STC 1000 and heater set up for redundancy

Discussion in 'Anything DIY Related' started by Hammerhead, 6 Jun 2016.

  1. Hammerhead

    Hammerhead

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    Hi guys.

    Some time back I read a post about setting up an stc so it acts as the redundancy on the heaters thermostat. Please advise how I should set it up.

    Thanks.
     
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  3. ascheff

    ascheff

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    Heater thermostats are said to be unreliable, and also not very precise. You add an STC for redundancy by pluggin the heater into the STC and setting the heater thermostat a degree or two higher than what you want your tank to be, and the STC to the correct temperature. This way the STC switches the heater on and off, with a smaller temperature difference between on and off than what the heater usually is capable of.

    The redundancy comes in when the heater fails in the always on position, the STC will still switch it off, and if the STC fails in an always on position, the heater will switch off at a degree or two hotter.

    To also cover a always off position failure for the heater, you need to plug two heaters into one STC, so if one heater fails there is another to back it up. And lastly to also cover the STC failing in an off position, you need two STCs, with one heater plugged into each STC. I just got another STC, to do exactly this.

    This also allows me to run one heater on my inverter, and the other not, so that it doesn't draw too much power in the event of a power failure, but still have some heating on battery backup.
     
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  4. Hammerhead

    Hammerhead Thread Starter

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    Perfect thanks.

    The night before last my temp dipped to 22.3, I had the STC hooked up but only to display temp as it has been a steady 25 since I set it up in May.

    The heaters were purchased second hand 2 years ago and never used until yesterday. It was set on 25 by the previous owner so I just dumped them in and switched them on. In the morning the temperature was sitting at 26.9 so I unplugged them. When I got home the temp had come down to 25.5

    Last night I wired them to the stc but dialled the heaters to 23 yet this morning the temp is sitting at 24.8. When I activated the probe to heat with an ice cube the heaters light comes on so power us being fed to them.

    Is it possible that these heaters are stuck in the on position as they raised the temp to 26.9 and were still on and also came on even though the temp on them were set to 23?
     
  5. ascheff

    ascheff

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    Put them in a small volume of water, a bucket or tupperware, that they can theoretically heat to a very high temperature. If they just keep heating without ever switching off, they are stuck. If they still switch off at some point the thermostat might just not be accurate. I have Hydor heaters that were bought brand new, that heat the tank to 25 although it is set to 22 on the dial, the lowest it can go.
     
  6. Hammerhead

    Hammerhead Thread Starter

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    Yeah sounds like a plan. Need to disconnect from STC and rewire a plug..
    ... Bummer.

    Thanks alot.
     
  7. ascheff

    ascheff

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    Maybe keep it on the STC but set it to a very high temp so it doesn't switch the heater off?
     
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  8. ascheff

    ascheff

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    Also, if you ever buy a new heater that you don't want to cut and lose the warranty, just wire a Janus Coupler to the STC, and plug the heater into that. Bonus is it is double sided, so can add and remove a second heater easily.
     
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  9. Brendan6

    Brendan6

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    Multiplugs. They are awesome. I even have my sump pumps plugged into my "heat" multiplug so that detritus does not settle in my sump. Multiplugs are an STC's best friend.
     
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