Misleading fault indications [RE-wrenches]

Mark Frye markf at berkeleysolar.com
Fri Feb 29 17:18:29 PST 2008


Mark,

Perhaps you could respond directly to issues raised, will the DC negative to
ground fault persist and go un-indicated?
 
Mark Frye
Berkeley Solar Electric Systems
271 Vistamont Dr
Grass Valley CA 95945
(530) 401-8024
www.berkeleysolar.com
 

-----Original Message-----
From: Mark Edmunds [mailto:mark.edmunds at xantrex.com] 
Sent: Friday, February 29, 2008 5:00 PM
To: RE-wrenches at topica.com
Subject: RE: Misleading fault indications [RE-wrenches]


Wrenches,

I just saw this post, and it is truly flattering when a competitor tries
to call out your products with nebulous and unsubstantiated FUD (fear,
uncertainty, and doubt). So a few responses to the points raised: 

<<Using a fuse type GF protection system in a battery-less grid-tie 
inverter is reasonable to me >>
 
On this we can agree.  Xantrex alone has over 45,000 GT's fielded
worldwide and yes...the fused approach works for us, is code and UL
compliant, and also works for other volume players like SMA. We are
really happy that Outback views this as reasonable.  The whole grid tie
inverter industry is breathing a collective sigh of relief.  

 
<<If you want to talk about a real significant design problem - take a 
look at the fuse based GFP used on the Xantrex charge controller - if 
you have a low resistance ground fault from the DC negative to the 
grounding system it will not detect it - even though the GF fuse 
blows... which is not detected by the controller since the DC negative 
and ground are still connected. The PV array will still continue to 
produce power and the controller does not indicate a fault has occurred.

This does not meet the requirements of the UL1741 standard or the NEC in

my opinion.>>
 

Obviously this should be taken with a grain of salt.  Like we all
know...this is from a competitor serving their own objectives.  

Our fused GF detection approach is absolutely UL1741 compliant and,
similar to battery-less GT's, it does meet the spirit and intent of the
NEC.

Also, despite what Outback might want you to believe...virtually any
kind of fault with the XW charge controller will flag a fault indication
on the controller display AND on the system control panel.  In Xantrex's
opinion, you are far more likely to notice a message on your main system
display than noticing the position of a circuit breaker handle. Any
controller fault or even complete failure would cause it to disconnect
from the system and stop charging, along with the fuse clearing any
actual ground fault that might exist.  

Here are some additional thoughts that may lead you to question why
Outback is resorting to FUD to retain market share.
 

XW Charge Controller benefits:

-      Dynamic maximum power point tracking with no mini or full sweeps,
provides better energy harvest, especially in highly transient
conditions (sunny days with big fluffy clouds). Grid tie inverters
require a dynamic and accurate MPPT routine, why would anyone accept
less with a battery based system?

-      Convection cooled without sacrificing thermal performance.  Our
tests show that our thermal performance is better (full output current
to 45 C/ 113 F) while eliminating the possibility of fans failing.

-      Standard 5 year warranty with an option to upgrade to 10 years.
Outback only offers their optional 10 year warranty for California
Grid-Tie customers, since as Outback stated in a previous post,
"typically do not get the abuse that we see in the off-grid
applications". Xantrex optional XW Series Extended Warranty, which adds
5 years to provide 10 years total of warranty coverage is not specific
to California grid-tie customers. All installations within Canada or the
United States qualify, regardless whether they are off-grid or grid-tie.

-      Xanbus(tm) Network Enabled out-of-the-box. This means you don't
need to buy an Outback Hub ($195 MSRP ) or Mate ($295 MSRP) to get
charge controllers to share information, synchronize charging and
provide aggregated user level information. Again, saving installation
complexity and costs. 

-      Bundled battery temperature sensor; saves $29 (MSRP) as you don't
have to buy it separately as you do from Outback.

-      Built in PVGFP. This saves having to install the Outback breaker
approach saving $129 MSRP .  Since Outback has told you this is
wrong...is good for us.  I am guessing we will continue to have this
advantage since they can't go back now and rethink a safe and lower cost
fused approach.

 

Thanks for listening,

Mark


Mark Edmunds
Director Engineering
Residential Renewable Energy Group
Xantrex Technology Inc.


-----Original Message-----
From: Christopher Freitas --- OutBack Power
[mailto:cfreitas at outbackpower.com] 
Sent: Friday, February 29, 2008 9:21 AM
To: RE-wrenches at topica.com
Subject: RE: Misleading fault indications [RE-wrenches]



-------------

If you want to talk about a real significant design ...


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