4kw Solar PV Query

[danny-solar]

I know my thoughts on this but would like some other responses.  If you install a 4kw pv system does this come under G83 (if so why?)  Also looking at the Feed in Tariff levels it shows 4kw or less and 4kw or more for the different levels of payment.  surely it should be not exceeding 3999w and 4000w +.  Dont want to sound so pedantic but ive been asked by a customer to answer this so which level does the 4kw come into?

Any thoughts please - thanks

[Outtasight]

I don't think G83/1 has anything to do with the FIT limits and bands.  It only covers the safety aspects of the inverter.

It's curious why they limited PV to up to 4000W and for "retro fit" types (see table in the link page).  Does that mean you can have more than 4kW of AC output if it's a building integrated PV system (PV tiles) rather than retro-fitted panels?

http://www.energysavingtrust.org.uk/Generate-your-own-energy/Sell-your-own-energy/Clean-Energy-Cashback-Feed-in-Tariffs

I also assume it does mean 4kW of AC output. You could have more than 4kWp of PV attached to the inverter, given the infrequency of STC conditions in the UK.  An inverter with a slightly oversized array will waste some peak energy on rare occasions when it happens but produce higher average output the rest of the time and the inverter operates more efficiently when it is running closer to its maximum output.

[danny-solar]

So what your saying is you could have a 4.2kw system and due to efficiency/volt drop, etc and as long as the AC output was not over 4kw then this is okay under G83?

[Alan]

You could have a 10 K.W. inverter. When commissioning the system you would enter the P Max into the software curve for what ever load you wanted to produce.
If 4 K.W. was entered that is all it will produce.

Regards

Alan

[danny-solar]

Ok, so lets say for arguments sake that we had exactly 4kw of pv panels and a 4kw inverter.  Would this come under G83?

[Ted]

Strictly the G83 limit is 3.6kW - but in practice the DNO can accept a higher figure. Western Power accepted my 6kW wind turbine under G83. It will depend on local circumstances.

[itsnewtome]

Speak with your DNO. Ours will accept upto 10kw under G83 as long as you enquire with them first. Up to 4kw they just need informing after the install.

[Paulh_Boats]

I expect the limit will be 4kW generated, which will be measured at the inverter output (generation meter).

There is no calibrated and practical way to measure power into the inverter due to MPPT tracking, so it has to be output power through an Ofgen approved meter.

The Sunny Boy SB3800 maximum ratings are 3800W AC output and 4040W input. Allowing for 2% losses on DC side that's 4120Wp of PV.

cheers
Paul

[AidyB]

We are working to the assumption the rate is paid on the DC rated kWp power.

Every install over 3.68 kWp we apply to the DNO unless installed with the SB3800 with a limited at 16A.  This is because we would like to use a 20A fuse so that it doesn't trip.

Some of them have said no to 4kWp installs and it often takes four weeks.  We can't really take the risk of not asking as it could come back to bite us later.  Because a kWp can be exceed if you've a 3.6kWp system on a 16A breaker this can sometimes blow it as well.  It's very annoying.

AB

[Ted]

We are working to the assumption the rate is paid on the DC rated kWp power.

As Paul said, that is the wrong assumption. It is the inverter output that is the relevant figure. The inverter is the SSEG, not the PV panels and the FITs boundaries are based on AC power levels.

Every install over 3.68 kWp we apply to the DNO unless installed with the SB3800 with a limited at 16A.  This is because we would like to use a 20A fuse so that it doesn't trip.

Some of them have said no to 4kWp installs and it often takes four weeks.  We can't really take the risk of not asking as it could come back to bite us later.  Because a kWp can be exceed if you've a 3.6kWp system on a 16A breaker this can sometimes blow it as well.  It's very annoying.

What sort of MCBs are you using? A 16A rated one should cope with 20A without tripping.

Are the SB3800 specifically programmable for output Amperage? Or are you using kW and not taking floating voltage levels into account?

[AidyB]

We are working to the assumption the rate is paid on the DC rated kWp power.

As Paul said, that is the wrong assumption. It is the inverter output that is the relevant figure. The inverter is the SSEG, not the PV panels and the FITs boundaries are based on AC power levels.

Every install over 3.68 kWp we apply to the DNO unless installed with the SB3800 with a limited at 16A.  This is because we would like to use a 20A fuse so that it doesn't trip.

Some of them have said no to 4kWp installs and it often takes four weeks.  We can't really take the risk of not asking as it could come back to bite us later.  Because a kWp can be exceed if you've a 3.6kWp system on a 16A breaker this can sometimes blow it as well.  It's very annoying.

What sort of MCBs are you using? A 16A rated one should cope with 20A without tripping.

Are the SB3800 specifically programmable for output Amperage? Or are you using kW and not taking floating voltage levels into account?

I talked to the person in charge of the FiT at Ecobuild and he thought it was the kWp of the panels.  I trust you more, but have asked to speak to someone 'official' and will let you know.

I'm not a spark, but the general MCB is the one of the consumer unit we're fitting into   ;-) 

The SB3800's are, I believe, specifically programmable for the output, though seeing a UK grid drop below 230V would be unusual enough in itself wouldn't it?