Electric Tankless Water Heaters – The Nitty Gritty Detail

Lets say that you have decided  an electric tankless water heater is right for your needs, and so the next step is trying to decided which model is the most appropriate.

 

You could get the low-down from a supplier or ask a local installer for information (this is what I’d do!). If you’d like to know the important things to know first, then this article may help. Just be mindful of the fact that it isn’t a black and white ‘this is what you do’, rather an overview of what to look out for.

If in doubt, do consult your local installer.

 

There are a couple of things to bear in mind when determining which tankless water heater to choose:

1. The quantity of water that will need to be heated at one time – known as the flow rate. Calculating the flow rate for say, a dish washer, can be done by this quick method.

• Turn the fixture on to its normal position
• Place a container under the fixture and collect the water for 10 seconds
• Measure the amount of water in the basin/container and then convert this to gallons (e.g. 0.25 gallons)
• Multiply the calculated quantity of water by 6 to calculate the flow rate in gallons per minute (0.25 gal x 6 = 1.5 GPM).
• For any one time, add up the gallons per minute (GPM) for each of the household units needing the hot water.
• The flow limits for household water fixtures are set by The Federal Energy Policy Act 1992 ( see http://www.eere.energy.gov/). Tankless manufacturers size their units based on the temperature rise needed for any given flow rate.

 

2. The difference between your groundwater temperature and the desired output temperature of the hot water – is known as the temperature rise.

• The difference between the groundwater temeprature and your ideal water temperature  = the temperature rise.
• To make this simple,  lets show you by saying the groundwater is 80 degrees and you’d like your hot water to be a scorching 120 degrees, then the temperature rise is 40 degrees. (for information, your groundwater temperatures is roughly the same as your average yearly air temperature).

 

You will be able to calculate the right size and sort of tempra tankless water heater, once you have got your temperature rise and flow rate worked out.

 

You will need to remember that using this calculation, you will be working out how much hot water at any one time is needed. Whilst tankless systems don’t actually run out of hot water, this water will be split amongst all the units you are using at the same time in the house. So estimate the number of fixtures you think you’d need at one time — chances are it won’t be every fixture.

 

Whole-house systems are quite often powered by gas and propane-powered heaters as they tend to provide more oomph than electric models. Electric models are used more often in point-of-use scenarios, however they are still used a lot for whole-house systems as they are less expensive than the gas powered systems. If you want a shower in your pool house or hot water for an outdoor kitchen, you might decide to opt for a small electric tankless heater.