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Old 07-31-2018, 10:10 AM   #1
Mini-Skoolie
 
Join Date: Dec 2014
Posts: 19
Year: 1996
Coachwork: Goshen
Chassis: frieghtliner mt55
Engine: cummins isb
Rated Cap: 25
About to wire my system - disconnects / just want to make sure my mind is working

I am about to start connecting wires - just want to get another opinion to make sure my research is paying off and I am not about to destroy something

Components :

Magnum PT-100 Charge Controller
(2) 6v Lifeline Batteries GPL-L16T
Dimensions 1200n/12 Pure Sine Inverter
(4) Trina Solar Panels XL 290w
Midnight MNDC250 Disconnect Box (this is where I need the most help)

Firstly, I am planning on running my 4 panels in series. Will a 15A / 150vdc breaker be fine?

Panel specs : Model Number TSM-290PA14
STC Rating 290.0
PTC Rating 262.8
Open Circuit Voltage (V) 37.1
Short Circuit Current (A) 8.31
Power % Ī 0/3

Secondly, grounding to the chassis has been a but confusing and someone who installs systems told me to just not ground anything since the engine batteries and solar batteries should not be grounded to the same metal. Some clarification here would be great.

Also, if I end up not grounding to chassis, within the MDNC250 disconnect box, as it recommends the option of mounting a 63A / .5A dual GFPDC breaker -

if I install without this breaker would my thinking be correct in wiring the PV+ to a breaker (15a?) , then into the charge controller, then Battery + from charge controller to another breaker (what size breaker here? same as PV+ or is this based on battery specs?) then this breaker to the +post within the MNDC box the post is connected to the battery and the rest of the current leads to the 250a breaker that is for the inverter.

That last paragraph might be confusing to read without the wiring diagram I am basing my design off of -here is a screen shot of the wiring diagram in the MNDC installation guide :

Any clarification / recommendations would be appreciated
Omingnome is offline   Reply With Quote
Old 07-31-2018, 02:59 PM   #2
Bus Nut
 
Join Date: Jun 2016
Location: Orange County, CA
Posts: 849
Year: 1990
Coachwork: integral
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
You may want to reconsider wiring your panels in series. There have plenty of threads here over the years on this subject about the pros and cons of series and parallel wiring - the general consensus of opinion is that parallel makes more sense on buses/RVs/boats/etc wherever there's a chance of partial shading. It's not like you're going to save much money by running lighter cable for the few feet from the bus roof down to the CC!

I have 2kW of panels split into two separate tiltable arrays, each array of four panels paralleled in a fused combiner box before sending power through a 4AWG downfeed cable to its CC. If one panel is shaded it won't make much difference overall, but if one of your panels is even partially shaded you've lost your power production. You should try to design your system for redundancy and to minimize single points of critical failure - pessimists make the best engineers because they always think that $hit happens (and it does)!

John
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Old 07-31-2018, 06:05 PM   #3
Mini-Skoolie
 
Join Date: Dec 2014
Posts: 19
Year: 1996
Coachwork: Goshen
Chassis: frieghtliner mt55
Engine: cummins isb
Rated Cap: 25
Quote:
Originally Posted by Iceni John View Post
You may want to reconsider wiring your panels in series. There have plenty of threads here over the years on this subject about the pros and cons of series and parallel wiring - the general consensus of opinion is that parallel makes more sense on buses/RVs/boats/etc wherever there's a chance of partial shading. It's not like you're going to save much money by running lighter cable for the few feet from the bus roof down to the CC!

I have 2kW of panels split into two separate tiltable arrays, each array of four panels paralleled in a fused combiner box before sending power through a 4AWG downfeed cable to its CC. If one panel is shaded it won't make much difference overall, but if one of your panels is even partially shaded you've lost your power production. You should try to design your system for redundancy and to minimize single points of critical failure - pessimists make the best engineers because they always think that $hit happens (and it does)!

John
John, I was actually planning on doing 2 and 2 so I can tilt 2 and leave 2 flat, however the PT-100 seems to want higher voltage - and I am not entirely sure why, but Magnum has a PV calculator and when I enter the specs for the 4 panels in 2 strings, it says voltage is too low. Perhaps you can help me understand this better or take a look

https://s33.postimg.cc/4xjav7iwv/Scr...7.08.38_PM.png

https://s33.postimg.cc/flrn79n9b/Scr...7.08.52_PM.png
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