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Sometime back I made a relay board to control my table lamp using bluetooth. It worked perfect and so now I would like to upgrade to a beefier power relay.

The aim is to be able to control any household device. Mainly air conditioner, water heater, room heater.

I am based in India (230V, 50Hz). We use the Type M power plugs for power devices (BS-546 standard) that support 16A max current. I am assuming that none of the devices would consume more than 16A in steady state.

Based on this, Maximum Apparent Power = Vrms * Irms = 230V * 16A = 3.68 KVA

I am looking at the O/E/N 62 Heavy Duty Power Relay Form 1A(data sheet here). In it the relay parameters are:

  1. Max Current = 30A
  2. Maximum Power Rating = 7.5 KVA

So I should be fine using this relay?

What about the life expectancy of the relay?

As per the datasheet, electrical life = 10^5 operations. Assuming I operate the load (close and open relay contacts) 5 times a day and ideal conditions, that gives me 500+ years.

Any way of getting a more 'realistic' estimate on the lifespan of the relay?

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  • \$\begingroup\$ The 30A rating only applies to the '1A' version with a single form A contact. Note that the life is 100,000 operations (resistive)- should be a bit more at lower current (if purely resistive, if you don't slow the turn-off, if the coil voltage is at nominal etc.) If it's occasional switching it should be fine- at once per second it won't last more than a day or two. \$\endgroup\$ – Spehro Pefhany Feb 3 '15 at 17:20
  • \$\begingroup\$ @SpehroPefhany Yes I should have mentioned that I am planning to use the 1A form. Why would I want to switch at once/second? It would mainly be used to switch power devices (Air conditioner, water heater etc.) \$\endgroup\$ – Ankit Feb 3 '15 at 17:23
  • \$\begingroup\$ You probably wouldn't.. but keep in mind the lifetime limitation if your switching happens to be frequent. \$\endgroup\$ – Spehro Pefhany Feb 3 '15 at 17:37
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You've got a factor of 2 safety here. I'd say you should be fine. Make sure you start paying attention to wire routing, insulation choice, grounding, etc. There's lots of ways to get hurt if you don't do things right.

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