# EM Relay Parameter Calculations

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?

• 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. Feb 3, 2015 at 17:20
• @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.) Feb 3, 2015 at 17:23
• You probably wouldn't.. but keep in mind the lifetime limitation if your switching happens to be frequent. Feb 3, 2015 at 17:37