Note that it has some "Made in Ontario" criteria to qualify - be careful about what you buy.

PrinceLH

Re: Newbie Looking For Advice

train82499 wrote: »

The Ontario Government's microfit program brochure is here

http://microfit.powerauthority.on.ca/pdf/microFIT-Program-Overview.pdf

Note that on the cover of this brochure the panels are on top of the roof. A system with panels mounted as illustrated would likely not work anywhere in Ontario starting when the snow flies ie anytime December to mid April (normally!). Keep them near the edge and at a nice angle. There is a complicated formula for the angle depending where you live and etc, but 45 or 50 degrees is likely close enough for a permanent installation (unless you are good at climbing and readjusting everything several times a year).

Other info is here:
http://microfit.powerauthority.on.ca/

The program is for up to 10K rated projects, which is a good sized system, and pays well at $.80 a KWH - about 10 times what hydro costs us (before tax and other increases set for later this year).

Note that it has some "Made in Ontario" criteria to qualify - be careful about what you buy.

I have a good situation, where I am, in Belleville, Ontario. I have a direct view of the southern sky, a flat garage roof and just a three foot climb to a workable roof from there. I can adjust the panels, if need be, and plan to build the framework, once panel one arrives tomorrow. The framework will be for three panels, to start, and I have come across some unique MC4 three head connectors. Each panel has it's own box and 3 foot cables. I can take the three panels, plug it into the 3 into 1 connectors and downconnct the approximate 50 feet to the inverter. I am concerned for the need of some kind of breaker or fuse for these panels, as they enter the 3 into 1 junction. I know it's a small operation to start, but as I can afford to add more, I intend to. Installing satellite equipment is my sideline, solar is a natural progression for me to pursue.

Solar Guppy

Re: Newbie Looking For Advice

You must fuse the panels before the 3 to 1 combiner if one panel gets shaded it could burnt up by the other two feeding into the shorted panel, that's what the fuse protects against.

PrinceLH

Re: Newbie Looking For Advice

Solar Guppy wrote: »

You must fuse the panels before the 3 to 1 combiner if one panel gets shaded it could burnt up by the other two feeding into the shorted panel, that's what the fuse protects against.

OK, so I need to fuse the panels before(a fuse for each) or after, from where the combiner feeds to the inverter?

BB.

Re: Newbie Looking For Advice

Generally, assume negative ground is your common return wire. Normally, you never put fuses in your return/ground referenced circuit. So connect all of the "series string panels" (even one panel is a "series string of cells") negative leads to a common negative connection.

So that leaves the positive connections. Each panel string + output (when you have three or more parallel connections to your panels) should go to a fuse/breaker "combiner box", then the output of each of those protective devices then goes to the "common" positive bus to run back to your GT inverter (or solar charge controller, etc.).

You could choose to make the common connection at the array, and use heavy cable back to the inverter/charge controller. Or you can "home run" each panel connection with "smaller gauge wires" and make the final fuse/breaker/bus connections near the controller--which ever you prefer.

-Bill

PrinceLH

Re: Newbie Looking For Advice

What fuse size would be the best way to proceed? Since I only intend to put three panels for each inverter, it may be a more cost efficient way to go, then a junction box.

PrinceLH

Re: Newbie Looking For Advice

Solar Guppy wrote: »

You must fuse the panels before the 3 to 1 combiner if one panel gets shaded it could burnt up by the other two feeding into the shorted panel, that's what the fuse protects against.

Can you get away, with fusing just one of the panels, or possibly two and still get the same protection?

PrinceLH

Re: Newbie Looking For Advice

After further review, I think that I will go with the 2 conductor #10 AWG downwire, approximately 50'. I will add three 15 amp fuses to the positive branch of each of the panels and then use a three position combiner for both positive and negative. Does this make a sound circuit? Three 120 watt, 12v panels, leading down to a 500 watt grid tie inverter? Any and all opinion will be helpful.

BB.

Re: Newbie Looking For Advice

15 amp fuse per panel is fine. And, you cannot get away with less than three protective devices (you want to protect against any single failure--and you don't know which circuit/panel will fail in the future--hopefully, none).

Are you planning on "busing" the wiring (3:1) at the array (50' away) or at the controller (running 10 awg * 3 cable sets * 50')?

• 10 awg 7 amps 50' using voltage drop calculator = 0.8 volts drop

You really want to be at 3% of Vmp drop (17.1 volts or so) = 0.52x volt drop maximum...

You really should be at 8 awg wiring if you are "home running" each set of panel wires back to the controller for busing (or heavier)--But, most likely, the system will work fine--just a couple percent more loss (less power to the GT Inverter).

(I am guessing--I don't know anything about the solar panels or the GT inverters).

-Bill

PrinceLH

Re: Newbie Looking For Advice

BB. wrote: »

15 amp fuse per panel is fine. And, you cannot get away with less than three protective devices (you want to protect against any single failure--and you don't know which circuit/panel will fail in the future--hopefully, none).

Are you planning on "busing" the wiring (3:1) at the array (50' away) or at the controller (running 10 awg * 3 cable sets * 50')?

• 10 awg 7 amps 50' using voltage drop calculator = 0.8 volts drop

You really want to be at 3% of Vmp drop (17.1 volts or so) = 0.52x volt drop maximum...

You really should be at 8 awg wiring if you are "home running" each set of panel wires back to the controller for busing (or heavier)--But, most likely, the system will work fine--just a couple percent more loss (less power to the GT Inverter).

(I am guessing--I don't know anything about the solar panels or the GT inverters).

-Bill

Right now, I'm planning on busing. I may decide to go with a combiner box, once I take into consideration the amount of switching and the cost for these special MC4 divider/combiners. At least with a combiner box, if I were to choose to add more than three panels, it would allow more flexability. I will also take the 8 AWG as good advice.

PrinceLH

Re: Newbie Looking For Advice

Looking at putting in 15amp fuses inline for each panel that I add. A question that I have been looking at is this: My downlead is 8 AWG, but having a problem find a fuse holder that is lower than 10 AWG. Can I use the 10 AWG fuse holder and if so what is the percentage of loss that I may expect, putting 4 panels daisylinked, all fused? Also having a hard time metal finding panel clamps that you screw down, on the framing, while mounting. Where is a good place to find the small clamps? I've checked this site, but may have overlooked them. So far, you guys have been very helpful and I'm still pulling together all of the equipment that I need for this project.

BB.

Re: Newbie Looking For Advice

PrinceLH wrote: »

Looking at putting in 15amp fuses inline for each panel that I add. A question that I have been looking at is this: My downlead is 8 AWG, but having a problem find a fuse holder that is lower than 10 AWG. Can I use the 10 AWG fuse holder and if so what is the percentage of loss that I may expect, putting 4 panels daisylinked, all fused?

Yes, just trim out a few strands to get the rest of the cable to fit into the holder--You will not lose any significant power doing this and it will still be safe (14 AWG is "safe" for a 15 amp circuit).

Also, to be clear--Typically "daisy chaining" for electrical folks means to put things together in series, not in parallel.

You are installing these panels in parallel.

Also having a hard time metal finding panel clamps that you screw down, on the framing, while mounting. Where is a good place to find the small clamps? I've checked this site, but may have overlooked them. So far, you guys have been very helpful and I'm still pulling together all of the equipment that I need for this project.

You might review this post for an alternative:

Solar Guppy wrote: »

I have about 12kw of PV using these 1.50 a piece Home Depot Gutter clips to mount my panels to the roof. 4 hurricanes and one tornado later no issues

On the frst 6kw, I directed mounted to the panels, on the last 5kw added, I used the clips to secure 2x2 aluminum screen rails and then the solar panels to the rails.

Probably have less than 1K into all the racking for over 86 panels

There are lots of clips and mounts available from NAWS--So I am not sure exactly what you are looking for. Take a look at the catalogs or mfg. website for part numbers (not all numbers are listed in NAWS website)... You are in Canada, so finding a local source for mounting hardware may make more sense for you.

-Bill

PrinceLH

Re: Newbie Looking For Advice

BB. wrote: »

There are lots of clips and mounts available from NAWS--So I am not sure exactly what you are looking for. Take a look at the catalogs or mfg. website for part numbers (not all numbers are listed in NAWS website)... You are in Canada, so finding a local source for mounting hardware may make more sense for you.

-Bill

H*ll, they are so far behind the loop, here in Canada, that it's almost impossible to get up and running. I cannot even find single stranded 8AWG cable at Home Depot or Lowes.

niel

Re: Newbie Looking For Advice

"I cannot even find single stranded 8AWG cable....."

technically you won't find it anywhere as a single stranded wire would be just a solid wire and not considered stranded at all.

Kamala

Re: Newbie Looking For Advice

Perhaps replace the word "single" with "any".:roll:

PrinceLH

Re: Newbie Looking For Advice

niel wrote: »

"I cannot even find single stranded 8AWG cable....."

technically you won't find it anywhere as a single stranded wire would be just a solid wire and not considered stranded at all.

What I meant by single stranded, was 8AWG in one coaxal type cable, not double for plus and minus.

Kamala

Re: Newbie Looking For Advice

Whoa! #8AWG coaxial? I think what we have here is a failure to communicate.

Such a cable might exist, but it's not reasonable for this application. Coax is usually a high frequency signal cable not intended for use in high current applications.

Typical coax.

niel

Re: Newbie Looking For Advice

this is the corrected use.

Kamala wrote: »

Whoa! #8AWG coaxial? I think what we have here is a failure to communicate.

Such a cable might exist, but it's not reasonable for this application. Coax is usually a high frequency signal cable not intended for use in radio frequency applications.

Typical coax.