Metering an Outback GT System [RE-wrenches]

Darryl Thayer daryl_solar at yahoo.com
Sun Dec 31 21:39:21 PST 2006


Hi Keith
you probibly have the answer by now, but I have used
an outback system where on one leg of a split phase
(120 volt) system a 240 volt cyclops reversing meter
has one meter leg in the (input-output) of the Outback
and the other meter leg in the output leg of the
Outback.  When the power just passes through the
Outback (input/output equals output) the meter reads
nothing, when the Outback consumes power the meter
reads negative and when the Outback puts power into
the system it reads postive.  (A non reversing meter
would only read the solar contribution)

For your case (240 volt both legs) you would need to
use two such meters one for each leg of the split
phase system.  To know the contribution, the meters
would be added together.

If you use an analog CT meter take one CT on the
input/output and connect it antiparallel with a second
CT on the output, do this on both Legs.  Then the CTs
cancel when the input/output and output are equal. 
The analog CT meter must be reversing to compensate
for Outback consumption, but only one way for just the
output of the solar.  
Darryl

--- Keith Cronin <kcronin at islandenergy.net> wrote:

> 
> 
> I am looking for some suggestions for the following
> scenario:
> 
>  
> 
> We installed a 10kW PV system with Outback with
> 3048's, 12- 8D's on a
> clients home that generally uses a lot more energy
> than the system makes.
> They have a 400 amp service to the home and we have
> one dedicated panel for
> emergency loads in the event of a power failure.
> They are not confident the
> system is working to spec, and want to get the
> numbers tighter.
> Unfortunately, their energy consumption falls into
> the category of a small
> commercial client, and we have not had the privilege
> of ever knowing what
> their initial electrical bill was, due to the home
> being brand new.
> 
>  
> 
> The challenge:
> 
>  
> 
> What is the best method for aggregated/cumulative
> energy created by the
> system, that is being sent to the sub panel and also
> being sent back thru
> the input-output of the system?
> 
>  
> 
> We did put a CT type Osaki meter on the outputs to
> the sub panel to "read"
> what the system in the home is using, but are at a
> crossroad on the input-
> output portion due to the Outback's can sell on
> their input breakers.
> 
>  
> 
> We do have a mate and 3 MX 60's, but the client is a
> bit older, and can't do
> the base calculations. 
> 
>  
> 
> Feedback appreciated!
> 
>  
> 
> Keith Cronin


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