[RE-wrenches] Nabcep - grid tie---Off grid

[Windsun@wind-sun.com]

I have to agree. We have done off-grid for 30+ years, so it was a very 
simple transition for us to also do on-grid because the system design and 
configurations are much simpler.

Over the past few years we have seen more mistakes by those that are only 
grid-tie familiar or certified when designing off-grid. I think the single 
most common mistake they make is to use the yearly average insolation 
instead of worst case. Other very common mistakes we see in the many systems 
we have refurbished or redesigned are failure to account for battery 
temperatures vs capacity and charging, proper battery sizing, and phantom 
loads.

Apparently NABCEP does not go into off-grid systems very deeply, perhaps 
because the market is smaller and they can be much more complicated.

..................................................................................................
Northern Arizona Wind & Sun - Electricity From The Sun Since 1979
Solar Discussion Forum: http://www.wind-sun.com/ForumVB/
..................................................................................................
----- Original Message ----- 
From: "Dana" <dana at solarwork.com>
To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
Sent: Tuesday, November 24, 2009 9:40 AM
Subject: [RE-wrenches] Nabcep - grid tie---Off grid


> Just got to weigh in on this one.
>
> It cracks me up to see the grid tie generation's attempts at off grid
> design. It is such an experiential design mode. It can be conceptually
> taught in a class. But it has to be lived to really be made whole. The 
> finer
> OG designers I know have almost all lived off grid. It is like 
> transmission
> repair mechanics! I used to do tune-ups and do a timing chain on occasion
> long ago, but fix a transmission, either automatic or manual, forget it, 
> not
> me as it was to specialized.
>
> Perhaps you have a good idea here, Jay. I hate to see an additional layer
> added here but you bring a good point to light. I am currently the #4
> designer to work on both a SHW and Grid tie with battery backups that do 
> not
> work and the battery bank is cooked and was not large enough to do much 
> more
> than a couple of hours of back up at most though the client was promised
> that it would support the house for several days. It is sad to see people
> taken by NAPCEP Certified and non certified installer/designers who wade 
> in,
> make more of a mess, charge a bucket load and wander off citing the owner 
> is
> asking too much.