Any HVAC experts here?

Discussion in 'General Electronics Chat' started by blueroomelectronics, Nov 18, 2010.

  1. blueroomelectronics

    Thread Starter AAC Fanatic!

    Jul 22, 2007
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    In heat pump applications, they are 99.9% always jumped together.

    They share the same transformer, and only the reversing valve circuit controls the refrigerant direction flow for heat/cool cycles.

    If you have a unit that has separate compressors for heat and cool, then you cut the jumper and let each compressor use its own transformer and control.

    And yes, thats all that the jumper connects is the Heat and Cool relays.

    A split system requires independent control over each. A Heat-pump does not.

    A heat pump is simply an A/c running backwards. Instead of expanding the refrigerant indoors, the refrigerant is compressed indoors. (By pumping the refrigerant backwards through the TXV (Thermostatic Expansion Valve) )
    Last edited: Nov 19, 2010
    blueroomelectronics likes this.
  3. blueroomelectronics

    Thread Starter AAC Fanatic!

    Jul 22, 2007
    Thanks rm I don't have a TR-16 but would like to build a kit with similar functionality plus Ethernet and a little more. IMHO a modular, open source, internet connected thermostat kit would be fun & functional. Same four wire using the existing thermostat wiring as the TR-16

    Thermostat PIC16F917 (I'll have to dig for an 18F with LCD preferred)
    RS485, LM75, 2.5 digit LCD glass, four buttons
    (possible opto in, relay, humidity)

    Controller PIC18F67J60 with Ethernet
    Six GP relays with HVAC jumper, two optical inputs, SW RS485, HW RS232 DCE
    (optional DS1388, EEPROM x 4, LM75 freeze detect, 315/433MHz RF TX/RX modules)

    Comments welcome.
    Last edited: Nov 19, 2010