Mains Relay pin-out

Hi Enrico, The pin-out doesn't make it *not* compliant. Whether a particular relay

*is* compliant with a particular standard depends entirely on the relay and the end use. Without more information on the application, it's hard to say.

Bob

Hi Bob,

Ok

In Europe, Safety Regulations states that the distance between the Primary circuitry (Mains) and the Secondary circuitry must be at least

8 mm (314 mils).

The pin-out I sketched in my previous post is not compliant to the Safety Regulations because the distance between the COM pin and the coil pins is smaller than 314 mils.

What do you think about it?

Enrico

8mm may be the creapage distance. A common technique is to put a slot in the board. This normally requires a shorter disance between the terminals

Make sure you are comparing apples and apples.

Yes there are these regulations for creepage and clearance distances often related to heavy power, transformers and power circuits within electronic assemblies and numbers of layers of insulation.

However there are devices like triacs and even some opto isolators that inside the device the distances are less than 1mm inside the device or even the legs of the device (e.g. TO220 package).

Transformer windings usually have extra layers of insulation between windings to overcome these problems.

Inside the device there will be extra insulation layers as the relay more than likely has internal parts/wires much closer than 8mm.

Check the manufacturer of the relay for compliance with the relevant standard you are quoting from.

I have seen worse cases of Class II (double insulated) mains connectors where the connector pins were closer than that, and the first layer of insulation could not be achieved without potting the connector in resin. The contacts were not finger guarded, or layer of insulation for BOTH sides of PCB assembly, once connector mounted.

Do some careful layout, low volts in one direction, mains volts in opposite direction, consider having some routing of PCB to cut small slot between the affected pins.

You are dealing with a low POWER relay, and there should be other fault protection devices (fuses etc) in the power run before the relay.

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If You use e.g. switches in Your secondary circuit which the user will touch, and which are not compliant, that would normally not be a problem if Your secondary circuit itself is compliant. So a safe transformer and no non-compliant parts like one of those relays. In that case the relay will make it non-compliant.

If You use one of those relays in e.g. a timer circuit and the switch that the user pushes is compliant to these safety standards and there is no other spot where the device is not compliant, there is no reason not to use one of those relays. But this is more or less like what Bob says, it depends on the actual application whether the resulting device as a whole will be compliant and whether the relay is usable.

That being said, there are also plenty of relais that have a layout that doesn't raise these questions.

Good luck! Yours sincerely, Rene

P.S. What is written on the relay like "Max Switching Voltage 250VAC" has nothing to do with insulation security, it has to do with what the contacts can handle. There are also many small lever switches which have texts like that on them that are absolutely not compliant when it comes to safety.