Design Review - Growatt SPF 5000 ES Grid Backup & Neutral Bonding

[LeRoyK]

I've made an additional update that simplifies this a bit by chaining the contactors together through the voltage protection devices. This makes the system all-or-nothing (ideally), such that both contactors are either fully engaged or fully disengaged (effectively acting like a 4PDT, with each pole carrying 40A).

I think you need to use 120V coils on your "Lost N Contactors" if you plan on wiring them in series as shown on your last schematic.

 

[automatikdonn]

I think you need to use 120V coils on your "Lost N Contactors" if you plan on wiring them in series as shown on your last schematic.

We are pulling from the GW outputs to drive the contactor. The neutral is only in circuit for monitoring purposes. You have to look closely to see though. That neutral never comes through and only lives on the input side.

 

[??????]

@LeRoyK - you're totally right, I was noodling that one. Updated in the attached.
@automatikdonn - I've separated the 120/240 and 240 load centers in the attached (but kept the parallel contactors, which could continue to be paralleled and scaled).

 

[LeRoyK]

Why did you change your "Lost N contactor" to switch both L1 and L2 on each contactor instead of one contactor switching L1 and the other switching L2 as you had it previously?

I think there is a chance that the two contactors will not disconnect simultaneously, so the last contactor to disconnect will have to break the full load.

 

[LeRoyK]

This reminds me of some Schneider inverters that I worked on a couple of years ago. we had 3 inverters in parallel each rated at 60A pass-thru current. We burned up the transfer relay in one of the units.

After doing some research I found this document.

 

[??????]

Thanks @LeRoyK and great point - although in this specific case I think we're still OK because our upstream OCPD in the 'Inverter Disconnect Service Panel' is 30A (downrated from 50A) so even if one contactor switched all the load, we'd still be within the 37.5A fault current operating range with even a single contactor (rated at 40A per pole).

If our upstream OCPD is > 30A though, then yes I'd agree that the design has an issue. Either way, I think it's a good idea to group phases by contactor as you said - this makes it so there are no design philosophy changes as the upstream OCPD goes above 30A.

Updated the schematic to reflect this change

 

[LeRoyK]

Thanks @LeRoyK and great point - although in this specific case I think we're still OK because our upstream OCPD in the 'Inverter Disconnect Service Panel' is 30A (downrated from 50A) so even if one contactor switched all the load, we'd still be within the 37.5A fault current operating range with even a single contactor (rated at 40A per pole).

If our upstream OCPD is > 30A though, then yes I'd agree that the design has an issue. Either way, I think it's a good idea to group phases by contactor as you said - this makes it so there are no design philosophy changes as the upstream OCPD goes above 30A.

Updated the schematic to reflect this change View attachment 72615

If you reduce the upstream OCPD to 30A then you only need one "Lost N Contactor".

 

[??????]

Agree - simplified schematic with single contactor, 30A max 120/240 load panel:

• L1/L2 input to AT does not disconnect from 'Inverter Disconnect Service Panel' in the event of a neutral leg failure
  • No cold start process needed since AT input never disconnects
• L1/L2 output from 'Lost N Safety Contactor' to '120v/240v Load Panel' is disconnected in the event of a neutral leg failure
• 30A limit to 120/240v Load Panel

Would like to create a similar schematic for the GW x2 and x3 and xn editions, as time permits...

 

[automatikdonn]

Here is a photo of the panel you wanted a peek into.

Starting from left to right I have
Inverter 1 50amp output breaker
Inverter 2 50amp output breaker
Inverter 3 50amp output breaker
AT 1 30amp Input breaker
AT 1 30amp Output breaker
AT 2 30amp Input breaker
AT 2 30amp Output breaker
Dinkle Connector Set 1 from Inverter 1 50 Amp output to 30 Amp AT1 Input (This part of the circuit is where I have issues and needs to be corrected)
Dinkle Connector Set 2 from Inverter 2 50 Amp output to 30 Amp AT2 Input (This part of the circuit is where I have issues and needs to be corrected)
240V POCO Mains monitor (This is for future use)




I did want to also answer the ferrel question - https://twcontrols.com/lessons/wire...lated-vs-non-insulated-and-ul-508a-guidelines

UL 508A 29.3.4 of the Wiring Methods section covers the use of ferrules in a UL control panel.

It states:

• 29.3.4 A connection to a terminal of a component shall be made by:
  • a) Wire inserted directly into a pressure wire terminal of the component;
  • b) Quick-connect terminal of the component, where the mating part is provided with a dimple, depression, or spring-type connection such that a mechanical snap-action connection is made that does not rely solely upon friction between the two parts;
  • c) Crimped-on pressure terminal connector or closed-loop eyelet;
  • d) Solder terminal specified in 29.3.2;
  • e) Wire-binding screw specified in 29.3.3;
  • f) Open-type eyelet specified in 29.3.5; or
  • g) Wiring ferrule specified in 29.3.6.

G of UL 508A 29.3.4 refers us to 29.3.6 for the specifications of how ferrules are to be used in an industrial control panel stating:

• 29.3.6 A wiring ferrule shall be:
  • a) Used with stranded copper wire(s) only;
  • b) Terminated in a connector rated for copper wire and rated for the number and size of wire(s) crimped to the ferrule;
  • c) Crimped with an appropriate tool as recommended by the ferrule manufacturer before terminating in a terminal of a component;
  • d) Sized in diameter appropriate for the number of wires and wire size(s) as recommended by the ferrule manufacturer; and
  • e) Crimped to the wires such that the length of the uninsulated portion of the wires does not result in the reduction of electrical spacings when the ferrule is installed.

 

[LeRoyK]

You could simplify things by putting the 240V loads on the "Inverter disconnect Service Panel" instead of having another separate Load center just for 240V.

 

[automatikdonn]

You could simplify things by putting the 240V loads on the "Inverter disconnect Service Panel" instead of having another separate Load center just for 240V.

In my head it makes sense to turn the whole system off if there is a malfunction. Specifically on the input side of the AT, if its broken then I don't want to keep providing it power. At least that was my line of thinking.

 

[LeRoyK]

Would like to create a similar schematic for the GW x2 and x3 and xn editions, as time permits...

When you do this remember my "burned up the transfer relay" experience.
I am guessing as you scale it up with multiple GW you will end up using a bigger contactor rather than paralleling multiple contactors.

 

[LeRoyK]

In my head it makes sense to turn the whole system off if there is a malfunction. Specifically on the input side of the AT, if its broken then I don't want to keep providing it power. At least that was my line of thinking.

In the current schematics, you guys are not disconnecting the input side of the AT, only disconnecting the loads from the AT.

 

[automatikdonn]

When you do this remember my "burned up the transfer relay" experience.
I am guessing as you scale it up with multiple GW you will end up using a bigger contactor rather than paralleling multiple contactors.

I agree, and that is what I was afraid of. In my current state of having 3 in parallel I would need a 100 amp minimum contactor. It's probably the best architecture, but $$$$

For instance these two contactors are pretty close

120V Coil - https://www.mcmaster.com/6564K795/
240V Coil - https://www.mcmaster.com/6564K796/

 

[automatikdonn]

In the current schematics, you guys are not disconnecting the input side of the AT, only disconnecting the loads from the AT.

You are not wrong. We need to shut down the outputs of the Inverter sooner. This is why I have a prototyping setup so we can work through these issues and get a resolution out the door.

 

[??????]

In the current schematics, you guys are not disconnecting the input side of the AT, only disconnecting the loads from the AT.

Good idea - however I can't think of a way to auto-disconnect the AT when running off-grid that doesn't introduce the cold start problem - needing a human-in-the-loop to physically close the AT contactor to bootstrap the system. We could add this - but we'd have a system that needs an external power source (be it a human with a screwdriver, or a battery-backed-up servo or similar) to cold-start.

Also re: high current contactors, something like this 200A generac ATS may work, but it looks like it's just a glorified knife switch that's operated by two opposing solenoids. Correct me if I'm wrong since I don't have personal experience with an ATS like this, but if it's solenoid actuated in both directions of the throws, that means we'd need a power source to 'fail safe'. If this were mechanically (spring) fail-safe, then this would work. Maybe it is? Anybody know?

 

[automatikdonn]

Good idea - however I can't think of a way to auto-disconnect the AT when running off-grid that doesn't introduce the cold start problem - needing a human-in-the-loop to physically close the AT contactor to bootstrap the system. We could add this - but we'd have a system that needs an external power source (be it a human with a screwdriver, or a battery-backed-up servo or similar) to cold-start.

Also re: high current contactors, something like this 200A generac ATS may work, but it looks like it's just a glorified knife switch that's operated by two opposing solenoids. Correct me if I'm wrong since I don't have personal experience with an ATS like this, but if it's solenoid actuated in both directions of the throws, that means we'd need a power source to 'fail safe'. If this were mechanically (spring) fail-safe, then this would work. Maybe it is? Anybody know?

I think you are correct. I do not believe that switch defaults to a no load situation but I don't have any experience with that model. I know my critical circuits version of the generac switch did not have a requirement for power input to maintain a connection. Whichever side of the coils were energized is what it would flip to. Great for switching between POCO and genset, but IDK about usage for load failure disconnect.

 

[LeRoyK]

Good idea - however I can't think of a way to auto-disconnect the AT when running off-grid that doesn't introduce the cold start problem - needing a human-in-the-loop to physically close the AT contactor to bootstrap the system. We could add this - but we'd have a system that needs an external power source (be it a human with a screwdriver, or a battery-backed-up servo or similar) to cold-start.

Sometimes I feel we are overthinking all this, I don't think that the inverters with the build-in transformers have this much fault monitoring and disconnects build-in.

I am not trying to derail your safety circuits, just trying to keep things in perspective.
Where do we stop?

 

[automatikdonn]

Sometimes I feel we are overthinking all this, I don't think that the inverters with the build-in transformers have this much fault monitoring and disconnects build-in.

I am not trying to derail your safety circuits, just trying to keep things in perspective.
Where do we stop?

I think we stop at a Full BOM and a working circuit that keeps peoples houses from burning down. The requirements for that are pretty simple IMO. If the neutral leg fails, turn off the things. If the utility power is being passed through, don't bond the neutral leg to the ground in the downstream panel. There has been a lot of great content, and if all someone wants to do is switch off the system when the AT fails, then they are likely to be done. In the spirit of answering questions people ask to the fullest possible extent, I would say we are very close conceptually, but no solid BOM. For me getting in parts to even test our theories has been a whole thing and it's very frustrating because I have a complex of not wanting to wait.. I believe they call it impatience.

The thread may be useful for other things, but I think we are trying to get to the answer for the OP. "This seems to be a very popular setup, but I haven't found anybody who's cracked the DaVinci code of using a Growatt SPF 5000 ES with a SEAUTO-TX-5000 Auto-Transformer and using the AC input of the Growatt in a 'utility first' configuration."

 

[??????]

Sometimes I feel we are overthinking all this, I don't think that the inverters with the build-in transformers have this much fault monitoring and disconnects build-in.

I am not trying to derail your safety circuits, just trying to keep things in perspective.
Where do we stop?

I think we're at a pretty good solution for a single GW with #133 and can probably call it a day after conductor/conduit schedules and layout/BOM are nailed down. I think #133 can work for multiple GWs in parallel as well, provided you can limit your 120VAC loads to < 30A.

Re: going overboard on failsafes: I'm not sure exactly what failsafes SolarEdge bakes in, but I do think there's a lot of circuitry that can go overlooked because it resides on a PCB instead of in an electrical enclosure. I agree with you that this post may seem excessive at points, but as an example, I know we're missing the temp sensor portion of the AT (pg 68 of attached pdf, screenshotted below):



I've got access to a SE7.6kW with the StorEdge option, so I'll try to make some time to see how it's set up. If anybody else is in a similar situation and wants to compare notes, please do.

 

[lns]

What do y'all think about connecting the SolarEdge AT directly to a small breaker panel WITHOUT any breaker? Would the AT just lose neutral when the Growatt can't provide the 240V ? I just have a wellpump to run 240v and booster pump on 120v, water softener and some lights.

 

[automatikdonn]

What do y'all think about connecting the SolarEdge AT directly to a small breaker panel WITHOUT any breaker? Would the AT just lose neutral when the Growatt can't provide the 240V ? I just have a wellpump to run 240v and booster pump on 120v, water softener and some lights.

I wouldn't recommend connecting anything without a means of OCPD.

When the GW stops putting out 240V, it is correct that the AT would stop making a neutral leg from it. However the purpose in this discussion is to prevent the loss of the AT while the GW is still putting out 240V. The intent is to create a protection mechanism that is built into split phase unit's that this model GW does not have.

In the event your AT failed, your 120V loads would become very unhappy.

If you don't want to build these circuits, then you could massively lower your risk by just dropping in a second redundant AT. It's unlikely that even a single transformer is going to fail, and two failing at the same time is even more unlikely IMO. That doesn't mean they can't or won't, it just means that in my experience its very unlikely.

 

[automatikdonn]

Good idea - however I can't think of a way to auto-disconnect the AT when running off-grid that doesn't introduce the cold start problem - needing a human-in-the-loop to physically close the AT contactor to bootstrap the system. We could add this - but we'd have a system that needs an external power source (be it a human with a screwdriver, or a battery-backed-up servo or similar) to cold-start.

Also re: high current contactors, something like this 200A generac ATS may work, but it looks like it's just a glorified knife switch that's operated by two opposing solenoids. Correct me if I'm wrong since I don't have personal experience with an ATS like this, but if it's solenoid actuated in both directions of the throws, that means we'd need a power source to 'fail safe'. If this were mechanically (spring) fail-safe, then this would work. Maybe it is? Anybody know?

I kinda liked your cold start idea, so I ran with it this evening. I wanted to take the new contactors for a spin anyways. I guess its not such a bad thing to have a human in the path in case there is a failure. I would guess you would want to at least come check it out, but that not might be for everyone. The only time you should have to cold start is maintenance (which you are likely there for) and or a failure.

Should be done processing in the next 15 minutes or so...

For those who are interested, I made a video of a cold start circuit that uses the GW 240v output as a bootstrap. The rest is pretty much off the chart we have been working on this thread.

 

[automatikdonn]

In the current schematics, you guys are not disconnecting the input side of the AT, only disconnecting the loads from the AT.

I have a video demoing this to show it is completely possible and to be honest not such a bad idea.

 

[??????]

@automatikdonn - this looks great! Really cool that you're birddogging this effort with the real world setups to validate the schematics - thanks for taking all this time to share.

Feedback:

1. Cold-start with a 3-position switch is a great idea - but I think it can be simplified further. If you can manually actuate one (or more) of the coils of your three contactors, you could just manually close the contacts for the ~2s that the voltage protection relay would need to 'pick up' the 120V monitoring and take over the job of electrically holding the coils on those contactors. I'll noodle this idea this weekend - I think I have an idea to remotely simulate a manual push button for folks who may not have physical access (i.e. cabin in the woods)
2. I think there may be a significant design flaw here with placing the 240V AT feed on the same panel as the 120V loads. If you do have a faulty AT (let's say it puts out 195V on one leg), the bootstrap process would expose the loads on that '120V load panel' to this voltage - which is exactly what we're trying to avoid. I think we need to place the ATs upstream of the contactors at all times to avoid exposing any 120V loads to stray voltages even during bootstrapping.
3. I think the wiring you have on the three contactors exposes them to the imbalanced load breaking problem that @LeRoyK brought up in #129 and #130 - if we've got two switched phases (L1, L2) on the 3PDT contactors you're using, I think we're limited to a max of two contactors, each contactor switching 150A (50A x 3 poles). Each phase would be distributed across the three switched poles of each respective contactor. Unless we find different hardware I think that's our physical design limit.