doug hess
03-05-2002, 01:29 PM
The float switches do not stand up well to the inductive load of pumps and fail frequently. I got fed up after umpteen failures and solved the problem with a 30 Amp automotive relay.
The wiring is simple. Run 12+ wire feeding the pump system to one relay coil lead and the relay C (common)contact). Connect the pump hot + wire to the other relay contact marked NO (Normally Open). Connect one float switch wire to the other relay coil lead and one to negative/ground, usually black color on boats.
Now when the float switch closed it only carries a fraction of an amp for the coil. The relay ontacts carry the pump power. Even if the relays goes bad after a couple of years replacing it is a lot less hassel than the float switch.
You can order the parts for $4.00 from www.allelectronics.com. (http://www.allelectronics.com.) Their 30 Amp relay with mounting tap, RLY 351 is $2.40. The prewired relay socket RLY5 is $1.50. They are also a good source of microswitches, VHF radio mikes elements $1.00, etc.
Doug,
The wiring is simple. Run 12+ wire feeding the pump system to one relay coil lead and the relay C (common)contact). Connect the pump hot + wire to the other relay contact marked NO (Normally Open). Connect one float switch wire to the other relay coil lead and one to negative/ground, usually black color on boats.
Now when the float switch closed it only carries a fraction of an amp for the coil. The relay ontacts carry the pump power. Even if the relays goes bad after a couple of years replacing it is a lot less hassel than the float switch.
You can order the parts for $4.00 from www.allelectronics.com. (http://www.allelectronics.com.) Their 30 Amp relay with mounting tap, RLY 351 is $2.40. The prewired relay socket RLY5 is $1.50. They are also a good source of microswitches, VHF radio mikes elements $1.00, etc.
Doug,