Impossibly simple home wiring circuit

Discussion in 'Analog & Mixed-Signal Design' started by clarky456, Jul 11, 2018.

  1. clarky456

    Thread Starter New Member

    Jul 11, 2018
    Hey guys, great forum, hoping to glean some things over time. I have a problem that I'm likely over thinking and would like some opinions on.

    Standard home ventilation fans, four of them, all on their own circuit (USA household current, 115vac). Flip the switch, the fan turns on. Modifying the home for automation and efficiency requires we tie the exhaust output into one stack and depressurize the stack using a single booster fan. Flip the switch and the individual fan turns on along with the booster fan. Im having trouble isolating the four circuits at the booster fan.

    I attempted to locate a 4pst-No contactor that would work well, no luck. Cant seem to find a contactor using 115vac for the coil. Plan was to use wire from fans to switch relay, relay switch to booster fan, thereby separating the 4 circuits. Latest idea was to find an inductance switch to control the booster, but most of the switches Im finding require an amp (1amp) to trigger. The fans hardly pull 1/15 of an amp.

    Im lost. Any ideas?

  2. Hymie

    Active Member

    Mar 30, 2018
    The simplest solution would appear to use a double pole switch (at each fan), with one pole switching the current to the fan and the other pole switching the booster fan.

    Alternatively (as you planned) wire a relay coil (rated 120Vac) across each fan, and wire each of the normal open relay contacts in parallel, switching the booster fan – there are plenty of suitable relays available.
  3. MaxHeadRoom


    Jul 18, 2013
    A contactor is a bit heavy for that application, I don't know where you have been looking, but that is about the most basic contactor you can find.
    For small load, the 4 contact cube relay are plentiful and probably a better fit for what you are doing.
    BTW, most of N.A. is now 120vac no longer 110vac.