Connecting protection fuses before relay

[eladn]

Hi. I'm planning to connect the protection fuses before the relays, and not after as shown in the tutorials. This way I would be able to have one fuse for a group of channels (for example all lights in an area/room).

I do so because of 2 reasons: (1) Such connection is viable in my house because, for example, the wiring to all the lights for the living room is being passed through a single connections-box. Using wiring of different protected circuits in the same box is prohibited by law in my country. (2) Grouping circuits use fewer fuses and save space in the power distribution box.

Can such a connection cause any problem? The relays module has a varistor per channel, and I read online that a fuse has to be connected over the circuit with the varistor. My question regards the location of the fuse. Schematically, I'm asking whether it is critical to have the fuse on the closed-circuit between the varistor and the device (like you suggest in your tutorials), or is it also fine to connect the fuse to the feeding phase (leaving the closed circuit between the varistor and the consumption end device without any protection, as shown in the diagram below). I don't really understand the theory behind the varistor's operation, so I don't know if it may be a problem leaving it with the device in a closed circuit without protection on it.
   

Thanks for the help!

[admin]

if you want many lamp protected together use one fuse. you can connect one relay output with breaker with all these lamps. "varistor" is use for protect overvoltage, not for overload, usually will not overvoltage, just sometime mistake connect with 3 phase line. so the important is protect for overload, maybe one channel have connected with too much load, so the current will be large, wire become hot. this protect by breaker or fuse. only after relay circuit can protect. i don't know what's means of before relay?

[eladn]

I mean that the output terminal of the fuse is connected to the input terminal of the relay, then the output terminal of the relay is connected directly to the consumer device. That way the fuse still protects the entire circuit from over current.

The only different between my connection scheme and the suggested version is that in my version the circuit of the varistor and the device is always closed and not protected (like in the schematic illustration from the post). If a very high voltage is stored in the device (due to magnetic energy when the relay is switched off) then it might incur high current trough the device and the varistor (because they are connected in parallel). Can this scenario actually happen? Is it a problem?

[admin]

if the AC load happen, so we suggest add RC snubber. when turn off relay, also will happen your what you said . so you can see there is a resistance on our "OMRON board" to cut the reverse voltage from relay's coin.

[eladn]

Sorry I'm not sure I understand. Have you meant installing the RC snubber over the consumer device or over the relay's coil? In the tutorials the KinCony's RC snubber is used over an AC relay coil. Can it be also used over the consumer device?

Or you meant using it across the relay coil? The OMRON relays are controlled by DC voltage. Can you use RC snubber over its control coil anyway?

[admin]

some load such as have coin, that will have interfere, so need add RC snubber to kill spark. such as AC contact or some big motor. whether need add RC snubber according to the load's type. if relay coin by DC voltage, not need add RC snubber. DC relay or DC contactor almost no interfere.

[eladn]

H32BS controls an OMRON relay via 12v DC for command. The relay is controlled by DC voltage. The load switched by the relay is an AC motor. Where do I connect the RC snubber in such configuration?

[admin]

H32BS+OMRON relay via 12v DC. even if the load is AC motor. also not need to add RC snubber. because OMRON relay's coin work with DC , not AC.

[eladn]

I am not sure. In your tutorials the RC snubber protects the built in relays (installed within the old H32B) from the coil of the AC contractor. In that case, the snubber is connected in parallel with the AC contractor. The AC contractor can be seen as a consumer device from the point of view of the built-in relay. So if we generalized this example, when we apply inductive AC load over relays we need to use an RC snubber over the relay's load contacts to protect it from the load consumed.

Now the question is how can we calculate the right resistor & capacitor for the applied load. In KinCony's RC snubber you probably used the right R&C for the AC contractor's coil as a consumer.

[admin]

whether add RC snubber, according to relay's coin use by DC or AC. R and C value you can see our video tour.