Growatt inverter limits

[derekisastro]

Not sure it's been discussed or confirmed and the search option has not helped me track it down but ...

I had 'heard' that the Growatt all-in-one hybrid inverters have limits placed on them even when 'passing through their grid connection?

In other words, I understand that they Growatt's/MMP hybrid inverters have inverters as well as solar charge controllers, battery chargers, ats, etc ... my understanding was that they would power devices via battery/solar as long as the battery solar had power AND that the load was under the inverter limit (let's use 3,000w as a standard example). If the battery or solar ran low, or the load went above the limits of the inverter that these systems could be set up to access the grid and use grid power to support loads, charge batteries, etc ... my understanding that this would occur if the load went above our 3,000w limit of the inverter (the example) and that the grid would support load in excess of the 3,000w. I have heard that even when using the grid, the unit was somehow limited to 3,000w loads? Is this correct?

Can someone confirm that they are able to power loads far in excess of the inverter limits when the unit uses the grid pass-through? Or, alternatively, can it be confirmed that when the batteries are below their voltage limit, and no solar exists (night time) that even when running of the grid, the unit is limited to, in our example, 3,000w watts?

The Growatt manuals don't seem to clearly indicate one way or the other.

Thank you,

D.

 

[will_fish]

I noticed in the Growatt SPF 3000 TL manual (top of page 7) it indicates to use a 40A AC breaker so that should give you an idea on max load for AC. We are installing this same inverter and will be using a 30A AC breaker. Given the inverter can only handle 3,000 watts, we'll only have circuits where we anticipate using 25A (or less) which means a 30A breaker should be more than sufficient to handle the load when on AC. We don't anticipate any high surge loads when running on AC power so not very concerned about the 30A tripping.

 

[apctjb]

40A AC Input/Output

 

[derekisastro]

Any confirmation that once the load goes above the 'calculated' 4800W AC pass-through that the Growatt device ... shutdown?

Ignoring the possible fact that the suggested 40amp breaker installed on the AC input trips.

It seems that the 40amp is still just a hypothetical right ... taken from the suggested installation in the manual? Has anyone ran loads on AC pass-through and can confirm what they've achieved?

 

[Hedges]

there are so many Growatt models - can you provide link to specs and manuals for yours?

Breaker is normally sized 25% higher than maximum continuous current, so it won't have nuisance trips.
40A breaker would be used for up to 32A load. (and wires capable of handling 40A without overheating.)

32A at 120V, if that is its spec, would be 3840W pass-through. Less if its spec is less.

Some inverters will draw power to supplement what can pass through from grid. But not necessarily above maximum rated current.
Mine for instance can pass through 56A and can generate 50A, but output is to be fused around 63A or 70A.

 

[derekisastro]

there are so many Growatt models - can you provide link to specs and manuals for yours?

Breaker is normally sized 25% higher than maximum continuous current, so it won't have nuisance trips.
40A breaker would be used for up to 32A load. (and wires capable of handling 40A without overheating.)

32A at 120V, if that is its spec, would be 3840W pass-through. Less if its spec is less.

Some inverters will draw power to supplement what can pass through from grid. But not necessarily above maximum rated current.
Mine for instance can pass through 56A and can generate 50A, but output is to be fused around 63A or 70A.

See the link for the manual a few commenters above.

How do you know 'yours' can pass-through 56/50amp? Is this based upon the calculations you have performed above or have you actually load tested your pass-through current?

From what I can see the manual for the Growatt does not specifically say what the pass-through load is rated for (only mentions a 'recommended' AC input breaker size). Additionally, it seems a little strange that they recommend only a 40amp breaker for the AC input, which is the same input that I assume is used for the AC charger function of the Growatt ... a function that is able to be selectable up to 60amp on the 24V model ... clearly if I am to use the 60amp charging current a 40amp AC input breaker is not going to cut it right?

 

[Hedges]

I may not have loaded it for that, but it is programmable to allow draw up to 56A, uses inverter to supplement above that. It is supposed to disconnect if current exceeds 56A to protect the relay.
Relay is actually 3 pole, rated 30A each, connected in parallel.

is the 60A for AC charging 60A at 48V?
I think mine has spec 140A charging max, 110A continuous. (inverter is rated about 6kW, so many of its specs are about 2x that of the 3000W Growatt.)

My multiple inverter (2s2p) setup is sufficiently oversize to the load that highest continuous current comes from PV backfeed rather than drawing from grid.

 

[stienman]

if I am to use the 60amp charging current a 40amp AC input breaker is not going to cut it right?

The inverter charging current is specified at the battery side, not the AC side. For a 24V system, the 60A charger will only charge at 1,500 watts, or about 12A from the AC line.

As far as the pass-through current rating, it's the same as the inverter rating, in the case of the model with the manual above that is 3KVA. Chances are good it'll work beyond that, but you should note that it has breakers on its AC output, and also that if the external power cuts out, then it has to provide as much power as it was passing through. If you choose to overload it, then it's going to cut its output, and at that point why even have it there in the first place?

If you're going to set it up in a specialized application, then you're already using it beyond its intended use, and you'll have to test it yourself.

But keep in mind this is very, very unit-dependent. The high frequency inverters operate differently from the low frequency inverters. Some low frequency inverters keep their transformer online even during pass-through mode, and some high frequency inverters don't have a true pass-through, instead use the inverter to drive the loads regardless of the main power source.

Bottom line, choose your inverter according to your load. If you want to run a 6kW max load, then buy a 6kW inverter. Don't look to buy a 3kW inverter, expecting it to pass 6kW, and hoping it doesn't break when it tries to switch over. If you're trying to use it in a backup fashion, then power the subset of loads you want backed up through it, and all other loads from the utility source. Or use a transfer switch, automatic or otherwise.

 

[derekisastro]

The inverter charging current is specified at the battery side, not the AC side. For a 24V system, the 60A charger will only charge at 1,500 watts, or about 12A from the AC line.

As far as the pass-through current rating, it's the same as the inverter rating, in the case of the model with the manual above that is 3KVA. Chances are good it'll work beyond that, but you should note that it has breakers on its AC output, and also that if the external power cuts out, then it has to provide as much power as it was passing through. If you choose to overload it, then it's going to cut its output, and at that point why even have it there in the first place?

If you're going to set it up in a specialized application, then you're already using it beyond its intended use, and you'll have to test it yourself.

But keep in mind this is very, very unit-dependent. The high frequency inverters operate differently from the low frequency inverters. Some low frequency inverters keep their transformer online even during pass-through mode, and some high frequency inverters don't have a true pass-through, instead use the inverter to drive the loads regardless of the main power source.

Bottom line, choose your inverter according to your load. If you want to run a 6kW max load, then buy a 6kW inverter. Don't look to buy a 3kW inverter, expecting it to pass 6kW, and hoping it doesn't break when it tries to switch over. If you're trying to use it in a backup fashion, then power the subset of loads you want backed up through it, and all other loads from the utility source. Or use a transfer switch, automatic or otherwise.

Thanks. That makes sense. It's somewhat a shame but makes sense. Still, a very good system, can't wait for mine to arrive.

 

[gelmjw]

I noticed in the Growatt SPF 3000 TL manual (top of page 7) it indicates to use a 40A AC breaker so that should give you an idea on max load for AC. We are installing this same inverter and will be using a 30A AC breaker. Given the inverter can only handle 3,000 watts, we'll only have circuits where we anticipate using 25A (or less) which means a 30A breaker should be more than sufficient to handle the load when on AC. We don't anticipate any high surge loads when running on AC power so not very concerned about the 30A tripping.

I My manual says Version 3.0 on the cover, the link is to 1.0.

HTH;
John

 

[fazeshift]

I have a pair of Growatt SFP 3000TL LVM-48P, currently only 1 unit installed, but have been testing for over a month.

First of all, I agree with the others - the inverter should be sized appropriately for the loads you intend to run. It has also been pointed out that the 40A current limit is the relevant number.

Any confirmation that once the load goes above the 'calculated' 4800W AC pass-through that the Growatt device ... shutdown?

Ignoring the possible fact that the suggested 40amp breaker installed on the AC input trips.

It seems that the 40amp is still just a hypothetical right ... taken from the suggested installation in the manual? Has anyone ran loads on AC pass-through and can confirm what they've achieved?

The 3000W rating is the continuous inverter output. The specifications chart in the back of the manual indicates that the overload algorithm is timer based: 5s@>150% load; 10s@110%~150% load. Based on that, it is reasonable that the unit can handle 4500W for 5 seconds or 3001-4499 for 10 seconds before it triggers overload and transfers to grid.

The 40A limit on the AC side should be considered a hard limit. Regardless of what AC breaker you put on your grid supply, there is a 40A breaker on the Growatt unit itself. That's the current limit it was engineered for. To go above that for pass-thru, it would need larger wire in/outputs, internal components, transfer relay, etc - all the stuff designed into the larger capacity models.

From what I can see the manual for the Growatt does not specifically say what the pass-through load is rated for (only mentions a 'recommended' AC input breaker size). Additionally, it seems a little strange that they recommend only a 40amp breaker for the AC input, which is the same input that I assume is used for the AC charger function of the Growatt ... a function that is able to be selectable up to 60amp on the 24V model ... clearly if I am to use the 60amp charging current a 40amp AC input breaker is not going to cut it right?

It was point out already by stienman - the 60A charging is the DC current to the battery. While that won't cause you to exceed the 40A AC limit, it is something to consider. The AC current needed to drive the charger still needs to be subtracted from 40A budget. Some very quick math: 60A * 24V charge = 1440W. If we assume the charger is 90% efficient (specs say 98% "max") then it might pull 1584W, or 13.2A @ 120VAC, so max grid pass-thru would be 26.8A, or about 3216W. Considering all of that, I think the advertised 3000W rating is accurate.

I haven't purposely exceeded the ratings, but I have tested with some of the more difficult loads in my house: full-size refrigerator, full-size freezer, (both older non-high efficiency) and office laser printer. The single Growatt handles them fine on invertor, even heavy current of compressor starts, defrost cycles and roughness of the PWM on laser printer fuser.

 

[stienman]

I can back up the Gro-watt's ability to handle surge loads. I have their 6kw low frequency off grid inverter, and it starts my 2HP 240V compressor without an issue. I'm going to be trying it on my 3kW air conditioning unit later this summer.

 

[Isla]

Growatt supports a zero-export application using which you can restrict or stop the export of power with the help of firmware during high loads and when it becomes down you can again set the export margin. This feature is beneficial for those customers who get less sunlight.

 

[Jimmynik1]

Anyone ever use a Growatt or other hybrid inverter or really any inverter in place of a backup generator and give it a designated breaker in a panel with an interlock kit to prevent back feeding the grid? I've hooked up several single phase 110 lines to one side of the panel just to have something in an outage. Wondering how the principle is applied here.
Thanks

 

[Hedges]

Yes - I have a breaker in my panel feeding Sunny Island, also backfed from Sunny Boy on Sunny Island. They power protected loads.
I also have an interlocked breaker next to the main breaker. I can shut off main breaker to disconnect grid, so battery and PV inverters then supply the balance of loads (which aren't normally powered during grid failure.)

My system provides 120/240V split phase. If you feed one side of your panel with 110V, you should turn off all 2-pole breakers. Otherwise, they will draw power from the 110V you supply and feed the other side of panel, causing many devices to experience brownout (low voltage.)

Usually not literally one side of the panel - the two phases are interleaved.

 

[Jimmynik1]

Thanks, yea I have no 220 stuff so I'm safe on that end. Been backfeeding with my predator 3k for years with both hots merged with zero issues. I just don't use the micro with more than one window unit ac on and I'm totally fine.
I'll likely just make a male 5-15r / 5-20 or even just use 10 wire and go to a 30a output from the inverter to female l1430 merging both hots, although just a 30a would limit my use and render it not so portable so most likely a 20a with a 30a or just 20a.
My predator has a l5-30p that I made go into a female l14-30 using both hots, hitting both sides of my panel.

 

[wattmatters]

Anyone ever use a Growatt or other hybrid inverter or really any inverter in place of a backup generator and give it a designated breaker in a panel with an interlock kit to prevent back feeding the grid?

I have a generic AIO that performs this duty. I feed the backup batteries from solar PV mostly but also have it supplied via a dedicated 20A circuit from my main circuit board if so desired. We are 230V per phase here.

The output from my AIO goes to a small distribution board with one circuit connecting to a transfer switch in the home's main circuit board which, when backup is selected, feeds power to all circuits connected on the backup side of the switch (and which are then isolated from the grid). Naturally this excludes the circuit which supplies the AC input of the AIO inverter.

I do however have a problem as I seem to be getting a ground fault which trips the RCBO when I test operation in Utility pass through mode. I'm still waiting for my electrician to come back to me to try and resolve it.

I'm not sure if it's a real fault or an overly sensitive RCBO. It's not super critical as my backup is charged with solar PV and I don't really need the utility pass through mode, but I would like for that option to be functional as it will occasionally be useful to provide UPS-like coverage at times to the house.

 

[Hedges]

Thanks, yea I have no 220 stuff so I'm safe on that end. Been backfeeding with my predator 3k for years with both hots merged with zero issues. I just don't use the micro with more than one window unit ac on and I'm totally fine.

Merging the two hots eliminates the problem of brownouts. 220V loads all see zero, and 110V loads on either phase see 110V.

But there may be a problem if your inverter or generator can deliver more than 20A. Some houses are wired with two separate circuits sharing one neutral. Red and Black are two hots, 180 degrees out of phase. White neutral carries the difference between red and black. If you drive both phases with the same 120V wire, white neutral will carry the sum of red and black, which could be 20A + 20A = 40A. So you would either ensure no such shared neutral circuits, or that no more than 20A is available to the panel.

 

[Jimmynik1]

Yea I read alot about multi branch wired circuits a while back when I did it. No real way as far as I know to know but its been fine in my current home for years now so I think just keeping my usage in an emergency to a minimum is best all around.
If the powers out in the summer its 1 big window ac and one small, fridge some lights and if its the winter its even less having a gas combi water heater only electric used is the recirc pump.

 

[derekisastro]

Yea I read alot about multi branch wired circuits a while back when I did it. No real way as far as I know to know but its been fine in my current home for years now so I think just keeping my usage in an emergency to a minimum is best all around.
If the powers out in the summer its 1 big window ac and one small, fridge some lights and if its the winter its even less having a gas combi water heater only electric used is the recirc pump.

Odds are that if any of your single pole breakers have any other color than a black conductor going to them, usually red, then you have a branch circuit somewhere. If your panel box is not a mess it's very easy to see if there are 2 live lines going into some Romex or something with only 1 neutral.

That is how I was able to determine the few multibranch circuits that I have. Just a standard 2 120V circuits on 12/3 or 14/3 Romex.