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Electric Water Heaters

Electric Water Heaters

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Frequently Asked Questions

An electric water heater supplies hot water to one tap or shower without drawing on the boiler. That makes it useful where the cylinder is a long way from the outlet, in an outbuilding with no plumbing loop, or in a cloakroom added after the house was built.
An unvented heater is a sealed system that heats water directly from the mains. Instead of relying on a separate cold water tank, it uses an insulated cylinder to hold temperature. That gives a steady supply at mains pressure, with less heat loss than a vented system.
An inline heater warms water as it flows through the unit, so there is no tank and no standing heat loss. Fitted close to the point of use, it suits kitchens, bathrooms and utility rooms where space is limited, and it only draws power while water is running.
A vented heater relies on a separate cold water storage tank and needs a matching vented tap. An unvented heater connects straight to the mains and runs at mains pressure, giving better flow. The two are not interchangeable, so check what the outlet requires before ordering.
Choose inline for occasional heavy draw, such as a shower used twice a day. Choose a small stored unit for frequent light use, such as a hand basin used through the day, because it is not repeatedly heating from cold at full power.
Under sink units mount in the cupboard below the basin and feed the tap from beneath, keeping them out of sight. Over sink models mount on the wall above and are simpler to run pipework to in a utility or workshop. Both do the same job, and the choice is usually decided by where the cupboard space is.
Our stored range is 6L and 10L. 6L covers handwashing and washing up in most cloakrooms and small kitchens. 10L gives more headroom where use is heavier or more than one outlet shares the unit. If the outlet feeds a bath or shower, an inline heater sized to the flow is the better answer than a small tank.
Wattage sets the flow rate. 3.5kW suits a hand basin, while a shower needs 7kW and upwards, and the range runs to 9.5kW. Undersizing is the most common mistake here: a 3.5kW unit fitted where a shower was intended delivers warm water at a trickle rather than hot water at pressure.
An inline heater draws heavily but only while water is flowing, so the total depends on minutes used rather than hours plugged in. A stored unit draws less at any moment but reheats through the day. For a hand basin used a few times an hour, a small stored unit usually costs less overall.
Inline heaters avoid standing losses entirely, which makes them more efficient where hot water is needed rarely. Where hot water is drawn many times a day, a small stored unit wins, because it is not repeatedly heating from cold at full power.
Electricity costs more per unit than gas, so an electric heater is rarely the cheapest way to heat a whole house of hot water. Its case is point of use: one outlet, no pipe run, and no waiting for hot water to arrive from a distant cylinder.
Inline heaters are usually designed for single point use, such as one sink or one shower. Higher powered models can serve more than one outlet at a reduced flow rate. If in doubt, size for the busiest single outlet rather than the total.
Yes. Mains pressure delivery and consistent output suit washrooms, kitchens and offices, which is why they are common in commercial premises as well as homes.
Yes. These combine mains water and mains electricity, and higher output inline units often need their own circuit and suitably rated cable rather than a spur off an existing one. Installation in a room containing a bath or shower is notifiable under Part P of the Building Regulations. Use a qualified installer.
deXpro unvented and inline water heaters come with a 2 year manufacturer warranty, covering both residential and commercial installations.

About Electric Water Heaters

An electric water heater supplies hot water to one tap or shower without drawing on the boiler. That makes it useful where the cylinder is a long way from the outlet, in an outbuilding with no plumbing loop, or in a cloakroom added after the house was built.

The deXpro range covers inline instant heaters from 3.5kW to 9.5kW, and 6L and 10L unvented storage units for under sink or over sink mounting, with digital temperature control. Sizing, the vented and unvented difference and installation are answered below.

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