hello everyone. Im sorry if this is a dumb question but I have to ask. Im putting together a small 12v battery backup in my house for emergency power. I have a 2500 cobra inverter that has to be grounded. Since this setup will be In the living room while in use, is it possible to ground it by attaching a grounding wire to a nail and sticking it in the ground of my wall outlet? Once again sorry if that's a dumb question. I just figured since the 3rd hole in the wall outlets are the ground that it would make sense. Thanks for any advice.
Dumb grounding question
- Thread starter James D
- Start date
MichaelK
Solar Wizard
With the small scale of your system, I think grounding to the house ground might be barely adequate, though a nail sticking in the socket is a bit tenuous? I'd get a real screw-together socket and proper attach just the ground wire to it. Something like this. Keep in mind that if something really went wrong, and inverter tried dumping all 2500W through the ground wire of the house, the house wiring ground might not be able to handle it.
MichaelK
Solar Wizard
Not a chance. A proper grounding rod is 8 feet long. Another potential grounding point are any metal water pipes that are known to go into the ground. What about about nearby metal posts sunk in concrete?
MichaelK
Solar Wizard
I'd say the best choice would be the house spigot. Is it a metal pipe that you see going into the ground?
Intuitively, I would not want a grounding connection attached to a flammable gas line. Maybe that's just me?
Intuitively, I would not want a grounding connection attached to a flammable gas line. Maybe that's just me?
MisterSandals
Participation Medalist
Just out of curiosity, is this a pure sine wave inverter? And what do you plan to do with this inverter in an emergency? What do you have for a battery bank?
And from what I've heard in this discussion, using the inverter on occasion without a ground sounds a lot safer than trying to put a nail in a receptacle.
John Frum
Tell me your problems
- Joined
- Nov 30, 2019
- Messages
- 15,233
Grounding is multi-faceted and complicated.
diysolarforum.com
Grounding Made simpler - Part 1: AC/houshold grounding
To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...
diysolarforum.com
MisterSandals
Participation Medalist
Is the size of your batteries a secret?
What I envision as small deep cycle batteries, even 3 of them, will not come close to powering the things you expect to power. And its very possible that your refrigerator will not run smoothly, if at all, from a modified sine wave inverter.
What I envision as small deep cycle batteries, even 3 of them, will not come close to powering the things you expect to power. And its very possible that your refrigerator will not run smoothly, if at all, from a modified sine wave inverter.
Sorry. 3 18ah 12 volts. Still kinda new to all of this
MisterSandals
Participation Medalist
Lets do some math. I will assume you have the same 27cuft EnergyStar refrigerator that I have. It uses about 125w when "running" which is about 1/3 of the time (20 min per hour). It uses about 20w when idling (40 min per hour).
125w x .33 x 24h = 990wh
20w x .66 x 24h = 317wh
1307wh per day
Your batteries (lead acid so 50% usable/dischargeable):
3 x 18ah x .50 x 12.8v = 345wh
15% inverter loss: 345 x .85 = 293wh
293/1307wh =
.22days x 24h/day = 5.28h runtime for just the fridge on fully charged batteries (everything operating at 100%)
Now are you sorry you joined?
125w x .33 x 24h = 990wh
20w x .66 x 24h = 317wh
1307wh per day
Your batteries (lead acid so 50% usable/dischargeable):
3 x 18ah x .50 x 12.8v = 345wh
15% inverter loss: 345 x .85 = 293wh
293/1307wh =
.22days x 24h/day = 5.28h runtime for just the fridge on fully charged batteries (everything operating at 100%)
Now are you sorry you joined?
Why would I be sorry. This is exactly the kind of information I need to know lol. Also I found a thick ground wire going from my electric meter into the ground. Would that work?
I am new to and will second what James said
This is great information
I am following this thread
Same question but mine is a emergency generator 24v
It will just be used to power (maybe) not all at once
Router
Modem
Tv
Power wheelchair charger
CPAP machine
If I use the plastic boxes on wheels ( like most plans have) where should I attach the grounding (from the screw on the inverter body) ?
I am thinking about using a WZRELB brand 24v 2000w inverter
I have 2 lithium 24v 32ah batteries parallel for 24v 64ah
Battery specs
Internal Resistance ≤0.8mΩ
Max Charge Rate 120A
Recommend Continuous Discharge Rate 200A
Pulse Discharge Rate（3 seconds） 400A
Fully Charged voltage 4.2V
Discharge cut off voltage 2.5V
Working Charge Temp 0~50°C
Working Discharge Temp –20°C~50°C
Storage Temperature –20°C~50°C
Same question but mine is a emergency generator 24v
It will just be used to power (maybe) not all at once
Router
Modem
Tv
Power wheelchair charger
CPAP machine
If I use the plastic boxes on wheels ( like most plans have) where should I attach the grounding (from the screw on the inverter body) ?
I am thinking about using a WZRELB brand 24v 2000w inverter
I have 2 lithium 24v 32ah batteries parallel for 24v 64ah
Battery specs
Internal Resistance ≤0.8mΩ
Max Charge Rate 120A
Recommend Continuous Discharge Rate 200A
Pulse Discharge Rate（3 seconds） 400A
Fully Charged voltage 4.2V
Discharge cut off voltage 2.5V
Working Charge Temp 0~50°C
Working Discharge Temp –20°C~50°C
Storage Temperature –20°C~50°C
I am not sure I know enough to be jumping in fully on this. But agree with MisterSandals for the most part. The one place I am not sure I agree is the grounding. First though, the ground wire by the power meter is the main one and is more than sufficient. It grounds the whole house so that little load is fine. The other one that showed a cheap plug would also work. You plug only the ground in and plug it into the wall. It handles a 15 amp circuit which is 1800 watts. It is more to send stray voltage to ground first and not through you. Second is the batteries and inverter. In many cases a cheaper modified inverter does not run many things well. Especially sensitive electronics. You would be better off getting 2 cheaper 800 watt full sine wave inverters to run your cpap and a regular refrigerator. Will Prow’s had a video that he recommended some inverters and I think it is on his site. I bought the 800 watt one and ran my cpap for several nights but it is 12 volt. I think you can get the 24v version of the inverters. The fridge is the same even if you have a bigger fridge it should still pull less than 800 peak. And like 250 watt normal. Get a plug in wall watt meter (kill-a-watt) from amazon, eBay or harbor freight to know for sure. The batteries are too small. I was powering 2 fridges about 450 watt draw. I used 130 ah x 48v lifepoe4 and recharging them with 4 x 310 watt solar panels and would not keep up. That is a different setup but using for reference… Every 24 hours or so would have to recharge to keep up. But hey in an emergency every little bit helps. Another idea is a small inverter generator to keep things charged. Run it over couple of hours to charge batteries keep the items going and stretch what you have out as long as possible. Good luck.
