Would you run 8AWG or 10AWG?

[wildcatden]

The Setup will be two Renogy 320W panels in parallel. I can NOT mount the panels in any other location so the distance is required.

1. Renogy 2-PC 320W Panels ( RNG-320Dx2-US ). 12AWG Output Cables with MC4 connectors. Voc=40.3V, Isc = 10.23 Amps.
2. Renogy 2-to1 Y-branch Connector - MMF+FFM Pair. Rated 50 Amps
3. 65 feet of 8AWG or 10AWG copper cables with MC4 (M&F) on one end and High Power Port (HPP/Anderson) connectors the other.
4. Goal Zero Yeti 3000X High Power Charge Port (14-50V, up to 50Amps (600W Max)).

My gut says just go with 8AWG because the cost delta is pretty much nothing. But I am not an electrician. Questions:

A. Do I need to put a fuse (maybe 40Amps) inline to be safe?

B. The panels are rated just above the 600W input max of the Yeti 3000X. The panels have a Vmp=33V and Imp=9.7A. It seems as if under absolutely optimum conditions, I might hit >600W. Perhaps using 10AWG or even 12AWG wire to ensure a voltage drop over the distance/resistance of the copper wire will ensure I don't go over.

C. For the 65 foot cable, I may not be able to get HPP on one end. In that case, I would have to get a short MC4 to HPP adapter cable in 12AWG. Does this cause an issue (heat? more voltage drop?) going from 12AWG at the panel to 8AWG copper and then back to 12AWG adapter for attaching to the Yeti3000X?

 

[Lt.Dan]

10ga is rated for 30a. Why use 8ga?

If you are really worried about power loss or anything, plug it into a voltage drop calculator with the length and gauge size. I bet you'll find its pretty minimal.

 

[wildcatden]

10ga is rated for 30a. Why use 8ga?

If you are really worried about power loss or anything, plug it into a voltage drop calculator with the length and gauge size. I bet you'll find its pretty minimal.

Yes, the calcs show the voltage drop is pretty minimal. I think my main concern is that I am looking at panels that are, at maximum/optimum output, just over the WATTS spec of the Goal Zero Yeti3000X HPP Charge port (14-50V, up to 50Amps (600W Max)).

Example, if the two (2) Renogy panels in parallel are operating at their optimum with Vmp=33V and Imp=9.7A I get WATTS too high (33V x (9.7x2)=640W at the panel.

Voltage drop calcs would should show the following with a parallel solar panel config:

65 feet of 8AWG with input of 33V x (2x9.7Amps) has a voltage drop of 4.78% (1.58V). (33V-1.58V x (2x9.7A)=609W
65 feet of 10AWG with input of 33V x (2x9.7Amps) has a voltage drop of 7.61% (2.51V). (33V-2.51V x (2x9.7A)= 591W

Perhaps, I am answering my own question here. Of course, my logic is to plan for the maximum output that the panels **could** produce under optimum sunlight conditions. I may need to look at some panels that are just a bit less.

Any input appreciated.

 

[Lt.Dan]

Yes, the calcs show the voltage drop is pretty minimal. I think my main concern is that I am looking at panels that are, at maximum/optimum output, just over the WATTS spec of the Goal Zero Yeti3000X HPP Charge port (14-50V, up to 50Amps (600W Max)).

Example, if the two (2) Renogy panels in parallel are operating at their optimum with Vmp=33V and Imp=9.7A I get WATTS too high (33V x (9.7x2)=640W at the panel.

Voltage drop calcs would should show the following with a parallel solar panel config:

65 feet of 8AWG with input of 33V x (2x9.7Amps) has a voltage drop of 4.78% (1.58V). (33V-1.58V x (2x9.7A)=609W
65 feet of 10AWG with input of 33V x (2x9.7Amps) has a voltage drop of 7.61% (2.51V). (33V-2.51V x (2x9.7A)= 591W

Perhaps, I am answering my own question here. Of course, my logic is to plan for the maximum output that the panels **could** produce under optimum sunlight conditions. I may need to look at some panels that are just a bit less.

Any input appreciated.

Ok I understand what you are after now.

Overpaneling by 9w is not going to hurt it at all. And like you mentioned, the odds of you hitting 609w are very slim.

 

[Mike 134]

No fuse the panels will only produce what they are designed to.

 

[Tomthumb62]

Goal Zero Yeti 3000X High Power Charge Port (14-50V, up to 50Amps (600W Max)).

Your panel's Voc is 40.3V. Depending how cold is gets where you are, this could be a problem. You cannot, not even a little bit, go over 50V, as this is the input limit of your Goal Zero charge port. If you go over it (or sometimes get a little too close), you will fry your Goal Zero and likely total replacement is the solution.

So look at all the data on the back of your panels, then add the coldest recorded temperature in your area in the last 30 years and use this calculator:

Photonik | String Voltage Calculator

Easily calculate the minimum (Vmp) and maximum (Voc) string voltage for thousands of panel models.

www.photonik.solar

What is the number it gives you?

Now if this number is over 50V, you may not be out of luck. If you don't plan to ever, not even for a moment, use your solar setup in the temperature you entered into the calculator (say you never use it during winter), then keep raising the temperature until you get to no more than 42-44V (and that is still awfully close to 50V, IMO), then decide if you ever plan to use your system in that temperature. If you do, then you simply need lower wattage panels, put in parallel, not series.

 

[wildcatden]

Your panel's Voc is 40.3V. Depending how cold is gets where you are, this could be a problem. You cannot, not even a little bit, go over 50V, as this is the input limit of your Goal Zero charge port. If you go over it (or sometimes get a little too close), you will fry your Goal Zero and likely total replacement is the solution.

So look at all the data on the back of your panels, then add the coldest recorded temperature in your area in the last 30 years and use this calculator:

Photonik | String Voltage Calculator

Easily calculate the minimum (Vmp) and maximum (Voc) string voltage for thousands of panel models.

www.photonik.solar

What is the number it gives you?

Now if this number is over 50V, you may not be out of luck. If you don't plan to ever, not even for a moment, use your solar setup in the temperature you entered into the calculator (say you never use it during winter), then keep raising the temperature until you get to no more than 42-44V (and that is still awfully close to 50V, IMO), then decide if you ever plan to use your system in that temperature. If you do, then you simply need lower wattage panels, put in parallel, not series.

Thank you. Not being an electrician or knowing some of the in's and out's, that really helps. Bottom line is I need to look at some different panels as the Renogy 2-piece 320W panels are just too much.

 

[wildcatden]

Not being an expert in solar, today I learned about "over paneling" for my particular battery the Yeti 3000X.

Short answer: The MPPT controller's HPP input on the Yeti 3000X is rated for 14-50V, 50Amps max, 600W max. If you supply more than 600W but stay under the Volts and Amps maximums, the MPPT controller will take up to its max 600W and "ignore" the rest. I assume it dissipates the rest with heat? To ground?

Reference:
https://community.goalzero.com/disc...nput-power-than-my-device-is-rated-for#latest

So bottom line is that as long as I keep the Volts and Amps below the maximums, I should be good. I live in the Bay Area. Using the Photonik String Calculator from earlier posts above, I should be able to use two (2) Bifacial 450W panels from Renogy for 900W (up to 1170W) by connecting them in parallel. I would end up with Voc of 41.25V and Isc of 13.89Amps giving me an STC input max of 41.25V and 27.78Amps (2x13.89Amps). Under extreme cold (-25 degree Fahrenheit), I would hit a maximum of 47.33V which is under the max for the Yeti 3000X MPPT controller.



Reference:
https://store-fhnch.mybigcommerce.com/content/RSP450DT/231123RSP450DT-120-G1 Datasheet.pdf

 

[Lt.Dan]

the MPPT controller will take up to its max 600W and "ignore" the rest. I assume it dissipates the rest with heat? To ground?

It will ignore the rest, but not dissipate as heat.

Dont forget the solar panels aren't "pushing" power. The MPPT is "pulling" power. So the MPPT will only pull what it wants.

 

[wildcatden]

It will ignore the rest, but not dissipate as heat.

Dont forget the solar panels aren't "pushing" power. The MPPT is "pulling" power. So the MPPT will only pull what it wants.

Thank you!!! I just learned something else (MPPT "pulls" power).

 

[Quattrohead]

Absolutely do not go over the volts no matter what, but the amps and hence the Watts you can go over by like 10-15% no worries

 

[wildcatden]

Absolutely do not go over the volts no matter what, but the amps and hence the Watts you can go over by like 10-15% no worries

As far as going over, I will be connecting my Renogy 450W panels in parallel. The Volts will stay under even at -25* Fahrenheit. The Amps will stay under in parallel (2 panels @ 13.98Amps = 27.89 Amps).

So at the coldest temp I accounted for (-25* F) I end up with maximum:

47.33 Volts (-25* F) x 27.89 Amps (2 Panels Isc value) = 1320 Watts.

Does this seem safe/ok/appropriate? I believe that the Watts is OK as it is just a product of the Volts x Amps and those specific numbers are below the MPPT controller maximums.

Sorry for all of the follow ups. Thanks in advance.

 

[SupraSPL]

I would say go for the 320 * 2 in parallel and use 8 gauge. Edit 450 x 2 even better. During those rare moments of perfect conditions the strings will ne maxed out and you lose some efficiency and some production. But the vast majority of the time the overpaneling will be serving you well and you won't be losing much to voltage drop most of the time.

 

[Tomthumb62]

I would end up with Voc of 41.25V and Isc of 13.89Amps giving me an STC input max of 41.25V and 27.78Amps (2x13.89Amps). Under extreme cold (-25 degree Fahrenheit), I would hit a maximum of 47.33V which is under the max for the Yeti 3000X MPPT controller.

Personally I would not be comfortable with that (47V is very very close to 50V). There are other causes (something something 'cloud edging') than can cause the voltage to spike as well. But where did you get -25F for the Bay Area? I'm not familiar with the Bay Area, but that seems to be crazy cold for being so far south and so close to the ocean.

47.33 Volts (-25* F) x 27.89 Amps (2 Panels Isc value) = 1320 Watts.

Also, in terms of "overpaneling", it depends on how your MPPT tolerates that. People do it all the time and yes you have the basic idea correct. If you don't go over input voltage, then you won't instantly fry it. Overpaneling is a risk in that it can give your MPPT an early death. The more aggressive you overpanel by the more likely your MPPT will die sooner than later due to excessive heat. Is the MPPT in your Yeti user-replaceable (usually they are not in these off-the-shelf solar generators)?

So a very conservative overpaneling amount as @Quattrohead suggests is 10-15%, which would be an extra 60-90W. A very aggressive amount is what you suggest, 120%, an extra 720W, 1320W total. You could go middle of the road for 50%, which would be an extra 300W, 900W total and this would give you benefit of overpaneling without (hopefully) giving your MPPT an early death. Would I do it? Nope, because I'm sure that Yeti wasn't cheap and I highly doubt it has much in terms of user-serviceability (it would be for parts or the trash bin, remove the battery for other use).

Finally, is there a reason you are set upon putting up only two very large panels? They are very heavy and more challenging to mount (you haven't yet mentioned where you will mount them), in addition to their high Voc. Why not put up three or more 200-300W panels? You will still need to put them in parallel to avoid getting too close to the max 50V input, but it will be much easier to stay under that amount.

 

[Quattrohead]

I am not following your math on those 450 watt panels but they will be wasted on that unit, the 320s are a good match.

 

[wildcatden]

Personally I would not be comfortable with that (47V is very very close to 50V). There are other causes (something something 'cloud edging') than can cause the voltage to spike as well. But where did you get -25F for the Bay Area? I'm not familiar with the Bay Area, but that seems to be crazy cold for being so far south and so close to the ocean.



Also, in terms of "overpaneling", it depends on how your MPPT tolerates that. People do it all the time and yes you have the basic idea correct. If you don't go over input voltage, then you won't instantly fry it. Overpaneling is a risk in that it can give your MPPT an early death. The more aggressive you overpanel by the more likely your MPPT will die sooner than later due to excessive heat. Is the MPPT in your Yeti user-replaceable (usually they are not in these off-the-shelf solar generators)?

So a very conservative overpaneling amount as @Quattrohead suggests is 10-15%, which would be an extra 60-90W. A very aggressive amount is what you suggest, 120%, an extra 720W, 1320W total. You could go middle of the road for 50%, which would be an extra 300W, 900W total and this would give you benefit of overpaneling without (hopefully) giving your MPPT an early death. Would I do it? Nope, because I'm sure that Yeti wasn't cheap and I highly doubt it has much in terms of user-serviceability (it would be for parts or the trash bin, remove the battery for other use).

Finally, is there a reason you are set upon putting up only two very large panels? They are very heavy and more challenging to mount (you haven't yet mentioned where you will mount them), in addition to their high Voc. Why not put up three or more 200-300W panels? You will still need to put them in parallel to avoid getting too close to the max 50V input, but it will be much easier to stay under that amount.

1. I got the "-25*F for the Bay Area" from the calculator. I used this VERY extreme example as the coldest it would get here in the Bay Area and thus the absolute highest voltage I might see from the panels. For example, if I put 0* F as the coldest temp I felt the panels would see, I get a maximum voltage of 45.84V. According to Google, the coldest recorded temp in the Bay Area was 27* F in 1932 which would yield a voltage maximum of 44.23 using the calculator. So overall, I am trying to calculate "worst case" (ie. maximum voltage).

2. I will reach out to Goal Zero to see how their Yeti 3000X MPPT tolerates overpaneling. In the reference link https://community.goalzero.com/disc...nput-power-than-my-device-is-rated-for#latest they state:

"You could also connect four Ranger 300 panels together (1200W) with our HPP to HPP combiner into to the HPP input of a Yeti 3000X and the Yeti will take up to its max of 600W."

3. I am putting up only two large panels:

A. The mounting location is going to be on the roof of a 10 x 14 shed. In my case, the shed roof points perfectly South and will get sunlight all day (really good sun from 10am to 4pm). In other words, it is the optimal location for my situation. My measurements indicate that two (2) 450W panels will fit nicely.

B. At some point, I will upgrade to a larger Yeti (or other maker) system. The Yeti 3000X can only supply 120V, 16.5A, 2000W (3600W surge) to a manual transfer switch. This is enough for my primary home backup usage which will be to run a KitchenAid Fridge, Rinnai Tankless Water Heater, Cable Modem/Wifi and some canned LED lighting in the primary living room. As an example, if I stayed with the Goal Zero stuff and went to a Yeti 4000 Pro, it can output 120V, 30A, 3600W (7200W surge) to a manual transfer switch. The Yeti 4000 can take input of 13.3-150V, 40Amp, 3000W max on it's HPP charging port (MPPT).

Thanks for the topic on possible voltage spikes and "cloud edging". This Yeti 3000X is aggravating.

 

[wildcatden]

I am not following your math on those 450 watt panels but they will be wasted on that unit, the 320s are a good match.

I guess I am trying to future proof for a planned upgrade to a bigger/better unit in the future. As an example, a Yeti 4000. Not saying I would go with that unit, but it provides an easy conversation with its 13.3-150V, 40Amp, 3000W max on it's HPP charging port (MPPT).

 

[hwy17]

I would run 10awg cause the 10awg to 8awg is a big price jump.

10awg is maybe arguably just barely arguably not correct, because NEC has like a 1.5x rule for PV current or something. But I would be fine with 21 amps on 10awg myself for sure. I can't imagine that the Yeti would have any problem with the slight over panelling.