Solar panel / which end is pos/neg?

[Solar Scott]

When running the PV line, which plug is positive to be red, and which plug is negative to be black? Does it matter?
One mc4 plug would described as female, the other would be a male. Premade PV cables (one red and one black) also have both ends on them.
Silly question I realize, but there is nothing designating pos/neg on the solar panel.

 

[dougbert]

red is positive and the MALE MC4 connection is positive, viewing from the panel point of view

also get a good multi-meter, you are going to need one anyway

Will Prowse has a web page on his recommended tools including various multimeters

 

[rodrick]

The best way is to use a dmm it will tell you which is pos and neg just put the panels in the sun and take a reading this is best way especially when working with used panels due to the unknown history things can get modified

 

[dougbert]

The best way is to use a dmm it will tell you which is pos and neg just put the panels in the sun and take a reading this is best way especially when working with used panels due to the unknown history things can get modified

yes the meter is the best way, especially on used panels. thanks, rodrick

 

[Solar Scott]

red is positive and the MALE MC4 connection is positive, viewing from the panel point of view

also get a good multi-meter, you are going to need one anyway

Will Prowse has a web page on his recommended tools including various multimeters

I installed (10) 400 watt panels in a single string on my south facing rooftop. Will only one end have voltage? To an earth ground?

 

[Solar Scott]

I installed (10) 400 watt panels in a single string on my south facing rooftop. Will only one end have voltage? To an earth ground?

I should say…..checking to an earth ground with my dmm.

 

[dougbert]

I installed (10) 400 watt panels in a single string on my south facing rooftop. Will only one end have voltage? To an earth ground?

the voltage will be between the POS end and NEG end (BTW be very careful with 400 volts DC - use PPE,)

if there is voltage on the frames or mount, it is not grounded

ground is only connected to the frames and mounts the panels are on.

 

[Solar Scott]

Thank you Dougbert. I will connect the frames/mounts to the existing earth ground by my meter on the end of the house with matching bare copper wire to ground frames. That will serve as (neg) for my dmm to identify the positive terminal of the PV string.
Correct?

 

[Solar Scott]

Existing earth ground

 

[dougbert]

Thank you Dougbert. I will connect the frames/mounts to the existing earth ground by my meter on the end of the house with matching bare copper wire to ground frames. That will serve as (neg) for my dmm to identify the possible terminal of the PV string.
Correct?

ah, no

the ground is in case of leaky panels. DC Current flows between NEG and POS.

only in case of a short (FAULT) does current flow on the ground.

Most solar systems do NOT have NEG as a GROUND, as in a car where NEG is GROUND to car frame

different animals

 

[rodrick]

You need to test the leads from the panels grounding is different than the negative from the panels

 

[rodrick]

Have you figured the total voc adjusted for temperature of your array. You have to watch the voltage going to your mppt you might want to give us some more details on your system

 

[rodrick]

Also you need to be dam careful with that many panels the voltage will kill you easily

 

[glandpuck]

If your panels are used, it may be a good idea to carefully inspect the MC4 connectors or just replace them altogether. YOU can purchase an MC4 crimper on bezos for under $30 that works just fine. As for the connectors, the original are now made by Staubli. These are good quality. The pins, plastic and the o-rings that prevent water intrusion are good quality as well as the tabs that lock the male and female together. I have also used Renology and they were also satisfactory. I have used the generic el cheapos available online and if you get lucky, great, but you may not. Also, with the el cheapos, they may not make a good connection if not a matched pair.

Remember to buy at least 2 of the plastic MC4 spanner wrenches to connect and disconnect them and screw and unscrew them.

Whenever I connect MC4 together, I apply a dab of dielectric grease to the male and female. This helps reduce corrosion, allows for taking apart in the future and blocks water. Its good practice to do this.

NEVER WORK ON THE PANELS IN THE DAYTIME WITHOUT A METER TO MAKE 100% CERTAIN WHAT IS HOT AND WHAT IS NOT.

IF YOU ARE INEXPERIENCED, WORK AT NIGHT WITH A FLASHLIGHT OR LAMP. if you are making connections outside and are inexperienced, make some test connections on a piece of wire indoors first to practice with the tools and test your connections with a meter for continuity.

 

[zanydroid]

Forget about earth ground for checking what is +/- on solar. Use the two MC4 connectors.

There is no connection between either + or - on modern panels and ground unless the panel is damaged.

 

[zanydroid]

Also, I noticed a picture of the earth ground (presumably the GEC). Don't mess with those, it often requires special splices to maintain code compliance. I would presumptively pick the EGC of the home AC system, and then as needed avoid double N-G bonding issues in other places. Even if you tapped the GEC directly you'll still run into problems if you have multiple N-G bonds.

 

[rodrick]

Haven’t heard from op getting concerned ?

 

[Solar Scott]

Have you figured the total voc adjusted for temperature of your array. You have to watch the voltage going to your mppt you might want to give us some more details on your system

Purchased EG4 6000XP, (split phase), (10) new 400W Canadian Solar panels and an EG4 100amp battery. LL-S. 6000XP takes 480v max, 4000 watts per mppt. Panels are 37.1 amps each, living in Missouri. So far, I have mounted my panels to the roof, and hung my inverter next to my main panel. Just getting started, and enjoying the learning process. I will proceed with cation.

 

[Solar Scott]

Also you need to be dam careful with that many panels the voltage will kill you easily

I will definitely exercise caution, I have enough experience with electricity to respect it.

 

[dougbert]

should start with 2 batteries for 200 amp-hr

 

[rodrick]

Purchased EG4 6000XP, (split phase), (10) new 400W Canadian Solar panels and an EG4 100amp battery. LL-S. 6000XP takes 480v max, 4000 watts per mppt. Panels are 37.1 amps each, living in Missouri. So far, I have mounted my panels to the roof, and hung my inverter next to my main panel. Just getting started, and enjoying the learning process. I will proceed with cation.

Looking at the voltage for a Canadian solar 400 watt panel the voc is 47.2 on the one I found

If you run 10 in series your voltage will be 472 volt without temperature adjustment this is to high you will destroy your inverter, you need to find lowest temperatures for your area then set your panels up according to voc and temperature adjustment

Doing some quick calculations I would suggest 8s max

you can exceed watts but voltage is a hard limit

 

[ShaneC]

If the panels are 37.1A then that would mean about 10.8V. VoC would be higher but not a problem.

 

[rodrick]

If the panels are 37.1A then that would mean about 10.8V. VoC would be higher but not a problem.

I believe that was the vmp I haven’t seen any 37.1 amp panels have you?

 

[Solar Scott]

I believe that was the vmp I haven’t seen any 37.1 amp panels have you?

 

[Solar Scott]

Pmax 400W
Vmp. 30.8
Imp. 12.99
Voc. 36.8
Isc. 13.85
From the spec sheet, (misread the 37.1 last night)