Gas generator to backup solar

[Roswell Bob]

Check out the "About My System" link in my signature.
I also use a gas generator as a back-up for my system.
I'm in Wisconsin, so our climates are most likely similar.

GO BADGERS!

 

[Roswell Bob]

Here's the charger.... https://www.renogy.com/20a-ac-to-dc-lfp-portable-battery-charger/

Yes, you can use this charger, but. your generator will be running for a good part of the day when it is cloudy. Battery is specified for 35A of charging current. Batteries are rated for 125AH. if you take the pair down to 50% discharge then you will have total 125AH to charge back up. With a 20A charger it would take you over 5 hours. with a 60A charger about 2 hours. If you have a 240W load the generator will never turn off as the 20A charger is just keeping up with the load.

A major reason for me going to LIFePO4 is because they take enormous charging currents and will keep the hours off of my generator.

 

[Hedges]

This is great info! Very similar situation with the exception my tiny house is 10x16. I do plan on a similar load but no water pump. Right now I am connecting the generator to the service panel from the outside through the wall and energize the tiny home receptacles that way. I would like to be able to switch from solar to generator power when needed and back to solar as much as I can. I’m trying to figure out how to make that switch? Should I just plug a charger into one of the wall outlets to charge the battery bank? That’s easy enough. Now how do I connect the inverter to the service panel. I’ve seen switch boxes that do that but is there a easier way?

thanks!

Look into bonding neutral to ground.
For grid connection this is typically done once at the main panel where utility grid comes in.
For portable generators and inverters, this is usually isolated. Some cheap inverters do not allow bonding of neutral.
If yours do, and you will not connect to utility power, a green screw is used to bond the neutral busbar in breaker panel to enclosure, and same busbar is wired to both neutral and ground of outlets.

If your inverter does not have an AC input and internal switch, easiest way to switch between two sources (inverter and generator) is with a pair of interlocked breakers in the breaker panel.
If the panel has convertible main lugs, you can replace with a main breaker. Install a "backfeed" breaker next to main breaker and add a sheetmetal interlock.
If your breaker only has space for branch circuit breakers, two of those can be backfed with an interlock.

At least some brands of panels have interlocks available. I've bought add-on interlocks or Square-D 100A/125A panels and 150A/200A panels.
I've also bought a Square-D 30A generator switch consisting of 100A panel, 100A breaker, 30A breaker, interlock, and 30A plug. I swapped the breakers for amperage I wanted.

Another way is if you have a plug feeding your breaker panel, it can connect by extension cord to either generator or inverter.

If you buy an inverter/charger with AC input, that should do everything for you including recharge batteries.

 

[kdwhite67]

Yes, you can use this charger, but. your generator will be running for a good part of the day when it is cloudy. Battery is specified for 35A of charging current. Batteries are rated for 125AH. if you take the pair down to 50% discharge then you will have total 125AH to charge back up. With a 20A charger it would take you over 5 hours. with a 60A charger about 2 hours. If you have a 240W load the generator will never turn off as the 20A charger is just keeping up with the load.

A major reason for me going to LIFePO4 is because they take enormous charging currents and will keep the hours off of my generator.

Thanks Bob, I think I'll be getting a larger charger if I go this route. I have some decisions to make....

 

[kdwhite67]

Look into bonding neutral to ground.
For grid connection this is typically done once at the main panel where utility grid comes in.
For portable generators and inverters, this is usually isolated. Some cheap inverters do not allow bonding of neutral.
If yours do, and you will not connect to utility power, a green screw is used to bond the neutral busbar in breaker panel to enclosure, and same busbar is wired to both neutral and ground of outlets.

If your inverter does not have an AC input and internal switch, easiest way to switch between two sources (inverter and generator) is with a pair of interlocked breakers in the breaker panel.
If the panel has convertible main lugs, you can replace with a main breaker. Install a "backfeed" breaker next to main breaker and add a sheetmetal interlock.
If your breaker only has space for branch circuit breakers, two of those can be backfed with an interlock.

At least some brands of panels have interlocks available. I've bought add-on interlocks or Square-D 100A/125A panels and 150A/200A panels.
I've also bought a Square-D 30A generator switch consisting of 100A panel, 100A breaker, 30A breaker, interlock, and 30A plug. I swapped the breakers for amperage I wanted.

Another way is if you have a plug feeding your breaker panel, it can connect by extension cord to either generator or inverter.

If you buy an inverter/charger with AC input, that should do everything for you including recharge batteries.

Thanks, I'll speak with my electrician and see what he makes of this? It's over my head. I'll check it out this weekend.

 

[Hedges]

Thanks, I'll speak with my electrician and see what he makes of this? It's over my head. I'll check it out this weekend.

Post a picture and model number for your breaker panel.
That'll show how much space remains and what can be done with it.

Do you have, or have you selected, an inverter?

 

[kdwhite67]

Look into bonding neutral to ground.
For grid connection this is typically done once at the main panel where utility grid comes in.
For portable generators and inverters, this is usually isolated. Some cheap inverters do not allow bonding of neutral.
If yours do, and you will not connect to utility power, a green screw is used to bond the neutral busbar in breaker panel to enclosure, and same busbar is wired to both neutral and ground of outlets.

If your inverter does not have an AC input and internal switch, easiest way to switch between two sources (inverter and generator) is with a pair of interlocked breakers in the breaker panel.
If the panel has convertible main lugs, you can replace with a main breaker. Install a "backfeed" breaker next to main breaker and add a sheetmetal interlock.
If your breaker only has space for branch circuit breakers, two of those can be backfed with an interlock.

At least some brands of panels have interlocks available. I've bought add-on interlocks or Square-D 100A/125A panels and 150A/200A panels.
I've also bought a Square-D 30A generator switch consisting of 100A panel, 100A breaker, 30A breaker, interlock, and 30A plug. I swapped the breakers for amperage I wanted.

Another way is if you have a plug feeding your breaker panel, it can connect by extension cord to either generator or inverter.

If you buy an inverter/charger with AC input, that should do everything for you including recharge batteries.

Thanks for the help! I have been looking at inverter/chargers and wondering where I connect the solar panels? I haven't come across any diagrams of that.... I see where the AC comes in from shore/generator power and where to connect the battery to the inverter/charger but not sure where to bring in the solar connection???

 

[kdwhite67]

Post a picture and model number for your breaker panel.
That'll show how much space remains and what can be done with it.

Do you have, or have you selected, an inverter?

Not with me. I will this weekend. I do have a 1000w renogy. With my lack of experience did I get ahead of myself by getting this one?

 

[kdwhite67]

I had a quick discussion with my electrician and he said we have 8 slots in the panel and what you were describing would take 4 and leave 4 circuits for the rest of the house with is plenty since it is so small... Thoughts?

 

[kdwhite67]

Thanks for the help! I have been looking at inverter/chargers and wondering where I connect the solar panels? I haven't come across any diagrams of that.... I see where the AC comes in from shore/generator power and where to connect the battery to the inverter/charger but not sure where to bring in the solar connection???

Thanks, I'll speak with my electrician and see what he makes of this? It's over my head. I'll check it out this weekend.

I had a quick discussion with my electrician and he said we have 8 slots in the panel and what you were describing would take 4 and leave 4 circuits for the rest of the house with is plenty since it is so small. Thoughts?

 

[Hedges]

Thanks for the help! I have been looking at inverter/chargers and wondering where I connect the solar panels? I haven't come across any diagrams of that.... I see where the AC comes in from shore/generator power and where to connect the battery to the inverter/charger but not sure where to bring in the solar connection???

An inverter/charger has AC input and AC output, also battery. PV would go to a separate charge controller that wires to battery.

There are some all-in-one with PV, battery, AC output. Some also have AC input.

Usually with separate charge controller you need to limit PV wattage or charge controller amperage to whatever the maximum charge current allowed by the battery bank. Some higher end brands can regulate charge current. Possibly an all-in-one can support small (or no) battery with programmable charge current, also have large PV array to feed larger draw by inverter.

 

[Hedges]

I had a quick discussion with my electrician and he said we have 8 slots in the panel and what you were describing would take 4 and leave 4 circuits for the rest of the house with is plenty since it is so small. Thoughts?

Here's one I use:

Square D QO 30-Amp 4-Space 8-Circuit Generator Main Breaker Outdoor Manual Transfer Switch QO1DM10030TRBR - The Home Depot

The Square D by Schneider Electric QO 30/100 Amp 4-Space 8-Circuit Temporary Transfer Generator Panel helps you change from utility power to a standby source with the flip of 2 QO main circuit breakers.

www.homedepot.com

8-slot box. It came with 100A and 30A breakers, which I removed and replaced with 70A and 70A. It feeds my house from grid or a (large) inverter.
Those breakers take up 4 slots because each is 2-pole. That leaves 4 more slots, up to 4 120V circuits. Should be plenty.

Not with me. I will this weekend. I do have a 1000w renogy. With my lack of experience did I get ahead of myself by getting this one?

1000W? The image says 3000W.

That one has AC input and internal transfer switch. So no need to wire breaker panel as transfer switch with interlocked breakers (unless you will have a 3rd source, like utility grid.)

Generator goes to inverter/charger input. When generator is running a relay closes to feed house from it, and batteries charge.

Looks like the inverter is 120V. Would probably connect the hot wire to both legs of the breaker panel, otherwise only half the slots could be used.

 

[kdwhite67]

An inverter/charger has AC input and AC output, also battery. PV would go to a separate charge controller that wires to battery.

There are some all-in-one with PV, battery, AC output. Some also have AC input.

Usually with separate charge controller you need to limit PV wattage or charge controller amperage to whatever the maximum charge current allowed by the battery bank. Some higher end brands can regulate charge current. Possibly an all-in-one can support small (or no) battery with programmable charge current, also have large PV array to feed larger draw by inverter.

This is my current configuration including 2 125AH Agm batteries wired in parallel. The inverter is a 1000w renogy inverter. With this current equipment are the interlocking breakers the easiest way to accomplish the switching between Solar and generator power and just charge the batteries with a seperate charger from a receptacle when the generator is needed?

 

[kdwhite67]

Here's one I use:

Square D QO 30-Amp 4-Space 8-Circuit Generator Main Breaker Outdoor Manual Transfer Switch QO1DM10030TRBR - The Home Depot

The Square D by Schneider Electric QO 30/100 Amp 4-Space 8-Circuit Temporary Transfer Generator Panel helps you change from utility power to a standby source with the flip of 2 QO main circuit breakers.

www.homedepot.com

8-slot box. It came with 100A and 30A breakers, which I removed and replaced with 70A and 70A. It feeds my house from grid or a (large) inverter.
Those breakers take up 4 slots because each is 2-pole. That leaves 4 more slots, up to 4 120V circuits. Should be plenty.



1000W? The image says 3000W.

That one has AC input and internal transfer switch. So no need to wire breaker panel as transfer switch with interlocked breakers (unless you will have a 3rd source, like utility grid.)

Generator goes to inverter/charger input. When generator is running a relay closes to feed house from it, and batteries charge.

Looks like the inverter is 120V. Would probably connect the hot wire to both legs of the breaker panel, otherwise only half the slots could be used.

This is the one. Sorry

RENOGY 1000W 12V PURE SINE WAVE INVERTER
Continuous Power: 1000W	Surge Power: 2000W
AC Output Voltage Range : 115VAC	Output Frequency (Nominal): 60 Hz
Output Waveform: Pure Sine Wave	Efficiency: > 90%
Operating Temp: -4°F - 158°F	THD: < 3%
No Load Current Draw: < 1A	Dimensions: 13.0 x 7.0x 3.0 In
Weight: 6 lbs.

RENOGY 4AWG INVERTER CABLES (A PAIR)
AWG: 4 (3 FT)

 

[Hedges]

This is my current configuration including 2 125AH Agm batteries wired in parallel. The inverter is a 1000w renogy inverter. With this current equipment are the interlocking breakers the easiest way to accomplish the switching between Solar and generator power and just charge the batteries with a seperate charger from a receptacle when the generator is needed?

The simplest is to have a cord and plug coming from the panel. Plug it into either inverter or generator.

If you plugged battery charger into house outlet, might forget to unplug when using inverter and it would try to charge battery by using battery to feed inverter and feed battery charger.
If battery charger simply plugged into generator it'll be used only when generator is running.

House wiring should have neutral (white wire) bonded to ground. Most devices only have a switch to turn off the hot. GFCI outlets only interrupt the hot. Assumption is neutral has no voltage, isn't a shock hazard.

The electrician should be able to decide how to bond neutral when using generator or inverter. The thing to watch out for is that some inverters are incompatible with bonded neutral (instead of producing 120V isolated, they produce +/-60V relative to battery.) Electrician will have to determine if bonding of neutral for inverter is possible.

Inverter 1000W continuous - that will supply up to 8A for AC loads.
It can probably power a refrigerator. Disabling defroster and icemaker would reduce power consumption.

If two, 100W panels (about 85w typical) you'll get around 800 Wh/day average (less in winter). So only fairly small loads can be run. A small fridge might consume all the power. You'll probably want to add more PV panels. look for local used sources, may also need another MPPT charge controller.

Inverter ought to have a fuse, about 125A. 4 awg is OK but fatter wires are always better.

 

[kdwhite67]

Here's one I use:

Square D QO 30-Amp 4-Space 8-Circuit Generator Main Breaker Outdoor Manual Transfer Switch QO1DM10030TRBR - The Home Depot

The Square D by Schneider Electric QO 30/100 Amp 4-Space 8-Circuit Temporary Transfer Generator Panel helps you change from utility power to a standby source with the flip of 2 QO main circuit breakers.

www.homedepot.com

8-slot box. It came with 100A and 30A breakers, which I removed and replaced with 70A and 70A. It feeds my house from grid or a (large) inverter.
Those breakers take up 4 slots because each is 2-pole. That leaves 4 more slots, up to 4 120V circuits. Should be plenty.



1000W? The image says 3000W.

That one has AC input and internal transfer switch. So no need to wire breaker panel as transfer switch with interlocked breakers (unless you will have a 3rd source, like utility grid.)

Generator goes to inverter/charger input. When generator is running a relay closes to feed house from it, and batteries charge.

Looks like the inverter is 120V. Would probably connect the hot wire to both legs of the breaker panel, otherwise only half the slots could be used.

For my application

The simplest is to have a cord and plug coming from the panel. Plug it into either inverter or generator.

If you plugged battery charger into house outlet, might forget to unplug when using inverter and it would try to charge battery by using battery to feed inverter and feed battery charger.
If battery charger simply plugged into generator it'll be used only when generator is running.

House wiring should have neutral (white wire) bonded to ground. Most devices only have a switch to turn off the hot. GFCI outlets only interrupt the hot. Assumption is neutral has no voltage, isn't a shock hazard.

The electrician should be able to decide how to bond neutral when using generator or inverter. The thing to watch out for is that some inverters are incompatible with bonded neutral (instead of producing 120V isolated, they produce +/-60V relative to battery.) Electrician will have to determine if bonding of neutral for inverter is possible.

Inverter 1000W continuous - that will supply up to 8A for AC loads.
It can probably power a refrigerator. Disabling defroster and icemaker would reduce power consumption.

If two, 100W panels (about 85w typical) you'll get around 800 Wh/day average (less in winter). So only fairly small loads can be run. A small fridge might consume all the power. You'll probably want to add more PV panels. look for local used sources, may also need another MPPT charge controller.

Inverter ought to have a fuse, about 125A. 4 awg is OK but fatter wires are always better.

I like the Idea of plugging into the Generator or inverter for simplicity to start with. To keep everything in one location what are your thoughts on housing the batteries, inverter and charge controller outside in a storage box made for these items. Winter night temps are an average high of 19°F (-7.2°C). The coldest month is January, with an average high-temperature of 19°F (-7.2°C) and an average low-temperature of -7.1°F (-21.7°C). I don't heat the tiny house all winter so the batteries will see fluctuating temps. Does it make sense to try to store the batteries inside so they get warmed up at least a few days a month in the winter?

 

[Hedges]

Indoor, moderating temperature is better. Unless batteries are a type that can be a fire hazard.
Wet-cell needs vent to outside and electronics separate due to corrosion and source of ignition.
Lithium can't be charged below freezing but lead-acid can.
Battery charger should have a temperature sensor to adjust charge parameters of lead-acid.
Make sure all loads disconnect and don't over-discharge battery. Some inverters have a 10.5V cutoff which is too low for battery protection.

 

[Arbee]

Hi, I am new to solar and I am installing a system into my tiny home that consists of two 100 watt rich solar panels, 40 amp mppt controller and two 125ah v max 12 volt batteries. I live in Minnesota and anticipate consecutive cloudy days in the winter months. I'm looking for advice on how I can integrate a 1000 watt honda generator I already own into the system when I need to supplement. I would appreciate recommendations.

I am new to solar, but I am extremely proficient in hooking up 110V generators (I take it that your 1000 watt generator does not provide any 220 service) to the home, including how to crank the generator automatically (if it is cranking battery equipped) when it needs to turn on (and off) and to safely integrate it into the home and still be UL 1008 complaint.

To do this safely you'll need a transfer switch. There are numerous manual ones but only one automatic one I know of for 110 volt generators. It comes in a 10 circuit https://www.apc.com/shop/us/en/products/APC-Universal-Transfer-Switch-10-Circuit-120-240V/P-UTS10BI and 6 circuit variety https://www.apc.com/shop/us/en/products/APC-Universal-Transfer-Switch-6-Circuit-120V/P-UTS6 .

I seem to recall at one point that Honda was bundling this automatic transfer switch under the own label, addition to APC selling to other dealers. Honda may still do so.

If you want the generator to start (or stop) automatically I recommend either of these: the more to do one: http://atkinsonelectronics.com/gscm-generator-start-control-module-rev-c-5-13/ or http://atkinsonelectronics.com/gscm-mini-60hz-usa-canada/.

It's pretty straightforward to start and stop a generator based on the presence or absence of either AC or DC current, the latter can also be set to a voltage threshold.

I've done what you wish to do it sounds like. If I can be of help please post back. Of course I am a hobbyist seeking to help for only good karma.

 

[kdwhite67]

Indoor, moderating temperature is better. Unless batteries are a type that can be a fire hazard.
Wet-cell needs vent to outside and electronics separate due to corrosion and source of ignition.
Lithium can't be charged below freezing but lead-acid can.
Battery charger should have a temperature sensor to adjust charge parameters of lead-acid.
Make sure all loads disconnect and don't over-discharge battery. Some inverters have a 10.5V cutoff which is too low for battery protection.

My batteries are VMAX SLR125 12Volts, 125AH Deep Cycle, Solar AGM Battery. To understand you correctly I should bring them in the house when I'm there and can warm them up once a month in the winter for a few days?

 

[Hedges]

AGM, good to install indoors, no need to move around. Only severe overcharging (e.g. hook up a basic battery charger and forget) will cause bulging and outgassing.
Just have batteries and inverter indoors. AGM is quite freeze resistant even at relatively low state of charge.
Main thing to get good life out of them is for them to achieve full charge (bulk, absorption, then float) which a good charge controller will do. If settings are adjustable, read manual for battery and fine-tune charge controller settings to match.
With all loads disconnected the batteries can sit all winter.
Don't let battery run down below 50% or maybe 70% depth of discharge, and recharge soon after. So turn off inverter if there isn't going to be sufficient solar charging to support it.