solar wiring issues

GailMarie · May 2010

I have an off grid cabin that has been wired for generator and solar separately. The utility shed is 40 feet from the cabin which houses the generator, 45W solar panels, charge controller, 1200W/3200W inverter and a deep cycle battery. There are two separate runs of wiring underground into the cabin. One is heavy gauge orange wire for the generator which is hard wired into the breaker box in the cabin. The other is "Romax" house wiring which is not yet hard wired, this was to be used for the solar set up. My question is this...can I use a pigtail from the 4 leg plug for the generator down to a 3 leg plug to plug into the inverter and use the heavy gauge wire until I get the "Romax" wire hard wired for solar? There are three fixed light fixtures in the cabin with compact florescent bulbs, outlets available for radio and perhaps a DVD player. (Not to be run all at once) Hope I've made sense of my situation.
Thanks for any imput.

Cariboocoot · May 2010

Re: solar wiring issues

It sounds like the existing system is a 240 VAC output from the generator feeding a breaker box in the house.
You want to disconnect the generator line and run 120 VAC from the inverter to feed the same breaker box via the same wires.
You could only feed one 'leg' of the existing 240 wiring or else you would have to tie the two together. One way to do this is to wire a separate 240 VAC outlet to a standard three-prong plug in to the inverter. You must make sure that at no time is the inverter output connected to the generator output. Having to physically disconnect a plug from one outlet and pout it in another one is a fairly safe way to accomplish this.

I have to admit I don't know what a "1200W/3200W inverter" is. They usually have one Wattage rating; either 1200 or 3200 but not both. I'm also leery of the (apparently) one deep cycle battery and 45W solar panels. There are signs here that your solar set-ups performance may be less than you want/need and may not be a good substitute for the generator.

BB. · May 2010

Re: solar wiring issues

GailMarie,

GailMarie wrote: »

I have an off grid cabin that has been wired for generator and solar separately. The utility shed is 40 feet from the cabin which houses the generator, 45W solar panels, charge controller, 1200W/3200W inverter and a deep cycle battery.

Eventually, we should talk about how much load you expect your solar panels and battery to support... For the most part, people tend to underestimate their loads and overestimate how much power they can get from their off-grid solar system.

There is a bit of electric theory involved--but it really is basic algerbra and pretty much equivalent to working out gallons of gas and miles per gallon type stuff.

So, eventually, we will want to know your peak power (Watts, Amps and voltage, etc.) and how much power you use--Watts*Hour, Amps*Hour, etc... And the size of your battery bank (usually in Amp*Hours and we need to know if 12 volt, 24 volt, or 48 volt bank).

There are two separate runs of wiring underground into the cabin. One is heavy gauge orange wire for the generator which is hard wired into the breaker box in the cabin. The other is "Romax" house wiring which is not yet hard wired, this was to be used for the solar set up. My question is this...can I use a pigtail from the 4 leg plug for the generator down to a 3 leg plug to plug into the inverter and use the heavy gauge wire until I get the "Romax" wire hard wired for solar?

Before you plug/re-wire anything, we really need to understand your setup and what equipment you have...

First, you cannot just "plug" the output of your generator in "parallel" with the AC output of your inverter... Normally, what is used is a "transfer switch" that can connect your load to either your AC generator or your AC inverter (and there manual and automatic transfer switches).

If you just plug the inverter output and generator output together, you will blow fuses/breakers and probably permanently damage some of your equipment.

But, to make things more complex, there are Inverter/Charger units... These units can plug the AC generator to an AC input and they have an internal Transfer Switch + battery charger (they are a combination units).

So, depending on exactly what you have and want to do--the answers will be different.

Regarding the 4 leg generator output vs 3 leg inverter output...

Many larger generators have 120/240 VAC output... So, depending on how your is wired, the plug:

Line A
Line B
Neutral
Ground

Line A:B = 240 VAC
Line A:Neutral = 120 VAC
Line B:Neutral = 120 VAC

And for the inverter, it probably is a 120 VAC unit:

Line X
Line Y

Line X:Y = 120 VAC

So, again, depending on what you are connecting, and what your loads are, the answers will be different.

There are three fixed light fixtures in the cabin with compact florescent bulbs, outlets available for radio and perhaps a DVD player. (Not to be run all at once) Hope I've made sense of my situation.
Thanks for any input.

Your loads are very reasonable for a small cabin (you are not using much power)... That is a good thing.

And, possibly, you will actually want to down size to a smaller inverter and generator set. Large inverters and generators tend to waste a lot of power.

-Bill

GailMarie · May 2010

Re: solar wiring issues

Thank you for the reply. I need to get back with you later on this. I want to write down all the items I have, including my estimate on useage that I came up with from a solar worksheet in Mother Earth News Magazine. It is really basic lights, and a radio. The battery is 12VDC and yes, only one. The panels (3) were a 45W kit from Harbor Freight which came with the charge controller. To clarify my shorthand for Cariboocoot; My inverter is a Chicago Electric 1200W continuous. But, they also note on it 3200W peak. Ok, again...thanks so much and I'll be back with more info for you. PS: The generator works just fine with how it is wired, just hate to use it.

GailMarie · May 2010

Re: solar wiring issues

Thanks for your imput Cariboocoot. Just a quick reply to say thanks and, I did try to clarify my shorthand on the inverter size in BB's reply. I will be back on later to give you more info. I think you guys will put me on the right track. Thanks!

mike95490 · May 2010

Re: solar wiring issues

GailMarie wrote: »

The panels (3) were a 45W kit from Harbor Freight which came with the charge controller.

Likely the best thing is to pack them back up, and return them. Nearly worthless for power production. If they were any worse, HF would be in jail

Useful as a learning tool.

Dyed-in -the-wool solar pros can get a few usable watts out of them, but mostly, all anyone gets is ruined batteries.

niel · May 2010

Re: solar wiring issues

if you are as you say "plugging the generator into the inverter" then don't do it. do not share wiring for them in any way and keep them 100% separate. this also applies to the load end of things as you can not combine their ac outputs either.

GailMarie · May 2010

Re: solar wiring issues

No no no...that's not what I'm saying at all. Here's the thing...wiring. Generator wiring is hardwired in camp, I just want to NOT use the generator, but use the wiring with a simple "pigtail" made from Romax with a 4 leg (one won't be used) female end to accept the 4 leg male end (which would normally plug into the gen.) and a 3 leg on the other end to plug into the inverter. Just simply want to use the wiring that is already hardwired in the camp and not use the generator at all.

GailMarie · May 2010

Re: solar wiring issues

To Mike90045...Why? I only have three lights and a radio.

GailMarie · May 2010

Re: solar wiring issues

Marc, I just re-read your post, and that is exactly what I want to do...drop one leg of the 240VAC and use the inverter. The camp was wired separately on purpose, but unfortunately the solar wasn't hardwired. I am thinking a knife switch at the breaker box would give me both options separately without all my "rigging" to use this weekend! Thanks for your knowledge.

Cariboocoot · May 2010

Re: solar wiring issues

Mike is right about those HF panels; several people have posted here regarding their performance and it seems they don't live up to expectations.

At best: 3 @ 45W = 135W @ 80% typical derating = 108 Watts. That means approximately 400 Watt hours per day (given four hours good sun equivalent) and a charge current of about 7.5 Amps max. It could potentially keep a 100 Amp/hr battery charged, but not much more. No inclusions here for other efficiency losses or the HF panels' reputation for putting out 50% of their rating or less.

Be careful using knife switches; exposed, non-spring-loaded contacts have high arcing potential. Keep the loads and sources off when switching!

GailMarie · May 2010

Re: solar wiring issues

Thanks Marc. Will pop in on Tuesday and let you know how I made out. Happy Memorial Day Weekend to all!

Cariboocoot · May 2010

Re: solar wiring issues

GailMarie wrote: »

Happy Memorial Day Weekend to all!

Huh? What's that? You mean Victoria Day? That was last weekend.

BB. · May 2010

Re: solar wiring issues

GailMarie wrote: »

I am thinking a knife switch at the breaker box would give me both options separately without all my "rigging" to use this weekend!

That is a "transfer switch"... Depending on what type of inverter and generator you have--Many times the better switch is a "two pole" version that switches both Hot and Neutral AC lines between the inverter and the generator... Many inverter (especially MSW, modified sine/square wave type) can shorted/damaged if they have their output grounded while their Battery Bank is also grounded to safety ground (ground rod, etc.). Some generators (especially larger sizes) may ground the neutral to the generator safety ground.

There are manual and automatic transfer switches, and those that you wire up, for example to the generator output... When the generator turns on, the switch automatically transfers from inverter to generator.

You could use two separate switches... Turn one on for inverter or turn the other on for generator--but that is not safe... It is very easy to forget and turn both on at the same time and cause lots of smoke.

-Bill

GailMarie · May 2010

Re: solar wiring issues

Cariboocoot wrote: »

Huh? What's that? You mean Victoria Day? That was last weekend.

Oops, sorry...Happy Victoria Day to you! Here in RI, it's Memorial Day.

icarus · May 2010

Re: solar wiring issues

Be very wary wiring a MSW into a hardwired breaker box, if that breaker box is grounded, or has a grounded neutral. Most cheap MSW inverters use a floating neutral, an they will go up in smoke right now if they are wired to a bonded neutral.

As for a knife switch, double pole double throw will work fine, except for the danger of of exposed conductors. I have several in use on various applications. Instead, however, I might suggest a large capacity A/B/Off battery switch, http://bluesea.com/category/1/productline/3

which is in essence a single double throw switch. You can also buy field configurable switches to nearly any configuration you need.

Tony

GailMarie · May 2010

Re: solar wiring issues

icarus wrote: »

Be very wary wiring a MSW into a hardwired breaker box, if that breaker box is grounded, or has a grounded neutral. Most cheap MSW inverters use a floating neutral, an they will go up in smoke right now if they are wired to a bonded neutral.

As for a knife switch, double pole double throw will work fine, except for the danger of of exposed conductors. I have several in use on various applications. Instead, however, I might suggest a large capacity A/B/Off battery switch, which is in essence a single double throw switch. You can also buy field configurable switches to nearly any configuration you need.

Tony

Thanks Tony...I will be very wary indeed! The box is grounded.

mike95490 · May 2010

Re: solar wiring issues

GailMarie wrote: »

To Mike90045...Why? I only have three lights and a radio.

Under the best conditions, at the factory, they may have been 45W.

So assume you have 135W of panel.

Lights, 3 lights and a radio, means nothing.

3, 23w lights, going from 6pm - 10 pm, and 6am - 7am = 5 hours = 345watt hours.

radio, add another 50 watts, for 3 hours. + 150wh = 495wh

Against a generous 5 hours of sun, = 675 wh harvest.

add in inverter losses, battery charging losses, and you are very close to just a bare break even.

But the big problem is the HF panels. They are a style that fades production 5-10% per year, after 5 years, you have very little power from them. And if they are not aimed properly for the 5 sunny hours, you don't get 135W, output fades with every degree of mis-alignment.

GreenPowerManiac · May 2010

Re: solar wiring issues

Leave it be that I step in right now, however, leave things alone would be the safest route.

Combining two different power sources and voltages creates at least two dangerous scenarios: Fire or Explosion and frying of sensitive equipment. Without a transfer switch on the house the wiring throughout the entire place will fry and cause a major blaze. Homeowners insurance will not pay to replace your home !

Two separate inverter 120v lines are out of phase and will fry one of two inverters. From personal experience, I share this grief and have learned the error of my ways. A $900.00 mistake. Get an inverter that's 240vac is the easiest route, yet expensive for high wattage.

The solar panel(s) need to be tested and scrapped/repaired if not working.
Here's what I'd do with the small solar panels if working: Set up a small 30amp load center with one or two breakers in it next to an existing load center. Don't connect any other wires to the new load center except a string of lights that doesn't get used that often. A 15 amp breaker is all that's needed and pull the hot(black) wire (switch off the breaker first) from the string of lights chosen and hook up to the new breaker. You'll have to bridge a neutral(white or gray) wire from neutral bar(new sub panel) to the main neutral bar to complete the circuit.

Now with that said, the solar panels can be routed D/C to a small charge controller and a few deep cycle batts. From the batteries to the inverter, from the A/C output to the new separate breaker/load center. Use the older wiring from, I believe you said, "3 leg Plug", to run back to the new load center hot wires(2), one at each post, and the neutral(white) to the neutral bar again beside the bridged neutral is fine. A neutral is a neutral and no circuit will complete without some form of neutral wire.

A load center with about 4 breakers would allow expansion of any more solar panels in the future, just add more batteries, bigger charge controller, and 1200 watt inverter should power the entire house with lights if you got those high efficiency ones like anyone else. These lights seem really cheap to operate, however, consume the most voltage starting up. Usually the first 30 seconds to a minute, then run at 6 - 25 watts.

mike95490 · May 2010

Re: solar wiring issues

GreenPowerManiac wrote: »

...... These lights seem really cheap to operate, however, consume the most voltage starting up. Usually the first 30 seconds to a minute, then run at 6 - 25 watts.

Lights do not consume voltage, they consume dark. And they consume the most dark, when first turned on. Eventually, when they are full of dark, they fail, and you can tell usually, the bulb shows dark spots at the ends, where the dark is trying to leak back out.

icarus · May 2010

Re: solar wiring issues

And electric motors consume smoke! When the motor develops a leak, the smoke leaks out,, indicating a fault!

Tony

PS Very good Mike!

GreenPowerManiac · May 2010

Re: solar wiring issues

Stinks learning the hard way, doesn't it ? Especially the smoke. Fried circuitry is always a unique "fragrance".

Not to get "Off-Topic", those high efficiency bulbs have mercury in most of them. Usually the cheap ones at Wal-Mrt. If they break, open the window or exhaust fan to pull the vapors out for a few minutes before breathing. Unscrew from the plastic base only.

My wife watches those Doctor TV shows and was an interesting concept on bulbs.

nsaspook · May 2010

Re: solar wiring issues

icarus wrote: »

And electric motors consume smoke! When the motor develops a leak, the smoke leaks out,, indicating a fault!

Tony

PS Very good Mike!

The production of "Magic Smoke" is a closely guarded trade secret. http://mysite.ncnetwork.net/res02dad/sitebuildercontent/sitebuilderpictures/smoke_machine.jpg

I can get a refill, but it's pricy.
department_56_general_village_accessories_no_box_P0000240872S0289T2.jpg

department_56_general_village_accessories_no_box_P0000240872S0289T2.jpg

GailMarie · June 2010

Re: solar wiring issues

Hi all...just to let you know, I survived my holiday weekend...no fires, (except for outside in the firepit), no batteries exploded, no wire smoking issues. Oh, and I had lights on in the camp.

I opened the breaker box and pulled out the Romax for DC current (which was not hooked up in the box, just hanging out waiting for me), put a female end on it (dropping the ground as the inverter is grounded in shed), and plugged in my little antique glass lamp with a 40W CF bulb. Charge controller stayed at 12.4 during cloud covered afternoon. Inverter stayed cool. I was happy.

And I have decided that rather than playing with electrical currents myself, I will call an electrician to install the transfer switch for me. Will post when that is done. Thanks again for everyone's expert advice.

russ · June 2010

Re: solar wiring issues

@NSAspook - The magic smoke should not be expensive at all - just follow most politicians around and you will see lots of it. Bit more difficult to capture than find though!

dwh · June 2010

Re: solar wiring issues

russ wrote: »

@NSAspook - The magic smoke should not be expensive at all - just follow most politicians around and you will see lots of it. Bit more difficult to capture than find though!

That's a different sort of Magic Smoke. Politician Magic Smoke is the kind that works with Smoke & Mirrors. It's usually combined with that special sort of Sunshine that is used in Blowing Sunshine Up Your ***.

solar wiring issues

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