Separate Cable for Neutral?

[SAS]

I installed a 220 volt timer that controls my hot water heater. I tapped into the existing wiring, which did not have a neutral - just two hot wires and a ground. I would also like this timer to control the hot water recirculation pump; that requires a 110 volt circuit. Since there is no neutral, I would either have to 1) run a new cable with a single white wire, 2) use the existing ground as a neutral, or 3) replace the existing run from the timer to the panel with a cable with 3 wires plus a ground. Using the ground is the easiest, but I suspect it is a code violation. Running a separate cable for the neutral is not a big deal, but if I do that does the cable size have to match the existing cable?

 

[Stuff]

With a few exceptions all wires must be in the same cable.
What about changing to a 240v pump?

 

[Sponsor]

 

[Reach4]

Is there no 120 volt circuit nearby that you could power the pump with? If not, maybe while running wires anyway, you could put in a new 120 volt circuit and add some handy outlets while you are at it.

You could use a separate timer to control the pump.

 

[LLigetfa]

What about using a 240V relay to control the 120V pump?

 

[Dana]

NEVER use the safety ground as a neutral! (Indeed a code violation.)

Using a separate wire for the neutral can work, but it MUST follow the SAME path as the hot wiring the full distance from the breaker panel to the load. If the hot & neutral are run along different paths covering a large loop area it creates an inductive loop antenna, emitting gobs of low frequency magnetic emissions whenever that load is active that can interact with everything from dimmers to home entertainment electronics. (Want a whole bunch of staticky 60Hz hum in your audio?)

 

[WorthFlorida]

I would leave the recirculation pump alone unless it runs 24/7. You placed a timer on the water heater to disconnect power assuming it is during the hours when no one is home. Is the pump on a sensor switch that only runs when water is in use? If it is why bother. If it is running all the time just get another 120v timer for it.