Xantrex XW60 CC MPPT any feedback Yet ?

nigtomdaw

Has anyone installed a XW60 mppt cc yet and formed any opinions as to is performance, uesability, functions, display information. Im aware that one person bought half a dozen and complained about the knockouts being difficult to remove , anyone else got an opinion of these new units,,,,while Im at it, has anyone got a Flexmax 80 upand running ?

tim

Re: Xantrex XW60 CC MPPT any feedback Yet ?

I've installed the xw in my system,1080 watts evergreen 180 panels. Only had 1 and1/2 hour of sun since installation.Did see a peak of 1141 watts during this peroid ,is this possible. The ground fault fuse is almost impossible to change when fully wired

Tim

Windsun

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Yes it is possible to get more than the rated panel wattage in cold weather.

tim

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Windsun

Thanks for the xwcc. have also found it easy to program.



Tim

Brlux

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Any idea/opinions on how this compares to the new Outback FLEXmax 80?
The FLEXmax is rated in maximum controller output current 80A which is easy to understand.
The XW60 is rated as maximum panel Ics 60A which under certain circumstances where a large voltage conversion is taking place it could result in an output current form the controller in the hundreds of amps? Which I find to be unlikely within it's capability's and makes it difficult to compare products.

niel

Re: Xantrex XW60 CC MPPT any feedback Yet ?

brlux,
i'm not sure where you're going with this as both controllers windup with higher currents when voltage downconverting and are limited in their output currents to each of their respective output current ratings. are you making an accusation towards xantrex?

Solar Guppy

Re: Xantrex XW60 CC MPPT any feedback Yet ?

XW-60 is 60 amps output limited, note the 60 amps is without the use of any moving parts ( fans )

All the other 60/80 amp models out there ( Outback , Apollo ) uses fans

crewzer

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Unfortunately, inconsistent specmanship places consumers into a difficult apples-and-oranges situation, and it can indeed make it difficult to compare products.

The NEC defines "maximum array current" as the array's STC Isc x 125% [ref NEC 690.8(A)(1)]. Allowing for this multiplier, the XW60’s maximum input current spec of 60 A Isc means that the array’s STC Isc mustn't exceed 48 A. I find the manual’s discussion of this issue (Page 2-2) to be confusing at best. On the plus side, as indicated, the XW is rated for 40 C operation without a fan.

The OutBack MX60 shares this same 60 A Isc / 48 A Isc input specification, along with the “official” 60 A output current spec. The MX60’s output can be user adjusted for up to 70 A output. However, it is fan cooled, and the output current must be derated above 25 C (77 F). The derating curve is included in the latest MX60 manual, along with a discussion of the 60 A Isc / 48 A Isc issue (page 82).

The new OutBack FLEXmax 80 is rated for 80 A output current at 40 C. It’s still fan-cooled, although the fan is apprently a higher-quality unit than before, and the convection cooling path seems to have been improved as well. The maximum Isc input is 64 A (manual page 10), which equates to an NEC equivalent of 80 A Isc.

HTH,
Jim / crewzer

Brlux

Re: Xantrex XW60 CC MPPT any feedback Yet ?

No, I'm making no accusations, I was just confused about capability's. The outback controllers state a maximum output from the controller where as the XW60 only advertises a maximum input current. I was trying to say the maximum input current seems to be of less relevance to the consumer than the output current because of the down conversion process. It seems as though under most circumstances you will be constrained by the output current before the input current will be a problem. Are you saying the XW60 has a 60A maximum output current as well as the 60A input?

Thanks
Brlux

Solar Guppy

Re: Xantrex XW60 CC MPPT any feedback Yet ?

I'm not sure how crewzer's ratings come into play, first I ever head of the wire derating being applied to the internal electronics. All Mppt charge controllers limit based on output current and most don't even have circuits to measure input current let alone limit to it.

Now the XW60 can do 100% duty cycle, the MX60 doesn't so it is possible to have Input and Output current the same on a XW60, I think the MX60 is limited to about 98%.

From your prospective, pick what ever box you like, but they are all limited on the current they provide to the battery and its 100% apples to apples, they all regulate to output current.

Brlux

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Ok thanks, my original has been answered and it was that the lack of advertising of the maximum output of the WX60 makes it difficult to compare apples to apples.

crewzer

Re: Xantrex XW60 CC MPPT any feedback Yet ?

I'm not sure how crewzer's ratings come into play, first I ever head of the wire derating being applied to the internal electronics.

The 690.8(A)(1)125% NEC multiplier is used to calculate maximum photovoltaic source circuit current. The NEC considers this maximum current to be continuous [690.8(B)]. This continuous maximum current should not be confused with the separate and additional 125% factor (minimum) required by NEC 690.8(B)(1) for derating wire ampacity.

HTH,
Jim / crewzer

nigtomdaw

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Wow see Wayne I told you !

Solar Guppy

Re: Xantrex XW60 CC MPPT any feedback Yet ?

crewzer wrote: »

The 690.8(A)(1)125% NEC multiplier is used to calculate maximum photovoltaic source circuit current. The NEC considers this maximum current to be continuous [690.8(B)]. This continuous maximum current should not be confused with the separate and additional 125% factor (minimum) required by NEC 690.8(B)(1) for derating wire ampacity.

HTH,
Jim / crewzer

Got my code book out

690.8 (1) exception and (2) exception: Circuits containing an assembly, together with its over current devices(s), that is listed for continous operation at 100% percent of its rating shall be permitted to be utilized at 100% of its rating

The overcurrent protection is electronic in this case and allows in the XW's case input and output currents to be 60 amps.

690.9 Overcurrent protection ( C ) would address specifiy the XW-60's case as to get 60 amps one would have to have a fused/breaker combiner between the array and the charger.

So the wiring has to be 125% rated current, not the charger as its exceptioned to being listed for 100% operational of it input current as Xantrex has listed the unit properly

crewzer

Re: Xantrex XW60 CC MPPT any feedback Yet ?

I agree that the second 125% multiplier [NEC 690.8(B)(1), wire derating] doesn't apply to the XW or the MX due to their current limiting features and the relevant exceptions in 690.8(B)(1) and (B)(2).

However, those exceptions apply to their specific article sub-parapgraphs, and not to 690.8(A). Accordingly, it remains my position that the first 125% multiplier [NEC 690.8(A)(1)] does apply for the purpose of calculating and defining "maximum" PV array circuit current. I believe the purpose of this initial multiplier is to allow for occasional though very real current excursions due to environmental conditions (i.e., edge-of-cloud, or surface reflections).

My position is hardly novel. Here are Apollo’s comments from their T80 instruction manual:

The T80 is designed to handle a maximum input current of 70 amps and a maximum output current of 80 amps – both of these ratings are continuous at 40 C… When calculating the maximum input or output current, remember to add 25% to the rated current of the PV array, this is the NEC required “headroom” to account for the PV’s ability to produce more than the rated output under some conditions... For the T80 the maximum allowable PV array according to the NEC would have an Isc of 56 amps.

Here are Morningstar’s comments from their TriStar instruction manual:

There are two standard versions of TriStar controllers:
TriStar-45: Rated for maximum 45 amps continuous current
TriStar-60: Rated for maximum 60 amps continuous current

To comply with the National Electric Code (NEC), the current rating of the controller for solar charging must be equal or greater than 125% of the solar array’s short circuit current output (Isc). Therefore, the maximum allowable solar array input to the TriStar controller for compliance with the NEC is:

TS-45: 36 amps Isc
TS-60: 48 amps Isc

Here are OutBack’s comments from an MX60 manual:

The largest PV array that can connect to an MX60 should have a rated short-circuit current of 48 amps STC (Standard Test Conditions)

To meet NEC compliance, the largest PV array that can be connected to the MX60 should have a rated short-circuit current of 48 amp

Regards,
Jim / crewzer

GreenerPower

Re: Xantrex XW60 CC MPPT any feedback Yet ?

To clarify Jim's points:
* If the PVs are connected to the CC directly without breaker, then 125% Isc applies to not exceed the CC's nameplate current rating to meet NEC.
* However, say if 48A Isc limit for a 60A CC would force you to need 2 CCs for your array, you can introduce a 60ADC breaker on the input side of the CC and can feed it with a PV array with 60A Isc. This still meets NEC since the CC is protected by this breaker. Just that you would waste PV energy on those days that refections or edge of cloud effect might let the PVs produce more than 60A. Note also that the CC (like MX60, XW60) limits the output to 60A so that the input drawn would not exceed 60A to trip the breaker. But this might cause the breaker to trip for PWM type CCs (non DC-DC converter type).
GP

Solar Guppy

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Well, Crewzer is correct, the NEC, as silly as it is makes every single charge controller only 80% of the true rating. I don't feel to bad, the compliance team at Xantrex went thru full CSA approval and didn't catch this.

Xantrex is in the process of updating the specs to not exceed 48A input current on the input side, even though its fully approved for 60A ... gotta love the NEC to make sure we don't harm ourselves.

I have also been told this is a ongoing battle with John Wiles and the manufactures, who is the sponsor of most the NEC 690 code.

crewzer

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Henry,

Thanks for making the extra effort to further research this issue. To me, it's not personally important that "I'm correct". What is important to me is that we share a common understanding of the "whats" and "whys", and that we use that information to develop better codes, products, designs, and services.

Thanks again,
Jim / crewzer

GreenerPower

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Solar Guppy wrote: »

...Xantrex is in the process of updating the specs to not exceed 48A input current on the input side, even though its fully approved for 60A ...

This is ashamed IMO. I think they should spec it as an (independent) electrical component. If it is capable for 60A DC continuous, that should be its spec. The system installer/integrator should be responsible for matching/selecting components - PVs, wiring, breakers, CC, inverter ... to satisfy codes.
I think the current XW-MPPT60-150 manual is fine (for the most part). Other considerations like the 48A Isc for PV should be in something like "PV application notes", IMO.

XW60 manual wrote:

Page 2-2:
Important: The Isc (short circuit current) rating of the array must not exceed the 60A input current rating of the Charge Controller at any time.

Ensure that the Isc rating under all conditions does not exceed 60A. A factor of 1.25 is appplied to the rated Isc at 25 C when the panel is colder than -21C.

Page 2-9:
The Charge Controller PV input is rated for 60A maximum Isc.

I would omit the "Isc" in the last sentence. This would allow the CC to be used at 60ADC for other DC applications like wind, hydro, fuel cells ...
GP

crewzer

Re: Xantrex XW60 CC MPPT any feedback Yet ?

I would suggest the manual’s wording look something like this:

The XW-60 is rated for 60 Amp operation at up to 40 C ambient. The National Electrical Code (NEC) Article 690.8 defines PV array current as 125% of the STC rated short-circuit current, or Isc. The justification for this definition is that a PV array can and will occasionally deliver output current greater than its nameplate specification. The Article also defines this calculated current value to be continuous. Accordingly, the XW-60’s input current rating of 60 A must be derated by 125% for PV applications, and the total STC Isc rating of a PV array connected to the controller must not exceed 48 A.

HTH,
Jim / crewzer

BB.

Re: Xantrex XW60 CC MPPT any feedback Yet ?

This reminds me of the NEC/NRTL arguments I used to have when designing computer systems...

From my humble point of view, there is a pretty large disconnect going on here.

The Solar Charger/Inverter is rated to manage up to 60 amps of input power (and XX amps or XXXX watts of output power). This has no relationship to the about of input current/power available as both major brands are "self regulating" in terms of current/power throughput and neither will fail if "exposed" to current in excess of their input ratings (Xantrex for sure, I remember them stating that they will simply limit power to safe rated levels--I believe that Outback also self regulates too).

To take a side trip here, when we look for appliances, I don't plug my laptop into a 40 watt maximum outlet, or plug my 200 watt TV into a 200 watt max outlet, or my 1,000 watt heater, etc... They all plug into a US standard 15/20 amp 120 VAC service with a maximum rating of 10,000 amps of short circuit current available (limited by magnetic flux/saturation by the transformer on the pole).

So, back to the Inverter/charge controllers--they are (or at lest should be) rated for power use and should be rated as being safely connected to a circuit with XXX amps of available short circuit current available.

Going back to AC house wiring, the main panel circuit breakers are rated to interrupt 10,000 Amperes. The safety ground wires (as I recall from decades ago--I could be wrong) are rated for a minimum of 6 awg bare (or 8 awg insulated--and some deratings for length if long runs--IIRC this was for a 125 amp service) and are rated to safely pass enough current to trip the upstream breaker--125 amps in this case.

These breakers and ground wires (and by extension house wiring and appliances) all rely on a cascade of protections--and do not force (IMHO unreasonable) operational/protection requirements on any one particular piece of equipment.

The Transformer is protected by design to 10,000 amps maximum, the drop wiring is sized for maximum continuous load and to handle a 10,000 amp short term surge, the house main breaker and branch breakers are sized to both interrupt 10,000 amps, pass enough current to trip the local breaker, and pass 100% (+/-) of rated current. The house wiring is sized to pass 100% rated current to the outlets and enough current to trip the branch breaker. The device cord is sized to pass 100% of rated device load and enough current to trip the upstream protective device (notice that you can use 16 awg cords on a branch circuit that is wired for 15-20 amps with 14-12 awg house wiring). By the time you get to the device, it is built by design to not draw more than its designed current and to "safely fail" (for now, assume no fire or shock hazards).

And the safety ground from the outlet to the main panel ground is sized to pass enough current to trip the branch breaker without failing, and the main panel to earth ground is sized large enough to ensure that the main service breaker is safely tripped.

So, back to the solar arrays... The wiring should be sized to handle 100% of the rated power plus safely manage the maximum over current as defined by either the source's ability to supply current and/or by the protective device feeding the downstream device. So, in the case of solar arrays, the wiring should be sized by the Isc+125% and/or the protective device should be sized to insure that it can break the maximum current available from the solar panel (with batteries, this is a problem as they have very high currents available--virtually never a problem for the standard home solar array system).

And, I would even go farther that the array wiring only needs to be sized as the same size as a safety ground wire (don't have an NEC book handy, but IIRC for a 125 amp service that insulated ground wire would only need to be 8 awg)--which is much smaller than the normal NEC rating requirements for standard AC branch circuit runs (again, if I remember correctly).

So, back to the device itself. I have a little 40 watt power brick on my laptop right here. There is no way in heck that it can sustain a 15 amp internal short circuit as would appear to be required by the 60/125%=48 amp interpretation of NEC for the Xantrex requirement.

Instead, the little power brick is designed to use 94V2 or 94V0 flame rated printed circuit boards, may (or may not) have an input fuse (not required). And the plastic case probably has some metal for heat sinking and protection. And the case of the brick is (or should be) made with a flame retardant plastic.

I don't care if the device is a solar charge controller, a Grid Tie inverter, an electric motor, a computer power brick, or anything else. The devices are safe to run at their ratings and will not exceed safe operating conditions as long as the input conditions (voltage, frequency, wave forms) remain within specified limits.

The only requirement is that they operate and fail safely with specified limits and that if the input source exceeds any of those limits, then it is the responsibility of the "facility" to provide upstream protection for the wiring and device.

So, getting back to "brass" tacks--what is the maximum ratings of the input box to the Xantrex Grid Tied inverter. That would include the size of the knockouts, the volume of the wiring/junction box and the wiring attachments. Notice (as far as I recall) there is no condition on the operational requirement of the device (other than that the terminal/j-box ratings must support that current/voltage). How the device under load fails (pop internal fuse, pop a trace, pop a transformer winding, etc.) does not matter--The only thing that matters is that the device under load fails "safely".

There can be some hand waving on whether or not the input current rating of the branch wiring for the Xantrex GT Inverter needs to be Iinverter-rating (not Isc or Isc) Irating*125% (as I recall, there were some exemptions where you could run at 100% of rated circuit current for some specialized installations)--but in actual design and operation, pretty much everyone well oversizes their input wiring to keep voltage drop/I^2*R losses to a minimum and using 125% (or even 125%*125%=Isc over-rating * Branch over-rating) ratings are going to easily met (in all but the shortest solar panel wiring runs).

So--the end results of my argument is that if the Xantrex unit (for example) is rated for 60 amp input maximum and the unit self regulates to 60 amps maximum, then I do not see a reason to run 48amp*125%=60 amp wiring from the solar panels to the inverter and limiting the solar panels to Isc/Imp of 48 amps.

Instead, I would suggest the system be designed for 60 amp input, the wiring should then be sized to 60amps*125% NEC branch circuit rating. And check the Isc*125% (fine with me) against safety wire requirements (if I am correct that safety ground requirements allow smaller awg wiring)--and use whichever requires the larger awg. It gets a bit more complex if there are combiner boxes and series protection required for parallel strings--but that is beyond my basic argument here.

For the solar panels, I would design them for Imp (or even higher--as 99% of the time most installations very rarely see Imp and 10-20% larger arrays will rarely be limited in harvest capacity in temperate climates--and in any case the GT inverter will self limit its total power conversion).

And in the case of failure (shorted input on the Xantrex inverter, or failed wiring insulation), then normal NEC design/installation requirements should easily and safely handle those abnormal conditions.

As always, this is my own opinion and is not a recommendation for anyone to violate NEC/NRTL/Building/Fire codes.

-Bill

Solar Guppy

Re: Xantrex XW60 CC MPPT any feedback Yet ?

From what I hear we can place this blame squarely at one person, John Wiles, who somehow is the author for the 690 NEC code stuff. If you can't change his mind, it won't ever change.

I've read allot of his writings and to this day I don't understand how he got to be the gate keeper for this stuff.

I think anyone who designs electronics would simply shake their head as it has no factual basis for this Isc+125% stuff. If UL or CSA lists a device for X amps , its a safe device, period. NEC should for wiring and distribuation only.

BB's analogy to home wiring is dead on, I guess lucky for everyone Wiles hasn't been allowed to re-write the code on home appliances :cool:

A little on the background on PV and NEC

http://www.homepower.com/view/?file=HP120_pg102_CodeCorner

it also has links to where John works ...

http://www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/C-S-Resources.html?agree=agree

This is one of the "code corner" docs written by John in 1991.

code corner 21, J Wiles wrote:

Unfortunately, in PV power systems there are few UL listed
products and therefore the standards and the interface control that
UL listing implies do not exist. The National Electric Code is the
only recourse available for designing and installing PV systems
with some degree of safety.

Well everything is Now UL listed, but someone doesn't want to give up regulating something that have never been in there domain to begin with

http://www.nmsu.edu/~tdi/pdf-resources/cc21.pdf

BB.

Re: Xantrex XW60 CC MPPT any feedback Yet ?

By the way, fixed my post above where I was trying to type about branch wiring ratings based on inverter input current and not Isc ratings per say. (fixes in bold).

Well, that 1991 statement by Mr. Wiles was only sort of operative at that time and did not really apply to NEC anyway...

NRTL's (like UL) are an outgrowth of the insurance industry. The basic UL documents (as I see them) are 1) design guidelines, 2) a design validation framework and service, and lastly, 3) source inspections to insure that manufacturers along the whole component/product pipeline are using the materials that they said they would use are actually being used...

For example, I spec some wire (per NEC and UL requirements). UL inspects a prototype of my design, makes sure that I used the correctly rated insulation, awg, termination, do a power on test (measure a few temps and voltages), and (depending on where it is used) maybe a high voltage and leakage current test.

UL writes up a report for the product (or component like circuit breaker, plastic, PC board) and then comes every 6-12 months to the factory and makes sure that every "controlled" item I called out in my design is still being used and that the UL approved tags/markings are present on the raw components.

So... Writing up a strange belts and suspenders NEC interpretation to somehow account for none-of-the-above happening (not UL/NRTL'ing the device itself) is transparently useless... It does not make the non-UL device one bit safer.

-Bill

halfcrazy

Re: Xantrex XW60 CC MPPT any feedback Yet ?

yes this is really screwed up i can understand wiring being oversized but if i buy a little box rated to handle 100 amp cont. and is ul listed where does the nec get off derating it?
so that really means that the new flex max or whatever its called is only a 60 amp controller? and dont get me started on john whiles it is all about his interpertation nothing to do with what the code book actually say's.
have had this argument before when i was told i couldnt have batterys in the living space and was shown a page from johns book with a nec reference i looked it up in nec and it had nothing to do with batterys????

blwncrewchief

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Since nigtomdaw asked about the FlexMax80, I thought I'd give a quick report. I got mine running in temporary test mode (re: rigged:-)) today. The weather has been too bad to get much done lately. Anyway, outside we had good sun and about 30F temp. Ran it from 11am to 1:30pm. hooked to 6 Evergreen 180s in parallel it ran 1000 - 1180 watts the whole time. I saw 1140 - 1180 watts for 1/2 hour at a full 80.0 amps out at 14.5 -14.9 volts. In 2.5 hours it produced 2.7kw. The temp in the garage was 60F and it just got noticeably warm to the touch, about 75F and the fan never kicked on. No complaints, and while I can't test it to lab specs, it seemed to perform well.

nigtomdaw

Re: Xantrex XW60 CC MPPT any feedback Yet ?

BCChief, thanks for that..... back on track with the original post I hope ?:roll:

crewzer

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Gents,

In answer to rplarry’s question, the FLEXmax 80’s manual indicates that its input current is NEC-limited to 64 A Isc.

With all due respect my esteemed fellow forum members, I must confess that I find the intent of the NEC’s 125% multiplier for calculating maximum and continuous PV array current to be reasonable when dynamic environmental factors are considered.

125% of Isc means ~140% of Imp, so that provides quite a cushion above STC full-power conditions, which we all know are rare. But, PV array power surge excursions do happen, as these discussions clearly describe:

http://forum.solar-electric.com/showthread.php?t=1592
http://www.outbackpower.com/forum/viewtopic.php?t=2571

Given the dynamic nature of PV system power production, I think it’s OK for the wire, breakers, and controllers to be appropriately derated beyond the “standard” NEC derating so that they can safely and reliably handle these types of power generation excursions.

I also think the NEC input current derating argument is a bit of a tempest in a teapot when DC-DC step-down controllers are concerned. As we know, it’s no challenge at all to configure a high-voltage / low-current array that will drive a controller like an FM80, an MX60, a T-80, or an XW-60 to its full rated output current for “low” battery voltages (i.e., 12 V or 24 V nominal) without “violating” NEC 690.8.

It’s a bit more of a challenge to configure an array for a 48 V battery system using any of these controllers if NEC 690-7 (temp correction factor), 690.8, and Vmp reduction due to hot environmental conditions are all considered. But, it can be done.

For a “60 A” example, eighteen Sharp ND-200U1 modules (200 W STC, 35.5 Voc, 28.5 Vmp, 7.82 Isc, 7.02 Imp) wired 3 (in series) x 6 (parallel strings) will create an array rated at 3,600 W STC. The array’s Isc will be 6 x 7.82 A Isc = 46.92 A Isc, which is under the 48 A NEC input limit for the MX60 and the XW-60. The array’s summer operating voltage should never fall below 64 at the battery terminals, which is enough for EQ’ing a 48 V flooded-cell battery bank. The winter Voc should not exceed 35.5 V x 3 x 125% = 133 V, which is below the operating limits for the two controllers. On a sunny and cold day, the controller could deliver the full 60 A at 60 V to a “48 V” battery bank. And, during “surge” events, either controller would limit output current.

My head hurts! :roll:

Regards,
Jim / crewzer

mike95490

Re: Xantrex XW60 CC MPPT any feedback Yet ?

125% of Isc means ~140% of Imp, so that provides quite a cushion above STC full-power conditions, which we all know are rare. But, PV array power surge excursions do happen, as these discussions clearly describe:

http://forum.solar-electric.com/showthread.php?t=1592
http://www.outbackpower.com/forum/viewtopic.php?t=2571

Given the dynamic nature of PV system power production, I think it’s OK for the wire, breakers, and controllers to be appropriately derated beyond the “standard” NEC derating so that they can safely and reliably handle these types of power generation excursions.

But what's the duration of the edge of cloud events, a minute or 2 at the most, then the panel heats up, and self limits again. With a large thermal sink/mass in the inverter, as long as the voltage on cold days never gets beyond the shutdown limit, and if the inverter can gracefully fold back higher than average power spikes, all should be fine.
These are just brief, transient spikes in amps, which (as I understand) never become constant current. To force a component to be continuously be de-rated up to 40%, when it can easily handle the brief surges is silly. And I work in aerospace where we de-rate 50% for most things.
The bank of individual FETS needs to be capable of the power, without degradation, but to take a surge, and assume it will be constant, with no reasonable explanation, is like changing codes to account for 2 blow dryers running in the bathroom at the same time that the garbage disposal, toaster oven, microwave, and dishwasher are all on too. That can overload a 100 A service panel too.

Solar Guppy

Re: Xantrex XW60 CC MPPT any feedback Yet ?

Crewzer,

By your post, it would indicate don't have the technical education on the internals of the controllers. For all Mppt types and all inverters, all regulation is processed which current limit is one of many things are computed within a switching cycle or two. Analog is typically faster, Digital a bit slower. For my last DSP design the controller switching cycle, would be about 40us for the digital control after its filters to adjust to maintain regulation and limits. It is impossible due to the input caps and inductor limit of rate of change to have an event of ANY type that would cause regulation failure. This is a fact, not an opinion.

Its unfortunate that Wiles and You think the NEC should have authority superseding UL/CSA, the tests required by these agency prove the safety of these devices and are extensive and well beyond anything that could happen in an solar installation.

The battery side is where the danger lies, literally 10'000's of amps for fault conditions, the solar side worst-case just shorts out and to a power of near zero, just shows what a load of cow dong this NEC 690 stuff is. UL/CSA requires faulting the FETs and making sure the resultant fireworks doesn’t' causes any unsafe conditions for users or the installations location. Nothing in the NEC, NOTHING , improves the safety of these listed devices.

I have absolutely no problem with designing for safety and NEC rules to make them uniform for installation, I do have an issue with people who are obviously unqualified in any way to make rules when the technology is already proven and listed as safe.


Related:

Here in Florida we have a agency called FSEC and are an arm of a State university, sound similar to Wiles employement. Its nothing more than a Jobs program for the well connected, about 50-60 well paid folks that have literally nothing to do except try and proclaim their relevance. They have a “mandate” from a 1975 state law ( what got them started ) to list and approve all solar products sold in the State of Florida. For the most part they are totally ignored except when they smell money.

On the latest Rebate program, after the State passed the program FSEC came out and said all installations and equipment had to be approved by them ( as they claim the 1975 law mandates ). Well besides the obvious silliness of them having to approve all UL/CSA listed devices ( sound familiar ) they hadn’t tested anything in years and had no current products listed for sale and was blackmailing the rebate program to pay them to get approval and test current products

I worked with others and got that overturned, it was my state senator that sponsor the rebate program and when I told her about FSEC ( she had never hear of them! ) things happened to go around them. As the bill made NO mention of FSEC needed to get rebate funds. I have little hope of FSEC getting scrapped, once a institution is created, to many hands get feed off the troff.


SG

BB.

Re: Xantrex XW60 CC MPPT any feedback Yet ?

For my 2 cents worth... The input current to the inverter should not be derated. That kind of goes back to my example of needing to plug my 40 watt 120 VAC laptop power supply into a 40 watt limited current wall outlet--we don't do that via the NEC or NRTLs.

And, we don't derate the wall power/current coming into a computer power supply to prevent the output from "over producing"... The power supply itself is responsible for the amount of power it outputs, and conversely, responsible for the amount of power that it takes from the "mains" or input.

There all sorts of qualification tests that can be performed on a UL/NRTL listed/recognized device by the listing agencies and those that write the NRTL standards.

Nothing that the NEC can do will make these devices any safer as they have no direct or indirect control over the design or manufacture of these inverters/charge controllers, etc...

Many of the older limits (like 60 VDC, xx amps, etc.--don't know the details of the current code) where points at which NEC did not "care about" the installations (too low of voltage or current to be worry to a facilities wiring plant).

However, in the NRTL documents, there are also limits based on isolation and power available to a baby's finger touch (for example). So, in my designs I would require double insulation/2mm spacing (there are other options like ground screen and a bolted safety ground) that would ensure that a single and subsequent failure will not "flash over" to the outputs.

Then I would have a second set of inspections/test to make sure that any external connections had less than (something like) 12 volts and 8 amps total output (say RS 232, network connections, USB, etc.).

If, for example, I did not have the approved double insulation from AC mains to DC output, no matter how little power my DC circuits output--those outputs would not be considered to be SEL (Safety Extra Low voltage) outputs--and therefore they could not be available to be touched by non-qualified personal (i.e., those circuits/plugs would need to be inside a locked cabinet and the cabling/plugs would need to meet, basically, the same requirements as a standard AC line cord set).

This was the level of design issues that every manufacturer and design engineer needs to go into with virtually anything connected to line power and should be done on the "off NEC" type equipment (solar panels, DC chargers, battery circuits, etc.).

Again, with the NRTL way of doing things, there is a cascade of requirements and protective devices that are identifiable, inspected, and tracked through the manufacturing process (and no-notice inspections by UL and others).

Somebody arbitrarily "doubly" derating the Solar Input Current to a modern Grid Tied inverter via NEC requirements is not understand the whole process here.

Solar Guppy is pretty non-Politically Correct in how he describes the problem--but from what I have seen in years gone by, he has been very accurate in addressing the issues.

If there is an issue with how a UL Listed device reacts to over voltage or over "availability" of current--then the place to address that is in the UL/CE requirements--not in the NEC.

NEC, from my point of view, addresses the safety and requirements for Facility Wiring. Listing/Recognition programs address the safety and requirements of the equipment connecting to the Facility Wiring.

I can understand there may be a whole in the section where solar panels can over voltage a Inverter/Solar Charger design.

But, from an NEC point of view, even if the Inverter "blows up"--it is the responsibility of the NEC code to ensure that the wiring from the Power Pole/Solar Panels/Protective Devices do not fail in an "unsafe" way.

It is the UL/NRTL regulations to ensure that the Inverter fails in a safe way when subjected to over voltage (over availability of current only matter if it exceeds the short circuit handling of the Inverter's input wiring box). We, for example can over heat, and do fire safety tests (like wrapping the device under test) in something like cheese cloth to ensure that a failed device will not catch fire.

If this is not enough, they can require what the old Bell Telephone Companies required (through Bellcore/Telcordia NEB(?) requirements).

These tests include putting a pan of alcohol inside various parts of our systems and lighting them off. Measure how much smoke was produced, see if there was any exposed fire/dripping plastic, could the fire be put out with a fire extengusher, etc.). We also tested our packaging for railroad coupling hits (train bumping a car loaded with our equipment)... Just a whole bunch of requirements.

Ending this... NEC is not the place to address these issues. It is the NRTL process (UL/CE/IEC) that these problems should be addressed.

Solar Guppy--just out of curiosity, what is the over voltage testing requirements (if I put more than 600 VDC on a grid tie type inverter's input, is it designed/tested to fail "safely"--or is that totally ignored in the certification process?

Also, how are the solar DC inputs "marked" for available current / interrupter device ratings? In times pasts, many of these important specifications could be kept confidential by UL and would only be released by manufacturer permission or to a UL inspector when reviewing a product for Listing (for example, did I use a terminal block correctly, voltage/current/temperature/materials/etc. on the AC input to my computer).

You can't probably answer exactly--but roughly how is it defined and inspected by UL/NRTL's?

-Bill

PS: The question to Solar Guppy has pretty much been answered in his statement about faulting of the FET's and such... Probably not much to gained my answering my questions other than the "available" current rating methodology one.

niel

Re: Xantrex XW60 CC MPPT any feedback Yet ?

from bb,
"NEC, from my point of view, addresses the safety and requirements for Facility Wiring. Listing/Recognition programs address the safety and requirements of the equipment connecting to the Facility Wiring."

i say here and now that wiles has not fulfilled this requirement when he mandated that the ground lead go straight into a home from the pv ground and the use of another seperate ground rod to be used without being properly intertied underground. this violates the safety of the home and those in it by allowing an unnecessary entry of lightning into the home. also improper operations of said equipment or ground looping can be created with wiles' ruling. he thought having a seperate ground would eliminate the possibility of ground loops being created, but this is not the case as this would depend on the soil conductivity and the distance between said ground rods. high conductivity in the soil is desirable and therefor could cause enough of a connection allowing loops to be created with the probability of the loops being reduced in size due to soil resistivity, but there none the less.
to put it simply that when you put anything up on your roof that needs grounded, like a tv antenna for example, would you feel good about running that ground wire into the house and to ground along with another one that goes to the ground outside? you can see the redundancy and dangerous nature of doing that. apparently wiles doesn't.