Inverter location

Hello,

As my installation is still in progress I have to ask you few more questions:

1) Can inverter stay in a room where there are other heating/cooling devices. The room is small (2m x 2m) and the temperature can reach sometimes 40*C (104*F). The inverter is Samil 5K
2) I have two strings, 12 panels each. Can I leave a array combiner on the attic, while inverter is in the basement? It will save a lot of cable but is that safe?
3) When you make MC4 plugs - do you use a soldering iron? Or just squeeze metal parts with pliers and screw plastic parts with hands?

M

Comments

  • BB.BB. Super Moderators, Administrators Posts: 30,640 admin
    Re: Inverter location

    Welcome to the forum "M".
    mi_cin wrote: »
    1) Can inverter stay in a room where there are other heating/cooling devices. The room is small (2m x 2m) and the temperature can reach sometimes 40*C (104*F). The inverter is Samil 5K

    A very handy rule of thumb for engineering--For every 10C (18F) increase in temperature, the life (batteries, electronics, etc.) is cut by ~1/2. So, for 40C above 25C (battery "design temperature"), the life would be reduced by 21.5 or a factor of 2.8 while the device/battery is hot.

    Also, thermal cycling is another "killer" of anything mechanical. Thermal cycling is a well used technique for accelerated aging for testing equipment.

    So, the GT Inverter should be in a cool room with good air circulation or on an outside wall/installation shaded from direct sunlight for best life.

    Your GT inverter will also add about 4-5% of the array's output wattage to the room as heat or the equivalent of a ~250 watt electric heater with a 5-6kW solar array in the middle of the day.
    2) I have two strings, 12 panels each. Can I leave a array combiner on the attic, while inverter is in the basement? It will save a lot of cable but is that safe?

    You are in Poland (I guess)--So US laws/regulations are not applicable...

    First, a combiner--How many parallel strings are you using? If you have 1-2 strings in parallel, you can just tie them together in a junction box (or inside the GT Inverter).

    If you have 3 or more strings, you need to use a "combiner" box with fuses or circuit breakers (this prevents one shorted string from being feed too much current from the other strings). There should be a fuse rating in the solar panel's specification sheet (something like 10-15 amp series fuse for many panels).

    In the US, some fire departments/locations are requiring an exterior mounted combiner box/DC disconnect before the wiring goes into the home (using rated electrical conduit).

    Also, if you will be using fuses/breakers in a combiner box--Again heat is a "killer"/problem for fuses and thermal type breakers... Hot/cycling temperatures can interfere with life/tripping point of breakers. A cool/shaded/ventilated area would recommended (although, my attic got much cooler when solar panels were mounted above our roof).
    3) When you make MC4 plugs - do you use a soldering iron? Or just squeeze metal parts with pliers and screw plastic parts with hands?

    MC4 connectors are "crimp" type. And are supposed to be used with the specified tool (for warranty claims and building permit requirements). I understand that some tools will put a special crimp/mark on the finished connector for verification.

    There is a lot of discussion here on the forum regarding, crimp vs solder vs crimp+solder connections.

    In the electronics/power industry, the "gold standard" is a proper crimp. Soldering a crimp connection has been recommended by some folks here, but from my point of view, the solder can make a cable fail from flexing sooner than a pure crimp.

    And only soldering a connection does not meet the requirements for a "mechanical" attachment of electrical connections (a wire connection gets hot, solder melts, and live wire slips out of connector causing an arc and possible fire).

    MC4 crimp tools are expensive--but required by code. If this is a "one off system" for you--can you borrow/rent a crimping tool? Some folks have used generic crimping tool for their MC4 connections.

    Using pliers to crimp is not safe. You cannot make a good crimp this way.

    Hope this helps.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • rollandelliottrollandelliott Solar Expert Posts: 834 ✭✭
    Re: Inverter location

    "MC4 crimp tools are expensive--but required by code."

    Yeah, but so are torque screwdrivers and I've yet to meet an electrician that actually used them.

    You can use a pair of pliars and crimp it good and solder it.

    I posted a survey about the throughalness of inspections and most don't even check wire gauge much less take apart components and check how good the crimp is.

    In the end it's up for you to decide what you feel safe with, because the inspectors are more than likely not going to catch your mistakes. Ironically they tend to focus on things that are noticible, but trivial like if the right warning stickers are present on shut off devices.

    you can certainly mount combiner in attic and the cooler the room the better for a GT inverter.

    If given the choice I tend to suggest mounting them inside instead of outside because the tempeature swings are not as great. Even if it is in a hot utility room or south facing garage.
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