Digital Thermoelectric Temperature Controller Heat Cool

GreenNeedle

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19 Jul 2007
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Your heater doesn't need to be attached to it!!! The heater already has a thermostat in it which cuts it off when it is already at or above the set temp.

Could be used to switch fans on though.

AC
 

scottturnbull

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30 Oct 2008
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An electric fan is an inductive load. The relay will be subjected to a high voltage spike when switching off. If the relay isn't designed for handling an inductive load, it will degrade quickly and need replacing. In the summer, the controller will switch the fan on and off repeatedly, exacerbating the issue. There are workarounds, like using a diode in parallel with the load.

I'm afraid that's about the limit of my understanding in this area.

You should quiz the seller about using it to control a fan, as it might be designed for a refrigeration unit. Aptsys can probably give you more detailed information on whether it will work properly.
 

Hoskins

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15 Nov 2008
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They use these in reefing to control computer fans to get rid of excess heat in summer or from halide lights. I know plenty of people who use these for that purpose. They also overcome the potential disaster situation where the heater / thermostat bimetal strip get stuck and creates the tank to overheat
 

Luketendo

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25 Feb 2008
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West Sussex, England
SuperColey1 said:
Your heater doesn't need to be attached to it!!! The heater already has a thermostat in it which cuts it off when it is already at or above the set temp.

Could be used to switch fans on though.

AC
This is used to turn the heater off in case of a failure, ie to stop the heater from way over heating. Most people use them on Marine Aquariums where this would wipe out all livestock pretty quickly.

I've bought myself one for my Marine Aquarium, it's the ATC 300 version which is cheaper because it cannot control cooling equipment.

The ATC 300 can be gotten for about £25 and when you take the fact that it's small and can go on the front of your aquarium, it's pretty good as the display acts not just as an extra thermostat but a digital thermometer too (and a good one at that with a large red display.)
 

SteveyG

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18 Oct 2008
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Yaxley, Peterborough
It would be normal to derate relay contacts by at least half for inductive loads, but as the relay is rated for 25A there shouldn't be any worries about using all but the largest fans. Refrigeration units are probably worse for start up current anyway.

Using a diode won't work for AC loads as it will form a short for half of the AC cycle, however a snubber network will help if things really are that bad.
 
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