Connecting/Hard-wiring inverter to AC Panel offgrid

-Hubcap- · November 2014

Hello all!!

I have been scouring the inter-web for the correct way to connect my Samlex SA-2000K-124 Inverter to an AC panel for an off-grid application. As of yet I have had no luck finding any comprehensive instructions on how to accomplish this. From what I have learned the AC supply from the Samlex inverter is 120V and not 240v and is not directly compatible with standard AC Main Panels and or Main Lugs without some small modifications. I wish to wire my small space with standard outlets and lighting for a small office. Currently my 600 watt solar array wired in series charging 4-6V Trojan T-105's also wired in series and is a great solar generator! It has been a great learning experience and very fun but now I am stuck! Any help is appreciated!! Below is a link for my Inverter.

http://samlexamerica.com/products/ProductDetail.aspx?pid=135

Cariboocoot · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

Welcome to the forum.

Standard North American AC power is 240 Volt split-phase, meaning there is a center tap which provides neutral for 120 VAC on either side. In essence 120 VAC inverters just put out half of this. It is not a problem if you don't need 240 Volts, which you probably don't.

You can in fact wire the two 'hots' of a 240 Volt service together and power them from the same 120 Volt hot, especially with a small inverter (it will invariably fault and shut down before any part of the wiring overloads). Keep in mind that a 2kW inverter is roughly the equivalent of a single outlet: 15 Amps * 120 Volts = 1875 Watts.

So the wiring then becomes straightforward: ground to the ground bus bar, neutral to the neutral bus bar, and hot to the two hot bars which connect to the breakers. A simple jumper wire and you've got 120 Volts on both.

Does that explain it?

-Hubcap- · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

Thanks for the welcome!!

It does explain as well as verifies what I have been finding. I think I may be hung up on believing that I need a main breaker before the distribution breakers. I believe it would not need a 250, 150 or 100amp main breaker though would it need a 40amp main breaker? Or would the Inverter serve this function and use a main lug/sub-panel/distribution panel to distribute power? Or do I need a breaker to be placed between the inverter and main lug/sub-panel/distribution panel? If I just need a main lug/sub-panel/distribution panel are there any recommendations?

zoneblue · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

Any breakers you put after the inverter become a bit redundant, as Coot says, the inverter will shut down before any of them are likely to blow. But leave them in , they arent doing any harm.

Youll need to check where the earth neutral bond is. I think from memory for grid connects in the US this is done outside the house? Here, its always done in the main ac load center. That inverter is LF, and fully isolated, so has no bond of its own.

Photowhit · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

When wiring my small cabin, I found a 2 breaker box designed for 120 out of a camper, It was just right for tiny cabin, run from an 1800 watt inverter. If this is a "...small space..." with in a house, you don't want to wire into a home breaker box rather disconnect it from the home breaker box or run the home wiring from the breaker box into a transfer box so you can switch back from one source of energy to the other.

Cariboocoot · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

The N-G bond is usually in the main service panel. There is often a separate such bond, transformer CT grounding, at the pole (where used). The inverter may have an internal N-G bond (especially the type with built-in outlets) which should either remain or be broken if replaced by a panel connection.

In my cabin I used a sub panel which has no main breaker accommodation, as basically all it does is allow me to branch the inverter output into separate circuits which can be turned on/off with the breakers. Even at 3500 Watts it is unlikely any of the 15 Amp circuits will trip before the inverter faults.

-Hubcap- · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

Thanks for all the replies!!

The installation is a 100 year old chicken shed in my backyard that I have been rehabilitating over the years an I am finally getting around to putting a small office in there (with three kids I kind of have to!!). I have always been intrigued with solar and I am finally putting my money and my action were my mouth is. Watching the documentary "Tiny" and reading "Simple Solar Homesteading" finally got me off my duff. I have learned a Ton! And it has been a blast!

The inverter does have a ground on the chassis and I currently have attached to a 1/2" dia copper ground rod pounded 8' into the ground. When I move it to the permanent configuration I will ground the inverter to a rod as well as the panel. If I have to use separate rods for the panel and Inverter I'm not sure at this time. What I gather is that I can wire the inverter directly to a subpanel with a jumper in the panel due to the fact that it is not 240v which will distribute the loads via single pole 15amp breakers to the loads ie... outlets and lights via conventional wiring. The setup will run a 1800 watt wormdrive Skillsaw but will be infrequent.

A couple more question if I may. I intend on keeping the batteries in the office space to keep the batteries moderately warm. I am south of the Metro Denver area and we do have some cold snaps in the -20 range though it usually only for a week at a time. I will have a woodstove to keep it entirely off-grid but will also have a gas heater to the keep insulated space around 50-60 degrees or so all winter. I was going to do spray foam insulation though I believe it may be overkill and make the space too airtight and now I am going to use traditional batts. The questions are is this necessary to keep the Trojan T-105 batteries warm and secondly is it safe with the gasses it gives off? I currently have 4 T-105's wired in series and will mostly likely add another bank in series and connect the two in parallel in the future.

zoneblue · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

Depending on the laws of your land, battery accomodation can be untrivial to get right. I recently looked into the NZ standards and there are actually a total of 3 seperate codes that relate to batteries. Ventilation is obviously up there, but theres lots of things like offsets from equipment , ignition and combustibility, even things like seizmic restraint. Boggling stuff.

Cariboocoot · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

You may find the 1800 Watt saw won't run off the inverter at all; it's pretty close to maximum power.

As for the batteries, they prefer to be warmish to maintain capacity. They don't really produce a lot of gas, but here's the thing; when you close them in the concentration of hydrogen & oxygen gas can reach dangerous levels. Out in the open it's highly unlikely. So by trying to solve one problem you inadvertently create another.

The gases like to travel up as they are lighter than air. If you can create even a small vent that will let them escape away from the flame source it should be safe.

BTW 600 Watts of PV on a 24 Volt system is enough for one set of those batteries (19 Amps on an MPPT controller) but won't be enough for two. Expand the battery bank, expand the PV.

-Hubcap- · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

"BTW 600 Watts of PV on a 24 Volt system is enough for one set of those batteries (19 Amps on an MPPT controller) but won't be enough for two. Expand the battery bank, expand the PV."

Thanks for the heads up Cariboocoot! My first solar lesson not learned the hard way!!

zoneblue · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

And BTW i take back what i said about that inverter, it does have a built in neutral bond, and GFI. If those cant be defeated, then remove any neutral bond in the AC load center, as well as any additional GFIs. You dont really want chained GFIs. That inverter is a good example of a "mobile", not certified for hardwire. And its one of the very best of the cheaper inverters.

Hairfarm · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

Greetings HC,

I had the same issue. Here's my thread on this forum:
http://forum.solar-electric.com/showthread.php?19231-Connecting-12v-Prosine-2-0-to-breaker-box-sub-panel&p=149949#post149949

Photowhit · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

I followed up after Zoneblue called the Samlex one of the very best cheap inverters.

If you haven't purchased the inverter, I would seriously ask that you consider a different inverter. The Samlex you linked to only accepts dc in the range of 2-30 volts(30.0 VDC , +/- 0.4 VDC). This will not allow you to equalize while using the inverter. Though the Trojan batteries ask that you don't equalize unless out of balance, they also ask for a very high absorb voltage of 29.6 volts.

BB. · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

Samlex has other inverters. The PST series seems to do better with higher input voltages:

http://www.solar-electric.com/inverters-controllers-accessories/inverters/sasiwain1/samlex-pst-series-pure-sine-wave-inverters/sa10wa24vosi.html

Output Voltage
120 Volts AC, +/- 3%

Output Frequency
60 Hz

Output Waveform
Pure Sine Wave

Continuous Power
1,000 Watts

Surge Power
2,000 Watts

Input Voltage
24 Volts DC

Input Voltage Range
21.4 to 33 Volts DC

Peak Efficiency at Full Load
85%

Operating Temp. Range
0°C to 40°C (32°F to 104°)

Dimensions
15.6" x 9.3" x 3.3"

Weight
8.8 lbs.

-Bill

zoneblue · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

I was speaking in general terms of LF and brandname, not meaning to insult xantrex, exceltech, powermaster, or other 'better' 'cheaper' brands. I have already expounded i beleive in an over lengthy manner that the only sane decision for off grid homes, is to buy an inverter that is UL listed for hardwire.

zoneblue · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

To get clear about hardwire UL v mobile UL listing see

http://www.homepower.com/ul1741-vs-ul458

"Inverters used in residential-scale RE systems must be listed to UL1741, as required by the National Electrical Code"

Photowhit · November 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

I wasn't taking it as a slight, I was just checking out the Samlex inverters.

Code is relative, I think we should shoot for safe rather than to 'code' I think Bill has had more than a passing interest in this!

Pretty much it's up to the inspector. Many/most of the installs I see don't comply completely to code. All wiring above 30 volts DC must have restricted access, in conduit or other... Many Outback and Magnum are installed with out this feature, you can even see it on their web sites.

Also NEC is not adopted every where, I live in Missouri which was having a push to adopt NEC 2011 and I thought we had adopted 2005? but here's a site that suggests we haven't adopted a code, or perhaps it so far back they ignore it..lol. Please note Arizona is also a state without state wide adoption.

Insurance companies may want to know more information, and will likely disqualify even code compliant installs or increase premiums, they seem to want the low hanging fruit, check around and find someone who will if this becomes a problem. This should be a stop on the list of anyone having solar installed. Also may need to inform the mortgage holder as solar represents a major change to the insured property!

-Hubcap- · December 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

Thanks for all of the replies!! I have purchased the Inverter. I actually had already purchased a 1500W Samlex and before I installed it I exchanged it for 2000w model just so I could run a worm-drive skillsaw if even for a minute! Kind of a pride thing. The installation is mostly an experiment/hobby install in an old chicken shed.

Thanks for the link hairfarm it is very helpfull!!

-Hubcap- · December 2014

Re: Connecting/Hard-wiring inverter to AC Panel offgrid

Its Alive!! Thanks for all the help!! Completed my first circuit of two standard outlets and one switched GFI exterior outlet for Xmas lights and everything is working great! It was a real hoot to see the Xmas lights working!!

Connecting/Hard-wiring inverter to AC Panel offgrid

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