DNO or NOT for a 4kw system

[duncster]

Guys - I am sure this has been answered but I am not clear.

I have been advised by two installers that if I have a 4kw system ie 16x250w panels I don't need a DNO providing the inverter is not capable of or is limited to 3.5kw as can be done on the SunnyBoy. He said he installs all systems like this and has never had a problem.

However, another installer is telling me that I can only have 3.66kw on the roof. I want to make a decision today all 3 installers say they can meet the deadline.

The reason I would like the 4kw is it will produce more energy on cloudier days and when the panels get older it will perform better even with the losses.

Advice will be greatly recieved or if somebody could point me in the direction of any documents on the Web I don't want it to be a Grey area black or white.

Cheers

 

[Echo]

If you have a g83/1 compliant inverter then DNO approval is not required. The Power one 3.6 is a suitable inverter for this type of install.

 

[Graeme Harrold]

Scottish Power is OK with 4KW on an SMA 4000TL as its dual certified. They only worry if TIC is above 4kW. If in doubt give the DNO a call, its their decision.

 

[BruceB]

Guys - I am sure this has been answered but I am not clear.

I have been advised by two installers that if I have a 4kw system ie 16x250w panels I don't need a DNO providing the inverter is not capable of or is limited to 3.5kw as can be done on the SunnyBoy. He said he installs all systems like this and has never had a problem.

However, another installer is telling me that I can only have 3.66kw on the roof. I want to make a decision today all 3 installers say they can meet the deadline.

The reason I would like the 4kw is it will produce more energy on cloudier days and when the panels get older it will perform better even with the losses.

Advice will be greatly recieved or if somebody could point me in the direction of any documents on the Web I don't want it to be a Grey area black or white.

Cheers

The installer saying you can only have 3.66kWp on the roof does not know what he is talking about.

The suggestion by the other 2 of 4kWp on the roof and limiting the inverter is OK. However the figure is 230V * 16A = 3.68kW not 3.5kW. Arguably, you could use a figure equating to your actual voltage which is more likely to be 240V.

A slight cheaper solution is to go for an inverter that is 3.6kW rather than 4kW, eg the Power-One Aurora PVI-3.6-OUTD.

Note just because an inverter is G83/1 certified does NOT mean it is limited to 16A. The output current is NOT one of the G83/1 tests.

Regards
Bruce