Givenergy inverter not generating

[hcbeynonhc]

I have a givenergy pv installation consisting of: GEN1 1 3.6 kw hybrid inverter and 2 strings of 4 ja Solar JAM54S30-405mp modules.
Data sheet for inverter states: starting voltage = 140V and a max input current = 11A
Data sheet for module states:
STC Voc = 37.23V, Vmp = 31.12V and Imp = 12.98V.
NOCT: Voc = 35.12V, Vmp = 29.47V and Imp = 10.38A
Both strings are on the same roof. With no shading.
The inverter does not start to generate until the monitored pv votages by the givenergy app reach 150V. This has not always been the case. Previous data shows the pv voltages at which the generator started were in the low 140’s.
My installer suggests having one string of 8 panels Into one mppt input.
My questions are:
Why doesn’t my inverter start to generate at or above 140V. Is the inverter faulty?
WI’ll I have more power one string or two strings?
Are there any other implications on 1 string Vs 2 strings.
Thanks for any advice you can offer me.

 

[binky]

Poor design, the Voc is the voltage when the panel is stalled ie no energy flowing, to get energy the inverter drops the voltage and increases amps VxA = power. Provided 8panels isn't too high a voltage for the inverter, (unlikely) and the panels are all in the same orientation, then you would be better off with a single string.

 

[hcbeynonhc]

Hi inky,
thanks for the reply. Which part of the installation do you think is a poor design?

 

[binky]

Hi inky,
thanks for the reply. Which part of the installation do you think is a poor design?

the wiring of the panels/ choice of inverter, it's clearly not quite getting the MPPT going. They could have fitted a Solis with a start up voltage of 90V and had no problems. Rewiring to a single input is easy enough to achieve, so I would let your installer do that and see what happens.

Voc - Voltage open circuit, this is the maximum voltage on the panels with no energy flowing. As soon as the inverter makes a circuit, that voltage drops as the MPPT ( maximum power point tracker) tries to create as much energy as possible by dropping voltage to something like the Vmp figure and raising ampage. At 32V and 4 panels thats 120V, so below your inverters spec of 140V, although generally they will run at lower than that voltage once running. Your system is right on the edge of what will work, so given a nice sunny day, it will probably be OK, but given cloudy darkish weather it may fail to start or keep dropping out. That in turn means you will lose low level outputs mornings and evenings, mid winter and during poor weather. Now, if they rewire the panels as a single string, then your Vmp is 8 x 32V = 256V, which will get the MPPT working nicely and maximise the benefits from your system. Most MPPTs will take 500V or more, so no issues with that

 

[hcbeynonhc]

the wiring of the panels/ choice of inverter, it's clearly not quite getting the MPPT going. They could have fitted a Solis with a start up voltage of 90V and had no problems. Rewiring to a single input is easy enough to achieve, so I would let your installer do that and see what happens.

Voc - Voltage open circuit, this is the maximum voltage on the panels with no energy flowing. As soon as the inverter makes a circuit, that voltage drops as the MPPT ( maximum power point tracker) tries to create as much energy as possible by dropping voltage to something like the Vmp figure and raising ampage. At 32V and 4 panels thats 120V, so below your inverters spec of 140V, although generally they will run at lower than that voltage once running. Your system is right on the edge of what will work, so given a nice sunny day, it will probably be OK, but given cloudy darkish weather it may fail to start or keep dropping out. That in turn means you will lose low level outputs mornings and evenings, mid winter and during poor weather. Now, if they rewire the panels as a single string, then your Vmp is 8 x 32V = 256V, which will get the MPPT working nicely and maximise the benefits from your system. Most MPPTs will take 500V or more, so no issues with that

Thank you so much for the information. The numbers clarify the situation For me. I’ll have a word with my installer, who also designed and supplied the system, why he chose this layout. Would a string of 8 into one mppt and a further string of 6 panels on another roof exceed the power handling of the inverter?

 

[johnb2713]

Is the other roof the same inclination and facing the same direction? No shading on either roof?

 

[hcbeynonhc]

Hi thanks for the reply.
No. The original roof is facing south. The other roof is facing almost directly west and has pretty much the same inclination. Approx 35 degrees.

 

[binky]

Thank you so much for the information. The numbers clarify the situation For me. I’ll have a word with my installer, who also designed and supplied the system, why he chose this layout. Would a string of 8 into one mppt and a further string of 6 panels on another roof exceed the power handling of the inverter?

sounds like a plan to me , although you would be better off with a larger inverter as the array will be 5.6kW and may need export limitation depending on if the DNO will accept it or not. My advice is always max the array out, size matters!

 

[hcbeynonhc]

Thanks Binky. Good advice.

 

[johnb2713]

sounds like a plan to me , although you would be better off with a larger inverter as the array will be 5.6kW and may need export limitation depending on if the DNO will accept it or not. My advice is always max the array out, size matters!

Maybe rethink this one, one set of panels facing south, the other facing west?

 

[binky]

Maybe rethink this one, one set of panels facing south, the other facing west?

I think that's the possible plan, or are you just thinking of keeping the overall array size down to around 4kw?

 

[johnb2713]

I think that's the possible plan, or are you just thinking of keeping the overall array size down to around 4kw?

My thoughts (maybe flawed) were that with 8 panels South Facing and 6 panels West Facing, connected in a single string, each would restrict the other through the day. Example from 9 am to 12 noon the South Facing panels would be restricted by the West Facing ones, later eg 3pm to 9pm the West Facing panels would be restricted by South Facing ones.
The real solution is a dual MPPT unit with a lower start up voltage.

 

[binky]

My thoughts (maybe flawed) were that with 8 panels South Facing and 6 panels West Facing, connected in a single string, each would restrict the other through the day. Example from 9 am to 12 noon the South Facing panels would be restricted by the West Facing ones, later eg 3pm to 9pm the West Facing panels would be restricted by South Facing ones.
The real solution is a dual MPPT unit with a lower start up voltage.

It's got a dual MPPT hence the two strings of the current setup.

 

[johnb2713]

It's got a dual MPPT hence the two strings of the current setup.

I understand that BUT it has a rather high startup voltage which is the cause of the problem? Most Victron's for example have a 120v startup voltage.

 

[bladerunnerpv]

Sounds like OP has 2x4 into MPPT#1 and 1x6 into MPPT#2 ?

or should that be 4x2 into MPPT1? - is there a common convention for series and parallel combinations ? (4s)x2 ?

Perhaps need a bit more info on the current system...

 

[binky]

I understand that BUT it has a rather high startup voltage which is the cause of the problem? Most Victron's for example have a 120v startup voltage.

It would be 8 panels south on one string, 6 panels west on the other, which should work fine.

Currently he has 2 strings of 4 panels on separate MPPTs

 

[johnb2713]

It would be 8 panels south on one string, 6 panels west on the other, which should work fine.

Currently he has 2 strings of 4 panels on separate MPPTs

I'm now confused...... are you saying that South and West facing panels will be fine as one string? I thought in the strings the current for whole string was limited by the lowest output panel, with 6 west facing surely that will inhibit the 8 south facing one at their peak time?

 

[Sharpend]

@johnb2713
For clarity.
Op has two strings of 4panels existing
All on south facing roof
Op is now suggesting increasing with an additional 6 panels on west facing roof.

Binky is suggesting the new arrangement as two strings, first string of 8panels on south facing and second string of 6panels on west facing.

 

[johnb2713]

@johnb2713
For clarity.
Op has two strings of 4panels existing
All on south facing roof
Op is now suggesting increasing with an additional 6 panels on west facing roof.

Binky is suggesting the new arrangement as two strings, first string of 8panels on south facing and second string of 6panels on west facing.

Ah ok, I hadn't read close enough, now I understand.

Thanks - J

 

[binky]

Ah ok, I hadn't read close enough, now I understand.

Thanks - J

I think you are having a senior moment