Series or Parallel

[jimmy747]

Hello everyone, I did a lot of research before posting and found many controversies on parallel vs series. I am an electrician so I understand the benefits in effeciency
of conecting my 6 400 watts panels in parallel.. I bought an overkillled hybrid inverter for expansion. But for now I will start with 6 panels and my Growatt SPF 5000 ES.
I am thinking of connecting the 6 panels in parallel with in line 10 A fuses, a DC disconnect box but no combiner box. They will be mounted on the roof of my garage. I am an experience electrician but new to solar. I would greatly appreciate feedback from expert in the field before I commit to a specific configuration. Thank you in advance. Jimmy.

 

[sunshine_eggo]

Insufficient information. Voltage data needed for inverter and panels.

PV Vmp must be > peak battery charge voltage.

Typical 400W panels in 6P would likely have a Voc around 50V and Vmp around 41V.

 

[timselectric]

It takes a minimum of 150 volts to even wake up the SCC (Solar Charge Controller) of the 5000ES.

 

[jimmy747]

I apologize for lack of info. My project does not involve batteries. Here in Aruba between 11 am and 5 pm the panels will be in full sun. I just want to power a 24,000 split unit AC during that time. The unit consumes about 1,300 watts max when starts and dropped to around 400 watts. Should the AC unit need more than the panels are providing let’s say a rare day of clouds, the SPF 5000 ES will take what is missing from the grid. Growatt manufacture confirmed that. I just watch another video explaining that in series is safer. FYI I am. Or expecting any shade. It’s wide open. Thank you

 

[sunshine_eggo]

Doesn't matter. It's still a 48V inverter even if it doesn't need batteries, and as tim indicated, PV voltage must be high enough to trigger charging.

https://watts247.com/manuals/gw/Growatt%20SPF%205000%20ES%20datasheet.pdf

Panels must be in series.

 

[timselectric]

Yes, in SUB that's how it will work. (No battery required)

 

[jimmy747]

ok thank you guys for the help. So. If I connect my 6 Trina 400 watts panel in series, then VMPP 41.1 X 6 = 246 volts. More than sufficient, right?
The 5000 ES can take up to 450 VDC.

 

[timselectric]

That would work fine.

 

[MichaelK]

I apologize for lack of info. My project does not involve batteries. Here in Aruba between 11 am and 5 pm the panels will be in full sun. I just want to power a 24,000 split unit AC during that time.

No, most likely, that is not true. In which direction exactly will the panels be facing? Due South, or SW, or what? Any solar array that is in full sun at 11am can NOT be in full sun at 5pm, unless you have a rotating array that can track the sun. For a South-facing array, you really can't expect more than ~10% of the output you'd get at noon, so most likely you are greatly underestimating the amount of power you can make.

 

[jimmy747]

No, most likely, that is not true. In which direction exactly will the panels be facing? Due South, or SW, or what? Any solar array that is in full sun at 11am can NOT be in full sun at 5pm, unless you have a rotating array that can track the sun. For a South-facing array, you really can't expect more than ~10% of the output you'd get at noon, so most likely you are greatly underestimating the amount of power you can make.

WOW! ok thank you. That is why I came here. You guys know so much more! I just checked the roof is facing southwest 225 degree.

 

[Hedges]

Try this:

Solar Irradiance Calculator

www.solarelectricityhandbook.com

 

[MichaelK]

I apologize for lack of info. My project does not involve batteries. Here in Aruba between 11 am and 5 pm the panels will be in full sun. I just want to power a 24,000 split unit AC during that time. The unit consumes about 1,300 watts max when starts and dropped to around 400 watts.

Another important issue is the starting surge. You mention 1300W at starting, but is that the running wattage as it first starts to operate? That's not really the same as the starting surge (inrush current), which is the amount of power needed to get the compressor motor turning. What I'm imagining here is that the actual starting surge (first 500 milliseconds) might be ~4000W-5000W, then drops down to 1300W after the motor is running, and then drops down to 400W as the air-con starts cycling on and off. Is that an accurate description of events?

Do you have a clamp meter that can measure inrush current? Exactly how did you measure the 1300W number? What I am afraid will happen here is that the inrush will exceed the amount of power coming in, and the whole system will just shut down.

Going back to your other post, about having the SW facing roof, based on my own experience, I'd say your panels will only be at 50% power at 11am and 5pm, with a solar max around 2pm. At either 11 or 5, you will basically need at least 2X the number of watts of panels you need at 2pm to run the air-con. And that's just the running watts, not the inrush. Assuming you need 3X for startup, and only 50% output at 11am, that would mean 8,000W of panels for a battery-less system. Can't imagine your roof has that much space?

 

[Supervstech]

Utah, see if you can add more panels facing se and sw

 

[jimmy747]

Try this:

Solar Irradiance Calculator

www.solarelectricityhandbook.com

thank you for the link. I checked the Solar radiance for aruba and got this. Good /bad?
The fixed tilt irradiance is roughly 1,750 kWh/kWp — sunny, really sunny. It is also windy and salty. Aruba luckily sits just out of the hurricane belt and has yet to get the full force of a

 

[Hedges]

Some of the calculators consider local weather/clouds, others do not.

Purpose for this calculator is to understand how tilt and orientation affect power production vs. month.
You can optimize that for your needs, and you can make multiple arrays/strings of different orientation (e.g. morning and afternoon sun), paralleling them.

You also need to consider "NOCT" or "PTC" ratings of panel rather than "STC". Perhaps adjust for your local temperatures. Wind is good, salt can't help.

 

[sunshine_eggo]

Some of the calculators consider local weather/clouds, others do not.

Purpose for this calculator is to understand how tilt and orientation affect power production vs. month.
You can optimize that for your needs, and you can make multiple arrays/strings of different orientation (e.g. morning and afternoon sun), paralleling them.

You also need to consider "NOCT" or "PTC" ratings of panel rather than "STC". Perhaps adjust for your local temperatures. Wind is good, salt can't help.

NMOT is sometimes used too. It's typically the worst case.

 

[jimmy747]

Another important issue is the starting surge. You mention 1300W at starting, but is that the running wattage as it first starts to operate? That's not really the same as the starting surge (inrush current), which is the amount of power needed to get the compressor motor turning. What I'm imagining here is that the actual starting surge (first 500 milliseconds) might be ~4000W-5000W, then drops down to 1300W after the motor is running, and then drops down to 400W as the air-con starts cycling on and off. Is that an accurate description of events?

Do you have a clamp meter that can measure inrush current? Exactly how did you measure the 1300W number? What I am afraid will happen here is that the inrush will exceed the amount of power coming in, and the whole system will just shut down.

Going back to your other post, about having the SW facing roof, based on my own experience, I'd say your panels will only be at 50% power at 11am and 5pm, with a solar max around 2pm. At either 11 or 5, you will basically need at least 2X the number of watts of panels you need at 2pm to run the air-con. And that's just the running watts, not the inrush. Assuming you need 3X for startup, and only 50% output at 11am, that would mean 8,000W of panels for a battery-less system. Can't imagine your roof has that much space?

Thank you so much MichaelK for all the I formation. Tomorrow I’ll do a test again with the clamp meter and report exact number

 

[MichaelK]

Tomorrow I’ll do a test again with the clamp meter and report exact number

Please remember that you MUST use a meter that can read inrush. I had a plain vanilla meter that I first attempted to use, designed to read running current. For one blink of an eye, I saw 17A, before settling down to read a steady 10.1A. I thought, Ahah, the starting surge is 17A.

No it wasn't. It just happened to clip the last of part of the starting surge, that the meter was not fast enough to record. When I finally tested my pump with a nice Fluke inrush meter, I saw that the actual inrush was 38A.

I've put the very expensive Fluke meter away for safe-keeping, and use this UniT-216C meter now on a daily basis. It's as accurate as the Fluke to within 1%.

ONE UNI-T UT216C 600A True RMS Digital Clamp Meters | eBay

Model UT216C UT216D. Jaw Capacity 30mm 30mm. Zero Mode √ √. Analogue Bar Graph 61 21. Product Size 220mm x 75mm x 40mm. Product Net Weight 231.7g. Product Color Red and Grey. LCD Size 38mm x 24 mm.

www.ebay.com

 

[sunshine_eggo]

To add to @MichaelK 's post, if if your meter has a "MAX" function, that's generally not an inrush unless the documentation says it is. Inrush functions are usually labeled "INRUSH" on the meter unless documented to be otherwise.

 

[jimmy747]

Try this:

Solar Irradiance Calculator

www.solarelectricityhandbook.com

Thank you for the book and

Thank you so much MichaelK for all the I formation. Tomorrow I’ll do a test again with the clamp meter and report exact number

Hello Michael. WHen I tried to use the calculator from Hedges it craches, I live in Oranjestad Aruba. I have a Tactix 403057 meter and google does not know if it can or not measure inrush. So. I did another test. The amps on the York 24,000 BTU ramp ramp up gradually. Long story short, from 0 to 8 amp. If I turn on turbo it goes up to 10. So. 230v X 10 amps is 2,300 watts. so 5 hours is 11,500 watts (expensive here! Keep in mind I am not trying to zero out my bill here. Just trying to run AC almost free. Between 1 pm to 5 pm, the sun passes right over and look directly at the roof. Looks like I am going to buy 6 Cadian Solar 550W panels. (I will receive the specs shortly). So 6 X 550W = 3,300 watts. Lets say I get 70% of that 2,310 watts, I would be pretty close to free AC. I am now thinking of buying a 2.4 Kwh battery. If the Growatt hybrid inverter doesnt get enough from the panel it will take what is missing from the battery. Should the battery gets to 70% discharge (example) it will take what is missing from the electricity company. In Aruba it is very common to go with weeks and months with blue sky no rain no clouds. That is my understanding so far. I hope I am on the right track. Thank you all for the help. I will be awaiting feeback ?