Dti Guide

[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.

 

[finchy]

Lol - like your take on sap solar king. Sounds about right.

 

[infinity]

Does anyone have anymore info regarding the release of the DTI?

Is anyone following the decision tree procedure regarding bonding the frame work? It makes sense to me.

 

[Worcester]

We reprinted it and laminated it so that it was simple to follow

 

[Worcester]

Extraneous-conductive-part - A conductive part liable to introduce a potential, generally Earth potential, and not forming part of the electrical installation.

If it's on a wooden / slate / tile roof is it likely to introduce Earth potential? ...

 

[jason121]

Question
If you connected 10 panels at 37v voc and giving 370v,
Would you get a shock if touch the live DC only???

 

[Worcester]

Not if it double insulated as you don't have a potential difference.
Same as you don't get a shock if you touch one side of a car battery, put both terminals of a 9V PP3 battery on your tongue.
And why birds don't get fried on the overhead lines.

 

[Gavin A]

Does anyone have anymore info regarding the release of the DTI?

Is anyone following the decision tree procedure regarding bonding the frame work? It makes sense to me.

since about August / september last year.

The old guide made no sense at all anyway, so we'd been thinking about stopping doing the bonding anyway when the new DTi guide came out and confirmed what we were already thinking.

 

[jason121]

Not if it double insulated as you don't have a potential difference.
Same as you don't get a shock if you touch one side of a car battery, put both terminals of a 9V PP3 battery on your tongue.
And why birds don't get fried on the overhead lines.

so were does the threat of shock come into play if the DC comes into contact with the rails ? or am I being thick ??

 

[Gavin A]

the threat of shock comes for the installer if one pole was connected to the rails (eg by a cable trapped by a panel), AND they also managed to be touching the other pole somehow at the same time as touching the rail. That'd complete the circuit, and give the installer a belt.

Quite hard to do mind, but possible.

 

[jason121]

wouldnt that create a short circuit
Top rail live bottom negative fault flow thru panel ??