Grounding

fm.109 · July 2016

Hello community,

I am here to ask just one particular question (for now).

How do you ground equipment and panels in a solar installation.

Are there specific guidelines to be followed? if so then how and what should be done to adequately ground the system.

I am designing an installation that has the following items:

1 Fridge
1 Deep Freezer (old)
8 15 Watt Energy Saver Lights
4 Ceiling Fans (80 - 100 Watt each)

All this to be used as a backup power for 6 to 8 hours a day max throughout the year.

Also a guidance on the system design would be appreciated

fm.109 · July 2016

Image: https://us.v-cdn.net/6024911/uploads/editor/fa/s6m7nsq1d8os.jpeg

fm.109 · July 2016

Just to add, the power backup is required after every 2 hours. That means there will be 2 hours of mains electricity then one hour of backup.

fm.109 · July 2016

The system has to run solely on solar and no other backup suck as generator or UPS etc

vtmaps · July 2016

Your questions don't make any sense to me. You ask about grounding a solar installation and describe only the loads.

Then you say it has to be only solar powered but will use mains power every 2 hours.

--vtMaps

BB. · July 2016

If you have risk of lightning--Then grounding becomes more than "NEC" minimum grounding requirements.

Also, grounding can get into MSW vs PSW type AC inverter chosen and how you connect to your loads (AC grid power, pure off grid, transfer switch, etc.). You say no genset (genset grounding has its complications too)....

How big of AC inverter (Watts) and how large of battery bank. Fixed installation (?), not RV?.

-Bill

fm.109 · July 2016

Well the solar here would be used as a backup power since we have routine Load shedding on a daily basis.

After every 2 hours we have 1 hour of power shortage. It is a fixed installation and the grounding would only be for the solar panels and equipment.

Think of solar being used as a UPS in this case, where it automatically switched the mentioned items on solar when there is load shedding.

fm.109 · July 2016

I made a document so you guys can check if my diagram and calculations need improvement

BB. · July 2016

For some reason, the Word graphic(s) not showing in my "Open Office" software. Next time, if you can, print to PDF and uploading the file will usually work better.

FM.109, I forgot--Are you in the Dominican Republic or Haiti? Grounding of AC mains (neutral to earth/safety ground in main AC panel is typical standard for North America) can vary in different countries. Do you know the standard for your location? Are you running 230 VAC 50 Hz? Do you have 'poliraized plugs' (one hot pin, one neutral pin)? Do you have a requirement for Ground Fault Interupter (RCD or Residual Current Disconnect/Device in Euro Speak)?

In general, grounding for the inverter is pretty easy. Green wire to inverter case (green wire may connect to cold water pipe and possibly a 8 foot+ ground rod near the main panel). The more difficult part comes with trying to figure out the Hot/Neutral AC voltage configuration. Also--The choice between MSW (modified square/sine wave inverters) and TSW/PSW (True/Pure since wave) inverters. MSW inverters, generally, cannot have a Neutral to Earth bond connection (the AC MSW output is not isolated from the battery bank--ground bonding both battery bank and AC output creates a "dead short" through the inverter).

The battery bank, if you negative ground the battery bus (again to cold water pipe and/or ground rod), that is typically enough.

If you run the risk of nearby lighting strikes, then using Surge Protection Devices (on AC output for sure, on Solar panel input recommended) can help reduce damage (direct lightning strikes are going to cause damage--Using lightning rods/grounding system on out side of building/near solar array will be a big help).

You can get Inverter-Charger Inverters... They have the AC Transfer Switch built in, and have an AC charger (if you choose to charge from AC power).

For folks with intermittent power (afternoon power outages, etc.), the inverter-charger + battery bank is your "large UPS". You can start without solar panels (put the money in battery bank+inverter-charger first), and see how much energy you use--Then add solar panels as your wallet allows.

With Lead Acid batteries--You pretty much need about 6 hours of charging (solar, AC mains, genset, etc.) minimum of "reliable" charging energy. If you don't have a reasonably reliable AC mains (i.e., power available for a random hour or two only a few times a day)--Then you would really need solar/genset to keep the lead acid batteries happy.

-Bill

fm.109 · July 2016

BB I am in Islamabad, Pakistan and we do have lightning here but usually it is not severe unless it is monsoons.

Well interesting update on the grounding part so that means i should opt for true/pure sinewave inverters in this case.

Would it be better to opt for multiple inverters rather than a single inverter? for example i use one inverter for lighting and fans while one or two inverter for the fridge and freezer? does spreading the risk prove a better choice and would it be cost effective?

Inverter charger would be my choice you are right however i need to accurately size for solar as well in order to understand how much i would truly be spending. if it is viable then i would surely opt for solar.

fm.109 · July 2016

These are my calculations however, your opinion on it would be much appreciated or anyone for that matter

Grounding

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