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Small Cabin Forum / Cabin Construction / Wiring an electrical panel
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Link44
Member
# Posted: 2 Jun 2023 00:37
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I have a couple questions before I do something silly. I had this idea that I could take a panel and run 1 phase from my solar generator and the other phase from a propane generator. Everything would be 110v so no 220v double breakers. The hots would all be separate but the grounds and neutrals would be on the same buss.

This way I could have lights in silence but if we wanted a margarita would could kick on the generator to have the outlets work. Any problems with this scenario?

Thanks

razmichael
Member
# Posted: 2 Jun 2023 07:21
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No comment on the actual wiring plan but wonder if you would be better with a transfer switch (automatic would be nice but since you have to start the generator anyway, manual would be cheapest). The advantage in my mind is the wiring is normal and, if you have an issue with solar (batteries etc) the generator will run everything as the backup. Add a charger in and you get the batteries charged up faster when you need to use the generator. Maybe something to consider.

Brettny
Member
# Posted: 2 Jun 2023 08:19
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Dont do that. Combining power sources in a pannel can be dangerous. Does your inverter power your margarita maker?

Just run your generator to power a battery charger and a few specific outlets.

DmAK12
Member
# Posted: 2 Jun 2023 09:13 - Edited by: DmAK12
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Quoting: Brettny
Combining power sources in a pannel can be dangerous.


It's not any different than a NEC approved residential solar setup in parallel with a utility, so I don't see an issue. I have friends that have their solar tied into their main panel. Definitely should be on seperate breakers.

travellerw
Member
# Posted: 2 Jun 2023 09:41
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While I can't see any issues as long as the grounding is proper. The generator should be floating ground and your only grounding point should be the panel (panel wired to grounding rod). The ground and neutral should be bonded at the panel with a ground conductor ran back to the generator and inverter. Essentially one ground point at the panel bonded to the neutral. This allows the breakers to clear a fault.

Now, with all that said.. A automatic transfer switch would be a better/more standard solution. They can be had on Amazon for pretty cheap and if you watch the Amazon Warehouse, they often come up under $100. The good ones switch so fast that devices don't notice.

P.S. Grounding rules still apply with an ATS

Link44
Member
# Posted: 2 Jun 2023 13:09
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I dont actually have solar panels. I have a Bluetti solar generator. I was hoping to run the essentials on that so I have peace and quiet and a generac RV propane generator for the outlets. It seemed to be reasonable to use 1 panel since I wont have 220v.

Happened to run into an electrician doing some works for the company I work for this morning. He said it would work but opened me up to possible problems if something went wrong. He suggested 2 panels, so they are completely separate or since the lights are all LEDs a junction box would work for the 2 circuits of lights.

I think I'll just throw in another 4 circuit box. I can keep them completely separate and if the solar generator dies I could plug the cord into an outlet to power the second panel with the generator. Everything would still be on breakers. I'll run a ground rod for each panel.

Thanks for the thoughts, sometimes my brain boils.

ICC
Member
# Posted: 2 Jun 2023 18:46
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An automatic transfer switch is designed for what you want to do and will protect all the equipment as well as protect all the people.

An NEC approved grid-tie solar panel system also has some automatic switching that prevents solar power from entering the grid if the grid power drops. It is not a simple dual connection of two sources to one service panel.

Without a transfer switch of some kind (manual or automatic) there can easily be a danger of electrocution to people depending on how the connections are made. With portable devices being connected and then disconnected and removed I have seen serious mishaps just waiting to happen.

It's generally not a good idea to be innovative when electricity is concerned.

Link44
Member
# Posted: 3 Jun 2023 12:26
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Quoting: ICC
It's generally not a good idea to be innovative when electricity is concerned.


This made me laugh but I get the point. I'll check out transfer switches and see what 1 will work best for me. Sometimes my bright ideas are not so good in practice.

Thanks

ICC
Member
# Posted: 3 Jun 2023 13:19
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If the total amperage is 30 or less there are RV transfer switches that can be used where there are no infections being done. Those are still good switches but are not NEC approved because they are aimed at RV's and not residential or commercial buildings covered by NEC

@campingworld

ICC
Member
# Posted: 3 Jun 2023 13:21
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That one is not instantaneous switching but is fast enough for most tasks

Brettny
Member
# Posted: 3 Jun 2023 14:49
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Quoting: DmAK12
It's not any different than a NEC approved residential solar setup in parallel with a utility, so I don't see an issue. I have friends that have their solar tied into their main panel. Definitely should be on seperate breakers

Those are solar setups that complete shut down all output when the main power is out. This isnt the same.

toyota_mdt_tech
Member
# Posted: 3 Jun 2023 19:41
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How about 2 panels, one for solar lighting and small loads, another panel for outlets and heavier loads from the generator.

So 2 isolated systems and if power ever comes in or you decide to hook to grid, make one panel a sub panel from the main and tie the 2 together that way.

One main load center for generator, a smaller panel for solar and lighting. Run a wire between the 2 for later hookup if it ever comes to that.

ICC
Member
# Posted: 3 Jun 2023 23:50 - Edited by: ICC
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Quoting: Brettny
Those are solar setups that complete shut down all output when the main power is out.

That is correct, as far as it goes. That is to protect linemen who may be working on a powered down grid.

Thete is more to this than meets many an eye. I did not have time to be more precise. I wanted to discourage interconnection of 2 random AC power sources.

The inverters used to connect the pv panel output to the grid also have to detect voltage, Hz kfrequency) and phase and synchronize those before connecting to the grid.

(We know a sine wave has peaks and valleys and change current direction 60 times a second in the US and Canada. If the frequency and the phase are not matched equipment will be damaged. In simple terms the peaks of each power source must be matched to be the same.)

The OP was asking about connecting an engine powered generator and a solar generator (basicly a battery and an inverter in a box) to the same service panel . Pretty much the same idea as a grid tied pv panel system in simplest terms. But that has the same syning problems as grid tied solar.

To potentially make for an even bigger mismatch would be a situation where one AC was pure sine wave and the other a square or modified wave.

A proper transfer switch will totally disconnect both the hot and neutral from the service panel before connecting the hot and neutral of the second power source. That total disconnect time may only be a fraction of a second but that is all the separation required. Never will source A and source B be connected together.

If anyone is thinking that it would be okay to manuallt trip snd set breakers to replucate the operation of s proper transfer switch I wouls simply state all it takes is to get the sewuence wrong once. And what if someone else goes to flip the breakers some time?

If connecting two different AC power sources to the same service panel the voltage, frequency and phase of each must be synced or equipment damage will occur. That is why certain Honda and other brand inverter generators may be parallel connected eith the special connector cables. They have syncing capabilty. Similarly some off grid inverters can be stacked in parallel for increased amperage as well as connecting to provide 240 VAC. They all sync voltage, frequency and phase.

Link44
Member
# Posted: 4 Jun 2023 14:56
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Quoting: toyota_mdt_tech
How about 2 panels, one for solar lighting and small loads, another panel for outlets and heavier loads from the generator.


I was thinking about this too. The stud bays are all still open so nows the time to make it right.

The Generac is 3400 watts so it's just under 30 amps.

gcrank1
Member
# Posted: 4 Jun 2023 19:55 - Edited by: gcrank1
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I have a psw inverter that takes inputs from a battery and generator that has an internal transfer switch. When run off the battery alone all is quiet, start the gen and it switches to the gen alone and can run a charger to the battery (a fancier, more expensive version has in internal bat charger; I like individual replaceable components). Shut off the gen it switches back to bat power.
My power for use comes off the front inverter panel.
Some could/would take that to a elec panel, my place and needs are small enough that I wont.

Brettny
Member
# Posted: 5 Jun 2023 06:15
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Quoting: gcrank1
have a psw inverter that takes inputs from a battery and generator that has an internal transfer switch.

Mine does that too but I have never used it. If I'm running the generator I want it to charge my batteries. How ever you could run the generator power to the transfer switch and a battery charger. That would be useing as much power as you could from the generator in the least amount of time.

travellerw
Member
# Posted: 5 Jun 2023 10:54
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Quoting: gcrank1
(a fancier, more expensive version has in internal bat charger; I like individual replaceable components)


That is what I have with the Growatt. Start the generator and the Growatt auto switches all the plugs, plus charges the battery (current is adjustable). It works amazingly well, but my generator is just a little too small if I want to run a high draw item (AC, hairdryer, Air Fryer, ect). I had to dial the battery charger WAY down or the generator overloaded in those cases.

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