G83 pre install application

[TedM]

The system would comply with G83.

The FiT band is determined by the Total Installed Capacity (TIC) which has to be declared by the owner/installer. Normally this is based on panel sizes but the definition is open to interpretation. Once people at OFGEM start talking to me again (they seem to be it a bit of a huff with me at present) nailing the definitions of TIC and DNC down to sensible language is one of the next tasks.

Definitions of TIC and DNC are in this:

http://www.decc.gov.uk/assets/decc/...0100331172153_e_@@_fitlicencemodification.pdf

“Total Installed Capacity” means the maximum capacity at which an Eligible Installation could be operated for a sustained period
without causing damage to it (assuming the Eligible Lowcarbon Energy Source was available to it without interruption), a declaration of which is submitted as part of the processes of ROO-FIT Accreditation and MCS certified Registration;

“Declared Net Capacity” means the maximum capacity at which the installation can be operated for a sustained period without causing damage to it (assuming the source of power used by it to generate electricity was available to it without interruption) less the
amount of electricity that is consumed by the plant;

It's quite crazy that TIC is used for some purposes and DNC for others. And why does one say "could" and the other say "can"?

 

[TedM]

The system would comply with G83.

The FiT band is determined by the Total Installed Capacity (TIC) which has to be declared by the owner/installer. Normally this is based on panel sizes but the definition is open to interpretation. Once people at OFGEM start talking to me again (they seem to be it a bit of a huff with me at present) nailing the definitions of TIC and DNC down to sensible language is one of the next tasks.

Definitions of TIC and DNC are in this:

http://www.decc.gov.uk/assets/decc/what%20we%20do/uk%20energy%20supply/energy%20mix/renewable%20energy/policy/fits/1_20100331172153_e_@@_fitlicencemodification.pdf

“Total Installed Capacity” means the maximum capacity at which an Eligible Installation could be operated for a sustained period without causing damage to it (assuming the Eligible Lowcarbon Energy Source was available to it without interruption), a declaration of which is submitted as part of the processes of ROO-FIT Accreditation and MCS certified Registration;

“Declared Net Capacity” means the maximum capacity at which the installation can be operated for a sustained period without causing damage to it (assuming the source of power used by it to generate electricity was available to it without interruption) less the amount of electricity that is consumed by the plant;

It's quite crazy that TIC is used for some purposes and DNC for others. And why does one say "could" and the other say "can"?

 

[Worcester]

Thanks TedM,

With you having nailed the G83, looks like I've asked a question that's another can of worms! - Perhaps this next bit (FIT sizing / Declared Net / TIC) should be in a different thread?

From what you've said above, I would interpret that it is being limited by the inverter in this instance, especially as the definition refers to 'the installation' not the panels. - It would be good to get it nailed down!

If so this is good news for non south facing and more northerly located installations.

Gordon

 

[solarfred]

There is some confusion between G83 and FIT. The G83 limit of 16 amps is monitored by the DNO as they are responsible for the supply system and need to know who is putting what/how much, back in to the grid in any locality. The 16 amp limit is unambiguous because if you have a G83 approved inverter the output is capped at that limit otherwise it does not conform to the type testing certificate that should be included in the MCS installation paperwork. So the output of the inverter will be 16 amps /3680 watts @230 volts or 3840 watts at 240 volts. My DNO uses 240 volts and I have that in writing. They also are happy that the G83 inverter solves their problem as it is capped at 16 amps. What is installed on the roof is of no interest to them at all and is not their responsibility. The G83 installation certification clearly states it is DNC which is required as the output number.The installation diagram should identify the TIC (under OFGEM rules).
The 4 kw limit is dictated by the FIT system as OFGEM have decided that, that is the point at which the tariff payments drop from the highest rate to a lower rate. An installer wants to give the customer the maximum available output from the system and will normally try to install 4 kw on the roof to get as near to the 16 amp output for as long as possible. Using the limit of 3680w as the limit to install on the roof is completely wrong. The two limits are set for different reasons - one for safety and one for dictating how much gets paid out to customers under the FIT scheme. The confusion seems to be that you need more than 4 kw on the roof to get the maximum 16 amps from the inverter unless conditions are STC which is unlikely to happen in the UK very often. So to argue that it is the limit of the output of the inverter which dictates the total installed capacity is wrong as the limit of the FIT bands is not decided on the same set of rules (afaik) and has no bearing on the system output but only the FIT bands set by OFGEM. The inverter dictates the output of the system and this is recorded on the installation report but the TIC is dictated by the collectors on the roof and this is declared by the installer when commissioning the system. Two different things entirely. The MCS just oversee the whole process. They insist that the TIC or what is on the roof is "what is on the label" ie. add up all the wp of the installed modules and that is the TIC as they have been told by OFGEM that is the rule.
I think the TIC should be nearer 4400kw as that would be more likely to get maximum output from the inverter when conditions are right and this is the problem.Will OFGEM change the rules? I have serious doubts. It is not a safety issue just an issue about how much cash gets paid out and right now I don't think more cash is on the agenda.
If the FIT application form used TIC instead of DNC then it would be a lot less confusing and make slightly more sense but as Ted points out to use a mixture of terms across two different rules just makes a complete nonsense of the scheme. The rules were likely not written by individuals that have ever installed a PV system so would they not understand the implications of interpretation of the terms used.

 

[TedM]

The main problem, I think, is that a lot of these terms pre-existed outside of FiTs in other electrical regulations (terms used in regs that apply to large power stations which might self-consume large quantities of power, for example) - and they have just been reused in FiTs, I guess, as a shortcut. Hence why the wording seems so obscure and the application of the terms so tricky.

The main reason for the 4kW cut-off in rates is because this was seen as a threshold as far as the costs of installing a system was concerned; i.e. bigger systems have lower costs due to scale - as the whole intention of DECC was to keep a relatively flat rate of return across all system sizes. Whether 4kW was the exact right figure to use is impossible to say but, given the average size of domestic roofs, is pretty good.

 

[claypole]

One scenario where G83/1 compliance and FIT band are clearly distinguished is where 3 phase is involved. G83/1 clearly allows you to output at 16A per phase, whilst the corresponding power output would obviously take you above the 4kw FIT band. I've been following this thread with interest and coming more and more round to the view that it is the inverter output that counts in both instances. For one thing, it is impossible to give a maximum output (dc) from an array. The sizes commonly referred to are only a nominal rating under test conditions. The manufacturing tolerance for most panels is +10% so the array output under std test conditions could already be 10% higher. If you then add cell temperatures below 25c or irradiance above 1000 the output could be higher still - how could you possibly define the max? The G83/1 certified inverter on the other hand is hard set to output maximum 16A. For G83/1 "fit and inform" surely this is the only information you need? Where it gets complicated is if you decide to make an application in advance because this form will ask for kva capacity. I would still say this figure is also governed by the inverter because again you can't give a definitive maximum output from the array. The Sunny Boy 4000TL supplied to UK is preset to comply with G83/1, maximum 16A and maximum 4000kva (which presumably would only occur when grid is at 250V). But why would you make a pre-application if your inverter is certified G83/1? I can see why people consider a nominal array >4kw is relevant due to the TIC / DNC questions on the FIT registration but surely in the case of the Sunny Boy 4000TL (and doubtless others, it's just that I'm only looking at this inverter) you can rightly declare both TIC and DNC as 4kw?

 

[TedM]

But why would you make a pre-application if your inverter is certified G83/1? I can see why people consider a nominal array >4kw is relevant due to the TIC / DNC questions on the FIT registration but surely in the case of the Sunny Boy 4000TL (and doubtless others, it's just that I'm only looking at this inverter) you can rightly declare both TIC and DNC as 4kw?

A pre-application under G83 is required in the case of multiple installs - stage 2.

Personally I agree completely with anyone who uses the inverter output for both TIC and DNC. The definition of "Eligible Installation" has to logically include the inverter - so that must also be included when calculating TIC and DNC.

 

[Worcester]

Here's the exact wording from e-on / Central Networks FIT application form:

What is the total installed capacity of your generator in kW or MW?
Note: Your unit’s capacity must not exceed 5MW or 2kW for a domestic micro CHP.
kW___________________ MW___________________
What is the declared net capacity of your generator in kW or MW?
kW___________________ MW___________________

They have used "TIC" and "DNC", so these words must be based on the DECC definitions, so the defining factor is, once again, the inverter.

Perhaps this explains how one of the big supermarlets was able to offer a 4.2kWp system for domestic installations.

What it also indicates is that to maximise the revenue for the 4kW FIT tarrif, you'll need to be G59 compliant...

@solarfred
Maybe I missed it, but I can't see anywhere in the MCS documentation where it says to use kWp of the panels.

. The MCS just oversee the whole process. They insist that the TIC or what is on the roof is "what is on the label" ie. add up all the wp of the installed modules and that is the TIC as they have been told by OFGEM that is the rule.

MCS is about proper process, not regulation or definition, they leave the specification of G83/1-1 etc up to the others.

As far as I can see what this all really means is that domestic installs will max out at 3.68 kW, usually being defined by the inverter capacity, not the specified panel output.

And for anything over 3.68kWp,

DNOs are allowed to use their discretion to accept a >16A per phase system under G83 terms...

... the protection settings should conform to G59/2

Gordon

 

[claypole]

A pre-application under G83 is required in the case of multiple installs - stage 2.

Personally I agree completely with anyone who uses the inverter output for both TIC and DNC. The definition of "Eligible Installation" has to logically include the inverter - so that must also be included when calculating TIC and DNC.

Ted, I would apprecaite your further opinion on the following: For a further install that included a 2nd inverter or where a different technology was involved (eg combining hydro and pv) at the same site then I believe stage 2 pre app would clearly be needed. But.. if just the number of panels was increased (lets say to combined 5kwp nominal array size) whilst still feeding the same G83/1 inverter I'm thinking no pre app would be required and indeed no notification at all since the inverter max rating has not changed. With regard to FIT my initial thinking was that this amendment would have to be declared but again if we use the inverter max power figure for the original MCS declared TIC and DNC then again nothing has changed. Is it a requirement under MCS registration to include in your schematic the specific number of panels and their nominal output figure? And if yes, then presumably you would have to declare an amendment. Any body else with a view on this? Anybody done it?

 

[TedM]

I have asked OFGEM about things like inverter changes to existing systems. Their reply was that once you had a registered system all you needed to do was ensure that you did not break any of the terms of your FiTs contract with the electricity supplier. Most of these have conditions running to 4-6 pages.

I believe that any changes, including increasing the number of panels even if this doesn't affect the G83 limit, would still need to be advised to the DNO in keeping with the 28 day after commissioning rule and to MCS and the supplier.

 

[solarfred]

Here's the exact wording from e-on / Central Networks FIT application form:

View attachment 4007
They have used "TIC" and "DNC", so these words must be based on the DECC definitions, so the defining factor is, once again, the inverter.

Perhaps this explains how one of the big supermarlets was able to offer a 4.2kWp system for domestic installations.

What it also indicates is that to maximise the revenue for the 4kW FIT tarrif, you'll need to be G59 compliant...

@solarfred
Maybe I missed it, but I can't see anywhere in the MCS documentation where it says to use kWp of the panels.
MCS is about proper process, not regulation or definition, they leave the specification of G83/1-1 etc up to the others.

As far as I can see what this all really means is that domestic installs will max out at 3.68 kW, usually being defined by the inverter capacity, not the specified panel output.

And for anything over 3.68kWp,

Gordon

Gordon,

I spoke to the MCS staff at Ecobuild to try and nail down the issue and that is what I was told.