# How to connect two inputs to one output for a mains connection

I have a digital switching system in my home that controls the water heaters. One heater is shared between two rooms and I need a connection such that it can be turned on from either room.

I'm looking for something like an OR gate that will work for mains rated 250V/5A. What can I effectively place in the blank space to physically achieve this?

• It is possible that what you actually want is a two-way switch, not an OR implementation. It's probably a good idea for you to google "two-way switch", and confirm if that is what you're after, or if OR functionality is really what you want. – Dampmaskin Feb 8 at 17:21
• I do in fact want OR functionality. The person in each room should be able to turn the geyser on independently of the other. With a two-way switch there would be too much confusion. – Aurarius Feb 9 at 7:43

simulate this circuit – Schematic created using CircuitLab

Figure 1. (a) Typical 2-way switching as used on stairways. (b) OR switching.

• If you want either room to be able to switch on or off then use (a).
• If you want the heater to be on if either or both rooms require it then use (b).

If you want to switch the input to the digital system then:

simulate this circuit

Figure 2. Switching an input for a digital controller.

• Option b is exactly what I'm going for. I'm unsure of how to physically achieve that. I have two inputs that will come from the switch of each room and need to pass that into a single output for the heater. What device can I use to do this? – Aurarius Feb 9 at 7:49
• Option b of Figure 1 or 2? Why are you looking for a device? I thought you had one. – Transistor Feb 9 at 7:59
• I've edited the question to add an image. I have the switching system but can't directly short the two lines coming from the switched and connect it to the heater right? – Aurarius Feb 9 at 8:07
• So you want Figure 1b? Just connect the two switch wire at the heater terminal. – Transistor Feb 9 at 8:10
• Alright thank you! I was worried that might cause an issue of some kind if both switches were on. – Aurarius Feb 9 at 8:29