To me it doesn't matter if there is a 120 volt panel somewhere in the building or not. This is all pure speculation on the part of people on this internet forum. The fact remains that if someone posts a question on how to hook up a welder to a three phase 480V service they are not capable of doing the work themselves. There is nothing wrong with the OP asking the question, there is however in my opinion only one correct answer to it and that was already given in the first response. I have no problem giving advice for residential work but three phase wiring is absolutley no place for a novice or DIY. Anyone who needs to ask how to connect something to a three phase service is not qualified to do it. There are way too many varibles in the situation - just look at what people are throwing around on this board right now - Delta's, Y's, high legs, buck transformers, step downs, step ups - heck why dont we just recommend that they install a phase converter while were at it...

It sounds to me like you're saying the inside aircon unit is powered by the outside unit, which in turn is connected to a 240 volt source. If the inside unit requires 120 volts, you can NOT power it from the outside unit unless you have a 3-wire-with-ground cable to the outside unit. The reason for this is that with a 2-wire cable you are using the groundING conductor for 120v power. This is not only a code violation, it's dangerous. In some cases where a fault exists in the house wiring, this can put line voltage on the cabinet or casing of a grounded device. This can be DEADLY. If the inside unit needs 120 volts and that voltage is derived from the outside unit, you will have to rewire the outside unit with 14-3 or 12-3 cable, whichever is specified in the installation manual. An alternative to rewiring is to use a 240:120 volt transformer to derive the power for the inside unit. The transformer will have to be sized for the load the inside unit presents. The breaker rating is per pole. A double pole 30a breaker is still called a 30a breaker. It can supply 30a of 240v power, or two circuits' worth of 30a / 120v power. In any case its overprotection limit is always 30 amps. Hope this makes sense!

The following is a very general discussion and may not apply to this situation. As Pete said, you've provided rather little detail. If you have a 120 volt motorized timer, it may be possible to rewire it so that the timer motor is powered by 120 volts and the contacts switch a 240 volt load. BUT, there are some concerns. 1. If the timer isn't rated for 240 volts, using its contacts at that voltage would be a code violation, if not outright dangerous. 2. If the timer has a single pole switch, only one hot leg would be opened, making a proper separate DPST disconnect essential if it's not already there. 3. If you have only 120 volts at the remote location, you probably have only two current-carrying wires and a ground. You can't (safely) derive both 120 volts and 240 volts from this combination. It might be possible to use a small transformer to operate the timer motor, but the cost would probably be nearly the same as replacing the timer with a 240 volt model. Bottom line is - you're better off to either get a 240 volt timer to match this pump, or a 120 volt pump to match this timer. Again, this is based on the limited information you provided. You may wish to offer more.

The fact that the new cooktop did not work when you connected both the white and bare wires from the cooktop to the bare wire from the supply cable means that you have a bigger problem with the house wiring itself. (It should work) Your entire grounding system could be messed up. This can effect the efficiency of other safety measures in the electrical system, such as the breakers may not trip when necessary, resulting in a fire. You need to have this fixed by a qualified electrician who has the ability to track down the problem. Then, you can keep the cooktop too. The next one you try may not work either. 250.140 Frames of Ranges and Clothes Dryers. Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be connected to the equipment grounding conductor in the manner specified by 250.134 or 250.138. Exception: For existing branch-circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be connected to the grounded circuit conductor if all the following conditions are met. (1) The supply circuit is 120/240-volt, single-phase, 3-wire; or 208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system. (2) The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum. (3) The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE serviceentrance cable and the branch circuit originates at the service equipment. (4) Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment.