# In an AC supply why does two single phase 110V wires connected to hot and neutral produces 220V

I have seen people connect 110V to the hot end and 110V to the neutral end of the socket to give a 220V to appliances like refrigerators.

My understanding is that current flows, whenever there is a voltage difference between wires like a 110V hot wire and 0V neutral wire, giving 110V supply to a device.

1. But how is it possible where two 110V wires are supplying being at the same voltage able to run a device?

2. Also, how does 110V + 110V produce 220V mathematically?

• The signals are out of phase. When one is at +110V the other is at -110V, with 220V between them. – Unimportant Apr 4 at 19:58
• The difference between $110 \,[\text{V}]\cdot\sqrt{2}\cos(\omega t)$ and $110 \,[\text{V}]\cdot\sqrt{2}\cos(\omega t + \pi)$ (a 180 degree phase shift) is very much not zero. – nanofarad Apr 4 at 19:59
• If there's 110 volts on the wire, it's definitely not neutral. It's hot and cold, as they're called, with neutral being the midpoint between them. Or, less ambiguously, L1 and L2, or X and Y, as opposed to N (aka W). ...There really are a lot of different names for them, aren't there? – Hearth Apr 4 at 20:09
• "220V to appliances like refrigerators" It's a big refrigerator that needs 240V. All the refrigerators I've ever been that close to are designed for 120V. In a typical North American wiring scheme, the only 240V appliances are the stove, the dryer, and the furnace (if it's electric). And while a 3-prong 240V socket looks like an oversized 120V socket, it's got ground and two hot wires in opposing phase (so, 240V between them). – TimWescott Apr 4 at 21:43
• Please be aware that different parts of the world have different electrical systems. Yours seem to be two phase household mains. In other parts of the world you can have three phase household mains, where your observation is no longer true. – Justme Apr 4 at 22:20

simulate this circuit – Schematic created using CircuitLab

Figure 1. On a split-phase supply L1 and L2 are 180° out of phase.

• L1 - N = 110 V.
• L2 - N = 110 V.
• L1 - L2 = 220 V.

You saw something other than what you thought you saw.

• You may want to add something that comes to my mind, reading the OP's first paragraph. There are Multi-wire Branch Circuits that feed kitchen countertops, for example, where the wiring to the outlets look like this. These are permitted under NEC, though there are special requirements at the entrance panel breakers (both L1 and L2 are required to simultaneously "break" in the event of an over-current or a dual-AFCI or GFCI event on either leg.) It might be that the OP is referring to one of these. – jonk Apr 4 at 22:10
• Go ahead, @jonk, if you want to edit or post a supplementary answer. We don't have them this site of the Atlantic. – Transistor Apr 4 at 22:35
• I might, if and only if I see additions from the OP. Otherwise, it's mostly a waste of time, I think. The OP needs to clarify a few things based upon what's already been added here. – jonk Apr 5 at 1:04