Surge power required to activate Automatic Transfer Switch (ATS)

[frivan]

1 hour ago, TaliaB said:

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.

No offense to Christoff83 but adding a relay to that circuit may be the least of the not allowed worries. Mechanical interlocking contactors were probably best practice 50 years ago. Put a PLC on it and monitor each phase. Then you can protect, delay or even sync as you wish.

[Christoff83]

10 hours ago, frivan said:

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.

Haha I saw that little one liner about igniting somewhere yes.

[Christoff83]

10 hours ago, TaliaB said:

@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

Morning, thank you for picking that up - I am aware it is in manual though - the problem I described definitely occurs while in Auto.   It is currently in manual as that is the only way for me to test the setup at the moment.

[Christoff83]

10 hours ago, frivan said:

The ATS has a coil and caps. I think these cause inrush currents that the inverter can't provide.

That is probably the answer then...

I mailed the supplier to ask for a guideline on how much startup current is required but in fairness, they probably wouldn't know...

[Christoff83]

10 hours ago, frivan said:

No offense to Christoff83 but adding a relay to that circuit may be the least of the not allowed worries. 

Morning,

Thank you.

I wouldn't mind understanding what else to be worried about...

If I'm busy here with something non-compliant, illegal, dangerous or otherwise worrisome, I would rather reconsider my approach.

I know that question now deviates from the original post - which was about the ATS - but my assumption was that the approach would be acceptable if proper cabling was used, my setup was wired correctly, appropriate fusing and breakers were in place, no open contacts were exposed and that only a qualified electrician touches the DB Board & mains.

Thanks again

[frivan]

Personally I am only worried about safe operation and feel you should put focus on earthing. In terms of complying to regulations you would have to decide if this is an appliance, fixed installation, UPS, SSEG or whatever. This will introduce different requirements.

[Christoff83]

Hi all,

Coming back to this one quickly...

In consideration of previous feedback given here, I've gone back to do some more research and consulted on-site but informally with someone more knowledgeable.

I still wish to proceed with this backup but as stated before - needs to be safe and compliant and all above board.

So, I'm rebuilding this setup - this time putting the applicable components in surface mount DB's and adding the required DIN mounted fuses and SPD's.

One thing I don't have covered at all - and it was one of the last inputs given on this thread too - and that is earthing.   A topic I really don't understand well yet.

So on earthing, am I correct in saying:

• we have the following to earth:  the solar panel mounting system (frame etc.), ATS metal housing, inverter metal casing.
• components inside the house i.e. those on the board I'm building (ATS, inverter) can get joined and connected to the municipal earth back in the house's main DB.
• the solar panel mounting system (frame etc.) could be connected also to the municipal earth; or ground spike.  My research into this has not yielded any conclusions.

 

Question:

• The inverter used, (as per picture higher in this thread), has a "grounding terminal" on its chassis.  ALSO, the inverter's AC side has a 3-pin output.  I can understand why/ how to earth the chassis - from the grounding terminal into the earth inside the DB - it's meant to protect against a fault where the inverter's metal casing gets energised.  This will cause EL to trip.  But the earth coming out of the AC side confuses me.  What do I do with this?

 

Much appreciated

Christoff

 

 

 

 

[Christoff83]

Side note on the original purpose of this thread:  the ATS that won't switch to backup automatically as it seemingly overloads the 375va inverter.

I spoke to the seller/distributer who said that is not expected, I could bring it in to test.   Have not had an opportunity as yet.

Sourced a different (slower) ATS in the meantime but that is also completely untested, still in the box.

[Christoff83]

Quick update:   I took the ATS the supplier yesterday.   They performed a test and showed that the switching works fine when connected to two eskom sources.  Basically the same test I did.  Still doesn't explain why it won't switch with a 300W pure sinewave inverter.   They also can't tell me what the inrush currents are.  Still, they were helpful and offered a refund.

Following from the discussions in this thread, the cause of the ATS not switching Automatically to backup is then probably too much inrush current for the 300W inverter (which has a 700W peak).

So I'll be reverting to plan B or C then which is buy a bigger inverter or buy another ATS and hope for the best or go the relay route.   I did source a 10A 230VAC 8-pin relay + base (holder) which I'm experimenting with.

 

[Christoff83]

On 2023/04/04 at 7:33 PM, frivan said:

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

 

 

Thanks again for this.

While I don't quite follow your diagram...  I did source a relay and set it up on a test bed to basically perform an ATS function.

In short:  it's a 10A 230VAC 8-pin relay with --- I think 10KA dielectric strength.   Link to exact unit below.

The test setup was quite simple and it seems to work:

- Eskom 220V connect to the "Coil Terminals".

- Coil terminals jumped with wire to NC.

- Inverter connected to NO.

- Test load (220V lamp) connected to "Common terminals".  I would have called them "Load".

 

601282400040 | 10A 2CO 8PIN PLUG-IN RELAY 240VAC | J - Timers and Control Relays : Plug-in relays | ElectroMechanica (em.co.za)

9020SMA | 8 PIN SURF/RAIL MNT RELAY SOCKET | J - Timers and Control Relays : Plug-in relays | ElectroMechanica (em.co.za)

 

 

 

 

 

 

 

 

[Christoff83]

On 2023/04/04 at 9:05 PM, frivan said:

No offense to Christoff83 but adding a relay to that circuit may be the least of the not allowed worries. Mechanical interlocking contactors were probably best practice 50 years ago. Put a PLC on it and monitor each phase. Then you can protect, delay or even sync as you wish.

 

On 2023/04/05 at 8:31 AM, frivan said:

Personally I am only worried about safe operation and feel you should put focus on earthing. In terms of complying to regulations you would have to decide if this is an appliance, fixed installation, UPS, SSEG or whatever. This will introduce different requirements.

 

 

So this discussion has gone quiet but I'll keep it going as long as I'm working on it for any future reference in case someone else at some point tries to do the same as I am currently.

Recap:  I'm trying to build a small backup power supply for low power very essential circuits in my parent's house.  It's basically meant to carry the lights, alarm system, garage door (for emergency entry / exit).  I'm using a 12V 100ah battery, 300W Victron pure sinewave inverter, 240W solar panel and PWM solar charger - all components sourced from a decommissioned installation.  I bought an additional Automatic Transfer Switch to supplement this installation.  

Current Problems:

- ATS does not seem to switch automatically, which prompted me to start this thread.  Suspect inrush current required to activate the switching mechanism too much for the small inverter.

- My prototype build depicted in some posts above raised a few concerns here on this discussion around compliance and safety.

 

Status / Next steps:

- In terms of compliance, I sourced a copy of SANS 10142-1 Ed3 which I'm currently working through to extract any regulations and compliance requirements applicable to my situation.  So far though....  I'm seeing only basic safety requirements like using appropriate components, using protection (like CB's) which I'm already doing and the biggest requirement seems to be the "test finger" requirement meaning no exposed parts should be touchable with a finger even if inside an enclosure that was opened (unless the enclosure was unlocked first).

- I'm entirely rebuilding the prototype depicted in here housing all components in surface mount DB's and running all wires in trunking.  (Trunking does not seem to be a SANS requirement though....).

- I'm also investigating earthing - based on feedback provided here, earthing is a "must" and I will implement.  The investigating part is still due to me not fully understanding earthing even though I made good progress in this respect since the comments were made here.

- Then I'm trying to find a solution to Automatic Switching.  As stated above, my original ATS component does not quite work.  First question to ascertain here, is whether it would be safe and compliant to make use of an 8-pin relay as switching gear (10A 230VAC).  Functionally, I've set it up to work as required.  Can't see anything inside SANS10142 yet that would prohibit the use of such as a relay.  Safety is the other question.  I can see the contacts being physically separated and it switches based on a spring load and electro magnet so the contact can only be on one side at any given time.  I can't see a scenario where both Eskom and Backup can be connected at the same time.  The physical separation distance is small though...   

 

So that's where I am...

 

 

 

 

[frivan]

On 2023/05/25 at 9:42 AM, Christoff83 said:

While I don't quite follow your diagram... 

Hi Christoff. An 8 pin relay will just have enough contacts for the 230V connections. This means your inverter has to be on the whole time. The 11 pin relay in my drawing allows for using the remote on/off function that my inverter had. This will save on the no-load losses of your inverter.

[Christoff83]

11 hours ago, frivan said:

Hi Christoff. An 8 pin relay will just have enough contacts for the 230V connections. This means your inverter has to be on the whole time. The 11 pin relay in my drawing allows for using the remote on/off function that my inverter had. This will save on the no-load losses of your inverter.

 

Awesome thanks, I didn't realise that.

And you're comfortable using such a relay for a system connected to your home's DB instead of a more off-the-shelf ATS?

Thanks again

[TaliaB]

1 hour ago, Christoff83 said:

nd you're comfortable using such a relay for a system connected to your home's DB instead of a more off-the-shelf ATS?

@Christoff83I won't use a relay i will also not issue a coc if a relay is used as a transfer switch. If it could work it is not to say you should use it. There is good reasons for not using a relay to switch diffrent power sources. 

[Christoff83]

14 minutes ago, TaliaB said:

@Christoff83I won't use a relay i will also not issue a coc if a relay is used as a transfer switch. If it could work it is not to say you should use it. There is good reasons for not using a relay to switch diffrent power sources. 

Thank you.   As much as I'm trying to build something workable for the parents as quickly as I can...   this is also a learning experience for me.  

I've built working POC's now with an 8-pin relay as well as full 63A ATS.   I obviously want to make the solution work reliably, safely and fully compliant.

It's been quite surprising how many varying (and sometimes contradicting) views there are out there from people in the industry.

Anyway, thanks again!

[TaliaB]

55 minutes ago, Christoff83 said:

Thank you.   As much as I'm trying to build something workable for the parents as quickly as I can...   this is also a learning experience for me.  

I've built working POC's now with an 8-pin relay as well as full 63A ATS.   I obviously want to make the solution work reliably, safely and fully compliant.

It's been quite surprising how many varying (and sometimes contradicting) views there are out there from people in the industry.

Anyway, thanks again!

The other downsideI when using a relay you won't have seamless power transfer but if you use the correct ATS you could have transfer without interruption of supply to your appliances.

[frivan]

12 hours ago, Christoff83 said:

And you're comfortable using such a relay for a system connected to your home's DB instead of a more off-the-shelf ATS?

Your home's DB should be wired to protect itself and circuits connected to it. That is true whether you wire in a generator, inverter, appliance or whatever. For small loads a relay will work fine. 

[McGuywer]

@Christoff83 Pics please? I am following your journey.

[SOJ]

@christoff83 We are a major supplier of ATS 2/3/4 Pole ATs's in SA and I came across your interesting post regarding the non auto switching of the ATS you had. The reason how I came across your post was because I had a customer who also had this problem and had the same inverter as you did. In addition to this, we have had one other customer with the same inverter that also had the same problem. It appears that this ATS does NOT work with these inverters (our ATS's are slightly different). On further research, it seems that these inverters were design to work in an outdoor camping environment working from a car battery hence the inrush current issue.

We suggest and offer another solution that works perfectly.

Thank you once again.