Surge power required to activate Automatic Transfer Switch (ATS)

[Christoff83]

Good day all,

 

Hope you all are well.

 

I'm setting up a small load shedding solution for a low power use-case (around 250w at max, lower most of the time).   The setup in general, is a 375w Victron Phoenix inverter, coupled to a 12v 100ah battery and an Automatic Transfer Switch.  Load is carried by mains power but should switch automatically to inverter when mains drops.

 

The ATS I bought is this one:    (2 pole, 63A )

SOLAR Automatic Transfer Switch (ATS) 2P 63A (sircony.co.za)

 

I'm having some trouble and thought I could perhaps get some useful info or pointers here.

 

The problem is that the switch does not automatically switch from mains power to standby power; however it can automatically switch back from standby to mains.  I suspect that the problem is that the inverter I'm using is too small to activate the switch.  In my setup, I'm using a 375W Victron Phoenix to power a few lights.  When switching from mains to backup, the ATS just buzzes but doesn't switch.  It appears to me as if the inverter also records an "overload alarm".   There is no load connected, it's just testing the switch for now.  I peformed a few varying tests with a small load also and another (stronger / newer) battery - sall the same results.

 

My question is:  for this ATS, how much surge power is needed to activate the switch?   I will probably end up having to buy a larger inverter and don't want to guess.  Alternatively, could I have perhaps connected the ATS wrong or is there another type/range of ATS more suited to low power use cases (that is also in stock somewhere in country)?    The Victron inverter I'm currently using is rated for 700W peak, so I guess the ATS' surge is more than that when switching.

 

Thanks

Christoff

 

 

[McGuywer]

Interesting. I do not know the answer, following to get some insigts. How are you charging the battery?

[frivan]

Why don't you just use a relay instead of an ATS?

[TaliaB]

1 hour ago, frivan said:

Why don't you just use a relay instead of an ATS?

Noooo @frivanthat is a bad idea you need dead time switching between inverter and Escom mains hence the reason that a manual transfer switch has a off position 3 way switching.  @Christoff83i have used these types of ATS's on a 500w inverter with no problems has a 2 sec  delay though. I am not familiar with the ATS you purchased but strange it does not switch from mains to backup. Do you have a generator to make sure the ATS is actually working. Below picture of the one i used.

Edited April 3, 2023 by TaliaB

[frivan]

7 hours ago, TaliaB said:

Noooo @frivanthat is a bad idea you need dead time switching between inverter and Escom mains hence the reason that a manual transfer switch has a off position 3 way switching

Dead time for what? I used a moving contact for load, fixed contacts for mains and backup power. I am sure there are a few milliseconds in switching.

[Christoff83]

10 hours ago, McGuywer said:

Interesting. I do not know the answer, following to get some insigts. How are you charging the battery?

Morning,

 

Charging happens with an old 240W solar panel and PWM charge controller I had lying around.  Well, not lying around, the panel and PWM use to serve a similar purpose in my own house until I installed full solar a few weeks ago so I'm trying to put together a lights backup for someone else.  Seems to work well except for the ATS not switching in all directions.

 

Thanks

[Christoff83]

9 hours ago, frivan said:

Why don't you just use a relay instead of an ATS?

I thought an ATS would be the correct, safe and easy answer.    I'm not very knowledgeable on electricity and wouldn't want to DIY too much when connecting with mains power, especially in someone else's house.

[Christoff83]

8 hours ago, TaliaB said:

Noooo @frivanthat is a bad idea you need dead time switching between inverter and Escom mains hence the reason that a manual transfer switch has a off position 3 way switching.  @Christoff83i have used these types of ATS's on a 500w inverter with no problems has a 2 sec  delay though. I am not familiar with the ATS you purchased but strange it does not switch from mains to backup. Do you have a generator to make sure the ATS is actually working. Below picture of the one i used.

Hi

 

No generator to test.   I guess I could quickly wire up the mains and backup to two separate wall sockets and switch one off to see...    But with my inverter reporting an "overload alarm" I was assuming it is safe to assume that, that is the problem.

 

I'll do a wire up of two plugs and connect to the ATS to make 100% sure the ATS works well.

One thing I can tell you, based on switching back from backup to mains, is that it switches helluva quick.   The spec sheet for ATS claims <50ms.   Not sure if that response time requires a bit more power.

I'm trying to figure out whether to replace the inverter with a bigger one or find another ATS.   Another ATS will surely be cheaper but, then I still don't know if my 375 (700w peak) inverter will switch a slower ATS.  Or maybe just buy a bigger inverter at higher cost, but then I'm still guessing what size to get.  

[Christoff83]

One other test I want to do sometime this week is:   might be that my inverter is actually powerful enough to activate the switch with peak power but I might be losing some power with my cabling / connections.   I'm not knowledgeable on electricity so "to be safe and proper" I put DC breakers and fuses all over the place; specifically one DC breaker (63A) on the live line between the battery and inverter and also a DC fuse (80A) on the same line.  The cable is thick.

But maybe I screwed something up there.

[TaliaB]

1 hour ago, Christoff83 said:

One other test I want to do sometime this week is:   might be that my inverter is actually powerful enough to activate the switch with peak power but I might be losing some power with my cabling / connections.   I'm not knowledgeable on electricity so "to be safe and proper" I put DC breakers and fuses all over the place; specifically one DC breaker (63A) on the live line between the battery and inverter and also a DC fuse (80A) on the same line.  The cable is thick.

But maybe I screwed something up there.

Send some close up pictures of your setup including wiring of ATS

[Christoff83]

1 hour ago, TaliaB said:

Send some close up pictures of your setup including wiring of ATS

Will do...

Little bit scared to have that open for scrutiny..  but fair enough I guess.

[Christoff83]

OK...  Let me try some uploads:

[Christoff83]

This is unlabelled version of the backup setup I'm trying to build.   It's a wooden board meant to be mounted against the wall in the garage close by the DB Board.

This wooden board setup below has one solar input, one mains AC input and one AC output.  On the board itself is obviously a small inverter, ATS, solar charger and various breakers and fuses.

The labelled version of this picture I'll post shortly tries to explain what I'm trying to do here....

[Christoff83]

OK, so here's the labelled version with description of what I'm trying to do ....

This wooden board setup below has one solar input, one mains AC input and one AC output.  On the board itself is obviously a small inverter, ATS, solar charger and various breakers and fuses.

[Christoff83]

8 hours ago, TaliaB said:

Send some close up pictures of your setup including wiring of ATS

Done 

Let me know where to zoom in - I can post more.

[frivan]

I had a similar setup for the circulation pump of my solar collector. I used an 11 pin relay to switch the inverter on and change the load connection when the power failed.

[Christoff83]

38 minutes ago, frivan said:

I had a similar setup for the circulation pump of my solar collector. I used an 11 pin relay to switch the inverter on and change the load connection when the power failed.

Thanks.

Sounds a little beyond my skillset though....

[frivan]

If you can work on an ATS, you can work on a relay. See my proposed wiring diagram.

[TaliaB]

2 hours ago, Christoff83 said:

OK, so here's the labelled version with description of what I'm trying to do ....

This wooden board setup below has one solar input, one mains AC input and one AC output.  On the board itself is obviously a small inverter, ATS, solar charger and various breakers and fuses.

Wiring seems to be correct. What battery type is the 12v 100ah is it lead acid or lfp?How are you going to charge the battery beside the solar panel? You need to change the breaker and fuse on the solar side you can use fuse or breaker but max 20A 10A preferable as the fuse (80A) and breaker(63A) won't give any protection as you won't exceed 4 amp from your solar panel output when using PWM. Fuse and breaker on Dc battery side is ok @ 700w you will draw 65amps from the battery. On the Ac input from grid use 5 amp curcuit breaker. Still don't know why ats won't switch over as the wiring seems to be in order.

[TaliaB]

19 minutes ago, frivan said:

If you can work on an ATS, you can work on a relay. See my proposed wiring diagram.

This might work for this specific low current application, but should it arc across the contacts gone is the inverter. This is not best practice and not allowed to be used in place of a ATS. This is why relays aren't used, for example, in motor reversal applications. What they use are mechanically interlocking contactors that guarantee the "break before make" condition. They are contactors that are mounted side to side, with a pin that sticks out when the contactor is activated, and it prevents the other contactor from being activated.

[Christoff83]

39 minutes ago, frivan said:

If you can work on an ATS, you can work on a relay. See my proposed wiring diagram.

Thank you, I saw a video on YT just now of an 8-pin relay where a pin/blade in between two poles, physically moves to either side based on power applied to the coil which creates a magnetic field.   

[Christoff83]

38 minutes ago, TaliaB said:

Wiring seems to be correct. What battery type is the 12v 100ah is it lead acid or lfp?How are you going to charge the battery beside the solar panel? You need to change the breaker and fuse on the solar side you can use fuse or breaker but max 20A 10A preferable as the fuse (80A) and breaker(63A) won't give any protection as you won't exceed 4 amp from your solar panel output when using PWM. Fuse and breaker on Dc battery side is ok @ 700w you will draw 65amps from the battery. On the Ac input from grid use 5 amp curcuit breaker. Still don't know why ats won't switch over as the wiring seems to be in order.

Thank you for that review - it really helps a lot.

In response to your questions:

The battery:  it's lead acid "semi deep cycle" but really quite old.   It's been running backup to lights in my house for years.  I'm surprised it still has any life left in it.  I did suspect the switching failure to maybe be battery related so I tested with another battery (also old, but still strong), and no luck.  Not sure if the typically low c-rating of lead acid batteries could be to blame.  I never understood whether c-rating on batteries are continuous or peak. 

Battery charging:  Beside the solar panel...   I don't know.  Was wondering if it would be necessary.  If needed, I would probably try get creative with a transformer feeding into the PWM (as if it was solar); but at night.   Or just keep a battery charger close by for manual operation.

Fuse and Breaker on Solar Side:   Agreed.  Smaller, much smaller fuse and breaker needed to actually provide protection.  I couldn't find any; but will replace soon.

AC Breaker:  Agreed.  5 Amp breaker should be perfect.  The ones I have currently are 6A or 10A, also the smallest I could find on Sunday morning at Builders.  

 

I tested the switch again earlier today. Just buzzes but won't switch to backup.  I should have wired two wall sockets to Mains and Backup power to test whether the ATS actually works and will switch if ample power is available both sides, or just swopped the mains and inverter wiring.  

I am fairly sure though the ATS works.  I do get an overload alarm on the inverter when the ATS tries to switch.

Could there be any losses in the battery connection at the junction box - the galvanised bolts?    Maybe those cheap DC breakers I used are causing a loss; or the cheap MIDAS fuse holders?  

Anyway, many thanks for checking my wiring!

 

 

 

 

[frivan]

The ATS has a coil and caps. I think these cause inrush currents that the inverter can't provide. The pamphlet mentions that the unit can spontaneously ignite if you don't provide sufficient voltage... good luck.

[TaliaB]

@Christoff83 i saw now on your picture the ats switch left is on manual by the looks of it just check it needs to be on auto

[TaliaB]

@Christoff83https://www.power-sonic.com/blog/what-is-a-battery-c-rating/#:~:text=The battery C Rating is,10 Amps for one hour.