[RE-wrenches] Third Radian

Tue Apr 25 23:03:03 PDT 2017

Matt:

I have a question for you:  I have often considered mounting Class T fuses
directly to a bus bar as you have done.  Are you ever worried about physical
strain on the fuse itself without a fuse holder?

Thanks again for all of your input.

William Miller

Lic 773985
millersolar.com
805-438-5600

-----Original Message-----
From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of Matthew Sirum
Sent: Friday, April 21, 2017 4:20 PM
To: re-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] Third Radian

Greetings William,

I worked through this issue a little while back while designing and
installing a five Radian GS8048A system.  I designed a custom DC Bus System
which included two 1,500A, 150mV shunts.  One for metering DC to and from
the Radian inverter/chargers, and one for metering combined charge
controller production to the battery system.

Below I have copied and pasted a couple of sections of text from OutBack
Application Notes which you may find helpful.  I do not know if using a mix
of differently rated shunts is an issue or not; such as one 1,000A, 100mV
shunt and two 500A, 50mV shunts.  It is best for you to speak directly with
Applications Engineering at OutBack to inquire and confirm details for your
project.

Also; I suggest trying to find out from OutBack when the next generation
MATE System Display & Controller will be available.  The
MATE3 has a number of limitations and issues which will hopefully be
resolved with the release of the new MATE product.  It would be great if you
could get the new next generation product and not have to work with the
MATE3...  Assuming the new MATE will be better than the MATE3 and you would
be upgrading to the new MATE eventually.

Also to note with multi Radian systems, or I believe any battery based grid
interactive inverter system with multiple inverters which have H-bridge
electronics architecture; the AC energy may flow to and from the inverters
sharing a common AC "Grid" combiner and AC "Out"
combiner.  The Radian's AC "Grid" and AC "Out" terminals/connections are
common with each other when the inverter is "selling" in Grid-Tie Mode.
This allows energy to basically circulate to and from the multiple inverters
in the system before/as it is exported to its grid connection.  This affects
the MATE3 metering and graphing.  The more inverters and power capacity in
the system the more this is noticed and the more the kWh values may be
effected.  I believe this may also effect system energy production
efficiency as well.  This issue is recognized in whole house back up systems
and may not be noticed or as evident in systems with dedicated loads
continually served from the AC "Out" connections.

I have attached 3 pictures of my custom DC Bus System with the two shunts
for reference.

This (below) from an OutBack FLEXnet DC (FN-DC) Application Note
(FA‐RP‐12/14/15):
"A Note on Current Shunts
Although OutBack products come equipped with 100A and 500A current shunts,
the FD-NC has the ability to work with shunts as high as 1000A. The only
requirement is that the voltage and current ratio
(resistance) of the shunt remain the same. For example, the 500A shunts have
a ratio of 0.0001 at 500A and 50mV. A 1000A shunt should have a voltage of
1000A at 100mV."

This (below) from an OutBack Application Note entitled "Wiring and Combining
Methods for Multi-Inverter Systems" (R1-RL-8/14/15):
"Shunts and battery monitoring
As with smaller systems, a separate shunt is needed for charge controllers
and inverters in order to monitor loads and charging sources on separate
battery monitor channels. When selecting a shunt, keep the following design
considerations in mind:
1) A/V Ratio The ratio of amps to volts for a shunt must be 10,000:1 for
systems using the OutBack Power FlexnetDC (FNDC). An example of a suitable
shunt is one rated at 1,000A and 100mV.
2) Amps rating Shunt manufacturers recommend that a shunt not be loaded to
more than 66% of its rated capacity. This derating, combined with the
maximum 100mV limit on the FNDC, dictate that the largest recommended shunt
be rated at 1500A, 150mV.
3) mV rating The voltage drop across the shunt when passing the maximum
current for which the shunt is rated. For the FNDC, the maximum voltage drop
across the shunt should not exceed 100mV. That does not mean the maximum
shunt size is 1000A at 100mV. Taking into account #1 and #2 above, the limit
is 1500A at 150mV with a usable current limit of 1000A. This ensures the
maximum voltage drop across the shunt is 100mV (when passing 1000A).
4) Dimensions Ensure that the dimensions of the shunt are compatible with
the bus bars specified and that the assembly (bus bars + shunts) fit on the
backplane of the enclosure.
The shunt design considerations above, combined with the FNDC’s maximum
current monitoring limit of 1000A per channel essentially limit the system
size if FNDC battery monitoring is to be included.
Practically speaking, this limits systems that are to include FNDC battery
monitoring to:
a) At most five GS8048/GS8048A inverters or ten 3.0kW FXR inverters
b) The same limits on FNDC battery monitoring limit the system to at most
twelve FM80 charge controllers. Due to the 1000A current monitoring limit of
the FNDC, large systems will have to be split up into smaller sub-systems.
For example a system with 10 Radians and 20 charge controllers could be
split into two sub-systems. Each would have five Radians, ten charge
controllers and an FNDC. This would keep the current seen by each FNDC
channel to below 1000A."

I hope some of this information may be helpful.  OutBack may have removed
some of the Application Notes regarding larger multi Radian systems from
their website.  Give a shout if you can't find what you need, I may be able
to help out and send you what I have on file.

Best regards,

----MATT

Matthew Sirum
P.O. Box 1227
Greenfield, MA 01302-1227  USA
phone: +1.413.773.0611
email: MatthewSirum at gmail.com

--------  Original Message Below  --------

[RE-wrenches] Third Radian

William Miller william at millersolar.com Thu Apr 20 20:16:12 PDT 2017

Friends:

I am designing our first three 8K Radian stack.  I think I have a good
handle on the plumbing and wiring but I was wondering about one thing:
With three Radians and a PV recombiner, we are out of shunt ports on the
Flexnet DC.  Have any of you dealt with this?

My proposal is to gang the negatives for two or three Radians and run them
through a 1000A/100mV shunt.  The ratio is the same as the 500/50 offered.
Will the FNDC accept that analog input?

Any other considerations that might not be realized at first?

Thanks in advance,

William Miller

[image: Gradient Cap_mini]
Lic 773985
millersolar.com <http://www.millersolar.com/>
805-438-5600