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Thermostat change in triangle tube HL-45 tank

Hi was wondering if anyone hade any info on changing out the thermostat in my 1999 triangle tube phase 3 hL-45 storage tank. I received the replacement and it has 2 prongs and the instructions say if you have 3 prongs to disregard the 3 wire (green) and just use the brown and black.  Problem is mine has 4 wires so wants sure how to proceed.  The guy at the company said my storage tank only needs 2 wires.  I found the thermostat that’s in there online but it was only available in the UK and off of a coffee machine website.  Any help would be appreciated very much.  I attached some pics. 


  • Zman
    Zman Member Posts: 7,495
    edited March 2021
    Are there any markings on the wiring terminals?
    Do you have an electrical multimeter? You (or an electrician buddy) could figure it out quickly by turning the dial and checking continuity across the terminals.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    EBEBRATT-Ed Member Posts: 14,534
    You should only need 2 wires. Trace your wires and see where they go. If brown and black go to the boiler or pump relay like to terminals T T you should be ok. It would be better to get a cheap test meter and check it out. Basically when the thermostat calls for heat the contacts close and it should start the boiler or circulator or zone valve.

    Why are you replacing it? Have you proven the system will work with the control bypassed? You could have another issue