Dual power source entering home, best way to do grounding - Page 1
Forum section: electronics / general

author: Red Squirrel
author_rank: Super Contributor
timestamp: August 26, 2021, 08:23:36 pm
content: I want to bring in power from my solar shed into the house into a separate panel then have plugs around the house so I can plug stuff in and have it powered by solar. The solar setup will be on it's own ground rod and ground will be tied to neutral. Basically like a normal house setup. I am upgrading the inverter and checked and everything is floating so I can safely set it up properly. (got to watch that with some inverters)Goal is to have some important things like my servers be setup on a A/B switch that will probably be manually operated and just use relays to switch everything. So it will run on hydro most of the time but if I choose to I can transfer the power to solar. May also automate this at some point based on available power. Now since some things such as my servers are going to have a grounded chassis, which then may be grounded to rest of server rack along with other grounded chassis, what is the best way to do grounding if I have two power sources powering different equipment?My train of thought is that the A/B switch would always use the A ground (house) and not the B ground. So even when running on solar, I would be using the house ground. In theory both these grounds should be at same potential as they will go to earth ground but don't want to depend on that either. I could just connect them together but I feel this is probably not right to do.What is typically the best way to handle these type of scenarios safely? If I have some servers running on solar and some not, I also need to consider the potential between ethernet cable grounds or any other data cabling that has grounds. I imagine if I use the house ground for everything then I will be ok. This will only apply to the A/B switch, the actual wall outlets from the solar sub panel will use the same ground as shed. Basically what you would do with a generator, you'd have a ground rod at the generator if you were doing things proper.Am I on the right track in doing grounding properly?

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 26, 2021, 10:12:21 pm
content: Connect the grounds together. The grounding resistance prevents it from becoming a ground loop.

author: james_s
author_rank: Super Contributor
timestamp: August 26, 2021, 11:28:41 pm
content: I don't know about Canada but in the US the grounding system is required to be bonded together. Grounding strategy varies by region due to large differences in soil composition but in my area you are required to have a minimum of two ground rods and they must be connected together and to the panel via a single un-interrupted piece of 8awg copper wire. What I would likely do in your situation is run a #8 ground wire from the shed directly to the grounding bus in the panel, or if that is not practical, attach it to the grounding rod the house is tied to. The whole point of a grounding system is to create a single reference that is the same potential everywhere.

author: Red Squirrel
author_rank: Super Contributor
timestamp: August 26, 2021, 11:39:09 pm
content: Hmm good to know. So just tie the house and shed grounds together then. This simplifies things as at least I don't need to worry about any weird voltage difference between the two systems. Of course they wont be in phase but don't think that will matter right even if the neutrals are tied together for both systems?So what I think I will do is at the shed's electrical panel where ground and neutral are tied together, I will run another wire going to the house then connect that one to the main panel. I will also have a couple ground rods at the shed, and may even tie in at the water valve while I'm at it. (it's near the shed)

author: KeepItSimpleStupid
author_rank: Regular Contributor
timestamp: August 27, 2021, 12:48:59 am
content: In the US, if you were powering a "detached building", it would get a ground rod.So, the "detached solar shed" needs a ground rod.The "system" needs a single reference. Ground (the ground rod) and neutral get tied together in the main panel for utility power.Your "solar shed" is a sub-panel in reverse. Ground and neutral stay separated and run back to the main panel and effectively get tied to the same place.You can have multiple ground rods at the main panel.Your ground rod is there at the solar shed to deal with lightning AND making the earth equipotential as best as you can.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 27, 2021, 02:17:18 am
content: You can look into a "zero export inverter" to seamlessly blend grid power and solar power, without exporting any power to the grid.