diy solar

diy solar

Help - did I buy the wrong inverter? (Growatt SPF 5000 ES)

Tobster

New Member
Joined
Sep 2, 2022
Messages
13
I bought a Growatt SPF 5000 ES, 16x EVE LF280K grade B's and Daly 150A BMS, with the intention of running my house (all of it) off cheap off-peak electricity by charging the batteries overnight and discharging them during the day. The option of adding solar panels later is a nice to have, and the main selling point for this unit is a real time clock and ability to set up a charging time window for mains -> batteries.

I've just had a sparky out to survey the work for wiring it into the house, and there's a problem.
Though he kindly complimented my tidy battery job; he is convinced (and made a convincing argument, pointing his screwdriver convincingly at things), that the unit will not work for any more than a 5kW system. I thought that 5kW was just the solar/battery inverter and it would just automatically switch back to mains if you exceeded 5kW draw, but he pointed (with his screwdriver) to the AC input and output terminals, described the wire gauges that would be necessary to safely handle the usual British 63A, and said they will not fit into those terminals, so that's basically that.

He will do a bit more research to confirm his understanding (which is the same as mine; that the unit goes inline between the meter and consumer unit and the house is effectively "off-grid, grid-suppliable"), but otherwise thinks that I need an inverter with load sensing that can provide up to its maximum draw to supplement the incoming grid, and not back-feed into the grid, and some more intelligence in the consumer unit might be needed to prevent back feeding in the event of a power cut.

Is this assessment correct? If so, can anyone recommend a unit that will do the job? (charge a 48V battery string overnight on a timer, take solar panels later, and not stop working if I put the oven, washing machine and dishwasher all on at the same time?)
 
The pass-through AC input to AC output is limited to pass-through relay amperage rating. On the 5000ES that is 40 amps.

Add a subpanel with only loads you want to backup. You can move breakers from original panel to subpanel if subpanel is same manufacturer that takes same breaker style.
 
Last edited:
The pass-through AC input to AC output is limited to pass-through relay amperage rating. On the 5000ES that is 40 amps.

Add a subpanel with only loads you want to backup. You can move breakers from original panel to subpanel if subpanel is same manufacturer that takes same breaker style.
So does that mean if I pull between 21 and 40A (up to 9.6kW) it'll just shut off the inverter and switch to utility, no bother?

I note that the AC Input/Output connections section in the book says to use 8 AWG wires on the 5000, which the internet says will carry up to 50A.
 
Solar power AC supplementing is after the pass-through relay so not carried by relay contacts.
 
So does that mean if I pull between 21 and 40A (up to 9.6kW) it'll just shut off the inverter and switch to utility, no bother?

I note that the AC Input/Output connections section in the book says to use 8 AWG wires on the 5000, which the internet says will carry up to 50A.
Your electrician was correct but overly generous. Instead of 5kw you should consider the AIO to be around 4kw max. If it is installed between utility meter and your distribution box than your available grid power will also be limited to the AIO's rating. It is running through the AIO in this situation.

You could install a transfer switch with the two power feeds being the grid and the AIO. When operating on grid your limits would be the grid supply but when operating with the AIO you have to keep loads under the max inverter rating. If this is an auto transfer switch it could be setup to transfer to grid if inverter kicked off on overload.
 
My understanding is that the 5000ES is an ‘off grid’ inverter and should not be able to feed back into the grid ( on paper that is ‘ . Has it been approved ( 240 v 50Hz 1phase ) for use in these countries for connection as a ‘grid assist’ / ‘grid pass through’ system or can it only be used in conjunction with a transfer switch feeding its own sub panel totally isolated from the main grid panel ? I think the main concern of the power utility is the possibility of it accidentally (by fault) feeding back into the grid electrocuting a linesman working on the system.
 
My understanding is that the 5000ES is an ‘off grid’ inverter and should not be able to feed back into the grid ( on paper that is ‘ . Has it been approved ( 240 v 50Hz 1phase ) for use in these countries for connection as a ‘grid assist’ / ‘grid pass through’ system or can it only be used in conjunction with a transfer switch feeding its own sub panel totally isolated from the main grid panel ? I think the main concern of the power utility is the possibility of it accidentally (by fault) feeding back into the grid electrocuting a linesman working on the system.
Off grid with grid pass through and grid assist.
Not capable of backfeeding to the grid.
Can be set to either 50 or 60 Hz.
Not UL listed. So won't usually pass an inspection, if that is desired.
 
Off grid with grid pass through and grid assist.
Not capable of backfeeding to the grid.
Can be set to either 50 or 60 Hz.
Not UL listed. So won't usually pass an inspection, if that is desired.
Thanks , that is what I expected.
 
Is this assessment correct?
Yes

If so, can anyone recommend a unit that will do the job?
There are dozens of options.

So does that mean if I pull between 21 and 40A (up to 9.6kW) it'll just shut off the inverter and switch to utility, no bother?
No. It will result in an overload fault and the inverter will switch off. No power will be passed through. Some of these inverters are capable of short duration peak loads higher than their rated capacity but I would not expect them to be able to sustain such a load for long.

Some options to consider:

i. Decide which loads you wish to be powered via the inverter and which are to be powered by the grid only. For instance, if there are heavy loads which are mostly only going to be used when grid power is cheap, then there is little point adding those to the circuits the inverter will service. You can split the house circuits into two, with an off-grid panel that is supplied by the inverter and grid-only panel.

ii. Whether or not you decide to restrict which circuits the inverter supplies, it still needs to be of sufficient capacity to manage the demand. If you expect to draw, at times, more power than the rated capacity of the unit then you can expect it to shut down. Keep in mind that when operating in grid-pass though mode, which will be required to charge the batteries (since there is no solar PV), the battery becomes one of the demands.

iii. you can work on ways to limit which loads operate concurrently so as to avoid excessive demand.

iv. you can increase the capacity of supply. This might mean an inverter with higher rated capacity, or adding one or more inverters to operate in parallel

v. change tack and use a grid-tied hybrid inverter which operates in parallel with the grid. This requires local authority approval.
 
Back
Top