diy solar

diy solar

Parallelly connecting of one PV array for two inverters one on grid and one off grid

SAMANTHA GUNARARNE

New Member
Joined
May 7, 2022
Messages
1
I have an ongrid system installed 4 kw .
now there are grid failures frequently
I have an off grid inverter and some batteries
Can I share the Same PV array for the Off grid Inverter
Can I connect the two ends of the PV array DC cables parallely to the two inverters one Off grid and one On grid permanently
 
Doesn't the on-grid system require the grid to function? If you drop the grid I don't think you can use it for an off-grid SCC unless you have a very special grid-tie system.

If you do then yes, you can switch them but not use them both at the same time.
 
Can I connect the two ends of the PV array DC cables parallely to the two inverters one Off grid and one On grid permanently
As mentioned you could A/B switch them.

A better way - but costs money- is to employ one of the top-shelf systems that are designed to run gridtie but switch off the grid feed when grid goes down. They employ batteries so the switchover is seamless and will automatically return to grid feed when grid samples up and stable again.

A second way to use batteries is mildly inefficient and doesn’t use panels grid-down is a decent battery charger. You would have an inverter behind a transfer switch; the inverter feeds a “critical loads” panel when transfer switch is in inverter position, while the other position the grid (from main service panel) would feed the ‘critical’ panel.

A third way is a separate system using an AIO that is always up and available feeding the ‘critical’ panel but of course that would require additional panels. More expensive but essentially a UPS-dependable system.
Can I share the Same PV array for the Off grid Inverter
And the qualifier is that if your system is doing AC microinverters and not a central SCC / inverter to feed the grid you can’t really share panels anyways.
 
Just curious, what happens if you do that (output PV to two inverters).
 
Just curious, what happens if you do that (output PV to two inverters).
Microinverters? Because they are a charge controller essentially I think they would get confused the other’s load would make the other constantly modulate and vis versa

Inverters run off batteries…you can use many inverters on one battery bank. But why!??
 
Interested in the why not?
Panels feed DC to on grid inverter, if you came out of the DC switch and went to a victron charger to charge batteries. Wouldn't it share the panel current between Ingrid inverter and batteries?16555946958264384062521113784685.jpg
 
Both will fight for control over the MPP.
Neither will be happy.
-- unless the switches can select one or the other to output to--
 
You can’t think of panels as a voltage source like you can a battery. Their voltage and current and therefor power output fluctuates based on the load on the panel, how much sunlight it is exposed to, how evenly that sun is applied across the array (or singular panel for microinverters), and the panels temperature. MPPT (Maximum Power Point Tracking) controllers will sweep through the range of current draw to find the voltage/current combination that results in the maximum power (Watts) being produced. For a microinverter or grid tied string inverter that power is immediately converted to AC power that is pushed back into the grid (or an AC coupled inverter with batteries). For a solar charge controller that power is converted to a set voltage for charging the battery bank. If you have 2 MPPTs connected to the same panel in parallel they will not sync up. At best they will constantly sweep their range and arrive at the wrong power point to generate the most power from that panel. At worst one or both of them will give up the magic smoke.

A better option would be to split your array in half and purchase a hybrid inverter. The hybrid inverter would power your critical loads off the panels connected to it, battery, generator, or utility in whatever order you set in the settings. There are models of hybrid inverters that can grid tie and push power back to the utility just like your current grid tie does, and you would just set it to do that after the batteries are charged and loads connected directly to the inverter are satisfied. These inverters usually have an automatic transfer switch built into them, meaning if the power goes out it will automatically disconnect from the grid and continue to power the loads until solar and batteries are exhausted, and will reconnect to the grid when it comes back up. There are even some that can AC couple an existing grid tie inverter that meets UL1741SA and use those panels to power loads and charge the batteries.

There are ways to accomplish what you want to do, but running 2 inverters DC coupled off the same array of panels is not one of them.
 
better option would be to split your array in half
Quite a good writeup there.

I read that amused. I’ve been running a small aio for a few months but just purchased a second 40A SCC to better utilize my (small) overpaneled setup. Your thoughts here reflect sound discernment of the situation imho
 
So thinking about this set up, if I add two more DC switches connected to panels so I can switch from panels supplying grid to panels supplying off grid then would there be a problem?
I'd assume main house switch will only get power from one source at a time. As inverter for on grid would not power up if no panels connected. Does this sound feasible?
 
Hi, bumping up this topic. Could anyone recommend good A/B manual switch for 1 PV array towards 2 inverters. Thanks
 
i used a 3-phase AC changeover switch for my first experiment.

Now i'm 'designing' and ATS based on battery voltage: battery charged, switch PV to grid inverter; battery drops to say 50% which should happen at night, switch PV back to battery charger inverter for morning charge.
 
Just curious, what happens if you do that (output PV to two inverters).
I’ve done it, both inverters tripped off-line quicker than I could blink an eye. What happens probably depends a lot on the inverter design and what type of protection is implemented. I have 2 strings I can switch between inverters.
 
Back
Top