ebay grid tie inverter question

[Frank Stone]

Hello, this is my 1st post here, and I signed up here to hopefully get some info about installing a grid tie inverter into my existing small solar panel system.

I currently have four 80 watt 18V solar panels that connect to a combiner/breaker box, then to an MPPT controller, and then to a AGM battery.

I also have a 1000W pure sine inverter connected, and use the system for running my cloths washing machine ect, or in case of power outage.

when I'm not using it, it's just sitting there, doing nothing, so what I'm thinking about is installing a grid tie inverter to actually give my power bill some savings.

I've been looking at those cheap grid tie inverters on ebay and wondering if they actually work for a small 320W system such as mine is.

Such as this one: http://www.ebay.ca/itm/300W-500W-1000W-micro-grid-tie-inverter-for-solar-home-system-MPPT-function-/320967582067?pt=LH_DefaultDomain_0&var=&hash=item4abb28a173

So my question is will this device actually dump electricity into my home and save my power bills a bit or not?

Are these garbage?

Are the SAFE? The last thing I need is a fire!

I talked to the local power company and they said NO WAY, don't hook that up because it is a fire hazard, and if I wanted a grid tie inverter installed, I would have to pay thousands of dollars for THEM to come connect it into my house breaker panel, and I would have to change my home insurance policy as well.

So what do you think?

Thanks!
:)

[Dave Schwartz]

Regardless of whether they are garbage, the information you received from your power company is (almost completely) correct.

These devices do not have any safety authority (e.g. UL, ULC, CSA) approval and cannot be connected to any public grid in North America.

The principle problem, regardless if they do everything required of a grid-tie inverter (and the manufacturer will probably claim they do, but without that regulatory approval that means nothing), is that a consumer could easily connect it and overload their house wiring and cause a fire.

Your circuit breakers are not there to protect your appliances - they are there to protect the branch circuit. A branch circuit is only allowed to be fed from one location: a rated panel though a breaker rated for the circuit (usually 15A for circuits with lights and your common duplex receptacles).

The problem with using this inverter as another source on the branch is that an appliance could now draw 15 amps through the breaker (without tripping it) and 2.5/4/8 amps through the inverter (without tripping it either). But depending on the topology you can't see, some segment of the circuit (and certainly your 15-amp rated receptacle) could see 17.5/19/23 amps which is likely over the current-carrying capacity of the wiring and could cause a fire.

If you do have a fire and non-certified equipment is found to be connected, your fire insurance will be voided and you will likely be charged with creating a hazard and billed for the cost of the FD putting out the blaze.

P.S. You don't have to pay your power company to connect a grid-tie inverter to your service. As long as the Electrical Safety Authority (ESA) certifies the installation is proper and to code (which requires the use of certified components and is also much easier to get if a licensed electrician does it) then the power company has to reconnect you. I have two: a standby generator and a microFIT solar installation and at no time did I pay the power company to do any electrical work other than the mains disconnection/reconnection when the meter base was replaced for the microFIT installation.

P.P.S. Very funny that the ebay item has a string of windmills on the top label but the listing specifically says they cannot be used at all with wind generators.

[Andy Rhody]

I'm not sure what country you're in but here in the USA the cheap ebay Chinese grid-tie inverters are not UL approved so therefore they are illegal and insurance companies would be upset about them but that said, the people over at the Windy Nation website have been doing about 4 years of testing with the Chinese "Sun G" wind and solar grid-tie inverters and have had a high degree of success and also have had no fires. Sometimes an inverter may fail but a component just goes out.

Some Sun G wind inverters do have that dump load feature but the Sun G solar inverters don't so in your case you'd need to get another controller with a divert feature so when you're battery is full, it would divert the excess power to the solar grid-tie inverter.

So if you have four 80 watt panels that makes 320 watts. I'd get a 400 or 500 watt Sun G solar inverter which means that you won't be overworking it which gives you a decent safety margine. That might be around 200 bucks (US) from ebay and maybe something like a Xantrax controller which I think may have a divert feature for less that 200 bucks.

Don't give up!

PS: Depending on how you wire your 4 solar panels, the Sun G's come with a 10 volt to 30 volt range or a 22 to 60 volt range.