a few questions regarding panel changes

Hi, I have been involved in a complete re-configure of my system. Now in the final phase a few questions come up. First I have 8 panels which where sold in the 90's as "quad lams" they needed to be tied together (4 each) to create a 100 watt panel. One of them is experiencing a little de-lamination on the back. Any ideas on how best to test the 8 and possible come up with 4 to possibly get 1 usable panel for about a year. I have a volt meter of course but its does not have amps on it.
Second I am going to replace my old bayonet time delay fuse with a QO breaker box. How to determine the correct size. Thanks-

Comments

  • BB.BB. Super Moderators, Administrators Posts: 33,327 admin
    Re: a few questions regarding panel changes

    It won't be perfect--But you should get a DMM with a 10 amp (or whatever is the maximum current of your panels) and measure the Isc (short circuit current). That and measuring Voc (voltage open circuit) will find most of the bad panels.

    To find the rest of the "bad panels"--if they are Vmp~15-17 volts, you can attach them temporarily to your car battery (watch polarity--you can instantly ruin your panels if wired backwards) and measure ~Imp (there are a few types of failures where Voc and Isc look good, but the panels still don't work correctly).

    For an array with more than two parallel connected strings--I would use a fuse/breaker that is around 2x Isc or Imp... You will not get false trips and you should not get too much current and reduce the chance of a fire (from overheated panels/wiring in the case of a short).

    If you have only one or two parallel strings behind a solar charge controller, you don't really need a series protection fuse per string.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: a few questions regarding panel changes

    Thank you Bill, There are 5 parallel strings. a) 6x75w b) 4x90w c) 2x130 d) 2x 50w and the fifth would be what ever I could salvage out of the 8 quads to create 1 set of 100 watts. But do I in fact gain anything doing away with the disconnect currently in use: bayonet type of time delayed fuse. Providing its the correct size?
    BTW why are there not drain holes drilled into panel frames? I get moss growing in the bottoms. (Upper Pacific NW weather)
    Thanks again.
  • BB.BB. Super Moderators, Administrators Posts: 33,327 admin
    Re: a few questions regarding panel changes

    I am not sure I understand you 100%--But you only need one fuse/breaker per series string (say you have two "6 volt panels" in series--that is one "12 volt string). With a mix of panels, the fusing/breaker setup does get to be a bit of mess. With larger arrays, the protective fusing/breakers is important if there is a short or broken panel. The other panels can back-feed the short and over heat the wiring or cause an arc which can light-off debris in the area.

    For paralleling panels--ideally the Vmp of each string should be around 17-18 volts (at STC).

    Depending on the controller type PWM--cheaper type--You can parallel panels just fine as long as the Vmp is >~15-16 volts. If you have panels with Vmp over ~21-24+ volts--then you should look at a MPPT type charge controller for those "higher voltage" Panels. With large voltage miss-matches (for parallel connections), you can loose quite a bit of energy.

    For MPPT type charge controllers, the Vmp of each string should match all of the others within ~10%.

    For series connections of panels, their rated Imp current should be within ~10%.

    I am not sure about the drain holes for the frame--If you are talking about on the top near the glass--Be very careful, those are typically made from tempered glass an any nicks or pressure (and heat) at the edge of tempered glass can cause the whole pane to shatter (instant useless panel).

    I personally, would not drill/work around the edge of the panels attempting to drill / file / cut drain areas. I think you are left with soap and bleach to keep the moss down.

    You can try small zinc or copper strips (stripped copper house wiring?) silicon glued to the top edge of the glass (let the metal ion containing rain water wash down the face of the panels)--out of the way of the solar cells--I have not tried it, but zinc and copper is supposed to be a decent biocide for moss growing on roofs--perhaps it would work here--attach the zinc/copper directly to the glass--you don't want to risk corrosion if there is an electrical connection to the aluminum frame.

    Don't know if it would work--but might be worth a shot on a couple panels and see what happens.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: a few questions regarding panel changes

    Thank you maybe I am wrong in my description. I have the panels wired parallel by group (ie: the 90 watts together, 75 watts and so forth, the only series is the quad lams) each group has it's own wire to a combiner box, the combiner box goes to fused disconnect before it goes to the solar controller/ battery bank. The controller here is a Trace c60 (I know trace is no longer but the same controller is available under new name).
    So the query is would I gain anything by changing out the bayonet type fuse in the disconnect opting for a breaker? Since I have all this torn apart.
    One other question I have a DR series (1512) inverter which the transfer switch fuse appears bad I have not been able to find a replacement. Not a diy project?
  • BB.BB. Super Moderators, Administrators Posts: 33,327 admin
    Re: a few questions regarding panel changes
    deepspace wrote: »
    The controller here is a Trace c60 (I know trace is no longer but the same controller is available under new name).
    They are now Xantrex/Schneider Electric... But from what I understand, still pretty much the same product shipping today.
    So the query is would I gain anything by changing out the bayonet type fuse in the disconnect opting for a breaker? Since I have all this torn apart.
    If the fuse is protected from the weather and not causing you any issues--There is no pressing reason to use circuit breakers instead. Some people like the ability to turn off panels/strings using the circuit breaker like a switch to work on system, check the output of each string, etc...

    As always, having a couple spare fuses (or even circuit breakers) on hand is always a good idea. Fuses and Breakers tend to be the most unreliable parts of an electrical circuit (by design).

    Really a personal choice vs costs.
    One other question I have a DR series (1512) inverter which the transfer switch fuse appears bad I have not been able to find a replacement. Not a diy project?

    It can be very difficult to find parts for any electronics that are over 10 years old--most vendors have dropped support/repair services for such devices, and the independent repair shops also are limited to old spares and cannibalizing used equipment.

    Although--fuses are usually pretty much the same decade after decade. Perhaps you can post the name/part number of the fuse or a photograph of it...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: a few questions regarding panel changes

    Thank you for the help. So I am to interpret I really have little to gain by changing out my current disconnect in favor of breakers. My fear was added resistance. The fuse number for the DR inverter is: Buss 17430-18 its rectangular with a reset button outside the case. I was not present during the "surge" which blew it so I have nothing to work with.
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