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2 wire system requires a ground for minisplit installation??

2 wire system requires a ground for minisplit installation??

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  #1  
Old 06-18-19, 08:02 PM
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2 wire system requires a ground for minisplit installation??

Before I start assembly, I'd like to make sure that the unit will work, either without a ground, or with an earth ground (grounding rod.) Could someone please advise hopefully before tomorrow AM? I have an old 2 wire system. Thank you. Frank
 
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  #2  
Old 06-18-19, 08:10 PM
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You haven't given us any information. How can we help you with wiring as every unit is different.
I can tell you that you will not need a ground rod.

Are you saying that you only have a two wire AC connection ?
That won't work. You need a ground along with the power wires from the panel.
 
  #3  
Old 06-18-19, 08:57 PM
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Will it work? Maybe.
Will it be safe? No.

You really should run a new cable from the panel. Or at very least, install a GFCI breaker.
 
  #4  
Old 06-18-19, 09:24 PM
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Yea, you need a ground!

Yes, yes, yes you need a ground. And no, that isn’t (and you don’t need) a ground rod. The grounding electrode ( and conductor) and should be in place already at the service.
Yes you need an Equipment Grounding Conductor, (or ground wire), sized to your branch circuit feeding the unit, ( see NEC table 250.122 for sizing) and correctly bonded to the disconnect and the ground point in the unit. This is for safety! If your phase conductors ever short to ground there will be no way for the breaker to trip if the ground cannot carry the return current to the panel. Otherwise the case, enclosure or metal parts will become energized and just sit there waiting for someone to touch it and get shocked. BTW, a ground rod may dump some voltage into the earth but not enough to decrease the potential enough to eliminate a shock hazard, and it will not provide a path to allow the breaker or fuse to trip.
 

Last edited by pcboss; 06-19-19 at 06:55 PM. Reason: Changed GEC to EGC
  #5  
Old 06-18-19, 09:36 PM
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Ok, let me try to explain again. My house has an old 2 wire system with no ground. The minisplit has terminals for hot, neutral and ground. Hot and neutral are obvious, but what to do with ground? I was proposing to connect the ground terminal to a properly installed ground rod, which while it might work does not seem to be recommended. Or I could not connect it at all, also not recommended. So what is the best solution, short of installing a whole new panel? I have numerous appliances with 3-prong plugs that are plugged into the old 2 slot outlets with adapters, but in this case with such an expensive piece of equipment I wanted to be a little safer. Your help continues to be very much appreciated. I hope this explains things a little better. Frank
 
  #6  
Old 06-18-19, 09:49 PM
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I am sorry I'm still a little confused. If I were to run a properly sized ground wire directly from the ground terminal on the unit to the old fuse panel, that would be correct? But where to connect? To the metal box itself? And should I assume that the old box is grounded? Sorry I'm not more savvy- that's why I'm here. Please advise. Thanks again. Frank
 
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Old 06-18-19, 09:59 PM
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We could help you with the panel if you can post a picture of it with the cover off. Assuming you have a 120/240v service..... there should be three service wires in your panel and a ground connection to a ground rod or possibly a metal city water service. In this case..... the neutral and ground SHOULD connect to the same location in your panel. We can determine that by seeing what you have.

How-to-insert-pictures.
 
  #8  
Old 06-19-19, 03:13 AM
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I have numerous appliances with 3-prong plugs that are plugged into the old 2 slot outlets with adapters
This should never be done unless you have a ground wire or metal conduit in the junction box for the outlets.
Those adapters are meant to provide grounding through wallplate screw, which is grounded to the metal junction box.

Installing GFCI is the only approved and safe way. The GFCI will trip when there is a leakage current to anywhere (ie. through a person) other than back to neutral.
 
  #9  
Old 06-19-19, 06:29 AM
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My house has an old 2 wire system with no ground.

You haven't made it clear whether your house has an old 2-wire 120 volt service or 3-wire 120/240 volt service. When you say you have an old 2-wire system is this the service to the house or the existing branch circuit?

PJmax is right, we need to see a picture of your service panel with the cover removed. A picture of your service connection outside at the weatherhead might also be useful.

What is the voltage required for the new mini-split?
 
  #10  
Old 06-19-19, 11:21 PM
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Pjmax is right. Letís start here. You have a panel fed from your service. Assuming that same panel is the closest to the service or only panel fed from that service. At that location (typically) is the ONE place you bond/connect the incoming neutral to the Grounding Electrode System, which includes any or all of the following. Ground rods,cold water bond, ufer ground, gas pipe bond, as well as the panel enclosure etc. So letís rhink about this. (And hopefully we get a picture). You should have 2 phase conductors and a bare wire from the utility, that transitions to 2 phase conductors and an insulated neutral st the weather head. Then all three enter the panel and land on terminals as above. Then you bring a GROUND to the new ac unit from the ground/ neural bar in the panel to the equipment. NOW our have a path for fault current to return to the panel and travel through the breaker to trip it. Note. A ground rod at the unit will not allow the OCPD to actuate and is not code correct. By the way, having a two wire system to outlets in the rest of the house doesnít matter at alll. Bring the ground to the panel with the OCPD ( breaker or fuse). And consider using GFCI receptacles or breakers elsewhere in the house to increase safety whee concerned.
 
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