Dti Guide

[moggy1968]

got my inspection tuesday
are we now working to the new guide yet, does anyone have a link?
I can only find a provisional document

 

[Gavin A]

someone will post the link shortly, but this blog post from one of the authors is relevant if you're referring to the earthing of the array frame etc.

[h=2]Array frame earthing and transformer-less inverters[/h]One reason I am frequently asked about the publication date for the new guide is due to the proposed changes to array frame earthing on systems with transformer-less inverters. This section of the guide has not changed significantly from the published draft and I do not foresee any alterations prior to publication. As the new (draft) guidelines are widely accepted throughout the industry many of the MCS certification bodies (eg Elecsa) permit installers to operate to the new guidelines. My message to any installers who ask about this, is to suggest talking to their certification body and seeing if the CB can provide, in writing, that you can follow the new guidelines.

Solar PV installation guidelines - The solar PV blog » The solar PV blog

 

[moggy1968]

Frame is earthed anyway (fronius 3.6 TL used) but need to show him I have up to date documents.

 

[Gavin A]

ah right, ok, well in that case you aren't working to the draft guide anyway, in which case the 2006 version is still the official guide, and you're still working to it, so there shouldn't be a problem.

 

[yellowvanman]

Check out GN7 which has been updated for Amd 1, decision tree states that it needs bonding if extraneous or earthed if the frame is an exposed conductive part.

In the introduction to this special location it refers to the DTI Guide (2nd edition) and says that it is currently being re-written as the Installer Guide to Photovoltaic Installation 978-0-901452-48-1 - under the auspices of the MCS scheme.

There is also a decision tree on RCDs as well!

 

[SRE]

Has the new v3 DTI Guide been issued yet? I haven't seen it but noticed that some of the training providers were offering training last week for it (not that I'd be spending cash on training when I've got plenty of time to read it this time!!) I just wondered if I'd missed it and if I haven't how can you do a training course on a guide that hasn't been published?

 

[JulianC]

Had my assessment last Thursday (passed with no non-cons and assessor thought our installation was 'outstanding', since you asked :cowboy::biggrin5 Anyhoo, I'd just got back off me hols in the early hours of the day before so I asked him if we were working to v3 yet. The answer was no and he didn't have a clue when it would be issued, although it was supposed to be 1st Oct.... <edit> he did mention something about the DTI guide and MIS3002 being merged into one document </edit>

Training companies seem to be manure powered these days...

 

[Worcester]

he did mention something about the DTI guide and MIS3002 being merged into one document

I'd be suprised if that happened, as of course systems > 50kWp aren't covered by MCS... also the problem is that the DTI Guide, is just that - a guide, whereas the MCS tends to be legislative and not open to interpretation. I may be wrong as of course it was issued through the MCS website ..... Worcester rambles off into the distance ....

 

[Gavin A]

I had a long chat with one of the main authors a few weeks back who said it was all done other than their revision of SAP, which I suspect is still the stumbling block, as IMO their proposal is only marginally better than the previous abomination. They seemed not to know that there can still be massive differences within a region eg between the Yorkshire dales and the Yorkshire east coast there can be up to a ~25% difference in the average number of sunshine hours per year, yet these locations would all be treated the same under the revised version of SAP.

I pointed out how utterly useless this was, to the response that they needed to find a reasonably simple method of estimating performance... so they've gone for simplicity over accuracy.

 

[finchy]

I guess back when they started to dream up the change the industry was in a much better shape, with 10000 installs a week. Rogues and gold miners were signing up to MCS in there hundreds. Such a different landscape now, being back to a cottage industry things now take longer. Why rush.... ! Greg Barker the butcher of solar doesn't give a hoot, his moved on to the green deal now.

 

[Eco Deal]

when is the new SAP in force?

where can you see the new calculation ?

 

[Eco Deal]

a point about the green deal you may not know you can get the FITS from the green deal if you make a contribution to the install cost .

so if you pay say 50% of the installation you will get 50% of the FITS.

 

[Gavin A]

I thought you'd get all the FIT because green deal is charged at commercial interest rates and therefore not state aid.

why would anyone use green deal for PV if it reduces the FIT income?

 

[The Solar King]

SAP 2012 has been available in draft form for about a year. There is a new method of calculating irradiance based on postcode. There is no reason why this could not be refined further to satisfy Gavin's point. Irradiance is not the same as sunshine hours. It is better than SAP2009 but not perfect. The calculation is fun to say the least.

DTi 3 will be called something like the ECA guide. It should have been published by now. I was asking at Solar Power UK about the delay and was unable to get a straight answer. I know there are concerns in other technologies about the plethora of standards, (eg MIS and BS/EN) and what ends up taking precidence. Worcester is right to point out it is a guide, but it is the one we are measured against.

 

[Gavin A]

I'm seriously thinking about refusing to even use sap at all, see if they'll actually try to sanction us for using a more accurate method of estimating performance that we can back up with data from dozens of installations, and warranty to be within 5% of our estimates (allowing for variations in irradiance).

 

[finchy]

Hmmm I would stick to SAP - REAL might raise concerns with anything but !! It really is stupid why more accurate models can't be used, including outlined 20 year
forecast models, they should also publish variables each month. This would ensure level playing field with the financials. So customers can focus on the actual quality of the system!

 

[The Solar King]

SAP2012 breaks down irradiance on a monthly basis for each of the 21 areas defined for the UK.

Personally, I would rather give a customer a figure that under estimates by 10% than risk a situation where a customer is disappointed with the performance of their system.

Do not forget, there can be more variation when an installation is not optimum through orientation, horizon or shading.

 

[finchy]

I already use the monthly levels in my performance sheets which is available on SAP2009.

Yeah the fact we always beat sap, gives me some margin of error. I'm in the process of analysing customers Actuals vs sap and pvigs.

Also consider a poor spec system which results in shading knocking the whole array out due to wrong inverters. Micro/optimisers are the way forward.

 

[Earthstore]

The thing with any projections for performance, whether it is for 12 months or 25 years, is you can manipulate the figures to be whatever you want them to be, even with using SAP, as inaccurate as it may be.

Personally, I believe it is best to use SAP, as it should be used, then show them how all your other systems have out performed it, even get them to ask your existing customers for even more credibility.

You could also offer two sets of returns, SAP and knowledge of what you believe their system will produce, weather permitting of course.

 

[Gavin A]

Do not forget, there can be more variation when an installation is not optimum through orientation, horizon or shading.

yes, so why not use an accurate method of estimating their impact?

Sap is a disgrace. It's like half arsed undergraduate uni project that got turned into a standard that we're all forced to use because those in power decide that we have to dumb down the industry to the level that any bloke off the street can understand after half an hours training as part of a 3 day course.