Advice on SMA 4000TL

[keefy]

Has anyone fitted a SMA 4000TL and had one orientation with 10 panels and another orientation with 6 panels and does this work OK?

I was under the impression that both sides of the inverter need to have the same number on as this is how I have done them before.

Also the side with 6 will be removed next year when the roof is re-done and put back in the same position. Will it still work with just the 10 on whilst this happens?

Thanks in advance.

 

[BruceB]

The mppt inputs are independant. So provided the 10 and the 6 each meet the voltage/current limits for an input it will be fine. If you run some sunny design scenarios you will find it often recommends asymmetric inputs. It will also work with just one input energised.

 

[SolarCity]

Interesting that you appeal for the help of the very people that you so smugly taunted shortly after Barker's FITs cuts announcement.

 

[fiardor]

If you have equal panel strings you can plug both strings into 1 MPPT if you wanted!!!

10 and 6 however will give you a better start up in the winter with lower light levels.

 

[babba]

If you have equal panel strings you can plug both strings into 1 MPPT if you wanted!!!

10 and 6 however will give you a better start up in the winter with lower light levels.

what about 11/5 split..????

 

[keefy]

what about 11/5 split..????

Unfortunately lack of endless roof!

 

[fiardor]

what about 11/5 split..????

Err not sure to be honest only ever done 10 and 6 but it does depend on the panels VoC and the inverters start up voltage which i think on the 4000TL is 175v but it could be as low as 160v

So if your string voltage of the 5 panels is less than 160-175 volts then it probably wouldnt be advisable or cost effective as regards to production.

 

[babba]

Ye I know if the five can cause a kick in voltage its ok but the more panels on one string the the more volts for an earlier kick in and you will get something from the larger string on low light level days smaller string will struggle most of the time.

Just a thought..

 

[moggy1968]

also bear in mind it still needs to work in 10 years time. Voltage output decreases over time so if you cut it too fine on the voltages you may find in a few years the inverter is struggling to fire up.
On most inverters you can alter the start up voltage. You should be careful about reducing this too much though. If the start up voltage is too low the inverter may keep on switching on and off which reduces their life expectancy.

 

[matt25]

does anyone know why sma dont recommend 4mm on this inverter?

 

[Gavin A]

it would risk the inverter pushing the voltage up outside the G83 limits in areas with high existing grid voltage.

We've done it on very short runs with no problem mind.

For example, we were hoping to use an existing 4mm garage circuit on a 3600TL recently, but the grid voltage was already around 248V when we measured it. We tested it by switching a 3kW kettle on in the garage, and the voltage in the garage dropped by 6V. The reverse would have been true if we'd been generating 3kW, with a 6V rise pushing it over the 253V 10 minute average g83 cut out point. An inverter generating 4kW would presumably have led to a 7-8V rise.

These aren't 100% accurate figures, but give a good approximation.

This was on a 30m line, but still...

 

[fiardor]

Hey Gavin?

What if you have 2 x 4000TL's that keep cutting each other out in good sunshine so they cannot both be on at the same time as it pushes the grid voltage over the 262v threshold.

The voltage at origin is 246v.

The array is 90 metres away on a 16mm 3 core swa with 2 x 16amp mcbs and a 63A 100ma main switch wired in 16mm tails to meter and then 6mm to isolators and also 6mm from isolators to inverter.
The voltage on one inverter running is 252v then when the other fires up it rises to 262v and the first one cuts out.
The first one then goes into start up mode then fires up which then makes the second one cut out, and round and round we go.

Also the string voltages that are measured (250v approx per string) only appear as 150v on the display on the inverter so production is way down.

I can either instal one inverter (probably a Fronius) but would then need string fuses. Or try find an explanation to why this is happening with 2 x 4000TL.

Any advice would be gratefully received.

I have some photos somewhere and will post as soon as i can get them from the works pc.

 

[Earthstore]

It sounds like you are going to have to get the DNO to turn the voltage down a little, however, it may be difficult to get them to do this as they supply is within the specs that are required, it is your system that is putting it over.
Did you get DNO approval for your system or was it done under G83?
Why I ask if you had to get approvel (G59) then you may have more of a case with them.
Tread carefully, and they may be helpful.
I hope this helps.

 

[fiardor]

It sounds like you are going to have to get the DNO to turn the voltage down a little, however, it may be difficult to get them to do this as they supply is within the specs that are required, it is your system that is putting it over.
Did you get DNO approval for your system or was it done under G83?
Why I ask if you had to get approvel (G59) then you may have more of a case with them.
Tread carefully, and they may be helpful.
I hope this helps.

The DNO wont turn it down as its under 253v that much i know.

Err and from what i can tell there has been no DNO application let alone DNO approval for this system!!!!

The system was installed in September last year so its been a while.

It has to be G/59 as its UK power networks and they wont entertain anything over 4kw for G/83.

Starting to get a strong sense of forboding with whats coming next.

 

[Earthstore]

What has happened to the original installer, as I take it you are trying to sort this as a third party?
I have some ideas of what may happen, do you know why G59 was not applied for, and are they recieving FIT payments?