Looking for an automatic transfer switch.....I think.

[Dacflyer]

hi all,
Ok, I have looked at some of the other Automatic transfer switch related threads on here, But i couldn't find the answer i was looking for.
I am looking a synchronized ( zero crossing transfer switch ) Transfer sw. that is inverter prioritized. Looking for something that will switch over to mains once the inverter shuts down from low power, Then switch back over to Inverter once the batteries are back up to a certain voltage. ( 24v solar system )
all the transfer switches i find deal with mains power returning. But I don't want it to transfer back over to inverter if the batteries are at min. operating voltages.
So, I am looking for advice / suggestions on something safe to use , like something with zero crossing detection circuitry, Not just relays. I did this before, it worked, but not really good, sometimes it bucked..Not good...
If i had the money, I'd Buy a 24v AIMS inverter/charger... My 48v unit does this.
Looking something for my 24v set up now..
Thanks.. I hope i'm not too complicated to understand...

 

[time2roll]

Standard RV relay based transfer switch will do this. Connect the inverter to the "generator" input that has priority.
Available in 30a 120v or 50 amp 240 split phase.

 

[Dacflyer]

Standard RV relay based transfer switch will do this. Connect the inverter to the "generator" input that has priority.
Available in 30a 120v or 50 amp 240 split phase.

any particular model ?

 

[time2roll]

https://www.bestconverter.com/Transfer-Switches

The Progressive Dynamics or Boondocker would be my choice.

 

[Dacflyer]

Do these transfer switcher have Zero crossing circuitry protections ?
All the ones I'm seeing are just transfer relays and maybe a delay.
I'm looking more zero crossing fast switchover, Kinda like the Battery backup UPS's or Inverters.
Am I asking / hoping for too much ???

 

[TomC4306]

My MPPSolar PIP3048LV-MK units operate exactly as you describe.
Two in parallel running half my house 24/7. Computers, satellite gear, network gear, TVs no problem with switching.
50 volts 'to grid'. 52 volts 'back to battery'.
A dual pole,.30 amp breaker in my main panel feeds them.
Watts 24/7 also sells a 24 volt 2.7k version.

 

[Wakintx]

Moe's transfer switch:

Dual Power Automatic Transfer Switch|Solar Power Transfer Inverter ATS

The ATS controller will switch to grid power when the voltage of batteries is lower than the voltage transfer setpoints,and it will switch back to battery power itself when the voltage of batteries is higher than recovery setpoints.

moeshouse.com

Will has one on the board of one of his system setups, like his small van/RV setup

 

[Dacflyer]

I could make my own relay type of transfer switch, I'm just worried about phase bucking ( switching loads out of phase) or such.
would 2 SPST ( 1 NC and the other NO? ) be better than a single DPDT ?

 

[Dacflyer]

well, I Decided to build my own transfer switch box.. It's starting to look quite well.
it'll be a portable box for now (testing). I found a 30A DPDT relay. I'll be using this so that both inputs will be isolated, except for the grounds being shared. I'll have 2 individual 10A circuit breakers, 1 indicator light that will light up for the active input ( Inverter or Mains )and also an indicator light to show FAULT if either one of the breakers trips. and the outlet will be a GFCI. the relay coil will be tied to inverter output, so when inverter shuts down, the relay will transfer to mains. and when inverter power returns, the relay switches back automatically.
I'm still going to try and find or invent a zero crossing circuit to control the transfer...might be possible, maybe not.

 

[400bird]

I'm a bit curious how you transfer and match phases at the zero crossing when
1. The inverter just powered down so it's not outputting any voltage
2. The inverter and grid aren't synchronized, so it's unlikely they would have zero crossing at the same place.

Maybe I'm missing something.

Anyways, you came make any automatic transfer switch switch as desired (back to grid when inverter stops)
You'd wire your inverter to the main/primary (normally grid) input. Then put the grid on the back up, emergency, or second input.
So, anytime the inverter is outputting voltage the transfer switch will go to the default (inverter) connection which would normally be hooked up to the grid.

I realize it's advice too late for you as you are already building your own transfer switch, but maybe someone else is reading along.

 

[Dacflyer]

I see your point about transferring to mains when inverter shuts down.. but what about when it returns to inverter mode?
for example.. if my fridge or some other inductive load switches, will that put an undue buck ?
I might be thinking too much into this.. I just done wanna blow up my inverter when things switch over..

 

[400bird]

I haven't done testing and don't have the proof to back my thoughts.
If ensuring the phases are matched when switching sources I'd expect a zero crossing transfer switch to exist, but by your admission it's not an easy thing to come by, seems like it doesn't exist. So I'd say you don't need to worry about it.

 

[Dacflyer]

I haven't done testing and don't have the proof to back my thoughts.
If ensuring the phases are matched when switching sources I'd expect a zero crossing transfer switch to exist, but by your admission it's not an easy thing to come by, seems like it doesn't exist. So I'd say you don't need to worry about it.

Ya, ok,, was just a thought, I'll see how it does in my real world test.. I'll monitor the relay when it switches, see if there's any excessive arcing between contacts.