Can someone explain this relay pin drawing to me? It is a Releco C5-A30. Why are the contacts labeled twice, bold and not? Can someone explain how they'd wire this for just a simple N/O switch?
Electronic – Understanding multi-contact relay connection diagram
relay
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There is a mesh in symbols because even manufacturer agree on a common language, marketing issues differentiate them frequently.
Even the common assosiation RELAY AND SWITCH INDUSTRY ASSOCIATION I think it is not existe anymore, but they are publish a handbook about relays, the "Engineer's Relay Handbook"
Bellow is en extract of the above handbook (5th edition) the types of contacs are available throught the market.
The problem with DC over about 40V is that an arc can form much more easily, compared to AC where the 'zero-crossing' provides 100/120 opportunities per second (assuming 'mains') for the initial arc that can occur at the instant of disconnection to extinguish itself.
DC relays are always more expensive at a given current-capability compared to AC, because they need to separate the contacts further to achieve the same current interrupting capability.
Relay voltage ratings are also about insulation materials types, thicknesses, & distances between the contacts and the coil, so even though your circuit may have some mA-scale limited current capability, there's still potential for arc between contacts & coil, depending on how well or poorly the 24VDC-rated relay is designed & manufactured. I really would recommend going for a relay rated for what you're doing.
Best Answer
It's not a simple NO switch, it's a three pole dual throw relay switch.
As to the double numbering, the not bold numbers are European standard terminal markings where first digit is the pole, second is a contact codes 1 = common, 2 = NC and 4 = NO. The BOLD numbers are everybody else.
If you look at the socket for it, you will see the same markings.
If you WANT to wire it as a simple single pole NO relay, hook up your coil voltage across A & B, and use either pin pairs 4 & 7, 5 & 8 or 6 & 9 as your switch.