Original wiring is Romex 12/2 no ground.New heaters have chassis ground.Do I pull new Romex 12/2 with ground or can ground be added back to main panel?Wiring is 240 volt
Wiring – Baseboard heat wiring
baseboardwiring
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There can only be one point in the system where neutral and ground wires are joined, and this is usually in the main panel. Therefore, you must lift the bond from the generator, or disconnect the ground wire from the generator to the transfer switch.
If you lift the bond on the generator, you can run both ground and an insulated neutral back to the transfer switch. You will also run ground and insulated neutral from the main panel to the transfer switch, and ground and insulated neutral to the subpanel from the transfer switch. Note that neither neutral nor ground are switched in the transfer switch. The generator can optionally be grounded to a rod.
If you cannot lift the bond, disconnect the ground wire to the transfer switch at the generator (or don't run a ground wire at all). The subpanel will still be grounded from the unswitched ground wire from the main panel. The generator cannot be grounded to a rod because this would tie the neutral to ground in a second location through the bond.
According to Table 250.122 of the National Electrical Code, a 10 AWG copper conductor is fine as an equipment grounding conductor for circuits with up to 60 ampere protection.
National Electrical Code 2014
Chapter 2 Wiring and Protection
Article 250 Grounding and Bonding
250.122 Size of Equipment Grounding Conductors.
(A) General. Copper, aluminum, or copper-clad aluminum equipment grounding conductors of the wire type shall not be smaller than shown in Table 250.122, but in no case shall they be required to be larger than the circuit conductors supplying the equipment. Where a cable tray, a raceway, or a cable armor or sheath is used as the equipment grounding conductor, as provided in 250.118 and 250.134(A), it shall comply with 250.4(A)(5) or (B)(4). Equipment grounding conductors shall be permitted to be sectioned within a multiconductor cable, provided the combined circular mil area complies with Table 250.122.
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Best Answer
Under NEC 2014, you can leave the conductors alone and add (retrofit) a ground wire.
It is not necessary for the ground wire to follow the same route as the conductors. However the ground wire must go to the ground bus in the same panel the heater is powered out of.
Circuits which come out of that same panel can share ground wires. So you don't have to home-run all the way back to the panel, if you can reach the ground wire of another circuit also served out of that same panel. However the entire route of the ground wire must be as thick as the conductors, i.e. at least 12 AWG in this case.
If your jurisdiction hasn't adopted NEC 2014 yet, well... I don't know what to tell you. I would investigate whether they're likely to.