PV, Generator, and Grid Installation: Help??

System

Looking for some words of wisdom please:

Have an existing max 3.5 kw PV grid tied via Fronius inverter. The grid is unreliable in our area, frequently losing power, again last week for five days due to our dear friend Irene. Enough is enough, Looking now at installation of a medium duty backup generator.

Would prefer not to have to trot out the gen set and run heavy extension cords every time the power goes out, especially to power my well pump, so looking ideally at a permanent install.

Am a bit dismayed that the power from the PV array is not available to minimally power the house when grid is off and sun is up, but it would not matter as I really need 5 kW on start surge for my 3/4 HP well pump anyway (330' deep).

Am looking at an 8 kW gen set (LP fuel, which I have, to avoid messing with gasoline storage / refill) versus a 6 kW mobile generator with a water proof disconnect box to plug in same. Either way, the main idea and question herein is: I want to wire it in so that when the generator is on, the inverter senses the AC on the panel and thus allows the PV array to add to the available generator current. Ideally I would not switch critical loads to a new transfer switch load panel, but simply have the generator power the whole panel from both Gen and PV, taking care to turn off heavy current draw before kicking in the generator.

Recognizing I can't just pull the 240v from the generator to both legs of the panel as I need to disconnect the grid .... How does one do that ??? Can I simply wire up a DPDT in a disconnect box to disconnect the grid and connect the generator? Seems the inverter would be happy enough with that and would sense voltage and allow current transfer, but there has to be a better way to do this i.e. auto-sensing such that the auto-start generator feature is enabled and the generator kicks itself on and off while decoupling from the grid while running, other than sensing if grid power is there.

If auto-sensing, then I guess maybe I need to transfer priority circuits to a new transfer switch /lothe ad center which generator is feeding, or switch the main 200A panel to a load shedding type?


Arrggghhh!!! I'm in over my head and need a sanity check please on the best options and how to go about same. (Basic Wiring diagram? Not to do this myself, just to understand what is recommended.)

Cariboocoot

Re: PV, Generator, and Grid Installation: Help??

Welcome to the forum.

What you're looking for is a "whole house transfer switch". I'm not sure if such a thing is even available, as it is unusually (but not impossible) to have a generator capable of supplying an entire house, especially at the modern 48 kW level.

At that point I'm going to leave this alone and let the "Grid-Tie people" respond because I personally consider it inadvisable to try and synch GT inverter systems to generators (or off-grid inverters) in order to get power out of them when the grid goes down. Some here have tried it, and the two words that I use to describe the process and their experiences with it are "headache" and "nightmare".

niel

Re: PV, Generator, and Grid Installation: Help??

whole home generator backups are out there and i've seen advertising by generac quite a bit lately for this. that will work as long as your fuel is available. some are gasoline and some are nature gas or propane. gasoline and propane are bought elsewhere and brought back to your home and thusly can run out. the trouble with that is the places you buy the fuel from may not have power and may be closed for the same reasons as you have need of it for. natural gas is fine providing there are no underground breaks in the supply pipes for whatever reason.

also a generator will have a bit of a delay to it that a quality sine wave inverter on batteries won't have. this means you can use inverters for critical items that a power interruption would mess up and of course some operations for night use to keep the peace as generator noise can be a problem at times.

both will use a transfer relay or relays to feed a panel that houses all of the powered circuits you wish to be backed up. what you have experienced is the incentive many of us have had to show interest in solar and even employing a generator. solar can power some items outright or just keep batteries topped off with the main charge from the utility and/or generator depending on your priorities and preferences in setting up a system. many variables are possible in a system setup.

BB.

Re: PV, Generator, and Grid Installation: Help??

Practically/generically speaking--You cannot run a GT PV Inverter with a Genset for several reasons:

1. GT Inverters are typically around 60 Hz +/- 0.5 Hz or so... Standard AC gensets do not hold frequency tight enough.
2. GT Inverters do not regulate their output power. And gensets generally do not like to be fed current power (i.e., 2kW of load, and 5kW of Solar PV at noon-time).
3. There are Inverter/Generator type generators (Honda, Yamaha, etc.) which have accurate enough frequecy output, but, again cannot take AC Current back into the motor... In theory, if you have 3kW load and 2kW GT power, the genset may make up the missing 1kW... And it is possible that the GT inverter would over voltage and shut down (gracefully) for ~5 minutes. It could work--but it will be your dime to see if your inverter generator + loads will operate in such conditions (note, many of the smaller inverter/generators are 120 VAC only output and most GT inverters are 240 VAC split phase).

There are Hybrid Inverters that support both AC Grid Tied and Off Grid power (when utility power fails). The Xantrex/Schneider XW 6kW 48 volt (and variants) is very flexible, plus support AC generator/autostart too (more or less, a giant whole house UPS with Solar + Generator support).

Not cheap--and even for a week without power may not be worth the XW Hybrid solution (battery bank is the big cost, plus replacement every 7-10 years or so). Only you can make that decision.

If you can conserve power needs during an outage (just enough power for lights, electronics, and central heat)--Perhaps you can build a simple battery backed system (with generator and/or solar support) to carry you "quietly" through the night.

-Bill

mike95490

Re: PV, Generator, and Grid Installation: Help??

dadamsinky wrote: »

.....Either way, the main idea and question herein is: I want to wire it in so that when the generator is on, the inverter senses the AC on the panel and thus allows the PV array to add to the available generator current. ....

Will work if:

Your genset is 60.000hz, for the inverter to sync

Your genset can be "overdriven" by the PV power, when the fridge or air conditioner shuts off

or you also purchase a
XW6048 inverter $$

4, 12V deep cycle batteries (just to keep the inverter alive, not to supply power for more than the 20 seconds it takes to get the genset up to speed with the

Autostart module $

XW 600V 60A Charge controller $$ (to hook your high voltage array to, and bypass the Fronius

System2

Re: PV, Generator, and Grid Installation: Help??

Guys,

Thanks for the feedback. OK, sounds like a lot of cost, risk, and not a lot of sense to try to recover the PV power during an outage.

--> Plan B: Larger 10 kW portable generator and a manual plugin connection to the main panel AFTER manually disconnecting the main and the PV side and lifting the non-essential circuit breakers.

BB.

Re: PV, Generator, and Grid Installation: Help??

Even with a manual plug, you should still have some sort of transfer switch. It is just too much of a chance of fireworks (and worse) to use a non-interlock type system for generator to AC power usage.

Fully automatic transfer switches with generator control/weekly excessive are not cheap--But if you want something automatic (when you are not home, or when nobody is home) is an OK way to go.

It is possible to create an off-grid system (inverter, battery bank) and back feed the Off Grid Inverter (DC battery bank powered) with a GT inverter (or micro inverters--yes, with some products, you can actually feed energy backwards through a off-grid inverter and recharge the battery bank). Some systems will control the battery bank charging automatically (Sunny Island, Xantrex XW Hybrid), others you would have to roll your own dump load/AC interrupt (doable--but you need to have knowledge to do it). The genset would either power the AC loads (without the GT back feed) or recharge the battery bank with an AC battery charger--and the GT/Off Grid inverters would do their thing for the AC.

It is very difficult to say something cannot be done--It really depends on your needs, knowledge, and bank account to fund your own experimentation/purchase off-the-shelf items you need.

-Bill

keyturbocars

Re: PV, Generator, and Grid Installation: Help??

Here's another possiblity for a manual "transfer switch" interlock...

http://www.interlockkit.com/

solar_dave

Re: PV, Generator, and Grid Installation: Help??

keyturbocars wrote: »

Here's another possiblity for a manual "transfer switch" interlock...

http://www.interlockkit.com/

That is a cool idea.

keyturbocars

Re: PV, Generator, and Grid Installation: Help??

solar_dave wrote: »

That is a cool idea.

I agree. It's what I chose to use, even though it is a bit expensive for what you are actually getting. However, compared to the alternatives, it is economical. I also like the ability to select any of the circuits in my house.

solarvic

Re: PV, Generator, and Grid Installation: Help??

keyturbocars wrote: »

Here's another possiblity for a manual "transfer switch" interlock...

http://www.interlockkit.com/

Does anyone think the interlock system could be used on an off-grid inverter such as a SW 4024 with the trace transformer? :Dsolarvic:D

adim

BB. said:

Re: PV, Generator, and Grid Installation: Help??

Practically/generically speaking--You cannot run a GT PV Inverter with a Genset for several reasons:

1. GT Inverters are typically around 60 Hz +/- 0.5 Hz or so... Standard AC gensets do not hold frequency tight enough.
2. GT Inverters do not regulate their output power. And gensets generally do not like to be fed current power (i.e., 2kW of load, and 5kW of Solar PV at noon-time).
3. There are Inverter/Generator type generators (Honda, Yamaha, etc.) which have accurate enough frequecy output, but, again cannot take AC Current back into the motor... In theory, if you have 3kW load and 2kW GT power, the genset may make up the missing 1kW... And it is possible that the GT inverter would over voltage and shut down (gracefully) for ~5 minutes. It could work--but it will be your dime to see if your inverter generator + loads will operate in such conditions (note, many of the smaller inverter/generators are 120 VAC only output and most GT inverters are 240 VAC split phase).

There are Hybrid Inverters that support both AC Grid Tied and Off Grid power (when utility power fails). The Xantrex/Schneider XW 6kW 48 volt (and variants) is very flexible, plus support AC generator/autostart too (more or less, a giant whole house UPS with Solar + Generator support).

Not cheap--and even for a week without power may not be worth the XW Hybrid solution (battery bank is the big cost, plus replacement every 7-10 years or so). Only you can make that decision.

If you can conserve power needs during an outage (just enough power for lights, electronics, and central heat)--Perhaps you can build a simple battery backed system (with generator and/or solar support) to carry you "quietly" through the night.

-Bill

System said:

Looking for some words of wisdom please:

Have an existing max 3.5 kw PV grid tied via Fronius inverter. The grid is unreliable in our area, frequently losing power, again last week for five days due to our dear friend Irene. Enough is enough, Looking now at installation of a medium duty backup generator.

Would prefer not to have to trot out the gen set and run heavy extension cords every time the power goes out, especially to power my well pump, so looking ideally at a permanent install.

Am a bit dismayed that the power from the PV array is not available to minimally power the house when grid is off and sun is up, but it would not matter as I really need 5 kW on start surge for my 3/4 HP well pump anyway (330' deep).

Am looking at an 8 kW gen set (LP fuel, which I have, to avoid messing with gasoline storage / refill) versus a 6 kW mobile generator with a water proof disconnect box to plug in same. Either way, the main idea and question herein is: I want to wire it in so that when the generator is on, the inverter senses the AC on the panel and thus allows the PV array to add to the available generator current. Ideally I would not switch critical loads to a new transfer switch load panel, but simply have the generator power the whole panel from both Gen and PV, taking care to turn off heavy current draw before kicking in the generator.

Recognizing I can't just pull the 240v from the generator to both legs of the panel as I need to disconnect the grid .... How does one do that ??? Can I simply wire up a DPDT in a disconnect box to disconnect the grid and connect the generator? Seems the inverter would be happy enough with that and would sense voltage and allow current transfer, but there has to be a better way to do this i.e. auto-sensing such that the auto-start generator feature is enabled and the generator kicks itself on and off while decoupling from the grid while running, other than sensing if grid power is there.

If auto-sensing, then I guess maybe I need to transfer priority circuits to a new transfer switch /lothe ad center which generator is feeding, or switch the main 200A panel to a load shedding type?


Arrggghhh!!! I'm in over my head and need a sanity check please on the best options and how to go about same. (Basic Wiring diagram? Not to do this myself, just to understand what is recommended.)

System said:

Looking for some words of wisdom please:

Have an existing max 3.5 kw PV grid tied via Fronius inverter. The grid is unreliable in our area, frequently losing power, again last week for five days due to our dear friend Irene. Enough is enough, Looking now at installation of a medium duty backup generator.

Would prefer not to have to trot out the gen set and run heavy extension cords every time the power goes out, especially to power my well pump, so looking ideally at a permanent install.

Am a bit dismayed that the power from the PV array is not available to minimally power the house when grid is off and sun is up, but it would not matter as I really need 5 kW on start surge for my 3/4 HP well pump anyway (330' deep).

Am looking at an 8 kW gen set (LP fuel, which I have, to avoid messing with gasoline storage / refill) versus a 6 kW mobile generator with a water proof disconnect box to plug in same. Either way, the main idea and question herein is: I want to wire it in so that when the generator is on, the inverter senses the AC on the panel and thus allows the PV array to add to the available generator current. Ideally I would not switch critical loads to a new transfer switch load panel, but simply have the generator power the whole panel from both Gen and PV, taking care to turn off heavy current draw before kicking in the generator.

Recognizing I can't just pull the 240v from the generator to both legs of the panel as I need to disconnect the grid .... How does one do that ??? Can I simply wire up a DPDT in a disconnect box to disconnect the grid and connect the generator? Seems the inverter would be happy enough with that and would sense voltage and allow current transfer, but there has to be a better way to do this i.e. auto-sensing such that the auto-start generator feature is enabled and the generator kicks itself on and off while decoupling from the grid while running, other than sensing if grid power is there.

If auto-sensing, then I guess maybe I need to transfer priority circuits to a new transfer switch /lothe ad center which generator is feeding, or switch the main 200A panel to a load shedding type?


Arrggghhh!!! I'm in over my head and need a sanity check please on the best options and how to go about same. (Basic Wiring diagram? Not to do this myself, just to understand what is recommended.)

adim

Hi there,

It sounds like you're working on integrating your PV array with a generator for a reliable backup system during grid outages. To achieve this setup effectively, consider using an automatic transfer switch (ATS) that can seamlessly manage the switch between grid and generator power. This would allow your PV system to continue operating and support the generator.

For more detailed guidance, you might find this resource helpful: https://force-v.co/pv-dg-synchronization/ . It provides insights that could be beneficial for your setup.

Best regards,