Transfer switch

[cwlutterloh]

Hello, new to Solar. In contract for install in a few months. I know the basics but still have a few questions. I'll have a grid-tied system using micro inverters. I know my system will be OFF not producing power when utility power is down as it is, so solar power doesn't get pushed back to grid to harm utility workers. With that said...

I would like power critical circuits. (refrigerator, freezer, wifi) I'm trying to see if my understand is correct and what all is necessary.

If power goes out and I have a manual transfer switch, I'd need to first switch OFF my main power then switch ON the transfer switch that would power a subpanel that would supply solar power the "critical" circuits in the main panel. Is that correct so far? The installer is offering to add a backup battery but 15K is too steep for my pocket book.

Do I "HAVE" to have an inline battery or separate inverter in the mix? Can't I just transfer the solar power directly to the preferred plugs? If so where does the excess power go if the load on the critical circuits is lower than what’s produced also what happens if I have too much load those circuits to power all plugged in?

My plan was to use transfer switch and plug a Bluetti or Jackery in one of the critical circuits wall plugs to keep it topped off and use the stored power via extension cords once the sun went down.

Or am I just completely off base and need to be schooled?

 

[OzSolar]

Do you have Enphase?

 

[chrisski]

Or am I just completely off base and need to be schooled?

I just ask that you do a power audit and see how much you really will use.

I looked at a Bluetti to run a 1000 watt Air Conditioner for four hours recently, and I looked at prices of a Bluetti AC 300 with t B300 battery packs and this came to Almost $7k. The AC 300 probably has an inverter big enough to power the air conditioner with the surge and a soft start, and the B300 battery packs would power it for four hours. If the weather was good, the same system would cover needs for days If cooking, refrigeration, and heating were propane.

IMO if this is a practical decision, for me who’ve been here for 11 years and have not seen Power problems at all except for a flicker, then that $7k is better spent having the electrician install a manual transfer switch with a 30 amp or 50 amp 120 VAC plug and getting a generator capable of powering providing 5kw+ of power.

I also think your installer is doing things IAW with the local code. There’s some threads on this forum that discuss house batteries and the NEC requirements becoming much stricter in 2020. May be for a by code permitted installation, won’t get cheaper. Your jurisdiction may not care about that.

 

[Goboatingnow]

Typically proper trabsfer switches are used to ensure islanding safety if maintained

 

[cwlutterloh]

Do you have Enphase?

Yes, the installer is using Enphase microinverters.

 

[cwlutterloh]

I just ask that you do a power audit and see how much you really will use.

I looked at a Bluetti to run a 1000 watt Air Conditioner for four hours recently, and I looked at prices of a Bluetti AC 300 with t B300 battery packs and this came to Almost $7k. The AC 300 probably has an inverter big enough to power the air conditioner with the surge and a soft start, and the B300 battery packs would power it for four hours. If the weather was good, the same system would cover needs for days If cooking, refrigeration, and heating were propane.

IMO if this is a practical decision, for me who’ve been here for 11 years and have not seen Power problems at all except for a flicker, then that $7k is better spent having the electrician install a manual transfer switch with a 30 amp or 50 amp 120 VAC plug and getting a generator capable of powering providing 5kw+ of power.

I also think your installer is doing things IAW with the local code. There’s some threads on this forum that discuss house batteries and the NEC requirements becoming much stricter in 2020. May be for a by code permitted installation, won’t get cheaper. Your jurisdiction may not care about that.

I don't plan on running an AC unit, just a refrigerator, freezer, WiFi router, and a few light bulbs.

Instead of a Bluetti, I may just get a 1000W Pure Sine Wave Power Inverter DC 12V to 110AC and run it off my EV at night.

BUT

Do I have the concept of the manual transfer switch correct? I would like to use it during the daylight hours to power only those critical circuits and then use the EV and inverter to cover the night hours. Just not sure about the excess power generated (where does it go?) or lack of power generated (harmful to applicances?).

 

[rs50pilot]

If you use a transfer switch you do not have to turn off the main breaker or use a separate critical loads panel.
I have a reliance 10 circuit. I have all of the 120v circuits in my house wired to it.
When the power goes out, you simply plug your power source into the transfer switch and switch which circuits you want to run from the transfer switch. You leave the main breaker on.

 

[cwlutterloh]

If you use a transfer switch you do not have to turn off the main breaker or use a separate critical loads panel.
I have a reliance 10 circuit. I have all of the 120v circuits in my house wired to it.
When the power goes out, you simply plug your power source into the transfer switch and switch which circuits you want to run from the transfer switch. You leave the main breaker on.

Ok, I thought I had to turn off the main to prevent power from going back to the grid. The power source I want to use is the solar array, can it be wired in both ways? Grid\house when utility power is on and transfer switch\house when grid is down?

 

[rs50pilot]

The switch isolates the grid. You can power it with solar, but you'll need an inverter.
I run a 20 panel enphase grid tied system, then a 6 panel off grid setup to a lv6548 and 20kwh of batteries. I leave all of my 120v circuits powered from the inverter/transfer all the time, the grid tied system is my ac input to my inverter.
So if the grid goes down the inverter is already on and I don't even know it. Well my 240v stuff won't work, so that's how I know.
During the day the off grid panels charge the batteries and provide power to the house, the grid tied backs them up and runs the 240v.
Works pretty good.

 

[cwlutterloh]

Ok, so can inline microinverters connect to a separate inverter? Wouldn't the microinverters already be converting the current to AC? Where would the transfer switch even come into play?

I'm trying to avoid using a battery all togther seeing that I have an EV I can use for that. (with separate inverter) I don't mind swapping the power cords around for night time. I don't get too many power outages. I'd just like to use the PV during power outage while the sun is out. What would I need for that?

 

[rs50pilot]

I have enphase iq7+. They will not output when the grid is down. Idk if what you have will but I doubt it.
The battery is there to take up the loads when a cloud passes over i.e.

The transfer switch just selects which source the input power is coming from. Grid or generator. It's dumb and doesn't do anything else.

Sounds like you are going to need an inverter that will ac couple in order to use what you have.

 

[cwlutterloh]

I have enphase iq7+. They will not output when the grid is down. Idk if what you have will but I doubt it.
The battery is there to take up the loads when a cloud passes over i.e.

The transfer switch just selects which source the input power is coming from. Grid or generator. It's dumb and doesn't do anything else.

Sounds like you are going to need an inverter that will ac couple in order to use what you have.

So do microinverters require grid power and not work at all or just need a 2nd route to power?

Ok, so I'd need an inverter that will AC couple because the microinverters already convert to AC right?

So would the wiring would go something like... PVs (with inline microinverters) --> transfer switch then
either --> main panel --> grid
or--> 2nd string inverter (that will AC couple) --> critical circuits in main panel

I'd still like to use without battery, I understand it sometimes won't handle loads due to weather or night, that's when I'd breakout the extention cords and EV car inverter.

 

[OzSolar]

Yes, the installer is using Enphase microinverters.

Here's the quick description on the Enphase "Sunlight Backup" system without batteries. It may do all you are wanting, and no transfer switch required (at least I don't think so, ha).

Understanding Sunlight Backup system for homeowners | Enphase

enphase.com

 

[cwlutterloh]

Here's the quick description on how Enphase "Sunlight Backup" It may do all you are wanting and no transfer switch required (at least I don't think so, ha).

Yeah, that sounds like what I'm trying to do. Thanks!

 

[rs50pilot]

So do microinverters require grid power and not work at all or just need a 2nd route to power?

Ok, so I'd need an inverter that will AC couple because the microinverters already convert to AC right?

So would the wiring would go something like... PVs (with inline microinverters) --> transfer switch then
either --> main panel --> grid
or--> 2nd string inverter (that will AC couple) --> critical circuits in main panel

I'd still like to use without battery, I understand it sometimes won't handle loads due to weather or night, that's when I'd breakout the extention cords and EV car inverter.

Micros need to see a 60ish hz signal from the grid to output power. Otherwise they are dead. It's a safety feature.

Do you plan on installing anymore solar panels?

If you use a transfer switch you will not need a critical loads panel.

Using an inverter without a battery is not reasonable in my opinion. If you have absolutely no chance of shading a panel then ok, it will work, but you need the battery to take care of starting loads. Even if it's a single 48v 50ah battery. Just something to take the inrush off of the system.

I suggest you look up the wiring for a transfer switch. Instead of generator in, the input source would be your inverter. But not your micros.

Your not going to be able to run your micros directly to the transfer switch and have them work when the grid goes down.

I don't know how your ev works or what it outputs, but it may be possible to plug it into the transfer switch and power the house, but how are you going to charge it?

More important, what's your budget? And how long do you want to power your house for? 5kwh doesn't go very far.

 

[rs50pilot]

Yeah, that sounds like what I'm trying to do. Thanks!

This would involve changing all of your micros and your combiner box.

 

[cwlutterloh]

This would involve changing all of your micros and your combiner box.

I'm getting a system installed March of next year. I'm doing my research to see what I need first.

That Enphase sunlight backup system looks nice but seems expensive. I like rs50pilot's idea, I could just go with a small battery if nothing else.

 

[OzSolar]

I'm getting a system installed March of next year. I'm doing my research to see what I need first.

That Enphase sunlight backup system looks nice but seems expensive. I like rs50pilot's idea, I could just go with a small battery if nothing else.

Unfortunately, I have no idea what it costs. Ask your installer to quote it and let us know if you don't mind. I'd sure be curious.

Adding back up power to grid tied solar reminds me of one of my favorite settings. "Easy, cheap, good.... pick any two."

 

[cwlutterloh]

Micros need to see a 60ish hz signal from the grid to output power. Otherwise they are dead. It's a safety feature.

Does that mean if I use microinverters, I won't have power when grid is down no matter what I try to install?

Do you plan on installing anymore solar panels?

I'm planning on 21 panels for now but have an area for 3 more should I need to add more later.

If you use a transfer switch you will not need a critical loads panel.

Using an inverter without a battery is not reasonable in my opinion. If you have absolutely no chance of shading a panel then ok, it will work, but you need the battery to take care of starting loads. Even if it's a single 48v 50ah battery. Just something to take the inrush off of the system.

I suggest you look up the wiring for a transfer switch. Instead of generator in, the input source would be your inverter. But not your micros.

Your not going to be able to run your micros directly to the transfer switch and have them work when the grid goes down.

If I go with a small battery just for loads and shading, I'd still need a 2nd inverter correct?

I don't know how your ev works or what it outputs, but it may be possible to plug it into the transfer switch and power the house, but how are you going to charge it?

My EV soultion would be your standard 12v car inverter 1000W and extention cords. This would not tie into the house at all just power devices. I could run my refridge for almost 2 days alone. If I can figure out how to use PV during the daylight I could use level1 charging to recharge the EV.

More important, what's your budget? And how long do you want to power your house for? 5kwh doesn't go very far.

Budget is minimum, only the essentials but the wife is demanding power when grid is down and I would like to at least power criticals. I mean the PVs will be just sitting there useless and that kinda bugs me.

 

[cwlutterloh]

"Easy, cheap, good.... pick any two."

I agree, I may just have to fork out the $$ for Easy and good.