Problem with Dankoff LCB 8A

System
System Posts: 2,511 admin
in Solar Water Pumping #1
I have a Dankoff slowpump hooked up to a 180 watt panel through a Dankoff (now ConEnergy) LCB 8A. I left for a couple of months, so shut off the pump by putting the LCB switch to "pump off" position and closed water valves. When I returned I was shocked to see the LEDs flashing on and off (slowly) and the pump trying to run. With the valves closed and am concerned that either the pump or the LCB have been damaged by the excessive pressure. After opening the valves, the pump will not spin, but continues its off/on impulse. I disconnected the water lines and tested the pump, it spins with no pressure load, but when reconnected under 120 PSI will not run normally. It seems to be drawing excessive current, causing the panel to short out, as the voltage in drops to 2 volts, out to 1 volt, cycling at about 5-10 second intervals with bursts of up to 20 volts. Panel produces 41 volts with no load.

Anybody else have this problem? Recommendations?

Dan
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Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: Problem with Dankoff LCB 8A

    sounds like the pump was bucking and or pushing against closed valves and this overheated the pump causing windings to short out within the pump. i don't know about if the electronics faired ok in this either, but i believe the pump is no good.
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  • System2
    System2 Posts: 6,290 admin
    #3
    Re: Problem with Dankoff LCB 8A

    I checked the resistance of the windings with an ohmmeter, measures 3.4 ohms. Not sure what it is supposed to measure, but this seems fairly reasonable. The LCB has a 10 amp fuse installed, which did not blow. At 24 volts the panel can only produce 7.5 amps before shorting out. The pump is rated at 8 amps maximum. I suppose it is possible that the windings are partially shorted, so the pump still spins at low water pressure.

    My question is why was the pump running at all with the switch in the "pump off' position? The moral to this story is to be sure and disconnect the solar panel completely from the LCB if you are taking the system out of use for an extended period. Don't rely on the switch on the LCB's circuit board.

    Dan
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: Problem with Dankoff LCB 8A

    Checked the pump today with a 12 volt battery, and it spins and pumps water just fine. So it must be the LCB. Should I get one that is more heavy-duty to replace it? An ammeter in line with the 12 volt battery read 6.5 amps, so maybe the 8 amp LCB is a bit under powered and may have led to premature failure.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: Problem with Dankoff LCB 8A

    i'm glad your pump is working. i am not sure what to tell you of the board and is up to you as to the best course of action for you. i know i wouldn't want that to happen again though.
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  • gpigeon
    gpigeon Registered Users Posts: 34 ✭✭✭
    #6
    Re: Problem with Dankoff LCB 8A

    Dan,
    Very interesting and good tip re disconnecting the Panels.
    I have a similar setup to you. Conergy 1304 driven via 160W panel through an LCB8 and have had ongoing problems, although not with the LCB, since installation about 2 years ago. Hopefully I have it sorted now and have had a few months without a breakdown.
    Sorry that I can't help with your problem but I have learned something that is not contained in the Installation manual. About 6 months ago my system started blowing the 10A fuse in the LCB. Conergy US advised me to install a 15A fuse. This also blew after a short period. The problem was a faulty check (non-return) valve in the discharge line.
    Regards.
    Bill W.
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