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Propex heater

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  • 04-11-2015 4:34pm
    #1
    spaceHopper
    Registered Users Posts: 3,967 ✭✭✭


    My camper came with a propex 1600 heater and it starts OK but the control unit next to it, not the thermostat / on off switch is buzzing, think it's a low voltage alarm.

    Looking at the diagram the heater is connected to the thermostat via a screw terminal block which is connected to the battery via a screw terminal block on the back of the zig unit.

    The heater is about two feet from the battery but I reckon it's 12V is feed by 10 feet of wire, and if I'm luck the ground is only feed by 5 feet of wire. I'm thinking linking the heater directly to the battery via a 5A fuse and a short ground wire.

    Then if I'm right the thermostat will still control the heater. And I won't have IR losses in the cable? What you think?

    While I'm at it I might up the thickness of the wire from the battery 12 and ground to the zig unit. Any recommendation on grade of wire. it's not in a hot zone so will heavy 220V cable be good enough? Or do I need automotive wire.


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    #2
    [Deleted User]
    Posts: 5,238 ✭✭✭ [Deleted User]


    Erm...what kinda buzzing? Arcing, switching or otherwise? Have you tried bypassing the switch?

    I'd put a switch in the new setup. One DC rated for full load breaking. Relying on the thermostat is not the best solution.

    Upgrading the power cable is your call. Are you trying to improve charge or load efficiency?
    It may not be needed. You can check the battery terminal voltage compared to the load voltage to see the losses.
    For charging circuits and switching regulators phat cable is good. For resistive loads it's not as important.

    Feed your parameters in here spec. the cable to 0.3% for a charger 3% for a linear load and whatever suits your pocket for switching loads.


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    #3
    [Deleted User]
    Posts: 5,238 ✭✭✭ [Deleted User]


    spaceHopper wrote: »
    so will heavy 220V cable be good enough? Or do I need automotive wire.

    Cable is cable Space. 220V insulation is good for 12V applications. 12V conductors running in the same conduit as mains must be on mains spec-ed cable (ahem...by must I mean according to wiring regs.)
    Solid core cable is not mechanically strong enough for a vehicle, it needs to be stranded to withstand the vibration.

    Heavy cable to me is 35mm²
    For 12V power: minimum I use is 2.5mm²
    For 12V signal: minimum I use is 0.75mm² if it's on a panel or 1.5mm² if it's running any distance.

    Minimum spec. on cable insulation is 80°C (ambient temperature and exothermic combined).


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