Question about Intermatic WH40 - Water Heater Time Switch - NEMA 1 Indoor Steel Case - DPS
The WH 40 is a double throw switch, meaning that it will switch two contacts simultaneously. If you are switching the pool pumps with this WH 40 they will all switch at the same time without the desired delay. (You do not mention how the pumps are switched).
To connect the timer for the elements, a live and a neutral are needed to run the clock.
A live is connected to the two switched 'in' terminals and two wires must then be run to each of the coils on each of the two relays.. A separate live must go to each pole of each relay, the switched live then goes through the thermostats and to the elements.
A neutral must also go straight to the neutral side of each relay coil and to each element, unless you are using double pole relays, in which case you can switch both the neutral and the live wires going to the relays (this is the preferred circuit). Then each switched live will go to a thermostat and the switched neutral will go the other terminal of the heater element. The elements you are using are very heavy and your relays will have to be able to handle around 120 amps at 110 volts or about 60 amps at 220 volts. At 220 volts your 40 amp contactors will only handle 8.8 kw with no safety margin.
If you want a safety feature to time the pumps and elements separately, you will either need two timers or perhaps a pressure switch or flow switch to isolate the heaters when the pump pressure or flow falls.
Come back to me if this layout does not agree with what you have in mind or I have not made any point clear enough.
Posted on Apr 01, 2011
The use of the WH40 timer is NOT appropriate for sequencing the pump and heater as you have described. If these timings are really critical you ALSO need to consider sequencing in the event of power failure. You would not be able to extend the pump running without power and when power is restored you have to have a timer that will reset to the desired sequence.
I will suggest a simpler method to consider. Use a flow switch to activate the heater. In fact a simpler pressure switch on the high side of the pump could turn on the relays to activate the heaters. This would be much simpler that trying to sequence based on run time AND also offer the safety feature should the pump fail or become weak. Just connect the pressure switch to gate power to the thermostats which in turn go to the relay coils which control the power to the heaters.
Posted on Apr 04, 2011
OK this is a pretty rough circuit.
basically, we come in on the phase to the main circuit , here we have a Fuse or Circuit breaker, through the fuse or CB, then to the, main switch, on to the Timers contacts, Normally Open, (You may NOT wish to use a set of contacts here, if so simply eliminate them)then onto the contacts of the Thermostat, Normally Closed, then to the "Hot" side of the Element, the other "Cold" side of the Element connects to neutral, and thus completes the circuit. The other set of contacts from the Timer, (You may choose to use only ONE set of contacts, as related prior?) this then, goes to the "Hot" side of the Pump Motor, with of course the Cold side going to neutral or return.
Make sure you correctly connect the Supply Power to the Timer and Thermostat's Power IN, this is to be connected at the COLD side of the Main ON/OFF Switch for the Phase wire IN.
Posted on Apr 01, 2011
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Posted on Jan 02, 2017
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