Solar inverter in 3 phase installation

[mi_cin]

Hello everyone, I'm new to that community.

I have a question about solar inverters. I have a 3 phase installation at home and few 3ph devices like electric oven or automatic garage gate. Is it possible to use 1Ph solar inverter in my house? Will extra power supply on one of the phases affect 3Ph devices?

Second question is about the installation. I connect PV arrays via fuse box to an inverter. Inverter is connected to the grid via single wall plug and.. that's it?

Marcin

[inetdog]

Hello everyone, I'm new to that community.

I have a question about solar inverters. I have a 3 phase installation at home and few 3ph devices like electric oven or automatic garage gate. Is it possible to use 1Ph solar inverter in my house? Will extra power supply on one of the phases affect 3Ph devices?

Second question is about the installation. I connect PV arrays via fuse box to an inverter. Inverter is connected to the grid via single wall plug and.. that's it?

Marcin

In most if not all countries with electrical code enforcement, a grid-tie inverter (no batteries) which connects to the public grid by a wall plug is not legal.
Whether the power utility will care about getting the grid input back from you as 1ph or 3ph is a question you would have to ask them. It will not appear any different in terms of loads inside your house than if you turned on some load that is only on one or two of the phases.

If you are planning on off-grid capability, the 3ph power for your oven probably does not actually need 3 phase, as long as you can meet the requirement for current for the elements you are using (which is not likely using an inverter!) The gate motor may actually need 3phase, and you would have to get a 1ph to 3ph electronic converter or change the motor to a 1ph motor.

[russ]

In most if not all countries with electrical code enforcement, a grid-tie inverter (no batteries) which connects to the public grid by a wall plug is not legal.
Whether the power utility will care about getting the grid input back from you as 1ph or 3ph is a question you would have to ask them. It will not appear any different in terms of loads inside your house than if you turned on some load that is only on one or two of the phases.

If you are planning on off-grid capability, the 3ph power for your oven probably does not actually need 3 phase, as long as you can meet the requirement for current for the elements you are using (which is not likely using an inverter!) The gate motor may actually need 3phase, and you would have to get a 1ph to 3ph electronic converter or change the motor to a 1ph motor.

The garage gate is almost certainly single phase - 3 phase is only used for motors and such

Question for you all - do you know how we identify the electrician here in Turkey? The guy with the screw driver - no formal requirements at all but he does have to have a screw driver.

[inetdog]

Question for you all - do you know how we identify the electrician here in Turkey? The guy with the screw driver - no formal requirements at all but he does have to have a screw driver.

I always thought that the world-wide answer was that it was the person you could not find when you are looking for an electrician.

[mi_cin]

In most if not all countries with electrical code enforcement (...)

What do you mean by "electrical code enforcement"? Any legal statement about that? I'm writing from Poland, are we under that law? How do you connect an inverter in countries under that law?

[inetdog]

What do you mean by "electrical code enforcement"? Any legal statement about that? I'm writing from Poland, are we under that law? How do you connect an inverter in countries under that law?

I am sorry that I have no idea what the official standard is in Poland or how strictly it is enforced.
But in US, Canada, UK the grid-tie inverter must be hard wired to a breaker in your main electrical panel and must be inspected by your local electrical inspection/enforcement agency (This and other forums use the term AHJ or Agency Having Jurisdiction, since the actual title varies a lot.) And once that has been done the power utility must come out and approve it too before you actually close the switch.
In the US the standard which applies to parts, design, wiring and workmanship is the National Electrical Code (NEC.)

I did find at least one reference to the situation in Poland (limiting myself to sites in English): http://energyinformative.org/grid-ti...solar-systems/
What I get from that is that there is no law requiring the utility to buy power from you, so you would be limited in any case to offsetting the amount that you use.
Some current meters will actually bill you for power which you send back to the grid, since they do not distinguish which way the net power flow is going.

[Mike90250]

What do you mean by "electrical code enforcement"? Any legal statement about that? I'm writing from Poland, are we under that law? How do you connect an inverter in countries under that law?

As inetdog states, and also your homeowners insurance (fire insurance) has a say too. If your house has afire, and they find a plug-in inverter contributed to it, they void your insurance, and leave you with nothing, the penalty for not following building code.

That said, there are a lot of people buying plug-in inverters and using them, and some are ok, and some have problems.

[mi_cin]

What I get from that is that there is no law requiring the utility to buy power from you, so you would be limited in any case to offsetting the amount that you use.

Yes, that's right. But the law is about to change, hopefully next year.

So speaking about 3Ph or 1Ph inverter.

a) If I use 1Ph inverter. All devices on that particular phase are extra supplied from PV. The 2nd and 3rd phase devices are not connected with my PV system. The surplus goes to the grid. The 3ph devices, like electric oven, work fine.

b) If I use 3Ph inverter. All devices on all 3 phases are extra supplied from PV. The surplus (which is now lower, because more devices are connected with my PV system) is sold to the grid. The 3ph devices work fine.

And the decision which one should I use depends on my power supplier.

Is that correct way of thinking? Please correct me if I'm wrong.

[Mike90250]

....And the decision which one should I use depends on my power supplier.

And you better price out the inverters. single phase inverters are made and sold by the thousands. 3 phase have a smaller, more industrial market, and likely cost as much a 5 or 6 single phase inverters ! Maybe better off getting 3, single phase inverters, and 3 arrays. Getting inverters to match the proper voltage (208VAC) may be a problem, 3 phase voltage is generally a bit different than single phase (230VAC) and may fal outside the inverter accptance window


A small phase load imbalance won't bring down the grid. It also depends on how the power meter responds to backfeeding on just 1 leg.

[mi_cin]

Ok, so to start with solar energy I can buy a single phase inverter (let's say 1kW) and connect it to any phase. It won't affect and speed up doing scrambled eggs on my 3-phase oven. Then I can buy another 1k inverter and connect it to second phase. Then third.

The only thing to take care of is power meter. If it supports one leg backfeeding and if it at least stops on backfeeding. I heard that sometimes it doesn't recognize current direction and counts PV kWh as power from the grid.

[Mike90250]

.... I heard that sometimes it doesn't recognize current direction and counts PV kWh as power from the grid.

The old, old meters, run just fine both ways. Most of the new electronic readout ones, just total the watts, in or out, it just counts them all !


And your building is never a "perferctly balanced" load, one light circuit may be on B, and the coffee pot on C, and fridge on A.

[konstant]

Solar power connection to a three phase supply is possible but you have to decide how you have to connect solar system to the grid.Connect your solar system to your supply phase with a single phase solar inverter. connect your system into all 3 phases of your supply with either a single, 3-phase solar inverter or 3 separate single-phase inverters.

[inetdog]

The old, old meters, run just fine both ways. Most of the new electronic readout ones, just total the watts, in or out, it just counts them all !
And your building is never a "perferctly balanced" load, one light circuit may be on B, and the coffee pot on C, and fridge on A.

As long as the power involved is low, backfeeding a single phase if probably not going to cause any complaints from POCO, but any substantial (commercial scale) backfeed will have to be balanced to keep the POCO infrastructure running efficiently.

Even some of the spinning disk meters now have circuitry that captures ticks as the disk rotates and adds them rather than counting up or down depending on direction. "They say" that this was done to prevent customers from putting the meter upside down in the socket to roll back the odometer.
Not sure whether that is true, but it sounds good.