Xantrex MPPT80-600 installation requirement

NorthGuy · March 2013

I may install more panels and, as one of the options, I'm thinking about using Xantrex MPPT80-600 which can handle strings up to 550V. I would need to install a combiner box and DC disconnect. I know several people installed it here.

My questions are:

1. Combiner boxes. I couldn't find any that could have 600V rated breakers. What have you used?

2. DC Disconnect. Don't seem to find any 600V breakers neither. Is my only option a fused disconnect?

3. The controller converts 500V voltage to ~50V. This may be hard to do without losses. Does it still have 95% efficiency as regular controllers do?

niel · March 2013

Re: Xantrex MPPT80-600 installation requirement

not sure of a combiner, but maybe something is available at midnite. i just didn't see one at 600vdc off hand to accommodate the 600vdc breaker listed below.

http://www.midnightsolar.com/

the wider the input to output ratio, the lower the efficiency no matter if it is a 600v max mppt cc or not. i doubt 95% with a 10x difference.

Cariboocoot · March 2013

Re: Xantrex MPPT80-600 installation requirement

I think most people would use MidNite's 600 Volt fuses http://www.solar-electric.com/mnatm.html
Their high Voltage combiner box: http://www.solar-electric.com/mnpv16-hv.html
And a high Voltage AC/DC disconnect like this: http://www.solar-electric.com/sqd600vodcar.html

There are a few good installers around here and if there's anything better they'd know.

unicornio · March 2013

Re: Xantrex MPPT80-600 installation requirement

I have heard of this charge controller, and I'm particularly a fan of the arrays with high voltage ...
in principle, technically there would be no problem to convert 600v to 50v with high efficiency ... once you convert dc to a high frequency ac, using good transformers, does not influence the voltage difference to get a good amount of performance in DC to AC conversions, and again, AC to DC ...
the more important in this installation is that must take into account extreme good insulation and moisture protection, that 600v is a tension not only lethal, is also a way to easily find some problems ...

offgrid me · March 2013

Re: Xantrex MPPT80-600 installation requirement

I have an 80 600 and find that it usually sits at around 95% conversion efficiency. It rarely gets even slightly warm so it cant be loosing much to heat. I have all 20 of my panels as one string so I dont use a combiner. I do have a fused disconnect that is rated to 600v dc and have not had a problem. For the past two years it has worked perfectly with no problems.
Ned

vtmaps · March 2013

Re: Xantrex MPPT80-600 installation requirement

NorthGuy wrote: »

Does it still have 95% efficiency as regular controllers do?

apparently so: http://forum.solar-electric.com/showthread.php?p=68011#post68011

--vtMaps

NorthGuy · March 2013

Re: Xantrex MPPT80-600 installation requirement

Thank you for your responses.

So, efficiency is not a problem. I still have concerns with high voltage. Even more so my wife. As Unicornio said, 600V might be deadly.

Looks like, on the combiner box side, I would need to go with fuses that Coot suggested, or even avoid the combiner boxes completely, as Ned did. On the controller side, disconnects are going to be expensive, but not that bad.

BB. · March 2013

Re: Xantrex MPPT80-600 installation requirement

600 VAC is "normal" limit for home and light commercial power (i.e., up to 480 VAC three phase power). Once you get past 12-24 volts--it is the available current that actually starts getting "scary" (at least to me).

The problem with DC is it sustains and arc very nicely. And if you have (for example) an open wire in the solar panel array, you can get an arc started that will run very happily for minutes to hours (when the sun is up). The solar panels are, more or less, very nice current sources--So any break in your wire run, or short to ground, and the voltage over ~12 vdc, an arc can be struck and sustained.

Above 24-60 volts--That is when bare skin (and wet skin) can sustain >0.005 amps (5 milliamps) -- which is the low limit to stop your heart (i.e., left and through right leg to ground). 400 Volts Vmp (voltage maximum power) can certainly drive 5+ milliamps much easier--but either can be deadly in the right (or wrong) conditions.

One other issue--It is very easy to make Ground Fault Detection devices (breakers, outlets, etc.) for AC power (basically a "current sense" transformer and a few cheap components. It is very difficult to make a 5 milliamp DC GFI circuit (cheap and reliable)... So, DC circuits that are around consumers (especially as the voltage rises) are more difficult to "protect" against "dumb" behaviors (running DC drill and stereo in the rain, etc.).

The difference between 18 volts and 400 volts Vmp-array is not that great in terms of dangers. And when you get up to a 48 volt battery bank with a Vmp-array > 72 volts, the differences (safety concerns) are even less.

-Bill

NorthGuy · March 2013

Re: Xantrex MPPT80-600 installation requirement

BB. wrote: »

Above 24-60 volts--That is when bare skin (and wet skin) can sustain >0.005 amps (5 milliamps) -- which is the low limit to stop your heart (i.e., left and through right leg to ground). 400 Volts Vmp (voltage maximum power) can certainly drive 5+ milliamps much easier--but either can be deadly in the right (or wrong) conditions.

I measured my body resistance. It's around 1MOhm whether foot to hand or hand to hand. My wife has similar resistance too. However, with wet hands the resistance goes way down - 100kOhm hand to hand.

So, when your hands are dry, you would need 5kV to get 5mA through your heart - that's what they have in overhead power lines.

But, with wet hands, you only need 500V. This is actually a little bit less than the normal operating voltage of MPPT80-600 would be. Probably it can kill you, but you need to be sweating for that to happen.

Cariboocoot · March 2013

Re: Xantrex MPPT80-600 installation requirement

Do NOT assume those calculations are correct. At least don't bet your life on it.

"That which does not kill us can still give you a nasty turn."

inetdog · March 2013

Re: Xantrex MPPT80-600 installation requirement

NorthGuy wrote: »

I measured my body resistance. It's around 1MOhm whether foot to hand or hand to hand. My wife has similar resistance too. However, with wet hands the resistance goes way down - 100kOhm hand to hand.

So, when your hands are dry, you would need 5kV to get 5mA through your heart - that's what they have in overhead power lines.

But, with wet hands, you only need 500V. This is actually a little bit less than the normal operating voltage of MPPT80-600 would be. Probably it can kill you, but you need to be sweating for that to happen.

NO! NO! NO! NO!

You are leaving out one very important factor: The high resistance you are measuring includes the resistance of the top layer of the skin. That has a high resistance, but a relatively low breakdown voltage. Once you have penetrated that layer the resistance becomes much lower. Comparable to the same distance through a salt solution in fact.
If you want to measure your skin-to-skin cross body resistance you should grab hold of both leads of a megger (megohm meter) and give the handle a spin. I think that you will get a much lower number if you can hold on long enough. And, no I do not really want you to do that.

An analogy would be that Kleenex has a very high resistance when measured with an ohmmeter. But I would not recommend using it as insulation on 300 volt DC wiring.

mike95490 · March 2013

Re: Xantrex MPPT80-600 installation requirement

NorthGuy wrote: »

I measured my body resistance. It's around 1MOhm whether foot to hand or hand to hand. My wife has similar resistance too. However, with wet hands the resistance goes way down - 100kOhm hand to hand....

odd thing about skin, once current begins to flow, resistance starts to go way down, and even more current flows. It happens quickly.

solarvic · March 2013

Re: Xantrex MPPT80-600 installation requirement

Why is everyone making an issue about the 600 vdc? Especially as most GT inverters run effocient at about 550 vdc.with a 600 vdc limit. So why would t be any different powering a charge controler at the same voltage? I use the identical square d shutoff that was posted here. You don,t need as big of a combiner box as shown. I already had an old box I put the littlefuse holder in and use a little fuse all located at the panels so if there is a problem the fuse will blow before I have problems at the house in my inverter. I did get a good shock when putting my panels up and my arm hurt 4 or 5 days before the pain went away. So don,t connect any panels together till you get all your boxes wired. Make sure your cutoff is open then connect the wires. You be ok then and make sure your panels are connected. I didn,t see any sparks or anything but I have respect after I got shocked. Solarvic

BB. · March 2013

Re: Xantrex MPPT80-600 installation requirement

Home sized GT Inverters are typically in the 300-400 volt nominal Vmp range. Why not for a battery based MPPT charging system?

I guess the hardware needed to down convert to 12-48-yyy volt battery bank is an issue.

-Bill

Cariboocoot · March 2013

Re: Xantrex MPPT80-600 installation requirement

BB. wrote: »

Home sized GT Inverters are typically in the 300-400 volt nominal Vmp range. Why not for a battery based MPPT charging system?

I guess the hardware needed to down convert to 12-48-yyy volt battery bank is an issue.

-Bill

Yes. Like the fact the Xantrex unit costs 2X what a MidNite Classic does and generally such high array Voltage is not needed. So why do it if you don't have to?

BB. · March 2013

Re: Xantrex MPPT80-600 installation requirement

Agree--The XW MPPT 600 volt is ridiculously expensive. I was just relating that 600 Volt array systems should not scare people away based on safety concerns.

-Bill

NorthGuy · March 2013

Re: Xantrex MPPT80-600 installation requirement

Cariboocoot wrote: »

Yes. Like the fact the Xantrex unit costs 2X what a MidNite Classic does and generally such high array Voltage is not needed. So why do it if you don't have to?

Say, you want to install 5kW array 300 ft away.

You would need:

- two regularly sized controllers - $1000
- 100m of wire (4 x #6 wires @ $2/m + 1 1/4 conduit @ $3/m, total $11/m) - $1100
- 2 combiner boxes with fuses/breakers - $400
- 10 MC4 cables of various length - $400

Total: $2900

You would probably say that #6 wire is to small, so it'll be $900 more to go to #3 wire, moving total to $3800

With XW MPPT80-600 you need:

- one controller $1200
- 100m of wire (2 x #10 wires @ $1/m + 1/2 conduit @1.50/m, total $3.50/m) - $350
- one combiner box with 2 fuses - $100
- 2 short MC4 cables - $50

Total: $1700

I omitted some stuff on the controller side, but that would be about the same for both.

Looks like good savings to me. Plus less work, which is especially important if you hire someone to do it.

Cariboocoot · March 2013

Re: Xantrex MPPT80-600 installation requirement

As I said, it is generally not needed. Specific instances where very long distances are involved aren't typical.

Ironically, the low demand for this HV controller is one of the reasons the price is so high.

I believe it was originally designed to adapt GT arrays to recharge batteries for back-up power on systems that didn't have built-in back-up like the XW. "How do I do this?" is a popular question around here.

600VDC is somewhat more dangerous than 600VAC, but heck 120VAC can kill you if the circumstances are right. And sometimes the high Voltage won't; there have been a few bad electrocutions in history. So if it doesn't always work when they're trying to kill someone with it you can see there's always an element of random chance.

NorthGuy · March 2013

Re: Xantrex MPPT80-600 installation requirement

Cariboocoot wrote: »

Ironically, the low demand for this HV controller is one of the reasons the price is so high.

I think the demand would be higher if it was 100-120A. Otherwise, it doesn't quite replace 2 regular controllers.

Cariboocoot wrote: »

... there have been a few bad electrocutions in history. So if it doesn't always work when they're trying to kill someone with it you can see there's always an element of random chance.

They use something around 2000V in a hope that this immediately kills the brain. I'm sure they would use more voltage if they really needed to. 2000V is not that far from 600V. Given the element of random chance that you're talking about, 600V may lead to the same result.

And if not, will not be very pleasant at best:

solarvic wrote: »

I did get a good shock when putting my panels up and my arm hurt 4 or 5 days before the pain went away.

I once got a jolt from 5000V electric fence into my head. That's only 200us, but I could feel it for hours.

Although there's an easy solution. You can do all the connections at night.

Dave Angelini · March 2013

Re: Xantrex MPPT80-600 installation requirement

BB. wrote: »

Agree--The XW MPPT 600 volt is ridiculously expensive. I was just relating that 600 Volt array systems should not scare people away based on safety concerns.

-Bill

Not when you figure in the cost of labor, balance of system components, simplicity, and a lot more than 80 amps out (look at the breaker) with a huge current limit on the input. On a $20K system it is in the noise. They may not sell like hotcakes at Wind/Sun but the serial number I last saw looked like they were moving product since I did the beta on the -600.

NorthGuy · March 2013

Re: Xantrex MPPT80-600 installation requirement

Dave Sparks wrote: »

... and a lot more than 80 amps out (look at the breaker).

Do they put out more than 80A or 4800W that they specify? That would be a very good news.

Also, you mentioned breaker - do they have built-in breakers?

Dave Angelini · March 2013

Re: Xantrex MPPT80-600 installation requirement

NorthGuy wrote: »

Do they put out more than 80A or 4800W that they specify? That would be a very good news.

Also, you mentioned breaker - do they have built-in breakers?

It all has to do with internal electronic current limiting. The output wiring is protected by a 100 amp breaker in your panel. If you are not in the desert with a ambient of 90F, the unit can output 90 amps all day long. As the circuitry heats up from air temp or just being at alot higher than rated current the output will current limit. I have seen 95 amp peaks with cloud effect.

Same with the input, it will current limit at 23 amps and you can see that with a 400V string of panels you can easily move quite a bit of power a long way down the hill.

Operating power circuitry at high temperature for too many hours shortens the life of the circuitry. You do not have the high temperature problem and so you can expect more right?

NorthGuy · March 2013

Re: Xantrex MPPT80-600 installation requirement

Dave Sparks wrote: »

Operating power circuitry at high temperature for too many hours shortens the life of the circuitry. You do not have the high temperature problem and so you can expect more right?

Temperature shouldn't be a problem. It'a at 12C ambient most of the year. And at summer time I would never get full power because of the winter tilt of the array.

I now have two XW MPPT60-150. I have never seen them above their 60A rating. I did see them right at 60A. Although, my current array is too small for that.

BTW: Do you know how MPPT60-150 and MPPT80-600 co-exist together?

Dave Angelini · March 2013

Re: Xantrex MPPT80-600 installation requirement

In several installations the -60 actually enhances a system with a -80 or two. In other installs they work really well off-grid. The enhancement is you can use the SCP in the living space and a --60 and -80 in the power room will have all the system data (all the chargers) available on a -60 in scroll mode.

It is yet another quirk from Xantrex that the scp does not add up the chargers and give you the total on the main system screen. One has to manually go to each chargers home screen. But, the -60 will give you the total and even better, it will scroll all the vitals to make it easy to troubleshoot. No buttons to push! Quite a few people who live offgrid need simple/robust systems that a significant other or whoever can get the vitals.

There are all kinds of power and array techniques that you can use in your climate. I have a great client out of Fairbanks near the Fort who has 7,000 watts of panels mounted flat on the ground. After snow he hoses them off from a hot spring. Stay warm summer is coming!

inetdog · March 2013

Re: Xantrex MPPT80-600 installation requirement

NorthGuy wrote: »

I once got a jolt from 5000V electric fence into my head. That's only 200us, but I could feel it for hours.

It is also limited current. A lot of the early execution chambers used a motor generator for the HV to be able to get high current.
Remember how in the old movies the lights in the whole prison dim when they throw the switch? Not sure that really happened. But in the good ones they show somebody flipping a smaller switch first and your hear the motor generator spooling up to speed.

NorthGuy · March 2013

Re: Xantrex MPPT80-600 installation requirement

Thank you Dave. Looks like -80 is the right beast for the job.

Dave Sparks wrote: »

There are all kinds of power and array techniques that you can use in your climate. I have a great client out of Fairbanks near the Fort who has 7,000 watts of panels mounted flat on the ground. After snow he hoses them off from a hot spring. Stay warm summer is coming!

That is an interesting arrangement. Mine are quite a bit upright. I can clean snow with a broom, but if I don't, it usually just falls down as soon as the sun comes up.

Xantrex MPPT80-600 installation requirement

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