Technical data

Site requirements
Observe the statutory regulations of the respective country, as well as those of the
local electricity and water supply companies. The installation site must be free from
frost at all times. In order to avoid thermal losses the distance between the heater and
the water draw-off point should be as small as possible (< 2m). Best performance is
guaranteed at a flow pressure of ≥ 2 bar / 30 psi, avoiding static pressures exceeding
6 bar/90 psi. Material of water pipes: cold water: steel or copper, hot water: copper.
Instant water heaters must be permanently connected to the electricity supply via a
double pole isolating switch with a minimum contact gap of 3mm in both poles. The
switch must be readily accessible but out of reach of a person using a fixed bath or
shower, except for the cord of a pull cord operated switch. The wiring must be con-
nected to the switch without the use of a plug or socket outlet. The supply cable
selected for installation must conform to the relevant table in the current I.E.C. regula-
tions. Electrical water heaters must be connected to the protective earth conductor! In
the interest of electrical safety a 30mA ELCB (Earth Leakage Circuit Breaker) should be
installed in all instant water heater circuits. An isolation valve must be fitted in a con-
venient position in the supply pipe to allow the water heater to be serviced.
78
Power conversion table
220 V 230 V 240 V 380 V 400 V 415 V
3.2 kW 3.5 kW 3.8 kW 12.2 kW 13.5 kW 14.5 kW
4.0 kW 4.4 kW 4.8 kW 16.2 kW 18.0 kW 19.4 kW
5.2 kW 5.7 kW 6.2 kW 19.0 kW 21.0 kW 22.6 kW
6.0 kW 6.6 kW 7.2 kW 21.6 kW 24.0 kW 25.8 kW
8.0 kW 8.8 kW 9.6 kW 24.4 kW 27.0 kW 29.0 kW
Guidelines for usage of hot water
Application
Required
temperature
Required
flow
Required volume
per usage
Handwashing 35 – 38 °C 2* – 4 l/min 0.5 – 1 l
Kitchen sink 45 – 55 °C 3* – 5 l/min 3 – 8 l
Shower 37 – 40 °C 4* – 8 l/min 15 – 30 l
Cleaning 45 – 55 °C 4 – 6 l/min 5 – 10 l
Bath 37 – 40 °C 8 – 10 l/min 100 – 150 l
* tap nozzles or special shower heads recommended for satisfactory flow results
Instantaneous performance calculations
Temperature rise [°C] =
Nominal power rating [kW] × 14.3
Flow per minute [litres] =
Nominal power rating [kW] × 14.3
Flow per minute [litres] Temperature rise [°C]
Temperature rise [°F] =
Nominal power rating [kW] × 5.7
Flow per minute [gallons] =
Nominal power rating [kW] × 5.7
Flow per minute [gallons] Temperature rise [°F]
General data for water heating
Mean temperature of mixed water
Mean temperature =
(Hot water [litres] × Hot water temp. [°C]) + (Cold water [litres] × Cold water temp. [°C])
Hot water [litres] + Cold water [litres]
=
(Hot water [gallons] × Hot water temp. [°C]) + (Cold water [gallons] × Cold water temp. [°C])
Hot water [gallons] + Cold water [gallons]
Physical constants
Temperature conversion
Temperature [°C] = (Temperature [°F] – 32 ) ÷ 1.8
Temperature [°F] = Temperature [°C] × 1.8 + 32
Volume conversion
1 litre = 0.22 Gallon (GB)
0.27 Gallon (US)
1 gallon (GB) = 4.54 Litres
1 gallon (US) = 3.78 Litres
Pressure conversion
1 bar = 0.1 MPa
= 14.5 psi
= 100 kN / m
2
1 ft head of water = 0.434 psi
1 m head of water = 9.8 kN / m
2
Useful formulae
Time and rating calculations (excluding heat losses)
Time to heat water [minutes]
=
Litres × Temperature rise [°C]
Nominal power rating [kW] × 14.3
=
Gallons × Temperature rise [°F]
Nominal power rating [kW] × 5.7
Nominal power rating
required to heat water [kW]
=
Litres × Temperature rise [°C]
Time [minutes] × 14.3
=
Gallons × Temperature rise [°F]
Time [minutes] × 5.7
Instantaneous performance chart
1 2 3 4 5 6 7 8 9 10 11 12 13
10
20
40
30
50
60
Temperature rise °C
Flow rate l/min
24 kW
18 kW
13 kW
9 kW
6 kW
3 kW