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Solid state 110 relays

[Deleted User][Deleted User] Member Posts: 6,928
I've used a lot of solid state relays, but never for heating/cooling equipment. Some quirks that might cause problems:

1) Heat is their enemy and the larger the load, the more heat they produce--you need a good heat sink and good natural ventilation (forced ventilation if you pack a lot of them in a small area).

2) Pay careful attention to the load rating. Resistive loads aren't as bad as inductive loads but even with resistive loads give yourself at least 25% headroom in the load rating. A filament burning out in a lightbulb will frequently take out a closely sized solid state relay.

3) They're extremely reliable--I had one set of four that probably each switched 40-50 times per hour for 4-5 hours per day for over 10 years. When they fry due to excessive load they fail open. I did however have one fail closed for a reason I never understood--this alone may be a "killer".

4) You can only test them with a load connected. You can't just use an ohm meter.

5) They're available in a number of "coil" voltages--I've only used low voltage DC but believe I've seen them for 110VAC.


  • [Deleted User][Deleted User] Member Posts: 43
    quiet ones

    Hello i have installed a few electric boilers and have one that is right behind the master bedroom and have some noise problems. Is there a solid state relay that can be interchanged there to make it quieter?

  • [Deleted User][Deleted User] Member Posts: 1,117

    I never seen one but I am sure someone makes them...

    Just a thought if you have no luck.... Can you move the contactor near the fuse box or out of the boiler room...Or did you try another one.
  • [Deleted User][Deleted User] Member Posts: 1,935
    mercury contactors

    you may consider mercury contactors.

    look for an industrial electrical supply house.

    high power solid state will most likely be very costly.
    heres one:
  • [Deleted User][Deleted User] Member Posts: 439

    These are the quietest that I know of , and are available up to 30 amp. Most DIN mounted " ice cube " relays are quiet as well...but do not offer dual coil voltages. If I had to live with 1 relay type , it would be RIB. Also , the brand name " Core " makes nice relays and transformers.
  • SolarstarSolarstar Member Posts: 82

    I've used thousands in 24/7 manufacturing application for heating... maybee changed out 100 or so . As Mike stated they don't like heat and voltage spikes (dead shorts) wipe them out.See PDF on Omrons.
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