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Posted by hubops on April 9, 2008, 8:52 pm
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On Tue, 08 Apr 2008 22:17:22 GMT, "RamRodOz Sword of Baal"
>
>> Slightly off topic - sorry.
>> I want to install a 12 volt back-up sump pump in my basement sump
>> hole, in tandem with the existing 110 v. submersible.
>> I'm thinking - submersible bilge pump with marine deep cycle battery
>> - but I'm not sure about a battery charger.
>> I would like trickle charge plus re-charge capability.
>> Would any old sump pump float switch work for the bilge pump ?
>> Any ideas or suggestions appreciated.
>> John T.
>
>DC is much harder to switch than AC (Alternating Current), so make sure that
>your float switch is capable of carrying the full starting current of your
>pump and it is rated for DC power.
>Alternatively use the float switch to turn on a 12 volt DC relay that can
>handle the pump starting current.
>This means that the float switch only need to carry the power that the relay
>coil needs, and the relay contacts carry the pump current.
>The relay contacts would need to be rated for the full power (amps) used by
>the pump. I would oversize it somewhat to allow for the starting current,
>which is much higher than the running current.
>I do not know how much higher the starting current is on DC motors as
>opposed to AC motors, but as a rule of thumb, AC motors starting current can
>be 5 to 7 times higher than running current
>You should be able to pick up an automotive or marine 12 volt DC relay to
>do the job. Make sure the relay is rated for continuous operation, IE not
>say a horn relay that is only rated for short operation.
>I would put a fuse the wire going to the relay for both the coil and motor
>in case of a fault. People tend to forget just how much power can come out
>of a battery when there is a bad fault.
All good points to consider - Thanks.
The bilge pump says 11 amps / max fuse 15 amps.
2000 gal per hour. $ 30. at Princess Auto.
John T.
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