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Negative head is where the shower head or tap is above the water level in the cold water tank. Positive head is when the shower or tap is below the water level in the cold water tank. Zero head is when the shower head or tap is the same level as the level in the cold water tank. Should the water level fluctuate, (and it will if it is a cold water tank in a conventional home), the pump may transition from positive head to zero head, to negative head.
A double boost ShowerPowerBooster is great for negative head situations, zero head situations, and situations where there is the minimum of positive head if you adopt a simple way of turning a pump on and off. Each pump takes only 12 watts of power so the transformer will not overload a lighting circuit so wired into a lighting circuit it can operate whenever a light is switched on and off even with a twin pump set.
1.0 The simplest way is to turn the transformer on and off at the plug socket.
2.0 The pumps take 12 watts each which is far less than a 100 watt light bulb so you can wire the transformer into the light switch or fan and it comes on and off with the lights or the fan.
3.0 An elegant solution is to buy a radio remote to switch the pumps on and off.
4.0 An automatic SPB will operate automatically if the Shower is gravity hot and cold or a hot tap is not a mixer tap (* see note at the end of this blog)
Automatic operation is sometimes possible in negative head situations. A ShowerPowerBooster will raise water to the height of a shower. When the valve is closed, it traps water in the shower head and hose. When the shower mixer is opened again after a period of time (in excess of 18 seconds), air enters the shower head and the water back flows through the automatic SPB. If the flow switch detects black flow of water flowing in excess of 1.5 litres a minute for two seconds – it starts the pump.