Configuration Questions

[pfelmey]

Hello All. My name is Pete and I am new to your forum. I started playing around with solar as a hobby less than a year ago. I currently have a Xantrex TR inverter mounted on a Midnight DR/TR E- panel,  a Midnight Classic 150 (probably one of the first shipped April) and 8-285 watt panels which I built myself and a 1200 amphour 24 volt battery bank and a 3000 watt generator wired to the E-Panel as an off-grid system. I have decided to go grid-tie and am currently building a new system which consists of 22 Lumos 285 watt mono panels, 2 Xantrex XW6048 inverters, a Xantrex XW Power Distribution Panel,  3 Midnight Solar surge arrestors, a Midnight MNPV12 combiner and breakers, and 2 Midnight Classic 150 charge controllers and will be increasing the battery bank to 1000 amphours at 48 volts. I will be taking the old system out as the panels and inverter must be UL Listed. I would have used Midnights XW e-panel too but do to space requirements and dual inverter integration, Xantrex was the better choice. I have several questions relating to the configuration which I would like some confirmation of my own calculations and would appreciate some help.

1. I would like to put 3 modules in series per string for a total of 7 strings divided between the 2 Classic 150 controllers ( 3 strings combined on 1 controller and the remaining 4 combined on the other).  However the panels are rated at 44.4 Voc for a total of 133.20 Voc and when temperature corrected for 0 degrees F* ( I live in New Jersey) gives me 157 Voc which places me in the controllers HyperVoc range.  The temperature calculation was done with your setup wizard ( it is accurate ) and it  is the most extreme condition which will rarely be seen here from my experience and would probably be so infrequent that I could live with a day here and there not producing any output. My question is would you recommend this setup or would you go to 2 panels per string and risk possibly losing the ability to charge the batteries in the summer. We need to consider the fact that the batteries will be fully charged most of the time as they will only be used as backup and the controllers will be operating at a modest capacity while in grid-tie operation. What configuration would you choose??

2.  The next question concerns the pv combiner circuit breaker sizing.  The panels have a maximum series fuse rating of 20 amps and Isc current of 8.6 amps.  When I use your classic 150 wizard for the configuration in question 1 and enter 20 amps in the wizard section for series fuse it tells me to use a 20 amp breaker.  When I do the calculation it is different.  3 panels series wired rated at  Isc 8.6 x 125% it equals 10.75 amps. then multiply again  10.75 x 125% for overcurrent protection equals 13.44 amps. Next size up available breaker is a 15 amp breaker  ( midnight continuous duty breakers only require 125%).  What is the correct breaker size??

3. The next question concerns multi-unit operation of the Classic 150.  This is an area of disappointment because other than showing how to connect the Master to Slave network cable in the manual nothing else is even said or able to be found about the operation or configuration in this mode.  below are questions concerning this mode of operation
             
               1. Does the Master control the Slave or do they work independently.  Keep in mind that they are both charging the same Battery Bank.  In other words when when the master goes from bulk to absorb is the slave synchronized with it or do they work independently.

               2. Do you have to configure each one with the exact same settings or do the settings come from the master?

               3. Can the PV source NEGATIVE be combined or must they be run separate . 

You really need to publish some information about this topic!!!!!!!

Anyway I would like to say that your products are excellent,  the couple of times I emailed support they were answered so quickly I barely had time to get out of my seat.  And it is so nice to see an american company producing a high quality product.

I am sorry it is a rather long post but I would greatly appreciate any help.

Thank You
Pete

[laszlo]

Hi,


re: 1. this is the "maximum series fuse" requirement  -- this is basically supposed to protect the solar panel itself. The panel is actually also a piece of conductor that can overheat and burn if subjected to over current. The answer of 20 amp from the wizard is AOK, but you can go smaller than the maximum.  Overcurrent protection for the array wiring is a different calculation - by the way, the 100% continuous output rated breakers such as the Midnite breakers  don't need Isc * 1.56, only Isc * 1.25. You need to look up the ampacity of your wire and then temp derate it based on the insulator's temp spec, (cf: http://www.armstrongssupply.com/wire_chart.htm) and then pick a breaker whose tripping current is less than the ampacity of the wire.

You have several other questions, so I'll let others take a stab.

[Vic]

pfelmey,

You Could get away with two panels per string,  and still EQ a cold batt bank with warm/even hot panels,  altho,  you would need more combiner breaker positions and breakers+wiring.  You will loose some efficency running the stirngs at that 107 Vmp.

The highest Voc  would occur at low irradiance,  as good sun in very cold conditions warm the cells,  thus reducing the Vin,  and  if the grid is present and/or the batts need charging,  you shuld not be in HyperVOC under this situation.

I've run my ststem six years with Vin to my MX-60 of 106ish volts.  This  is an efficency reduciton,  and this causes the MX to run a bit warm,  even when delivering a couple hundred watts of power.  The new system,  under construction,  here,  will run a Vin of 93 Volts -- 60 cell modules,  not 72 like the Lumos, FWIW.  Expect it to be a bit more eficient than running at 106-107 Vin ...  but there is no real hard data on this for the CL,  at this point ...

Think that your proposed batt bank wil be sufficient for the XW ripple suppression.

Good Luck with this nice large system.   Vic

[Halfcrazy]

Hello All. My name is Pete and I am new to your forum. I started playing around with solar as a hobby less than a year ago. I currently have a Xantrex TR inverter mounted on a Midnight DR/TR E- panel,  a Midnight Classic 150 (probably one of the first shipped April) and 8-285 watt panels which I built myself and a 1200 amphour 24 volt battery bank and a 3000 watt generator wired to the E-Panel as an off-grid system. I have decided to go grid-tie and am currently building a new system which consists of 22 Lumos 285 watt mono panels, 2 Xantrex XW6048 inverters, a Xantrex XW Power Distribution Panel,  3 Midnight Solar surge arrestors, a Midnight MNPV12 combiner and breakers, and 2 Midnight Classic 150 charge controllers and will be increasing the battery bank to 1000 amphours at 48 volts. I will be taking the old system out as the panels and inverter must be UL Listed. I would have used Midnights XW e-panel too but do to space requirements and dual inverter integration, Xantrex was the better choice. I have several questions relating to the configuration which I would like some confirmation of my own calculations and would appreciate some help.

1. I would like to put 3 modules in series per string for a total of 7 strings divided between the 2 Classic 150 controllers ( 3 strings combined on 1 controller and the remaining 4 combined on the other).  However the panels are rated at 44.4 Voc for a total of 133.20 Voc and when temperature corrected for 0 degrees F* ( I live in New Jersey) gives me 157 Voc which places me in the controllers HyperVoc range.  The temperature calculation was done with your setup wizard ( it is accurate ) and it  is the most extreme condition which will rarely be seen here from my experience and would probably be so infrequent that I could live with a day here and there not producing any output. My question is would you recommend this setup or would you go to 2 panels per string and risk possibly losing the ability to charge the batteries in the summer. We need to consider the fact that the batteries will be fully charged most of the time as they will only be used as backup and the controllers will be operating at a modest capacity while in grid-tie operation. What configuration would you choose??

I would go with the 3 panels in series. I think you will find even on those brutal cold days after a few hours in the sun the VOC will drop to 150vdc or less.

2.  The next question concerns the pv combiner circuit breaker sizing.  The panels have a maximum series fuse rating of 20 amps and Isc current of 8.6 amps.  When I use your classic 150 wizard for the configuration in question 1 and enter 20 amps in the wizard section for series fuse it tells me to use a 20 amp breaker.  When I do the calculation it is different.  3 panels series wired rated at  Isc 8.6 x 125% it equals 10.75 amps. then multiply again  10.75 x 125% for overcurrent protection equals 13.44 amps. Next size up available breaker is a 15 amp breaker  ( midnight continuous duty breakers only require 125%).  What is the correct breaker size??
The breakers in the Combiner protecting each string need to be sized acording to the PV manufacturers recommended Series fuse rating.

3. The next question concerns multi-unit operation of the Classic 150.  This is an area of disappointment because other than showing how to connect the Master to Slave network cable in the manual nothing else is even said or able to be found about the operation or configuration in this mode.  below are questions concerning this mode of operation
             
               1. Does the Master control the Slave or do they work independently.  Keep in mind that they are both charging the same Battery Bank.  In other words when when the master goes from bulk to absorb is the slave synchronized with it or do they work independently.

               2. Do you have to configure each one with the exact same settings or do the settings come from the master?

               3. Can the PV source NEGATIVE be combined or must they be run separate . 

You really need to publish some information about this topic!!!!!!!
One of the biggest reasons we have not published any data on Master / Slave set up is it is not supported yet. It is the next big feature boB will be working on as soon as he wraps up data logging and Auto Equalize though. The Classic does have a common negative so yes all the PV negatives can be bonded together if needed.

Anyway I would like to say that your products are excellent,  the couple of times I emailed support they were answered so quickly I barely had time to get out of my seat.  And it is so nice to see an american company producing a high quality product.

I am sorry it is a rather long post but I would greatly appreciate any help.

Thank You
Pete

[abrahamsolar]

I did not realize the Master/Slave function is not working as of 11-2011. Can I go ahead and connect the 6 pin phone cables so at least the hardware part of the M/S setup is finished? If so, it's then a matter of updating the firmware when that function is added. Thanks for the advice.

[Halfcrazy]

Installation of the Cable for networking should not hurt anything. The communications will require a firmware install when we have that software done.