Series confusion

[TimC]

Help please! I thought I had a grasp of series and parallel wiring of panels.

Here's my panels. Six total panels in 3S2P.


Just three panels are wired together 3S in this group. Voltage makes sense... 118v





Amps should be around 6a to 7a in full sun. But, it is reading 18. Why is it adding the amps and adding the volts? I'm measuring on the MC4s and they are not connected to anything yet. Is this normal? Will amps show up under 8a when these are feeding into my hybrid inverter?

I'm a rookie at this new clamp multimeter so if I'm just being stupid please tell me and I'll go back to the manual and learn the dang thing.

Thanks, Tim

 

[BentleyJ]

If the MC4's are not connected to anything the Amps should be zero.
If its 3S2P, when connected and operating in full sun you should be getting approx. 3 x 37V = 111V and 2 x 8.38A = 16.7A.

 

[BentleyJ]

You should be using the 60A setting in the clamp meter and the meter may need to be zeroed first.

 

[afmiller]

BentleyJ is right on both, also remember, in series voltage increases, in parallel the voltage stays the same. Amps increase

 

[TimC]

Thanks guys. Reminds me of an old saying. Procession of tools does not make you a mechanic!

I've got a lot to learn! Setting the 60A to zero results in a very low amp reading. I guess that's close enough to zero to count.

 

[BentleyJ]

Hall effect clamp meters do have some minor inherent inaccuracies. When I purchased a well rated AC/DC budget clamp meter, I compared it to a Fluke AC only, conventional clamp attachment and found the Hall Effect unit was off by a small amount but was acceptable in my opinion.

 

[TimC]

Thanks again.

I miscalculated my array voltage at 3S2P. I used VOC instead of VMP when I designed the array and may come up short on V for my Growatt which requires a minimum of 120v. So I might end up with a 6S array to drive up the voltage to satisfy the Growatt. I hooked them all up as 6S and achieved about 235v. I'll try 3S2P first and see if that works. Probably just shy of what is required. If that doesn't work I guess I'll have to go 6S or build in two more panels for 4S2P. I really don't want to do that as it means expanding my ground rack.

I don't know if 6S limits my production or enhances it vs 3S2P. Lots to learn!

 

[BentleyJ]

6S should not limit your production at all, in fact it should help it. With 6S the 120V startup threshold will be reached earlier in the morning and last longer into the evening. Also voltage will be maintained to a much higher degree during cloudy/rainy weather. It also simplifies the wiring to the Inverter/Charger.

 

[TimC]

Super. I'll wire it 6S then. It's a small system but it is just what I wanted to slow charge my EV on level 1. I have both L1 and 16a L2 capability now but I want to charge mostly from solar. I don't typically drive a lot of miles on an average miles per day basis so it should work out well.

I now have to find out about my inverter's neutral/ground bond status. I don't know if the EV will like an unbonded N/G. I had a problem getting my furnace to run on an inverter generator. I was afraid that N/G bonding would damage something on my new furnace so I didn't proceed to make the N/G bonding plug. Luckily I haven't had a winter grid outage recently. Another thing to learn but this is a fun project.

 

[svetz]

You might also be interested in:

• What does it mean to have solar panels in parallel and series?
• Figuring out how many panels in series and parallel based on your MPPT

 

[BentleyJ]

The issue with the furnace is possibly related to the flame rectification sensor which according to the Goodman Installation manual requires a low impedence between neutral and ground. Don't remember all the details without reviewing the manual but the circuit boards are sensitive to reverse polarity and improper ground.

 

[TimC]

The issue with the furnace is possibly related to the flame rectification sensor which according to the Goodman Installation manual requires a low impedence between neutral and ground. Don't remember all the details without reviewing the manual but the circuit boards are sensitive to reverse polarity and improper ground.

That sounds very familiar to what I found when researching that problem a couple years ago. And though I do have a Goodman furnace I think I read that most modern high efficiency furnaces have the same issue running off of an inverter generator. I think that's why my previous furnace was fried. I tried to connect to an inverter generator and it probably didn't have the safeguards to protect it from my ignorance. Of course it was 28 years old and maybe designed without inverter generators in mind.

I am going ro finish up wiring the panels to the Growatt mounted temporarily in my garage. I'll wire the AC output to a single 120v 15a outlet for the purpose of L1 charging of the EV. I expect that if I don't have the neutral to ground bond that the EV will deny the initial handshake it usually does on grid power.

With this Growatt Will suggests a small battery to run high demand appliances even though it does not "need" a battery connection. I'll only be pulling 1.4kW so it should be happy without the battery bank for now.

Thanks for you input!