Black Box To Turn On a Pump

As I understand it; When the solar panels are hot enough, the gas booster, which has its water supply in series with the closed circuit solar heating line, will be de-activated and the solar heated water simply passes through the gas booster heating element. Only the solar panel supplies heat.

When the solar panel temperature sensor indicates that it cannot supply heat to the water, the controller will activate the gas booster to heat the water instead. The gas heated water will still circulate via the solar panels and at the same time the controller feeds power to the circulating pump.

What you are looking for is a fully automatic system to avoid having to move the pump cord from one socket to the other and with no requirement for user intervention (other than setting the manual timer period).

Since it would be mandatory for the pump to be operating whenever the gas booster is operating the solar/gas controller would need to assume priority control over the system so as to avoid the pump stopping when it was already operating under manual timer control.

The simplest method involves working directly with 240Vac and unless you are certified to do so (qualified electrician) you should not attempt to carry out any modification or design. You need to be fully aware of the correct procedures and wiring techniques which ensure complete isolation of users from the 240Vac supply. Nevertheless, here is one method of achieving your requirements. I will not be able to specify the components, construction techniques or wiring specifications since this is fairly time consuming.

First, both the manual timer and solar/gas controller devices should receive their 240Vac supply from the same distribution circuit breaker (ELCB).

The control function you require can be done fairly simply using just

2 relays. Both relays would need to be rated for 240Vac motor/pump operation suitable for a 1HP motor(746W). The relay which supplies power to the outlet socket from the manual timer would need a single make contact (usually a SPDT relay) whereas the relay which supplies power to the outlet socket from the solar/gas booster controller must have a make contact and a separate break contact (usually a DPDT).

The Active line output from the manual timer must be routed via a break contact on the relay which is powered from the solar/gas controller and then to one side of the coil and also to one terminal of the make contact on the manual timer relay. The other terminal of the make contact on the manual timer relay is wired directly to the Active pin of the outlet socket. The other side of the coil on the manual timer relay goes to Neutral as does the Neutral pin on the outlet socket.

The Active line from the solar/gas controller is wired directly to one side of the solar/gas relay coil and also to one terminal of the second contact on this relay. The make terminal of this contact is wired directly to the Active pin on the outlet socket. The other side of the coil is connected to Neutral.

In operation, let us assume the pump is operating under manual timer control. The manual relay will be operated directly from the timer via the break (NC contact) of the solar/gas relay which is currently not operated. The outlet socket will supply power to the pump.

If, while under manual timer control the solar/gas controller activates, then the solar/gas relay will operate and it will now feed power to the outlet socket. When the solar/gas relay operates the NC contact in series with the manual timer relay coil and contact will open and thus cause the manual timer relay to release. The solar/gas relay has now assumed priority control over the outlet socket. Should the wiring not be arranged in this manner it would be possible for the pump to stop working when the timer period expired while in manual timer mode and if the solar/gas controller was now activated after the pump switched off, it would not be able to start again. No water would circulate and the gas booster might be damaged due to non-circulation of the heated water.

Again, I would urge you to not undertake any work if you are not a qualified electrician.

PS. I just realised a feedback path will exist to keep the manual timer relay operated if only the Active is routed via the solar/gas relay contact. To rectify this problem the Neutral line connected to the manual timer relay coil also needs to be routed via a separate break contact (N/C) on the solar/gas relay. This means the solar/gas relay must now have 3 contact sets instead of 2.

Hope I haven't overlooked anything else.

I have a swimming pool pump that I'd like to turn on if either one (or both) of two conditions exist:

Presently the pump's power cord can be plugged into either a clock/timer so it will turn on at certain times of the day that I choose,

OR

The pump's 240vac power cord can be plugged into a socket attached to a 'computer' on a solar heating system, and that socket will be turned on when the computer decides the solar panel temperature is not hot enough to heat the pool water. This allows a gas heater to turn on and heat the pool.

I would like to have the pump turn on if either one (or both) of the conditions exist, but I need some advice. What I envision is that the pump power cord will be plugged into some kind of back box containing a couple of relays. The black box will have two inputs, one from the clock/timer and the other from the solar computer. It either (or both) of the inputs has voltage, the output to the pump power cord will have voltage. If neither has voltage, there would be no voltage to the pump power cord.

I have the pump (750 watt), the clock/timer, and the solar computer. I need to build the black box.

I suspect this is not rocket science but choosing and connecting the relays is beyond me. I'd welcome any advice.

Please let me now if this is unclear and I will elaborate.

Thanks, Clark (in Melbourne, Australia)

Something like this- a utility box containing 1) two contactors, 2) strain-relieved cord that plugs into receptacle from panel, 3) two strain relieved ac-cords w/gnd'd plugs to computer and timer receptacles, 4) standard gnd'd receptacle for pump plug, 5) GFCI breaker in panel, 6) GNDs throughout: View in a fixed-width font such as Courier.

BREAKER PANEL

---------------- PUMP RECPT | | | +---------+ | | GFCI | ---|->HOT ---|----------------------------+ | ------------- | ---|->NEUTRAL|-----------------------+ | | | | ---|->GND ---|-----------+ | | | | | +---------+ | | | | ------------- | METAL UTILITY BOX---X--------------------+ | | | | GND | | | | | | | +-----------|-----------X | | | ------------- | | | | | | | | | | | | +------|-----------|----X | | | | |K1-----|----|---+ | K2-----|----|--+| | ------------- | || +--+ | | | | | +--+ | | || | | | || | | | | | | | | | | | || | | | || | ) O| O| | | | | ) O| O| || ------------- || | ) | | | | | | ) | | || || | ) O| O| | | | | ) O| O| || || | | | | | | | | | | | || || |+-+ | | | | | |+-+ | | || |+---------------+ | +------|----|--+| | || | +------|------||---|----X | X2 | || | | || | | | FLEXIBLE | || +-----------|------||---X--+ | | SJ 18GA ---+ | || | || | | | | | || | || | | | | | || +------------X------||-+--+ | | | | | || | || | | | | | | +--||-GND--------------------GND-^-^-^---+ V || | || | PUMP TIMER -| \-----------+| | || | RECPT -| |-----------|-+ || | -|_/------------+ || | || | -| \-----------------------------+| | COMPUTER -| |-----------------------------|-+ -|_/------------------------------+

K1,2 240VAC DPST CONTACTORS WITH 240VAC COIL CONTACTS RATED FOR PUMP HP

You should also have GFCI protection on the circuits that supply the timer and computer too.