Are there any latent costs that should be considered in the procurement of relays ?

Yes. Although relays appear relatively inexpensive when compared to the cost of an entire system, there is one big cost factor that is almost always overlooked. That is the cost of a field failure caused by a relay malfunction.

There is a simple method to determine the “add-on” failure cost of a relay. By dividing the minimum rated life cycles of a relay into its demonstrated MOBE, you can determine how many relays will be used before a failure will occur. Now, by amortizing the estimated cost of a field fallure over the number of relays to be used, you will know the “add-on” cost per relay.

Formula :

Add on Cost/Relay = Cost of Field Failure ÷ MCBF ÷ Min.Rated Life

Example :

$500 ÷ 1 000 000 ÷ 100,000 = $50