Cooling Pump wiring question

I added a CW-3000 chiller a few months ago to replace a PC cooler that went out on me. I have a SS-40 SA relay that closes the Black wire in my power strip and the chiller plugged into it. My VFD then controls the relay when I start cutting. This has all worked fine for months but now all of a sudden if I leave the chiller plugged into the power strip when not in use it emits a constant “trilling” sound. Operation works fine and the unit powers up and down as usual. I though maybe the relay was bad but replacing it didn’t help. Disconnecting the VFD didn’t stop it either. Is it possible I have to run the White wire across the relay instead of the black? Just checking here before ruin some more cables.


So, the “trilling” sound occurs any time the relay has power applied? I’m not exactly familiar with a “SS-40 SA relay”. Is this a solid state relay?

Is there any voltage on the control pins/connector/screws at any time other than when the VFD supplies an input? It sounds like your wiring setup is providing a stray control voltage to the relay when the VFD isn’t.

Good catch on the solid state relay. There were quite a few on Amazon that turned out to be counterfeit.

Disconnected control wires running from VFD to low voltage side of relay and it still happens.

I agree about the low voltage getting through I just don’t know why

Ok, Dan, since you didn’t give any voltage readings, I’m assuming that you aren’t that comfortable at that level. I’m also assuming that your wiring is correct and not changed since you said the system has worked fine until now.

If you unplug the chiller and plug it into a wall outlet, do you still hear the “trilling” sound?

If the chiller quiets down when plugged into the wall outlet, I would normally take some voltage readings at the output of the relay with the chiller plugged in to see if there’s some leakage through the relay (assuming solid state.) There needs to be at least a low power load on the output, because some relays will fool a volt meter.

When connected to the relay the chiller switch is always on, the noise stops if I turn the power switch off whether it is plugged into the relay or bypasses it.

I have some time today so I will do some troubleshooting and voltage checks. I’m going to build a new cable that removes the power bar from the equation.

I was trying to ascertain whether the chiller makes the noise while totally separated from everything else, but powered.

You haven’t said that yet.

When you said “chiller” I was expecting something with a refrigeration system, it’s just a cooling system.
It only has a current draw of 0.9 amps, and using an inexpensive solid state relay, I wouldn’t be surprised if the relay is leaking enough voltage to make the windings in the fan motor twitter.

Which is what I’m trying to guide the OP to.

As I mentioned if the power switch is off it doesn’t make the noise if using the cable with the relay or using a direct cable. If I turn the power switch on using the cable with the relay it makes the noise. Obviously if I turn the switch on with it plugged directly it simply powers on and runs

… and doesn’t make the “trilling” sound?

Troubleshooting is the process of elimination of parts that don’t contribute to the problem.

Eventually the only thing left is the problem.

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Replace the solid state relay with a mechanical relay, and the noise will be gone.

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Some testing this morning leads me to the same conclusion even though this is the second relay it was still an SSR. Thanks.

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