Water heaters for the bathroom and kitchen
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A water heater either keeps a tank of hot water ready or heats water only while the tap runs. Ariston's Pro1 Eco electric storage heater holds 50, 80 or 100 litres; its Aures instant heater for several taps draws 5 kW on an ordinary single-phase supply and heats water only when a flow sensor detects the tap is open.
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Types of water heater
| Type | How it heats | Example from a maker |
|---|---|---|
| Electric storage (tank) | an element heats a tank of water and a thermostat keeps it hot | Ariston Pro1 Eco, 50, 80 or 100 L |
| Electric instant (tankless) | heats water as it flows, only while a tap is open | Ariston Aures Multi, 5 kW or 12 kW |
| Solar | heats water with sunlight in collectors on the roof | see solar water heaters |
| Heat pump | takes heat from the air to warm a tank | Ariston Nuos Plus R290, named by the Ariston Group |
Sources: Ariston Pro1 Eco specification sheet; Ariston Aures Multi technical sheet; Ariston Group, water heating.
Electric storage water heaters
A storage heater, sold in southern Africa as a geyser, keeps a tank of hot water ready for the taps it serves. Ariston’s specification sheet for the Pro1 Eco lists what a modern tank includes:
- an electronic thermostat for setting the water temperature;
- a temperature and pressure relief valve on the tank;
- a magnesium anode against corrosion of the tank;
- an anti-legionella function that raises the water to 65°C once a month;
- an unvented kit supplied with the heater.
Heating a tank takes time and energy. Warming 50 litres of water by 35°C needs about 2 kWh — our calculation with water’s heat capacity of 4.19 kJ per kg per °C. With a 2 kW element that is about an hour, before heat losses.
Electric instant water heaters
An instant water heater has no tank. Ariston’s Aures sheet says the unit heats only when its flow sensor detects running water, so there is no standing heat loss, and that the multi-point model can feed more than one tap at the same time.
The power needed is much higher than for a tank. According to the same sheet, the Aures SM 5 EU draws 5 kW on a single-phase 220–240 V supply, with a 4 mm² cable, while the 12 kW SM 12 TR EU needs a three-phase 400–415 V supply and 6 mm² cable. Both are rated IP24, must be installed with the pressure relief valve supplied, and accept water pressure from 50 to 800 kPa.
The flow decides how hot the water comes out. A 5 kW heater warms water flowing at 3 litres a minute by about 24°C (our calculation); at 6 litres a minute, by about 12°C. Ariston’s sheet makes the same point: for a higher temperature, reduce the flow.
Water heater for the bathroom: choosing the type
- Number of taps and showers used at once — a tank serves several; an instant heater must be sized for the flow.
- Electrical supply — a 5 kW instant heater needs the cable and fuse its maker specifies; a 12 kW one needs three-phase power.
- Tank size — 50, 80 or 100 L in the Ariston range, against the household’s use.
- Safety parts — the relief valve must be fitted, as both Ariston sheets require.
- Installation — a qualified electrician and plumber; electrical rules in Tanzania are not covered here.
Water heaters in Zanzibar
Kitovu sells from stock in Zanzibar, and these appliances are not among its products. For one maker’s range in detail, see Ariston water heaters.