Tiny House Solar, Wiring Inverter to AC Electric

[Mike90250]

Better practice is to use one GFCI as each outlet, and not daisy-chain them. That $15 is cheap, till you start searching for the one that tripped and killed the blowdryer, and find it downstairs in the laundry room.
But in a tiny house, where you only have 3 outlets and can see the GFCI outlet from all the other locations, it would be fine.

boy-sticking-knife-into-socket.jpg

[jflorey2]

My bad it is 14/3 wire I used. It has hot neutral. And ground

14/3 wire has four conductors, usually two hots (red and black) a neutral (white) and a separate uninsulated ground. If it's Romex (most common) it is then wrapped in a white plastic sleeve to hold it all together.

From what you've said, you won't need more than 14/2. (Which is probably what you have.) That's three wires - one white and one black (for power; hot and neutral) and a bare ground.

are you saying I should use all gfci receptacles?

You only need GFCI one per outlet string. All the outlets downstream of the first GFCI outlet are protected by the first one.

and what would protect the ac line that is hardwired to the inverters from surge?

Nothing. (Breakers don't either.)

What Mike meant is that regular breakers won't trip. Let's say you go with the Suresine 300, which is an excellent inverter BTW. The most power it will put out is 600 watts, which is 5 amps. So if you have 15 amp breakers, they will never trip, because the current will never get above 5 amps for any amount of time. And those breakers need 15 amps to trip.

So what happens? The inverter, rather than the breaker, provides the protection. In this case it's safe because 14/2 can easily handle the fault current that the SureSine can provide.

in this situation I'm relying on the gfci receptacles as the surge protection?

GFCI receptacles don't give you surge protection either.

Quick aside on terms - there are a few things you might be talking about when you say "surge." The electrical meaning of that is an overvoltage caused by generator overspeed or flyback voltage or lightning strike; this can damage devices that are plugged in. Surge protectors clamp this voltage to a safe level.

You might mean overcurrent, which is what circuit breakers normally protect against. In this case you are relying on the inverter for that.

You might mean ground fault, which is a situation where some current is returned to ground rather than the real return. To use your 14/2 Romex as an example, all the current flows through the two power leads - it flows out through black (hot) and returns through white (neutral.) None should ever return through ground. If some does, then there's a good chance that something is wrong. Maybe you grabbed the hot prong of a cord while you were unplugging it. Maybe you were trying to use a metal knife to get some toast out of a toaster and touched the heating element. And now some of that current is flowing through you to ground instead of through the neutral like it's supposed to. It's a tiny current - more like 15 milliamps than 15 amps - so a regular breaker won't blow. GFCI's detect that small amount of current and trip open, thus protecting the person with the knife.

[PNPmacnab]

I started out with 100W panels and went to grid tie. I store my panels at the end of the season and handling them isn't that bad. I run a 60V system which allows me to easily heat water with excess solar energy. I bought 280W panels locally for $170 without problems. You don't need to live like a refugee. I have everything refrigeration, hot water, even a dishwasher with heated dry with a system not much larger than that. I schedule loads on sunny days so I don't need a massive battery I have only a car battery. Panels make a nice roof or shaded outdoor area. Everybody wants to under panel. It is insane.

[littleharbor]

Buy them locally. Don't have to pay shipping.

You wont need more panels. They are usually 39" x 65" or 39" x 77" for the 300+ watt panels. Do these dimensions work out with your roof.

[Brian53713]

With Renogy 100 watt panels being about a dollar a watt and free shipping, nobody has ever answered my question from months ago how do you get those larger panels delivered? Also much easier to deal with. And sturdier I have heard from you experts. And if it's a tiny house, easier to fit more 100 Watters

[erblasco]

Mike90250-

are you saying I should use all gfci receptacles?

and what would protect the ac line that is hardwired to the inverters from surge?

in this situation I'm relying on the gfci receptacles as the surge protection?


ps thanks for the post that inverter looks very good for what want to do

[erblasco]

My bad it is 14/3 wire I used. It has hot neutral. And ground

[Mike90250]

If you are still in the build out process of the tiny house, use standard household wiring (romex with ground wire) so that if you NEED to upgrade to a microwave, you won't have to rip wires out.

Morningstar has a nice efficient 300W inverter rated to be hardwired in, and will support being connected to outlets via GFCI. (suresine 300, 600w surge 10 min)

AC circuit breakers are less useful than one would expect, because of limited power the inverter can supply, won't always rapidly trip a breaker.. GFCI's will trip on a small leakage fault.

[littleharbor]

The example you have provided certainly does have a ground plus two conductors.
Here's a quote from Mike Holt's forum by a senior member.

"When nonmetallic-sheathed cable came on the scene I'm guessing late thirties or early fortys it did not have a ground. Ground wire was added Im guessing again around the early to mid fifties and it was a reduced ground. Full sized ground wire came about in mid to late sixtys along with the infamous alumium nonmetallic-sheathed cable. All dates are aprox."

[jflorey2]

If you want GFCI protection you need X/3 lines.

14/2 Romex has 3 conductors (2 power, 1 ground) and is compatible with GFCI outlets.

[Falsa_Nominis]

all I currently have is a small cabin with 2 standard 14/2 lines wired to 3 receptacles and the other to 2 led overhead lights on switches

If you want GFCI protection you need X/3 lines. We don't know where in the world you are therefore, we cannot deduce if your appliances are 115V/120V or 230V.

14 gauge solid core copper wire is rated for 15 Amps. On 115V/120V that is 1725 - 1800 watts, 3450 watts on 230V. You should limit 14 gauge it to 1500 Watts on 115/120V, 3000 Watts on 230V to be safe.

And what would be an appropriate set up for a cabin where I'm running a few lights a laptop and no major appliances.

Your inverter size depends the Power requirements of all your loads. Sum the power requirement of all the loads. You will need a inverter larger then that sum.

Your solar panel array size and battery bank size depend on your Energy consumption patterns and the solar resources at your location. Map out power requirements by time of day, from that you can develop a reasonable energy consumption profile.

[jflorey2]

I'd like to know why folks don't like 100watt panels?

There's nothing wrong with 100 watt panels from a functional standpoint. They are just more expensive than grid tie (200+ watt) panels. In general you are better off getting cheaper larger panels and using an MPPT charge controller to match the battery voltage.

However, if you have a stack of old 100 watt panels that still work, or can get them for free, then no worries - they will work.

[jflorey2]

I see this board has its share of idiots that try to beat down the new guys.

More like making sure the new guys get to be old guys.

If the GFCIs would not work that way, the engineers that design inverters would not include GFCIs in the inverters.

Inverters intended for installation into structures do not have GFCI's for the reasons I listed.

Inverters used for portable applications sometimes do have GFCI's - because if all you are doing is plugging an appliance in (or using an extension cord, and then plugging the appliance in) then a GFCI improves the level of safety.

Some inverters are used for both. For example, I have a Prosine 1000 that I use for portable applications (margaritas at the beach for example.) It has a GFCI outlet on it. It also has a version that is intended for hardwire installations, like RV's or small homes. It does not have GFCI protection on the output, for reasons I listed above.

You insulted the design engineers. Good luck in convincing anybody with more then three active brain cells, that you know what your talking about.

No worries there. I hope you make it to being one of those old guy "idiots" - and hopefully not through trial and error.

[erblasco]

I appreciate all the feedback it's giving me a good sense of what not to do.

all I currently have is a small cabin with 2 standard 14/2 lines wired to 3 receptacles and the other to 2 led overhead lights on switches

I have not purchased any panels or an inverter. I wanted to get a sense of what was a safe way to do this off grid.

I'd like to know why folks don't like 100watt panels? And what would be an appropriate set up for a cabin where I'm running a few lights a laptop and no major appliances.


what I gather so far isstarting from the battery bank I need to have:

a sine wave inverter that can be hardwired to

? Gauge wire

hardwired to a breaker box (with neutral and ground fused here?)

with electric lines going into the breaker box

[J.P.M.]

I see this board has its share of idiots that try to beat down the new guys.

Sure does, and not that he and I always agree, but to my observation, jflorey2 probably isn't one of them.

There are also a lot of newbies and others who are inexperienced with respect to the in/outs of solar electricity.

Know what you're talking about around here or accept the risks that go with posting to the forum of few(er) illusions.

While there are a lot of ill/mis informed folks who show up here, there are also a lot of experienced technical types who sometimes argue stuff out and usually get a workable consensus on the technical stuff or at least some exchange of informed information.