I have a metal electrical panel sandwiched in the wall between two bedrooms. The panel has a relay mounted on it. It's very noisy when switching. I'm dealing with 50A, so trying to use a SSR presents it's own set of issues in terms of thermal management.

Any suggestions for how to dampen the click from the relay?

  • \$\begingroup\$ I was thinking of mounting the relay to a rubber pad. Any idea if that would help? \$\endgroup\$ – Wise Shepherd Nov 12 '19 at 16:19
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    \$\begingroup\$ does the relay broadcast the acoustic noise, or do the wires? or does the mounting plate/wooden_board? is the noise a click, or a thunk? \$\endgroup\$ – analogsystemsrf Nov 12 '19 at 16:42
  • \$\begingroup\$ The noise is a loud click. I feel that since it's mounted to a metal box which is touching the wall, the noise may be getting amplified. \$\endgroup\$ – Wise Shepherd Nov 12 '19 at 16:51
  • \$\begingroup\$ @WiseShepherd I use a hybrid arrangement for a 40 A, 240 VAC application (called a stove and oven.) Engage the SSR, which is in parallel to the mechanical relay, first. Then, engage the mechanical relay. The mechanical relay will take over for the current in the SSR and you can either leave the SSR on or else disable it. Doesn't matter. Then, to shut off, engage the SSR again for a moment, disable the relay, then disable the SSR. You don't need a heat sink in this case. The SSR never gets a chance to dissipate much. It's never on long enough to matter. Still, sound to deal with. Oh, well. \$\endgroup\$ – jonk Nov 12 '19 at 19:05
  • \$\begingroup\$ @jonk how does that solution make it quieter? \$\endgroup\$ – Wise Shepherd Nov 13 '19 at 2:44

Buy a quieter one?

In all seriousness though a contactor/relay is always going to have some noise, that being said, unless it is a closed panel and/or the 50A circuit constantly draws the full 50A you should be able to find a fairly reasonable solution in the way of an SSR, there are companies that sell them as assemblies with a heat sink. A friend of mine works for one that offers single phase AC SSR assemblies capable of switching 50/60/70/80/100A depending on the assembly, and each is rated at 100% duty cycle up to 40C ambient temp.

  • \$\begingroup\$ Thanks. I've actually got a Crydom SSR on order with a heat sink rated at 1.7 C/W. I'll actually only be pulling 30A, and the on state voltage drop is 1.15, so that's going to be 34.5W and so 59 C increase in temperature. (I'm hoping that the on state voltage drop is actually less, as I've read that the datasheet provides worst case). The fact I'm putting this in a wall means less air circulation and so I'm worried I'll come up with cooling issues. \$\endgroup\$ – Wise Shepherd Nov 12 '19 at 16:19
  • \$\begingroup\$ 59ºC increase - you are right to be worried. What is the mains voltage? \$\endgroup\$ – Bruce Abbott Nov 12 '19 at 17:32
  • \$\begingroup\$ 240VAC. I'm setting up an EV charger. \$\endgroup\$ – Wise Shepherd Nov 12 '19 at 18:20

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