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Solid state relay to replace mechanical relay?

I'd like to change out the relay for a 1/3 hp motor (condensate pump) and replace it with a similar solid state relay. The noise of the mechanical relay is pretty bad, and it goes off a lot!! I've looked around, but can't seem to find one with similar specs. Anyone know of one? The relay I have now is a White Rodgers starter coil relay model 90-340. 24v coil/12 AFL/60 ALR @ 125vac

Comments

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,553
    edited October 2021
    Potter & Brumfield SSR-480D25 might do what you need. This is not an HVAC or Plumbing supply house product. You will need to find an electronics supplier. The internet has tons of them.

    That relay you are currently using maybe overkill. I'm guessing that relay in not in an enclosure... hence the noisy operation. You can try a less expensive RIB2401 relay (RIB stands for Relay In Box) to see if the lower noise is acceptable before you go for an expensive Solid State relay https://www.supplyhouse.com/Functional-Devices-RIB2401B-Enclosed-Relay-20-Amp-SPDT-with-24-VAC-DC-120-VAC-Coil
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • mattmia2
    mattmia2 Member Posts: 4,340
    Mouser or digikey is a good source for ss relays. i'm sureprised rib doesn't make one.
  • baj702
    baj702 Member Posts: 36
    Thanks for the reply @EdTheHeaterMan, cost isn't too important, I kind of like the idea of solid state. The specs* for the Potter & Brumfield ssr indicate that it has input voltage of 90 - 280VAC, where I need 24vac. This is the problem I'm finding with these ssr's, I can't find any with an input voltage of 24vac. Maybe I'm not reading this correctly?

    * https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=1308242_SSR&DocType=DS&DocLang=English
  • mattmia2
    mattmia2 Member Posts: 4,340
    Go to mouser or digikey, you can do a parametric search on trigger voltage and hp rating.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 2,553
    edited October 2021
    I think this may work
    https://assets.usesi.com/product-media/specification-sheets/USESI_6840_specification_sheets.pdf
    UPC: 79301700268
    Used in fire sprinkler systems
    Edward Young
    Retired HVAC Contractor from So. Jersey Shore.
    Cleaned & services first oil heating system at age 16
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 11,161
    Use a Rib Relay. You don't need an enclosure they don't make any noise and they have a indicator light.

    They have relays with 24 v coils

    Just make sure you pick one with a horsepower rating larger than your motor

    And they are cheap
  • ratio
    ratio Member Posts: 3,028
    Something like this might work for you:

    https://www.johnstonesupply.com/product-view?pID=L46-465

  • Jamie Hall
    Jamie Hall Member Posts: 17,797
    edited October 2021

    Use a Rib Relay. You don't need an enclosure they don't make any noise and they have a indicator light.

    They have relays with 24 v coils

    Just make sure you pick one with a horsepower rating larger than your motor

    And they are cheap

    It's that second to the last line there that's the joker (horsepower). The device which you are replacing is not a relay, it's a motor starting contactor. They are somewhat different beasts, although they look like they do the same thing. If you are indeed starting a 1/3 hp. single phase motor with this thing, look for it to be able to switch at least 15 amps.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • mattmia2
    mattmia2 Member Posts: 4,340
    Is it a motor starter with heater coils for overload protection or just a contactor? If the motor doesn't have protection then you need a motor starter.
  • baj702
    baj702 Member Posts: 36
    Thanks @mattmia2, @EBEBRATT-Ed, I bought the crydom ssr and the Rib relay. I'll test them both out and report back any differences. As far as a motor starter goes, I was under the impression that single phase and less than 1hp doesn't really need a motor starter. Both the relays are rated for 1hp, and the condensate pump I have is only 1/3 hp.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 11,161
    @baj702

    Sounds like your ok then.

    Just to be sure with regard to @mattmia2 comments see if the motor name plate says "thermally protected". It would be unusual for a motor that size not to be
  • JDHW
    JDHW Member Posts: 33
    I am with Jamie on this one. Some time ago (40 years) i was a student and working for a company that made lighting rigs for big rock concerts in the summer vacation. I was tasked with building a controller for the hosts (three phase) for lifting the lighting rig. The general setup is a square space-frame structure that has lots of lights hanging off (240 1kW lights) it and it going to be lifted by electric chain hosts at each corner. It would be good if all the lifts operated together - so i designed a relay based controller that allowed lifts to be selected and then moved up or down together.

    Time for testing - so I lashed up four chain hosts to big drums of cable in the factory. All four hosts worked together and lifted the drums up, Then I selected down and pressed to start button and there was a big bang and nothing happened other that the fuses blowing. The relay contacts had welded up from the lift and the lowering just shorted the mains, Contactors are better!.

    Induction motors take BIG starting currents 6-10 times running current so be careful when selecting switching devices.

    Regards
    John

  • mattmia2
    mattmia2 Member Posts: 4,340
    The horsepower rating of the relay accounts for the starting current of the motor.

    I just looked up the relay that you are using. I had the honeywell version of that relay controlling an electric baseboard radiator in my bedroom for years and it was mounted in a fan center just under my bedroom. I could hear it every time it pulled in or out. That particular relay design is pretty loud.
  • Jamie Hall
    Jamie Hall Member Posts: 17,797
    There is a reason those things tend to be a little loud. As @JDHW 's delightful tale suggests, there is a good chance that the contacts can weld -- if not the first time (big fuses do make a racket when they blow, don't they?!) after only a few operations -- if they are interrupting or making significant current, particularly inductive loads. Therefore, they have to be made to move far enough to interrupt the arc and do it fast enough so that the arc is extinguished in one half cycle. That takes a fairly ambitious spring and an equally ambitious coil to pull them in (opening is harder on them than closing, though). Hence, clank.

    You can do it with solid state circuits such as triacs or thyristors, for instance -- provided the rating of the devices is high enough to take both the full load current and any high voltages present from inductive loads.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JDHW
    JDHW Member Posts: 33
    Next phase (pun not intended) of the Jamie and John debate!

    Thyristors or triacs only stop conducting when there is zero current through the device. So high voltage switching transients are not a problem in the same way that they are in electromechanical devices. However, semiconductors have a tiny thermal mass so a overload current will fry them in milliseconds.Generous ratings on the current capacity.
  • Jamie Hall
    Jamie Hall Member Posts: 17,797
    JDHW said:

    Next phase (pun not intended) of the Jamie and John debate!

    Thyristors or triacs only stop conducting when there is zero current through the device. So high voltage switching transients are not a problem in the same way that they are in electromechanical devices. However, semiconductors have a tiny thermal mass so a overload current will fry them in milliseconds.Generous ratings on the current capacity.

    And it's that zero current that is the ringer in the deck, as it were -- inductive loads can play merry hob with the voltage/current relationships, and easily place a device into a state where it is trying to block based on voltage, but has very high current... zap! As you say -- generous ratings and big heat sinks...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • baj702
    baj702 Member Posts: 36
    OK, I bought a RIB2401B (Enclosed Relay 20 Amp SPDT with 24 VAC/DC/120 VAC Coil) and a Crydom CWA2425E (Solid State Relay 25 amp - 15-25A 18-36VAC input). Both rated for 1 hp motors.

    The relay that was in (White Rodgers 90-340) sounded like a hammer hitting steel, very loud and it carried far and wide. With the number of times the pump turns on during the heat cycle it sounds like a jack hammer.

    I replaced it with the RIB2401B and it was very quiet, nothing like the White Rodgers. You could hear it if you were within a few feet and were paying attention. It sounded like a silent light switch, very very subtle. This relay can have input of 24 VAC/DC or 120 VAC. Plus, you can default to normally open or normally closed. This was such a better relay/experience that I didn't even try the Crydom SSR. This solved all the problems, maybe I could get a teensy weensy bit quieter, but it's not noticeable.

    The only pro with the Crydom SSR is that it would be a mildly cleaner install in the jbox - lots of wires on the RIB2401B for all those extra options looks messy. The con is that you need a heat sink with it, not a terribly big deal but an extra component non the less.

    I'll keep the Crydom SSR as backup, and maybe when I have some extra time i'll switch it in - maybe.
  • baj702
    baj702 Member Posts: 36
    RIB2401B $19.95
    Crydom CWA2425E $51.87 + heat sink + thermal paste
  • JUGHNE
    JUGHNE Member Posts: 9,292
    edited October 2021
    You can mount the RIB on a J-box and put a cover on it to hide all the wires.
    A double pole RIB has a hole mess of wires, many are taped up, but all is hidden in the box.

    And the pilot lights are an added benny.
  • ratio
    ratio Member Posts: 3,028
    With the RIBs, I've been known to open the enclosure & cut off the wires for functions I don't need tight to the PC board (mostly the 120v coil tap & the NC contact). Makes for a cleaner install, & there're less ways for them to be miswired. Note: I'm not sure, but I suspect it voids the UL listing on it.