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Old 03-28-2011, 10:39 PM   #1
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Load shedding circuit

We have the normal 30 amps at the dock, but as liveaboards we often times have to manage the loads.* I installed an amp meter in the galley to make it easier, but often times we have to go to bridge to turn off the water heater or other large loads in order to run the microwave or another load. Sadly, I often times forget to turn the water heater back on, and don't realize it until the waters cold (normally when I'm in the shower)

I'm looking at ways to design an automatic load shedding device that will, once it reaches the set point, disconnect the water heater, drier etc.* Once the load is reduced (dinner in the microwave is finished) it will automatically reconnect the other loads.*

One thought I had was a current sensing relay. When it see's current aproaching say 28 amps, it would acitvate, and disconect what ever it was wired to.* I worry about it starting to chatter though if demands remained near the set point.*

I'd love to hear other ideas...................Arctic Traveller
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Old 03-29-2011, 05:03 AM   #2
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RE: Load shedding circuit

Look no further than the Graingers Catalogue.

They have a relay 30A that we have used as an automatic load shedder.

A single wire from when the master is operating cuts off the slave.

Works great , years ago they were $65. or so.
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Old 03-29-2011, 10:28 AM   #3
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RE: Load shedding circuit

When we had 30 amps I put all the high amps stuff on timers, so as one turned*on, another turned off.* We found the hot water heater only need to be run for one hour twice a day.* 4 to 5 AM and 4 to 5 PM.* The hot water is still on a timer.* Timers are cheap and easy to install.*

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Old 03-29-2011, 11:35 AM   #4
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RE: Load shedding circuit

Quote:
FF wrote:
Look no further than the Graingers Catalogue.

They have a relay 30A that we have used as an automatic load shedder.

A single wire from when the master is operating cuts off the slave.

Works great , years ago they were $65. or so.
I'm a little unclear on how you make this work. Whats the description of the relay you use? I'm quite familiar with relays, and relay logic, but what I want is something to monitor the current draw at the source, and then disconnect selected loads as the current nears the set point.* I also want to avoid having the load cycle on and off, such as would happen when the load was shed, the current drops, the load comes back on line, load shed again, current drops, etc.* I was thinking perhaps I'll have to include a timer to allow a minimum OFF time. * Thanks for your ideas..........Arctic Traveller
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Old 03-29-2011, 11:37 AM   #5
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RE: Load shedding circuit

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Phil Fill wrote:
.* The hot water is still on a timer.* Timers are cheap and easy to install.
*

Ya Phill, we already have the water heater on a timer, but since it's smaller, it runs longer, twice a day.* Your correct though it's a good idea, and saves on electricity.* No reason to make hot water when no one is home............Arctic Traveller
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Old 03-30-2011, 04:57 AM   #6
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RE: Load shedding circuit

Its been a while but I'll dig up the part number.

The primary device , say the refrigeration or air cond takes a wire from the compressor power when its operating .

When it is in operation the Grainger relay OPENS , disconnecting the , say hot water heater.

The load shedding chain can be as long as you like , Air cond on , no freezer , freezer on, no HW heater .

With enough ingenuity , "Living well in a dump" (only a 15A plug) can be done.
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Old 03-30-2011, 07:09 AM   #7
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Load shedding circuit

Normally I am not too big on adding more electric devices on the boat. Sort of a keep it simple guy,but this load shredder is interesting.*

I operate from a single 30amp dock line. When I have the AC on I flip the breaker on the water heater off.* This works pretty well but I do have to remember to turn it on, before the Admiral makes me walk the plank.

JohnP

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-- Edited by JohnP on Wednesday 30th of March 2011 07:09:24 AM
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