I have a board populated with Omron relays (G5Q-1A4-EU DC5) and I want to use them to switch circulation pumps (https://imp-pumps.com/pumps/ghn/). Is the previous relay appropriate to be used with said pumps?

From the information available on the pumps, they seem to act as a resistive load during operation. Is this behaviour only expected when they're under full load? If the relay switches off the pump while acting as a resistive load, is there a danger of an overvoltage appearing on the relay contacts?

If the relay mentioned previously is not suitable for this application, could it still be used if paired with the appropriate protection components? What would be the most suitable protection in this particular application? And if not, what kind of relay would be suitable for this application?

I know I just asked a ton of questions, but any help would be greatly appreciated. Thank you.

  • \$\begingroup\$ Which model pump you going to use? There are many listed and they are different so it’s hard to give an answer without this information \$\endgroup\$ – Leoman12 Jun 13 at 1:39
  • \$\begingroup\$ I'm considering the model GHN 25/80-180 (210 W) \$\endgroup\$ – puq_87 Jun 13 at 22:37

I would say those relays are inappropriate for a heavy motor load. Relays intended for a motor load will be much larger and more expensive. Motors have inductance that causes arcing during switching (particularly switching off) and draw a large surge current.

When "on" and up to speed the load is not that different from a resistive load, but that does not really help except that the relay contacts will not overheat if rated for appropriate RMS current.

Here is an example of a relay series that is rated for, and recommended for, motor loads. Of course you still should evaluate the lifetime and other specifications in relation to all your requirements.

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  • \$\begingroup\$ Would these relays need to be paired with other protection components such as MOVs or TVS diodes? What would be the most suitable one? \$\endgroup\$ – puq_87 Jun 13 at 22:51

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