Technical Help
This page attempts to assist the client in determining which of our products will best suit their needs based on the electrical supply and hot water requirements, no matter which model is chosen the client will achieve at least a 25% savings in power consumption using Stiebel Eltron instantaneous water heaters compared to a standard geyser.
Determining which model to choose
Instantaneous Water Heaters; also referred to as “On Demand” or “Tankless” water heaters, do not store water internally and therefore heat the water instantly as it passes through the unit. As a result of the aforementioned, the heat output is directly related to the temperature of the incoming water as well as the water flow rate through the unit that is measured in litres per minute, as a result it is important to first determine what your power supply at location is because Stiebel Eltron three phase instant water heaters perform substantially better than the single phase versions (please see “Electrical Supply” below).
Single Phase Instantaneous Water Heaters (DHC-E8/10, DHC8EL & DHC6EL)
- Stiebel Eltron produce the most powerful, efficient and reliable single phase instantaneous waters heaters on the market today.
- It is important to note that with single phase power supply the maximum element power rating that it can carry from any single phase instantaneous water heater is 12kW and it’s this power rating that determines the output flow rate of the instant water heater.
- The maximum output flow rate that one can expect from any single phase instant water heater so that it can heat the water effectively is approximately 6L/min. This flow rate would be determined by the power rating of the element i.e. 6kW, 8kW, 10kW etc., the temperature selected on the unit, as well as the incoming water temperature.
- Naturally it follows that the output flow rate in Summer would be higher and closer to the 6L/min whereas in Winter it will be lower because of the colder incoming water i.e. the colder the water, the lower the flow rate and vice verse.
- A bath cannot be filled (except in tropical climates such as in Durban) with a single phase instant water heater as the water heaters output flow rate is too low to effectively fill a bath which typically needs 10L to 12L per min to fill it.
- Single phase instant water heaters should only be used with water economy (low flow) shower heads as the large shower heads produce 8L/min and more which would adversely affect the flow rate and output temperature of these single phase units, of course it is prudent and always recommended to be water wise with low rainfall being experienced currently.
- Single Lever mixers must not be used with single phase installations and these greatly affect the performance of the heat output resulting in the clients struggling to maintain temperature, it is advisable to rather use a mixer that has a separate hot/cold water tap such as the ones illustrated below.
Three Phase Instantaneous Water Heaters (DHB-E, DHE and SHD)
- Three Phase power supply allows manufacturers to produce very powerful instantaneous water heaters with an element rating up to 27kW and with the much higher power rating of the three phase instant water heater elements these would effectively be the full replacement for a standard geyser.
- The output flow rate of three phase instant water heaters, depending on above mentioned factors, would be between 8L to 14L per min.
- Three phase also allows for the large combination water heaters… the SHD30/100, these have either a 30L or 100L capacity with a stored water temperature of 65 deg C and once that volume of water has been depleted it will work in instantaneous mode producing water at a temperature of 45 deg C constantly. The SHD range are perfect for use in areas that have high water hot volume requirements such as hotels, restaurants, clubs, schools etc.
Electrical Supply
Electricity will be supplied in either Single Phase or Three phase, below are two images that will easily assist in determining which phase you will have.
The image on the left would be similar to what the main breaker will look like for single phase supply, will have either one or two levers and will be labelled as 240V. The image on the right is similar to what a the main breaker will look like for three phase supply, will have either three or four levers and will be labelled as 400V.
