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Old 07-02-2022, 07:49 AM   #1
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Ground 12v wire to 120v ground wire

Can you connect the ground wire of a 12 volt (low amp computer fan to vent cabinet) to the ground connector of a 120 volt duplex outlet mounted to wall.
I'm assuming a ground is a ground, but you know what happens when you assume.
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Old 07-02-2022, 07:56 AM   #2
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Short answer is no. The 120v ground goes through the breaker panel to the neutral side of the shore power. It does not connect in any way to a 12v ground connection. Any 12v appliance in the coach should be grounded to the 12v house supply or chassis frame.
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Old 07-02-2022, 08:24 AM   #3
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Can you connect the ground wire of a 12 volt (low amp computer fan to vent cabinet) to the ground connector of a 120 volt duplex outlet mounted to wall.
I'm assuming a ground is a ground, but you know what happens when you assume.
I know my coach has the inverter grounded to the frame with a green ground wire. So I have to assume if it shorts the frame is going to be hot and must be also grounded at the ac power in. Check where your power cord comes in. See if the green power cord wire attatches to the frame. There wouldn't be anything to stop a hot skin condition if there was no ground. Also the generator wouldn't need to be bonded when on gen instead of shore power.
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Old 07-02-2022, 11:07 AM   #4
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I know my coach has the inverter grounded to the frame with a green ground wire. So I have to assume if it shorts the frame is going to be hot and must be also grounded at the ac power in. Check where your power cord comes in. See if the green power cord wire attatches to the frame. There wouldn't be anything to stop a hot skin condition if there was no ground. Also the generator wouldn't need to be bonded when on gen instead of shore power.
The 12 volt DC negative cannot be safely and effectively connected to a 120 volt AC cable ground wire.

Many people assume grounding is simple. I did until I learned differently. Grounding systems are safety systems. Follow instructions and building codes for how to connect them. These codes are the result of 150 years of experience with deaths, injuries, and property loss.

There are earth ground systems, chassis ground systems, equipment ground systems and many more. Some are similar. Some are radically different. Each has its purpose and may have safety and functional purposes.

12 volt DC RV systems often use the RV frame as a negative power pathway.
It is often referred to as a "ground". It is not the same as a house/grid power 120 volt AC "ground" system.

An inverter/charger/converter/transfer switch joins several systems. It has complex connections designed to manage the different "ground" requirements.

When connected to shore power, earth ground connects to the ground wire in 120 volt cable at the service entrance. No other earth, grounds are permitted. Requirements are not simple. See wiring codes for correct wiring.

When connected to generator power there may be no earth ground. If there is, it is to be close to the generator. The RV frame may be connected to the generator ground and/or generator earth ground.

When inverting 12 volt battery power to 120 volt AC power, the frame ground is connected to the 120 volt cable ground close to the inverter. There will probably be no earth ground.

As you can see, it is getting complicated. I have to say there are far more ground connection issues than I have described here.

The simple answer has been posted in above answers.

The 12 volt DC negative cannot be safely and effectively connected to a 120 volt AC cable ground wire.

It is best practice to run both a positive and negative wire from a 12 volt DC appliance back to the fuse panel.

Frame grounding near the fuse panel is likely. High current battery connections some times use the frame as a negative pathway because 2 awg copper cable is heavy and costs a lot.

I wish you good luck and happy trails ahead!
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Old 07-02-2022, 03:50 PM   #5
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Paul, I understand what you are saying. But in reality the 12v systems are grounded to the frame and so is the 120v. The ac should never see the ground in a perfect world but when something goes poof it does. The coach has to have the skin grounded. I have seen references to electronic 12v grounds in my manual. The Aladdin system is grounded to one. I'm guessing it's diode protected so it cannot see a back feed from whatever source. Especially the 120v ac.
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Old 07-02-2022, 03:53 PM   #6
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Can you connect the ground wire of a 12 volt (low amp computer fan to vent cabinet) to the ground connector of a 120 volt duplex outlet mounted to wall.
I'm assuming a ground is a ground, but you know what happens when you assume.
No, because it is unlikely that a 12v computer fan has a ground.

It likely has a positive and a negative (not a ground) cable that have to make a complete circuit loop though a 12v battery.
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Old 07-02-2022, 04:27 PM   #7
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Nec and rvia require the 12- and the ac to be grounded to the frame. The ground on the 120 doesn't connect to the neutral until it is at the main breaker panel at the rv park or home. It had better not be connected at the pedestal. As far as the op, I would simply look for a place to screw a ground wire to the frame of the coach or trailer. Electricity is not looking for a way to ground, it is looking for a path back to it's source. Try not to put any obstacles in that path.
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Old 07-02-2022, 04:43 PM   #8
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The AC Ground and 12v battery negative are both bonded to the frame. For safety reasons , the AC ground is not permitted to carry any current , except in a fault condition.
On shore power, the AC ground and neutral are bonded at the service entrance to the park. When on generator, the AC ground and neutral are bonded inside the generator.
Some RV manufactures will use any metal part connected to the frame as the DC negative. Other manufactures will run all negative wires to a common point on the chassis. For DC connections you should always run the negative to the commom point or the frame.
NEVER use the AC ground for DC power.
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Old 07-03-2022, 05:07 AM   #9
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Paul, I understand what you are saying. But in reality the 12v systems are grounded to the frame and so is the 120v. The ac should never see the ground in a perfect world but when something goes poof it does. The coach has to have the skin grounded. I have seen references to electronic 12v grounds in my manual. The Aladdin system is grounded to one. I'm guessing it's diode protected so it cannot see a back feed from whatever source. Especially the 120v ac.
Whether it will work or not is not the question.

A 120 volt AC ground system is designed to have NO Current when everything is working correctly. It is intended to only carry current when there is a malfunction.

Maintain the safety and function. Run the 12 volt DC ground separately.
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Old 07-03-2022, 08:49 AM   #10
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Thanks to all for the great response. Had no idea this would generate such immediate feedback.
Such a great forum and wealth of knowledge available.

in future , when needing a ground I will run separate to frame and keep 12v and 120 v separate.

But for my situation Nwcid was correct, that computer fan has no ground, but a positive and negative to make circuit loop.

All working good as i tapped off existing LED light circuit for positive and negative for fan.

Thank again to all for help and education. This is the best forum for anyone needing problem solving.
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