Hot Water Control Circuit

Discussion in 'General Electronics Chat' started by JOESEWI, Oct 11, 2009.


    Thread Starter New Member

    Oct 11, 2009
    I am looking to build an accurate hot water system that will allow me to control hot water in a vessel to within +/- 1C. This is a home project and I have most of the components, I believe, to build a proof of concept system.
    What I have on hand:
    1. A Watlow 988 PID Contoller
    2. A 100 ohm RTD device
    3. A simple on off heater with a potentiometer for temperature control.

    I plan to possibly add an SSR as a switch between the controller and the heating element. It seems pretty basic but I am not sure what components I need to get this all working together or how to tie them all together. Also, I am not sure if I have the controller output set up correctly to trigger the SSR. Any Help would be appreciated.
  2. markosillypig

    Active Member

    Jul 21, 2008
    how big is the vessel you want to heat the water in ???
    gallons or litres
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    #3. You only need a pot. The 988 with the RTD will control the temp set in the 988's display. You didn't say what the heater voltage and current is. The 988 has a built in SSR for currents up to 0.5A and voltages between 24 and 265VAC. It has an electomechanical relay for currents up to 5A. It has a DC output that can drive a bigger, external SSR for higher currents.

    I would suggest that you read over the 988's manual. Then come back with questions. You may have all you need.