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On-Demand/Tankless Water Heaters

Many home improvement and general interest television shows are showing stories on lowering heating costs by using tankless water heaters.  What our overseas friends have known for a long time is finally becoming apparent in the USA – tankless, or on-demand, water heaters are a great way to save money and energy resources.

 

First -  how does a standard US hot water tank unit operate? Let’s say you have an 80 gallon tank and the water is generally heated to the standard residential limit of 120 dgF (some can go slightly higher).  As you start drawing off hot water (such as taking a shower) cold water automatically enters the tank. The more you draw off hot water the more cold replacement water enters. Before long the replacement water will, naturally, cool down the remaining hot water. Once all the usable hot water is gone, the newly filled tank will need to sit while the replacement water is brought up to temperature.  

 

Tankless units can solve the problem of volume and high water temperatures.  As described above, the standard household tank unit is generally limited to heat at 120 dgF. Optimum water temperature for rinsing dyed fabrics is 150 dgF plus. Certain models of tankless heaters can reach 160 plus dgF.

 

With a tankless unit, the water supply coming into the unit is heated at the preset temperature level throughout all usage. There is no ‘fall off’ in temperature whether you run 10 or 100 gallons through the unit.

 

You may have noticed the term ‘certain models of tankless heaters’. There are many models across several manufacturers and they run in two (general) groups – home use and commercial.  Most home models can be either electric or gas powered and have regulators limiting them to a maximum 120 dgF.  For that reason I focused my attention on commercial models, which can still be used in the home. The caveats with commercial units is that you will need to use an adjustable thermostat and that they are powered by either natural or propane gas only.

 

These gas powered units require venting and, depending on the model and whether it comes equipped with an electronic exhaust system (using a single 110-115 v plug in outlet), the vent pipe can be run through an outside wall or up through the roof.

 

The adjustable thermostat is an important safety factor to keep users from being scalded when using hot water in other applications, like washing dishes or a shower. Thermostats have improved greatly over the past few years. Now there are remote controls so you don't have to walk to the unit to change the temperature.

 

A key factor in the efficiency of a tankless hot water heater is the flow rate. Flow rate is the amount of water moving through the heating elements and  is determined by two factors – how hot you are heating the water and the temperature of the water coming into the unit. The colder the incoming water, the slower it will run through the heat element thereby creating a lower flow rate. However, manufacturer studies show that when you are heating water to 150 dgF and above, as dyers do, most flow rates are at 2 to 3 gallons a minute regardless of incoming water temperature.  This should do fine for most homes.

COST

Commercial units are going to cost more than a residential unit or replacement tank unit - it's the nature of the beast.  Here are some rough guidelines:

  1. Heaters will run $800-1200
  2. A professional plumber needs to hook up the gas lines, install the vent outlet and - if you don't have an outlet handy, an electrician to run the 110v line for the exhaust fan plug. That is probably another $200-400 (depending on where you live). This is not DIY.
  3. Gas tanks - if you don't already have propane or natural gas available you will need to get a tank. Prices vary over the US, but I have heard $400-600 for an above ground unit. Add another $800 if you want to bury the tank. In 2006, Propane gas ran $2.20-$2.50 per unit in Florida. Other areas may be higher/lower.

Links for More Information
(listed in alpha order)
Bosch

Eemax
An exception - they have electric commercial units. A recommendation from a fellow dyer in CT.
1.800.543.6163

Noritz

p-817.421.0500
Contact: Paul Yochim ext: 222

Paloma / Waiwela
Thanks to Armour Van Horn for this lead.
800.873.3507
Rheem
1.800.621.5622
Rinnai
1.800.621.9419
Rob Sattenspiel (ext 4349 / mailto:rsattenspiel@rinnai.us) sold to the dyeing industry for years. He is a wealth of information and agreed to take our calls - treat him nice :-).
Takagi
1.888.882.5244
Propane Information
For regional costs on using Propane
Natural Gas
Info



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There is so much more infromation than space and attention span allow.
Feel free to send your questions off-line and maybe I can point you in a good direction.  I am a dyer but I also care very deeply about my household's budget and our use of the world's energy resources. If I can help others learn about these heaters I've done a little something to help the planet (and your pocket book).