Solid state relay to replace mechanical relay?

baj702

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

EdTheHeaterMan

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

mattmia2

Mouser or digikey is a good source for ss relays. i'm sureprised rib doesn't make one.

baj702

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

Go to mouser or digikey, you can do a parametric search on trigger voltage and hp rating.

EdTheHeaterMan

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

mattmia2

https://www.mouser.com/ProductDetail/Crydom/CWU2425?qs=sGAEpiMZZMu%2Bisyu8Ze4r8f/craOjFrm07nPK2ddo%2BI=

EBEBRATT-Ed

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

Something like this might work for you:

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

Jamie Hall

EBEBRATT-Ed said:

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.

mattmia2

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

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

@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

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

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

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.

JDHW

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

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...

baj702

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

RIB2401B $19.95
Crydom CWA2425E $51.87 + heat sink + thermal paste

JUGHNE

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

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.

rap1

Not sure if anyone is still monitoring this post but I need help with similar replacement. Actually replacing the 90-340 with the RIB20401b seems easy enough but my issue is I'm not really sure what the 90-340 is doing in the first place. Attached is a picture of the 90-340. it's mounted upside down. The coil input terminals (red and white) appear to go to my furnace. Terminals 4 and 5 (green and blue) look like they connect to a 24vac transformer. 4 and 5 are normally closed on the 90-340. My first question is shouldn't the 24vac be on the coil (input terminals)? And if 4 and 5 are normally closed, wouldn't that mean they are open when the coil has power? What's odd is that the input and 4 and 5 always have 24vac any time I put a a fluke meter on the contacts, no matter if the furnace is running or not there is always a constant 24vac (actually 25.5) on the input terminals 4 and 5 and also on the contacts on the transformer. Any thoughts on why this is wired this way and what it's doing? My understanding of relays is that a power state change at the coil or input results in a change on the load circuit terminals. So if the input always has power, I can't see how the load circuit ever changes? And if it's normally closed, it's open with power and with constant power wouldn't it always be open? Thanks in advance for anyone willing to help this novice out!

EdTheHeaterMan

rap1 said:

I'm not really sure what the 90-340 is doing in the first place.

Why does it need to be replaced. Is there something that is no longer operating that was operating previously?
Is there something that is operating that is not suppose to be operating? Basically, what has changed, and are you sure this relay is the cause of the change?

pecmsg

rap1 said:

Not sure if anyone is still monitoring this post but I need help with similar replacement. Actually replacing the 90-340 with the RIB20401b seems easy enough but my issue is I'm not really sure what the 90-340 is doing in the first place. Attached is a picture of the 90-340. it's mounted upside down. The coil input terminals (red and white) appear to go to my furnace. Terminals 4 and 5 (green and blue) look like they connect to a 24vac transformer. 4 and 5 are normally closed on the 90-340. My first question is shouldn't the 24vac be on the coil (input terminals)? And if 4 and 5 are normally closed, wouldn't that mean they are open when the coil has power? What's odd is that the input and 4 and 5 always have 24vac any time I put a a fluke meter on the contacts, no matter if the furnace is running or not there is always a constant 24vac (actually 25.5) on the input terminals 4 and 5 and also on the contacts on the transformer. Any thoughts on why this is wired this way and what it's doing? My understanding of relays is that a power state change at the coil or input results in a change on the load circuit terminals. So if the input always has power, I can't see how the load circuit ever changes? And if it's normally closed, it's open with power and with constant power wouldn't it always be open? Thanks in advance for anyone willing to help this novice out!

You’re reviving an 18 Month old post so let’s be clear, The motor your controlling HAS an overload?

109A_5

Hello @rap1,

With the information given it seem like the 90-340 is working fine. The coil is energized, opening the normally close contacts (so there is voltage across the open contacts) the relay controlled load is Off.

I think you need to discover the bigger picture of the purpose of the relay. Is there a control device that could turn Off the 90-340's coil and thus turn something else on ? Trace the wires and see where they go to. Why change a relay of unknown purpose ?

A relay can logically be inverting or non-inverting depending on the contacts used NO or NC.

Coil energized - controlled load is Off, thus logically inverting, your case.
Coil de-energized - controlled load is On, thus logically inverting, your case.

Coil energized - controlled load is On, thus logically non-inverting, a common use for relays.
Coil de-energized - controlled load is Off thus logically non-inverting, a common use for relays.

If both the NO and NC contacts are used, one load could be turned off and another be turned on.

Relays also provide control and isolation from incompatible Voltages and/or Currents.

HomerJSmith

1/3hp? That's a hell of a condensate pump. Do you mean a sump pump? Just askin'.

rap1

@EdTheHeaterMan - Thank you for the reply and question. The original 90-340 was humming really loudly. Loud enough that I could hear it in my kitchen which is a floor above. It's actually mounted to the floor joist. It was also getting very hot. Almost too hot to touch. I replaced it with a brand new 90-340 and it's doing the same thing. I've read good things about RIB relays and bought a 2401B as a replacement. I believe the 90-340 is currently controlling my furnace for my indirect water heater. So technically nothing is wrong as far as it functioning. I'm trying to reduce or eliminate the noise and heat issue with the 90-340.

rap1

@pecmsg thanks for the reply and comment. I'm seeing 25.4vac on the coil and load side. So yes technically it is an overload but is that enough to be concerned about? My understanding is that transformers and relays and the like can typically run a bit hotter. But since I'm considering replacing the 90-340 because it's humming and running hot... could those issues be the result of it being overloaded? It seems so but I have no experience with the tolerance involved here and if seeing 25.4vac is normal or not.

rap1

@109A_5 thank you for the reply and detailed information. I was actually expecting a control device like a thermostat to be turning the 90-340 on or off as even with my limited experience that seems logical. However I just don't see it. The coil and load terminals always have 24vac so I don't understand how the coil ever gets de-energized. I did trace the wires. Red and white (coil common) go into the furnace (through a Romex type sheath or leader) and blue and green (4 and 5 NC) connect to a 24vac transformer. And that is the 2nd mystery to me. I would have expected the transformer to be connected to the common with a device controlling it (like a thermostat calling for heat on and off so the transformer could energize and de-energize the coil to control the load side or furnace).

mattmia2

Sounds like it is functioning normally. Usually that stuff is rated for around 90c or more. Isolating the relay form the wood and the screws with soft rubber will help keep it from transmitting noise in to the structure.

What powers the transformer that is connected directly to the relay coil?

pecmsg

rap1 said:

@pecmsg thanks for the reply and comment. I'm seeing 25.4vac on the coil and load side. So yes technically it is an overload but is that enough to be concerned about? My understanding is that transformers and relays and the like can typically run a bit hotter. But since I'm considering replacing the 90-340 because it's humming and running hot... could those issues be the result of it being overloaded? It seems so but I have no experience with the tolerance involved here and if seeing 25.4vac is normal or not.

Not what I asked. Does the motor your controlling have an internal / External overload?

Jamie Hall

Would you be so kind as to take a few more voltages for me? Specifically: both coil terminals to ground. Both contact terminals to ground. Contact terminal to contact terminal with relay energized. Contact terminal to contact terminal with relay deenergized (you may have to disconnect one coil terminals to do this).

mattmia2

pecmsg said:

rap1 said:

@pecmsg thanks for the reply and comment. I'm seeing 25.4vac on the coil and load side. So yes technically it is an overload but is that enough to be concerned about? My understanding is that transformers and relays and the like can typically run a bit hotter. But since I'm considering replacing the 90-340 because it's humming and running hot... could those issues be the result of it being overloaded? It seems so but I have no experience with the tolerance involved here and if seeing 25.4vac is normal or not.

Not what I asked. Does the motor your controlling have an internal / External overload?

I think they hijacked another thread and really didn't explain at all what their relay was connected to.

rap1

@jamiehall Thank you for the reply and willingness to help. I can take the measurements you requested tonight when I get home from work and will update this thread.

rap1

@pecmsg

I am not sure what the relay is controlling so I'm not able to answer that. I'm going to pull the front cover off my furnace tonight and see what the wires from the coil are connected inside. I would imagine the fan motor but I'm not certain without checking.

pecmsg

By any chance your A/C is a heat pump?

ratio

rap1 said:

@pecmsg thanks for the reply and comment. I'm seeing 25.4vac on the coil and load side. So yes technically it is an overload but is that enough to be concerned about? My understanding is that transformers and relays and the like can typically run a bit hotter. But since I'm considering replacing the 90-340 because it's humming and running hot... could those issues be the result of it being overloaded? It seems so but I have no experience with the tolerance involved here and if seeing 25.4vac is normal or not.

Well within tolerances. A nominal 24 VAC xfrmr will run at about 27 volts & change unloaded, you generally won't see 24 until it's loaded down to about it's rating.

EdTheHeaterMan

rap1 said:

@EdTheHeaterMan - Thank you for the reply and question. The original 90-340 was humming really loudly. Loud enough that I could hear it in my kitchen which is a floor above. It's actually mounted to the floor joist. It was also getting very hot. Almost too hot to touch. I replaced it with a brand new 90-340 and it's doing the same thing. I've read good things about RIB relays and bought a 2401B as a replacement. I believe the 90-340 is currently controlling my furnace for my indirect water heater. So technically nothing is wrong as far as it functioning. I'm trying to reduce or eliminate the noise and heat issue with the 90-340.

You know the reason transformers and relays HUM at 60 cycles per second don't you! (Click on Spoiler)

Because they forgot the words!

Put the sheet music in plain view and they will not need to

HUM!