Questions for Schneider Experts

Horsefly · October 2016

I did a quick search and didn't find the answer to my question. I am in the midst of putting together an off-grid system based largely around Schneider Electric stuff: The XW-MPPT60-150 Charge Controller and the Conext SW4024 Inverter/Charger. I am also getting the Schneider System Control Panel.

I have two main questions.

First, I was considering getting the Schneider Battery Monitor as well. It rides on the Xanbus and seems like it may be useful in many respects. However, I found buried in the literature (p 5-49 of the owner's guide) that "The Conext MPPT 60 150, MPPT 80 600 & Conext SW Inverter/Charger are also capable of operating with the Conext Battery Monitor with firmware upgrades". I'd really prefer not to buy brand new stuff and have to do a firmware upgrade right away. Is this comment really only meant in the case of older existing installs of the inverter and CC? That is, is it a safe bet that if I buy a new MPPT60-150 and SW4024 they will have a new enough firmware to work with the battery monitor?

Second, I have done all the math to ensure that my temperature corrected Voc is below 140V and the current will be well below the spec. However, for some reason the spec for the CC says the maximum PV array for a 24V system is 800W. That's really small, and I can't for the life of me see how they get that number. In the owner's manual for the CC, is clearly states "Although the XW SCC can harvest a maximum of 3500 W, the PV array size can be as high as 6720 W (based on 48 A × 140 Voc = 6720 W)". This makes sense, but doesn't align with the spec. My PV array will have a nameplate-based power of 885W, and I thought I would be fine. Anyone know if I need to actually pay attention to this 800W limit, or go with the more logical wording in the manual?

Thanks to anyone who can help!

Steve

BB. · October 2016

Do you have a link for the manual with the 800 Watt @ 24 volt limit? In general, a "useful/cost effective" maximum array for a MPPT type charge controller should be closer to:

60 amps * 29 volts charging * 1/0.77 panel+controller typical deratings = ~2,260 Watt maximum cost effective array @ 24 volt battery bank

-Bill

Dave Angelini · October 2016

Bil has always had good math skills.
Steve, you are reading something wrong. When in doubt read the manual....
As for firmware, if you buy from the store here and the last I checked, they were drop shipping from Schneider so you will get correct firmware. You should ask them and be diligent. If you buy from the internet you are on your own.

My supplier also drop ships from Schneider so if you run into problems e-mail is below.

Horsefly · October 2016

BB. said:

Do you have a link for the manual with the 800 Watt @ 24 volt limit? In general, a "useful/cost effective" maximum array for a MPPT type charge controller should be closer to:
60 amps * 29 volts charging * 1/0.77 panel+controller typical deratings = ~2,260 Watt maximum cost effective array @ 24 volt battery bank
-Bill

Bill,

What I'm quoting is the first page of two of the spec sheet for the XW-MPPT60-150 Charge Controller. Under the heading of "Flexible" it says:
• Compatible with 12, 24, 36, 48, and 60 V battery systems

— Maximum array size
12 V: 900 watts
24 V: 800 watts
36 V: 2,700 watts
48 V: 3,600 watts
60 V: 4,500 watts

I get your math, as that is almost identical to what I used. I used 75% derating instead of 77%, and used 29.8V per my batteries, but either way, it gets a way larger array size than what that spec sheet says. I think that based on your expertise, I'm just going to ignore this silly 800 watts statement.

Steve

Horsefly · October 2016

Dave Angelini said:

Bil has always had good math skills.
Steve, you are reading something wrong. When in doubt read the manual....
As for firmware, if you buy from the store here and the last I checked, they were drop shipping from Schneider so you will get correct firmware. You should ask them and be diligent. If you buy from the internet you are on your own.

My supplier also drop ships from Schneider so if you run into problems e-mail is below.

Thanks Dave. I don't think I'm reading it wrong, but like I said the manual contradicts the spec sheet, so if I go with the manual like you suggest, I'm OK. The fact that the manual makes more sense is a plus!

Whichever way I go, sounds like I just need to get confirmation from where I buy the CC and Inverter that they have the latest firmware. That hasn't been decided yet, so I really am considering your alternative.

Steve

littleharbor2 · October 2016

Typo. should read 1800 watts.

Horsefly · October 2016

littleharbor2 said:

Typo. should read 1800 watts.

Ding! Ding! Ding! I think we have a winner!

I hadn't noticed it, but it's simply a linear 900W per 12V in all the rest of the numbers they put in the spec. So yeah, if I put 1800W instead of 800W, it fits the pattern. Whew!

Thanks littleharbor2!

mike95490 · October 2016

Compare the benefits of the Combox vs the SCP . HTML interface to a browser, logging, remote control via browser, scripts to save and reload settings, firmware updates. I have both, and the combox is the winner

new2PV · October 2016

As long as your input does not exceed 48Amps rated x 140V from your array you can put any panel configuration on it. However, your final string voltage should be at 130 % higher than your highest charging voltage for mppt headroom. Overcurrent protecting is recommended at 60 amps, and that schneider breaker if you do the research is a 100% current rated breaker at 60 amps. The output breaker is suggested to be 80 amps, but that is a 80% rated breaker, so you will need to size your conductors for 80 amps, but its not suggested to go larger than #6 awg on the terminals. The controller with a flooded battery with EQ mode will put out 60 amps @ 2.55 vpc=30.6 x 60=1836 watts into your battery.

Image: https://us.v-cdn.net/6024911/uploads/editor/ef/uk6u2gpwg58q.jpg

Dave Angelini · October 2016

mike95490 said:

Compare the benefits of the Combox vs the SCP . HTML interface to a browser, logging, remote control via browser, scripts to save and reload settings, firmware updates. I have both, and the combox is the winner

Mike the OP has a cabin so assumming he does not have the internet the current combox will not work (stay tuned).

I really like having both as I monitor system for clients and frankly some of them either can't learn how to use the combox or do not want to. The SCP allows just about anyone to make changes (with help sometimes).
I suppose one could set-up a combox and a home network and then get in with the tablet ap and go cellulier into the home network but kind of clunky and cells often do not work in remote places offgrid.
The other nice thing is using combox & Insight. Have you tried it?

Horsefly · October 2016

Sorry everyone I got distracted for a bit.

@mike95490, like @Dave Angelini said, this cabin as no Internet connection, and my main concern is making this system so that anyone coming to the cabin can fairly easily see the status of the system. The status screen on the SCP will be pretty easy to train everyone to understand.

@new2PV, thanks for the inputs. I have been calculating everything you mentioned except for the 130% higher than charging voltage for MPPT headroom. It took me a minute, but now I understand what you are saying, and it won't be a problem. I've going with 3 mono panels in series (nominally 120V total Voc, Vmax with temperature coefficient of 140V), and my battery bank is only 24V, with a 29.8V max charge voltage. Anyway, I should be fine there. Because the panels are in series, I'm not at much risk of over-current, but I do have a 60A breaker in my parts list for the PV side of the charge controller (as well as a SPD).

BB. · October 2016

If you are planning on 60 amps continuous current, then use 1.25x60amps=80amps minimum breaker and wiring.

-Bill

Horsefly · October 2016

BB. said:

If you are planning on 60 amps continuous current, then use 1.25x60amps=80amps minimum breaker and wiring.

-Bill

Bill - As @new2PV pointed out, the XW MPPT60-150 docs (page 2-10 of the install manual) says to use 1.0x protection on the PV side, so I've got a 60A breaker there. However, since I have one small string all in series I'll never get close to that limit. On the battery side you are right: 1.25x, which would actually be 75A, but the closest one available to fit my panel is 80A, so that is what is in my list.

BB. · October 2016

Sounds good.

-Bill

new2PV · October 2016

Only issue I see is trying to terminate your 4 awg wire in the controller, as the manual suggests tap off a small portion of #6 into the controller then go to your 4 awg wire, with a splicer as shown. If you can use MTW wire its a finer strand wire it will help with this, but avoid using it in conduit.

https://www.bgbsupply.com/product/Panduit-Splicer-Reducer-In-Line-Aluminum-PISR2-1/Multi-Tap-Connectors

BB. · October 2016

Generally finer strand wire needs a larger diameter hole to insert the cable.

Also, many standard terminal blocks only take solid or coarse stranded wire (like those designed for residential systems). Fine strand wire tends to walk out of their compression screw.

-Bill

new2PV · October 2016

BB. said:

Generally finer strand wire needs a larger diameter hole to insert the cable.

Also, many standard terminal blocks only take solid or coarse stranded wire (like those designed for residential systems). Fine strand wire tends to walk out of their compression screw.

-Bill

That is true, but it wont be an easy job dealing with that size wire in the mppt with its tight quarters. Might be best ask Schneider what wire type is approved for the controller. The mppt 60 uses clamp type terminals, which are better in my opinion than just a screw, as the breakers use.

new2PV · October 2016

Sorry to go off topic a bit, but one thing that you need to know is not to ground the battery negative terminal anywhere in the system, as this will defeat the ground fault protection. Also if the ground fault fuse blows this may happen........

Image: http://cdn2.bigcommerce.com/n-d57o0b/urs6hb/products/331/images/1344/04_101_warning_electric_shock_hazard_if_placard__97631.1432052831.1280.1280.jpg?c=2

BB. · October 2016

Yep, meet the code and, possibly, have a very dangerous/fire/electrocution prone system.

-Bill "I wrote a white paper about that" B.

Dave Angelini · October 2016

Definately disagree this one time with you Bill. The XW system has been saved from lightning and surges at least 4 times that I know of because of the excalating faults in the DSP logic of the system. It was specified to do this not by code but in developement at the national labs up in Livermore. It is still the best system out there! The Cadilac.

In my 80 + XW systems installed I have never lost a client to electrocution and I have never heard of this happening, to anyone!.

Horsefly · October 2016

new2PV said:

Only issue I see is trying to terminate your 4 awg wire in the controller, as the manual suggests tap off a small portion of #6 into the controller then go to your 4 awg wire, with a splicer as shown. If you can use MTW wire its a finer strand wire it will help with this, but avoid using it in conduit.

https://www.bgbsupply.com/product/Panduit-Splicer-Reducer-In-Line-Aluminum-PISR2-1/Multi-Tap-Connectors

Actually, like I said, my PV array will only be 3 panels in series (~900W). As such my current will be pretty low (Isc around 10A), so I don't expect to need 4AWG wire. Everything is still on paper at this point though, so I'm not too sure how long my run will be.

mike95490 · October 2016

I don't have internet at the battery shed, just on my cell phone, I use a wireless router at the battery shed, and the laptop sees it and can see all devices connected. (Morningstar, Midnight, XW) and setting up the Generator Support settings are much easier with the on screen menus and realtime power flow on the screen, I watch the power numbers on my android phone (combox) while I tweak the SCP.

Dave Angelini · October 2016

But not many people are going to have a cell account for their remote cabin Mike as they do not live there like you do.

Horsefly · October 2016

mike95490 said:

I don't have internet at the battery shed, just on my cell phone, I use a wireless router at the battery shed, and the laptop sees it and can see all devices connected. (Morningstar, Midnight, XW) and setting up the Generator Support settings are much easier with the on screen menus and realtime power flow on the screen, I watch the power numbers on my android phone (combox) while I tweak the SCP.

Trust me Mike, I've seen two demo videos of the combox (one on the Schneider site, and I think one on one of the other internet retailer sites), and I know for a fact I would really like it. Seeing real time stats and being able to make adjustments on one screen for both the inverter and the charge controller would be great. Problem is, I'm certain I would be the only one who would even be able to use it, much less appreciate it. Moreover, I'm only one vote on how we are spending money on this rig, and my sister and brother are going to be listening / reading the details of my recommendations, and I don't think I could sell them on the combox.

Steve

Horsefly · October 2016

Since I know have some Schneider experts watching this thread, I had a few more questions:

When I posted the weird 800W limit here (which we now know is a typo) I also posted a question via email to Schneider Electric. Soon after @littleharbor2 recognized it as a typo, I got the same response from the engineer at Schneider, along with a newer data sheet for the MPPT60-150 charge controller. In that new sheet I found a new obscure limitation that I'm not too worried about, but thought I would ask you guys. It says that the "Operating Altitude" is from sea level to 2000m (6562 ft). Our cabin is at about 8800 ft elevation. I can't imagine this kind of electronics being affected by elevation, but... Any of you guys use this charge controller at a high elevation install?
I know that once the system is up and running I will probably want to just leave it operating when no one is up at the cabin, even if it remain unoccupied for weeks or months. However, I know my siblings and I'm afraid one or both of them will suggest that we may want to shut down what we can, and have a procedure written down for getting things back on-line. I'm confident I can convince them to leave the charge controller working to keep the batteries topped off. I'm not so sure about the inverter. I'm including in the design breakers to disconnect the AC in and AC out to the Inverter, and a bypass (essentially connecting our generator directly to the load panel and removing the inverter from the system). So I could have a procedure to turn off the disconnects, bypass the inverter, and turn off the disconnect from the battery to the inverter. So here's the question: If people follow the right order of flipping these switches and then some time later someone comes up and follows the right order to but the inverter back on line, will it just work? Are there any settings for the inverter that would have to be re-entered? Is there any other harm?
Also on the inverter: The specs for the SW4024 says that it can handle a surge of up to 7000W for 5 seconds, and 4000W for 30 minutes. It also says that the maximum current draw from the batteries is 230A. However, 230A x 24V is only 5520W (at 100% efficiency, which I know won't happen). Where does the other ~1500W come from? If I assume the inverter is 100% efficient, 7000W would be pulling 291A from my 24V bank, and an optimistic 90% efficiency would pull nearly 325A. My breaker on the DC into the inverter is only 250A. I don't think it will be anywhere near 7000W, but there will be a short surge draw on the inverter when our well pump starts, and I hate to think it will pop the breaker. But more importantly, how to make the math work in the spec?

I know I'm down in the weeds of things, and probably worrying about stuff I don't need to worry about. But with the wealth of experience you guys all have, I figure I can get answers before I lose sleep over them!

Steve

Mountain Don · October 2016

Dave Angelini said:

But not many people are going to have a cell account for their remote cabin Mike as they do not live there like you do.

I would like to have a cell account that connects us with our remote cabin, but it just seems like a lot of money for little true benefit.

new2PV · October 2016

Steve, please tell us about the panels you plan to run?

Dave Angelini · October 2016

It might be worth it if you could integrate it with an alarm dry contact that would go out to Outback and Schneiders web portal.
Been trying to get this done with both of those companies. It is kind of a reverse Aux that might sell more boxes if there was a closure for fire or motion in the home. I can hear "Alexa" "Dave you know I can't open the pod bay doors because there is fire alarm at your other place"

Hey Don !

Horsefly · October 2016

new2PV said:

Steve, please tell us about the panels you plan to run?

Well, ok. SolarWorld SW295 Mono, or the SW285 Mono. Three panels in series. Anything above 235W per panel will meet my needs according to my calculations.

Although I feel I have a pretty good handle on the panels, I could probably manage to come up with questions. However, since I started this thread about my Schneider Electric questions, I was sticking to that topic. I'm happy to talk about the rest of the system, but I'm hoping you guys with experience have some thoughts on one (or more) of my three questions. Thanks.

Horsefly · October 2016

So nobody has any thoughts on my three questions?

BB. · October 2016

Not a Schneider expert--But my two cents:

1. At high(er) elevations, air is less dense and provides less cooling per cuft of flow... Make sure the controller is well ventilated (not near a ceiling, under a self, in a poorly ventilated equipment room/closet, etc.) and that will help a lot.

2. A) disconnecting loads during winter (snow, bad weather, possible controller failure) to prevent battery bank discharge is a good idea. A very small load (alarm, etc.) is not going to hurt--But there is always the risk (of a dead battery bank and a lot of $$$ to replace it).

with transfer/bypass switches--You want those with interlocks so that you (or somebody else) cannot short the output of an Off Grid Inverter to another AC source (mains, genset). For larger systems that did not have interlocks, they use a key switch to lockout the bypass breakers so that an untrained person could not short multiple AC outputs together (mains, genset, UPS system) (nobody knew where the keys were as we were shutting down/leaving the building--So I could not shut the system down). C) I do not know about the present SW family--Much older systems allowed you to change configurations--But those were not saved (over a reboot) until the settings where "saved through the menu system".

3. You are correct--The energy must come from the battery bank (there is no "surge current" storage/large capacitors in the Inverter). If you had a current clamp and oscilloscope connected, you would see the 120 Hz ripple (60 Hz + and - sine wave peaks--Technically a Sine Squared waveform)... Not a nice "smooth" DC current. Circuit breakers (and fuses) are rated for "fast" and "slow" break. Normal AC breakers are relatively slow... More or less (in North America), 80% or less of rated power, they should never trip. At 100% of rated current, the breaker will trip in minutes to hours (the trip curves have frustratingly wide trip zones). You should size the wiring+breakers to 1.25 the maximum continuous current you expect the system to supply. If your "surge loads" last more than a few seconds (typical motor start), you should think about up-sizing the breakers and wiring. Remember that breakers are there to protect the wiring, not the connected devices (i.e., the XXX amp breaker protects the X/0 AWG wiring, and will not prevent the AC inverter from internal failures (or limit internal damage from such failures). The following is a pretty good estimate of the RMS current (root mean square--or "average" effective DC current) for your inverter's input are:

4,000 Watts * 1/0.85 inverter eff * 1/24.0 volts nominal = 196 Amps DC input current "nominal"
4,000 Watts * 1/0.85 inverter eff * 1/21.0 volts battery cutoff = 224 Amps DC input current "typical worst case" continuous
7,000 Watts * 1/0.85 inverter eff * 1/21.0 volts battery cutoff = 392 Amps DC input current "typical worst case" surge

And the wiring+breaker (branch circuit for DC input to inverter), in my humble opinion, should be designed to support:

4,000 Watts * 1/0.85 inverter eff * 1/21.0 volts minimum input voltage * 1.25 NEC derating = 280 Amps (round up to next wire+breaker/fuse standard rating)

And for a standard flooded cell battery bank I would suggest a minimum of 800 AH @ 24 volts (200 AH @ 24 volts per 1kW of inverter capacity) for full rated output of the inverter (and support ~2x surge power for starting well pumps, etc.). Also, for various reasons, it works out to ~4,000 Watt solar array as a "cost effective" maximum for the 800 AH @ 24 volt battery bank (nominal recommendation).

Does this help?

-Bill

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