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Thread: Common enclosure for DC and AC

  1. #1
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    Common enclosure for DC and AC

    I am supposed to use a car battery for supplying a control Circuit (12 relays) through them I want to control 230v Contactor coils. My question is how can I protect the car battery from any accidentally AC touching the DC control wires (getting loose and fall off terminal or so)
    Thanks in advance

  2. #2
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    Quote Originally Posted by sam-sudan View Post
    I am supposed to use a car battery for supplying a control Circuit (12 relays) through them I want to control 230v Contactor coils. My question is how can I protect the car battery from any accidentally AC touching the DC control wires (getting loose and fall off terminal or so)
    Thanks in advance
    Welcome to the forum. You can use battery terminal protectors for protection:

    Name:  straight-terminal-protector.jpg
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    They make different configurations for top or side post batteries. Should be less than $15 for a set.

    Securing all the wiring to the enclosure and using a good quality electrical tape where applicable. Heat shrink is another option.
    Electricians do it until it Hertz!

  3. #3
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    install a partition inside the enclosure, separating AC and DC. i see them used in wire gutters regularly.

  4. #4
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    All of the above.

    Also remember that the wiring of the DC circuit will need to use the same insulation class as the highest AC circuit in your panel. It's worth mentioning because some battery cables use insulation good for 50V and under, you will not be able to use that.
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  5. #5
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    Quote Originally Posted by JFletcher View Post
    Welcome to the forum. You can use battery terminal protectors for protection:

    Name:  straight-terminal-protector.jpg
Views: 173
Size:  36.6 KB

    They make different configurations for top or side post batteries. Should be less than $15 for a set.

    Securing all the wiring to the enclosure and using a good quality electrical tape where applicable. Heat shrink is another option.
    guys I want to prevent AC current from running into the battery at the fault time God forbid I am thinking about using a power AC/Dc diode any ideas apart from that?

  6. #6
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    i am using the car battery to insure that I have a perminant power for the control

    i am using the car battery to insure that I have a perminant power for the control circuit plus for my indication lamps and switches i would rather take DC for them than AC as it's more safe than AC and for that I have to pass DC through Contactors that have an AC coils. and therefore if any DC wire falls on an AC one then I think the battery is in danger and so does the operator!!!!

    I hope that makes the question clearer.

    if I could find something can do the job of a one-way valve that would have rest my mind and wiped out all the worries

  7. #7
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    A "car battery" would possibly vent hydrogen gas, not a good thing in sealed electrical enclosures. The typical choice for that kind of application is a sealed gel cell battery, which is what they use in UPS systems. You would also need a battery isolator and a float charger for it. Also, 12VDC control devices are harder to come by, the industry standard has become 24VDC, so you would need two batteries.

    More simply, you could just buy yourself a 24VDC UPS that is already set up with the converter from AC to DC, the batteries, the float charger, the DC isolator, protective circuits and a single simple clean package to mount and wire. It will take in 120 or 240VAC and give you a clean stable 24VDC output for your controls.
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  8. #8
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    Use of a diode would rectify half the AC wave, but won't reduce your 230 V RMS to 12 VDC, you will still see a voltage rise in the 12V system if unintentional contact occurs to the AC system.

  9. #9
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    thanks

    Quote Originally Posted by Jraef View Post
    A "car battery" would possibly vent hydrogen gas, not a good thing in sealed electrical enclosures. The typical choice for that kind of application is a sealed gel cell battery, which is what they use in UPS systems. You would also need a battery isolator and a float charger for it. Also, 12VDC control devices are harder to come by, the industry standard has become 24VDC, so you would need two batteries.

    More simply, you could just buy yourself a 24VDC UPS that is already set up with the converter from AC to DC, the batteries, the float charger, the DC isolator, protective circuits and a single simple clean package to mount and wire. It will take in 120 or 240VAC and give you a clean stable 24VDC output for your controls.
    thanks but the whole thing is for a truck though so i have to utilize the car battery we have devices that need AC to work and the control that I am making is kind of selector switch to choose one AC source out of possible three sources

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