Discuss EPC, DNC and MCS - TLA headache! in the Solar PV Forum area at ElectriciansForums.net

Status
Not open for further replies.

SolarRoofSols

Regular EF Member
Messages
358
Location
Sheffield
I have just had a call from our EPC assessor who has had notification from his accrediting body that they are unable to accept the MCS cert as proof of size of installation (in the case of EPC being done after the install because without it the house would not get a D) because it shows the declared NET capacity, not the gross capacity in kWp.


anyone else come across this?

Their explanation is that the DNC in kWp is the figure with the SAP calculation already applied and they want the gross figure because the EPC software will automatically apply SAP on top of that.

Firstly, does this mean that for a 2.45kWp installation, using 10 x 245w panels and an inverter that does not cap output below 2.45kW that I have been putting the incorrect figure (2.45kWp) in the MCS database? Should I have been putting 1.96kWp as this is 80% of the TIC?

Secondly - when are the governing bodies gonna get their flabby backsides into gear and give us a break?! :61::61:
 

Gavin A

Electrician's Arms
Solar Guru
Messages
4,238
Location
Leeds
sap definitely works on the kWp rating of the panels NOT the max output of the inverter, so the figure the EPC assessor needs is the kWp rating of the array only.

A couple of months back I analised the Ofgem register, and 99% of all installs had the DNC and TIC as being the same figure, so I'd just run with the herd and put both the DNC and TIC as being the kWp rating of the panels on the MCS cert (we've had clarification from Ofgem that they use the kWp rating of the panels for TIC purposes for calculating FIT bands, so there's no advantage to using the lower figure for DNC). The only time you need to use the max inverter output is for G83 purposes for the DNO.
 

SibertSolar

Solar Guru
Messages
1,120
Location
Hampshire
Oh, just as a side note, interesting to see that Ofgem use kW (or MW) as their SI unit for TIC within this document.....(and not kWp)...or maybe I'm just being a little pedantic?
 

BruceB

Electrician's Arms
Solar Guru
Messages
1,437
Location
Bath/Bristol
No, you are not being pedantic. From what I have observed of OFGEM's dealings with installers (luckily not with me) a phrase involving ar$e and elbow springs to mind to describe their understanding of the legislation that defines TIC.

Their latest guidance (Sibert's link, dated 26 Jul 12) is interesting. They have avoided saying TIC = kWp of panels full stop, which has been their position to date. Perhaps they have realised their interpretation of the legislation to date is wrong?
 
I

Ian-LS

No, you are not being pedantic. From what I have observed of OFGEM's dealings with installers (luckily not with me) a phrase involving ar$e and elbow springs to mind to describe their understanding of the legislation that defines TIC.

Their latest guidance (Sibert's link, dated 26 Jul 12) is interesting. They have avoided saying TIC = kWp of panels full stop, which has been their position to date. Perhaps they have realised their interpretation of the legislation to date is wrong?

Only just picked up on this uodated guidance, so they have reissued guidance that was exactly the same as the guidance released last year? Despite them secretly behind closed doors and to a few installers saying that TIC = number of panels x the wattage. I'm not even suprised though really...arse and elbow indeed.
 

Eco Deal

Solar Guru
Messages
1,208
Location
Heywood Lancs
The SAP software is a simple case of using the array size in kwp , direction and shade factor.

The MCS can be used as documentry evidence ?

an DEA must use photo's or documents to prove somthing is their.
 

SibertSolar

Solar Guru
Messages
1,120
Location
Hampshire
Further info from Ofgem:

"...‘Plant’ is defined in Schedule A of Standard Licence Condition 33 as ‘any equipment, apparatus or appliance’.

The Feed-in Tariff legislation is silent on whether the TIC/DNC values are in AC or DC. We interpret the total installed capacity (TIC) of solar installations to be the number of panels multiplied by the panel rating.

From a Feed-in Tariff point of view, we interpret the DNC value to be ‘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.’

When assessing a ROO-FIT application, we must have regard for the definitions of TIC and DNC. The FIT Generator will declare the TIC and DNC of their installation as part of their application for ROO-FIT accreditation. In the main, we would consider the capacity rating of the generating equipment to indicate the TIC of the installation, with any other restrictions, such as capacity of connection limitations and parasitic loads, being factored into the DNC...."
 

BruceB

Electrician's Arms
Solar Guru
Messages
1,437
Location
Bath/Bristol
I will probably regret using up my life debating this point again, but here goes. Sibert's quote from Ofgem does not really hang together. Going to the definitions:

DNC: 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;

TIC: means the maximum capacity at which an Eligible Installation could be operated for a sustained period without causing damage to it (assuming the Eligible Low-carbon Energy Source was available to it without interruption), a declaration of which is submitted as part of the processes of ROO-FIT Accreditation and MCScertified Registration;

The substantive difference between them is the 'less the amount of electricity that is consumed by the plant'. The inverter is part of the plant (in bigger systems there might be ventilation and cooling apparatus also). The plant is part of the eligible installation. Therefore for TIC, the maximum capacity at which the eligible installation could be operated INCLUDES THE EFFECT OF THE INVERTER. So if the maximum an inverter can continuously produce is 3.6kW then the eligible installation will not be able to continuously produce above that, whatever the panels connected to it. So the TIC would be 3.6kW.

Ofgem are not interpreting it this way and the trouble is they and the suppliers can push the little guys (consumers and installers) around fairly easily. It might get tested in court if Ofgem and a supplier retrospectively try to reduce someone's FIT rate who they find is 'overpanelled'. I suspect most installers now would not want to take the risk of overpanelling and being later held to account. I suspect I would only do it now if I had a pushy customer who was himself a lawyer and willing to take them on.

In my view, Ofgem have backed themselves into a corner on this and do not want to lose face by revising their opinion, even though it is not backed up by the legislation.
 
I

Ian-LS

The good thing is that I think systems such as 4.5 kWp are now viable at the lower 14.5p/kWh rate due to the higher export rate and the fact the differnce used to be 21p and 16.8p/k~Wh and last year 43.3p/kWh and 36.8p/kWh
 

SibertSolar

Solar Guru
Messages
1,120
Location
Hampshire
I think you're spot on Bruce. I somewhat led the Ofgem contact I have into this with some loaded questions, as I was curious as to what their response would be. I even asked them to define "plant". It's not an area I would like to take them on in court but it does seem clear that there are conflicts in terms of understanding/definitions/implementation etc.
 
Status
Not open for further replies.

Permanent unswitched live colour?

  • Brown

    Votes: 46 65.7%
  • Black

    Votes: 24 34.3%

Electrician Talk

Top