I have an Intermatic pool timer box that has two 120 V poles. The LINE has two pins (Pin 1 = L1, Pin 3 = L2), and the LOAD side has two pins (Pin 2 = Load 1, Pin 4 = Load 2). Currently, I have two loads, a 1/2HP pool pump motor, and a salt chlorination controller. Both loads run on 240 V, two-wire. My question is, what would happen if only one of the Load pins became energized, while the other was not?

Since the two-wire configuration delivers 240 V to the equipment, I assume nothing would happen since the other wire would be open, and therefore the circuit could not complete. On the other hand, I worry about sending 120 V to the equipment which might damage it. Please let me know what you think. Thanks!


You are correct. The circuit is not complete if one line is open. However the load is still hot to ground. If someone gains access to any part of the circuit, they could get an electrical shock. If water or vermin get in, there could be a short circuit to ground. The circuit breaker should prevent a fire, but it is still somewhat of a hazard if something happens when no one is around. It is better for both lines to be disconnected when the power is supposed to be shut off.

  • \$\begingroup\$ thank you for your answer! I know the situation described above is undesirable, but I can't seem to think of a practical workaround. Here is the whole story... As described, the timer currently controls a pump motor and a controller for a salt chlorinator. I have a pool heater that would like to override the timer and energize the pump at night. However, if I use the supplied relay to bypass the timer, it will energize the pump AND the salt system, which I do not want. Can you think of a good way to bypass the timer to energize ONLY the pump? The heater supplies a 24v signal when activated. \$\endgroup\$ – Justin T. May 21 at 20:26
  • \$\begingroup\$ There is most likely a way to do what you want by adding some relays. In order to get assistance, you need to draw a schematic diagram of the existing circuit, explain how it works now and how it should work after the modification. \$\endgroup\$ – Charles Cowie May 22 at 0:39

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