Help Wiring Thermostat

System
System Posts: 2,511 admin
in Off Grid Solar & Battery Systems #1
Hi I hope you can help me. Im building a incubator and I need to keep it at a certain temp of course. Anyways I have a digital thermostat like one used in homes and im looking for some help on wiring a small 12v heater up to it. My plane was to use a old Computer Power supply for the power. Thanks for the help.
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #2
    Re: Help Wiring Thermostat

    How many watts is this heater??? I am guessing the power supply is going to be way too small.

    Plus the thermostat is for low current only.

    Most portable space heaters have built-in thermostats. look at using on of them.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #3
    Re: Help Wiring Thermostat

    A simple bi-metal line voltage t-stat will be much simpler to use. All it is an open on rise switch so within reason it doesn't care what the line voltage is (or what the current is within the limits of the t-stat). (Open on rise for heat, open on drop for cooling). Set at say 20C and it stays closed until 20C, then opens. Very cheap to buy and easy to wire as it is essentially just a switch.

    Low voltage or milivolt t-stats are really just relay drivers, triggering another device to open or close. I suppose (thinking about this as I write, an old fashioned low voltage ~ 12volt t-sat would control a 12 volt load, but would not carry much current.

    Tony
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Help Wiring Thermostat

    I will add a caveat about household thermostats in general: they have an on/off temperature range. In other words, although set at 20C they may allow a drop in temp below and/or rise in temp above. Thus at 20C "ON" may be 18C and "OFF" may be 22C. Exactly how wide the variance is depends on the particular thermostat. This may be important if you need to maintain a temperature with little fluctuation.

    The digital thermostat may or may not have closer tolerances, but would need to operate through a relay because as n3qik said they aren't designed for high current.
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  • System2
    System2 Posts: 6,290 admin
    #5
    Re: Help Wiring Thermostat

    The Heater im using is a 12v DC 16 Amp 200 Watt

    I'm need to be very accurate I need to stay within 80 83 degrees F and I just don't think I can do that with a space Heater. I have two different thermostats I can use a Digital one and an older dial one.

    So what would you guys suggest to do? I'm using a larger Cooler for this cheap incubator. I just need it stay in the degree rage of 80-83 for 90 days. Theirs only one catch it must stay dark Any suggestions???
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #6
    Re: Help Wiring Thermostat

    A three degree difference eliminates all consumer type of thermostats as they are + - 10 to 20 degrees.

    Found this on eBay
    http://cgi.ebay.com/WAFER-THERMOSTAT-ASSEMBLY-INCUBATOR-BROODER-/400152868796?pt=LH_DefaultDomain_0&hash=item5d2af837bc

    Looks like from a quick Google search, DYI'ers are using all type of thermostats.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Re: Help Wiring Thermostat

    Quick question... Why 12 VDC? Is this off grid or you just have a 12 volt heater handy?

    Are you trying to avoid 120 VAC for the thermostat/temperature controller?

    There are lots of high current/precision thermal controller options (relays, solid state relays, PID thermal controllers, etc.) for AC line voltage... If you are off-grid and have limited power available, then the components used become much more critical.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #8
    Re: Help Wiring Thermostat

    Yes im just using a 12v heater because i had one laying around. I would love to use 120vac if it made this project easier. What do u suggest i buy Heater and thermostat wise??
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