Single Phase Electric
Single phase electric instantaneous water heaters are small electrically powered units that heat water 'instantly' as it flows through the product. Instantaneous water heaters are compact, will not run out of hot water and have no stand-by energy losses but have to be wired to the electric consumer unit. The principal draw-back of instantaneous water heaters is that the available hot water flow rate is limited by the electrical power rating of the water heater. Single phase units have power ratings of up to 12kW and can provide maximum flow rates up to 6L/min (assuming a temperature increase from incoming cold supply of 30ºC). Units of 3 - 6kW are suitable for a wash hand basin. Units over 9kW can be used for a shower and wash hand basin (not at the same time) but they CANNOT be used with Thermostatic mixer valves. We do not advise instantaneous water heaters to be used with kitchen sinks.
Please note that units rated over 3kW are too powerful for connection to a 13A ring main and must be wired directly to the electrical distribution unit.Flow Rate Calculator Typical Installation
Depending on the power of the unit, they are suitable for applications such as hand basins or, at the higher end of the power range, for showers. This range of product is not suitable for filling baths as the flow rate of water supplied would mean that the time to fill a bath would be unacceptably long. (Filling a bath either requires a large storage heater or a powerful instantaneous gas water heater). The flow rate estimator tool below gives an indication of hot water flow rates that will be achieved for a given combination of electrical power and required water temperature rise. Please note that instantaneous electric water heaters are not generally suitable for use with thermostatic mixer valves. Close
These units are typically mounted directly under a sink, although because the units operate at mains pressure the location of the heater is a purely a matter of convenience. The mode of operation is much the same as a conventional electric shower, i.e. cold incoming water is heated as it flows over an electrically heated element.
The specific details details do vary a little from product to product, although they generally have a number of common features that are outlined below:
Hot Water Supply (A)
Instantaneous electric water heaters can supply one or more sinks fitted with standard taps or mixers. They do not store heated water and therefore have no standby energy losses and can be relatively small in size. They are ideally suited for light duty applications such as:
En-suite bathrooms or guest suites which are remote from the existing hot water supply
Hand basins in commercial premises
However due to the limited electrical power available from typical single phase electrical supplies in the UK they are unsuited to heavier duty applications requiring large volumes of heated water to be produced at a high flow rate. In particular they are not generally suitable for use with baths, or for larger sinks that need to be filled quickly. Whilst they can be used for multiple outlets, the temperature and flow rate of the hot water supply may vary if more than one outlet is used simultaneously. This can be a significant consideration in some applications, for example if a single instantaneous heater is used to supply more that one back-wash in a hair dressing salon.
(Consideration should be given to a storage heater if an instantaneous water heater is unsuitable).
Heater Location (B)
These units operate at mains water pressure, and are equally at home when located above or out of sight underneath the sink.
Electrical Wiring (C)
The electrical cable must be suitable for the power rating of the unit in accordance with Part P of the Building Regulations. The exact requirements for the cable will depend on the power of the unit and specific details of the installation, but typically will be in the range 6mm to 10mm. (Installation should be carried by a competent person in accordance with the relevant regulations).
Consumer Unit (D)
The unit must be wired directly to the domestic consumer unit with a dedicated fuse, usually in the range 40-50 amps.
These units typically include a pressure relief valve. This valve is a safety device that remains closed during normal operation, but in the unlikely event of a fault condition developing it can release hot water and/or steam to the waste. The vent should be connected to a waste (drain) in accordance with the manufacturer's instructions.
Service Valve (F)
A service valve is normally be fitted on the inlet (cold) pipe to facilitate any future maintenance.
Manufacturers' Installation and Operating Instructions
Please note that all units must be installed and operated in accordance with the manufacturers' specific requirements. Installation and maintenace must be carried out by competent personnel.
Instantaneous Water Heater Performance
The fundamental relationship between flow rate (litres per minute), available heating power (measured in kW) and water temperature is is given by the following formula:
Power in kW to Heat Water = [ Litres x Temp Rise oC] / [ Time in Minutes x 14.3]
Ideally the flow rate of water at the required temperature would be as high as possible but in practice it is limited by the available heating power.
(Note that the actual temperature depends on the incoming mains water temperature which varies according to the season but is typically 5oC in winter and 10oC in summer. (To calculate output temperature simply add the temperature of the incoming water (oC) to the temperature rise generated by the water heater, for example if the incoming water temperature is 5oC and the heater is able to increase the water temperature by 40oC then the outlet temperature will be 45oC) .
Excl. Tax: £186.00 Incl. Tax: £223.20
Excl. Tax: £158.00 Incl. Tax: £189.60
Hyco IN96T Aquila Instantaneous Inline Temperature Stabilised Water Heater for Hand Basins/Showers 9.6kWExcl. Tax: £154.00 Incl. Tax: £184.80
Excl. Tax: £124.00 Incl. Tax: £148.80
Excl. Tax: £117.00 Incl. Tax: £140.40
Excl. Tax: £257.00 Incl. Tax: £308.40
Excl. Tax: £257.00 Incl. Tax: £308.40
Excl. Tax: £353.00 Incl. Tax: £423.60
Excl. Tax: £109.00 Incl. Tax: £130.80
Excl. Tax: £101.00 Incl. Tax: £121.20
Excl. Tax: £219.00 Incl. Tax: £262.80
Excl. Tax: £179.00 Incl. Tax: £214.80
Excl. Tax: £234.00 Incl. Tax: £280.80
Excl. Tax: £204.00 Incl. Tax: £244.80
Excl. Tax: £139.00 Incl. Tax: £166.80
Excl. Tax: £126.00 Incl. Tax: £151.20
Excl. Tax: £108.00 Incl. Tax: £129.60
Excl. Tax: £228.00 Incl. Tax: £273.60