Induced current into cast iron keel - SailNet Community
 
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post #1 of 10 Old 04-14-2008 Thread Starter
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Induced current into cast iron keel

Hi again, your favorite newbie here
I run a 110volt portable heater (1500Watts) during the winter months, the most effective place to put the heater is on the floor directly above my keel, some of the guys at the dock say I could do major damage to my keel due to induced currents from the heater into the cast iron, speeding up the electolosys action, causing rusting and other nasties.
P.S. I run an extension cord from dock power plugged directly into the heater
no electrical connection to the boat at all..

Does any body think I may have a problem here ?

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post #2 of 10 Old 04-14-2008
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Hi again, your favorite newbie here
I run a 110volt portable heater (1500Watts) during the winter months, the most effective place to put the heater is on the floor directly above my keel, some of the guys at the dock say I could do major damage to my keel due to induced currents from the heater into the cast iron, speeding up the electolosys action, causing rusting and other nasties.
P.S. I run an extension cord from dock power plugged directly into the heater
no electrical connection to the boat at all..

Does any body think I may have a problem here ?
No. So long as the unit is properly earthed (3-pin plug) or double-insulated... they're talking total BS.

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post #3 of 10 Old 04-15-2008 Thread Starter
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I did the math a 1500 Watt heater @ 120 Volts will draw little over 10 Amps, thats quite a good bit of current, this will produce a good magnetic field around the cord that supplies the heater element. Maybe I should keep the cord away from the keel and not worry about the actual heater ?
Thanks 4 the vote of confidence Hartley !

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post #4 of 10 Old 04-15-2008
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I did the math a 1500 Watt heater @ 120 Volts will draw little over 10 Amps, thats quite a good bit of current, this will produce a good magnetic field around the cord that supplies the heater element. Maybe I should keep the cord away from the keel and not worry about the actual heater ?!
Sailbot, that's 10 Amps AC.

An alternating field of 10 Amps isn't going to do anything to an iron keel, even if you were to run the cord through the bilges (which I sure hope you don't do!)

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Thanks 4 the vote of confidence Hartley !
Glad to help!

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post #5 of 10 Old 04-15-2008
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The AC heater isn't a threat to the keel, but shouldn't be left unattended on the boat, since unattended heaters are a big cause of fires on boats. Also, the cord for the heater should have a GFI built-into it... or you're running a huge risk of electrocution.

Ideally, if you plan on doing this every winter, you really should have a shorepower setup installed in the boat, with proper grounding and GFCIs to protect the boat. A regular extension cord, run into the boat is generally a bad idea for any extended period of time. A marine shorepower cord is a much safer way to do things, since the ends twist-lock into the receptacles, and have screw-down sealing collars.

BTW, a 1500 Watt heater is going to draw 12-15 amps, most extension cords aren't rated for continuous use of that kind of draw. A shore power cord is rated for 30 Amps... and can handle that kind of load without any trouble.




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post #6 of 10 Old 04-15-2008 Thread Starter
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I have the twist lock 30Amp plug at the dock end into a regulsr 110Volt Female plug NO GFI though.Thanks for that.

Good news about the keel though

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post #7 of 10 Old 04-15-2008
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I would add that if your power cable is running an earth line and if your heater has an earthed metal case and if the earthed metal case is in contact with any metal of your keel (or anything else metal or at all conductive to water), then you might just have and earth loop, which might conceivably generate some stray current, even if the power and neutral lines are otherwise perfectly insulated.

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I don't believe the heater is sitting on the metal of the keel, but on the cabin sole, just above the keel.




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I think you need to install a proper shorepower setup as soon as you can, since using a makeshift rig as you are is a danger for both you and your marina neighbors.




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post #10 of 10 Old 04-15-2008 Thread Starter
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Good point Sailingdog , I will certainly get a proper hookup with GFI and proper Plug houseing.
The heater's case is plastic and not grounfed to the ground prong (I only have 2 wires going to the heater HOT and NEUTRAL), It does not touch anything metalic..

By the way this thread is going there is more danger to me.
Somtimes silly questions, they may save a life

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