Instant Hot Water Heaters

There are two basic systems for heating hot water; Tank Hot Water Heaters and Instant Hot Water Heaters, here I am going to discuss Instant Hot Water Heaters and the things you need to consider before you make a final decision on what to purchase.

So what is an Instant Hot Water Heater, put simply it is a water heater that works on demand, ie when you turn on a hot water faucet it heats the water, there is no storage system. Because of this there are a number of critical areas that have to be considered in the selection of an Instant Hot Water Heater:

1. What is the energy source?
It could be electricity, town gas or bottle gas – Propane. If it is gas there should not be a supply problem, but if you are using electricity you need to make sure your power board can handle the power demand of an electric instant hot water heater, which depending on the flow cpacity can be high. So if you are going electric, get an electrician to check your power board before you purchase. Yes it might be a pain but in the long run could save you big time.

2. How many outlets will it be supplying?
Each outlet will have a specific demand, some will be small and others potentially larger. A basin faucet can vary considerably depending on how much you turn up the flow, if it cools down, no big deal, but a shower is a different matter, most people don’t appreciate a cool shower, so depending on your shower head you may need to increase the heaters flow capacity. Some heaters will only handle one outlet, others are designed for multiple faucets.

3. Where is the instant water heater to be mounted?
This is critical if you are using a gas instant hot water heater. Why? Because you have to vent the exhaust gasses to the outside of your home if you mount it inside. The vent ducting might be simple or it could be very complex and expensive. Bottom line is if you mount the hot water heater inside, the exhaust gas which contains CO, carbon monoxide has to be vented to the outside. For an electric instant hot water heater there are no fumes so it can be inside or out.

4. Distance from Outlet:
Potentially the longer the pipe run the more potential for heat loss and the more water you waste before hot water arrives. By far the most efficient way to use instant hot water heaters is to have one for each bathroom. This way you can size them accurately, you waste little in heated water and their energy efficiency improves dramatically, but doing this is best done a build stage so the total demand energy requirements can be calculated, and the water piping set up correctly with good quality insulation. Insulation is critical with any hot water piping, but more so with instant heaters, particularly when supplying several outlets.

5. Temperature Rise Ability:
All instant hot water heaters will quote what their temperature rise ability is at a particular flow rate. Here is an example for one particular water heater; the Stiebel Eltron Tempra 24 operating at 208 volts 18 kw.

From this you can see how critical is it to size an Instant Hot Water Heater carefully, otherwise you will find yourself having insufficient hot water for your needs. Size up and spec your instant hot water correctly and you will never run out of hot water.

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