Description of Types of Alternative Hot Water Heating Methods: electric, gas, high efficiency gas, oil, high efficiency oil, solar, tankless coils, instantaneous water heaters, point of use water heaters
How to use multiple water heaters in series for more hot water and lower hot water cost
Guide to range boilers & guide to side arm coil water heaters
Solar water heater suggestions to save on water heating cost
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Here we discuss alternative methods of providing domestic hot water, comparing the characteristics of various hot water heating methods and describing different ways to heat water for washing and bathing.
Thanks to Carson Dunlop, a Toronto Home Inspection Firm and Home Inspection Educator, for permission to use sketches shown in this article.
Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
There are easy steps one can take to determine why the hot water pressure or quantity in a building are inadequate. We discussed tankless coils for making hot water, anti scald valves, and the problem of clogged hot water piping or clogged tankless coils. Then we discussed steps to increase hot water quantity such as insulating water piping and water tanks, and the use of extra tanks to pre-warm or store hot water.
Below we describe some alternative ways to make hot water, either to replace or to supplement an existing hot water supply system. After knowing what the hot water problem really is, there are steps we can take to get more hot water or to increase hot water pressure.
A Comparison of Alternative Hot Water Heaters & Sources
The following articles discuss alternative ways to produce domestic hot water for washing and bathing.
Electric water heaters: if you have no hot water or insufficient hot water, check that the electric water heater power is on - check the water heater switch as well as other fuses or circuit breakers that control the heater. If the water heater has power, check that the water heater electrodes have not been damaged. Finally, check the water heater and its heating elements for scale deposits.
Range Boiler Water Heaters an older form of indirect-fired hot water heating used with separate heating boilers
Scale, mineral deposits, lime reduce hot water quantity: because scale, mineral deposits, lime, and silt in any water heater, and certainly scale on electric water heating elements can reduce the amount of hot water available as well as slowing water heater recovery time, see Water Heater Noises where we discuss deliming and scaling in water heaters.
Side Arm Coil Water Heaters similar to instantaneous and tankless coil water heaters, often used with range boilers
Solar Water Heaters using solar collectors, an indoor water tank, pump and controls, using minimal "on-grid" energy
Tankless Coil Hot Water Increase a heat exchanging coil immersed inside of a heating boiler heats provides (somewhat limited) hot water. various tricks can significantly improve the safety and water quantity available
Scale, mineral deposits, lime reduce hot water quantity: because scale, mineral deposits, lime, and silt in any water heater, and certainly scale on electric water heating elements can reduce the amount of hot water available as well as slowing water heater recovery time, see Water Heater Noises where we discuss deliming and scaling in water heaters.
Multiple Hot Water Sources? How to Use Separate Oil, Gas, or Electric, Solar, Wind, or Combination-fuel Water Heaters for More Hot Water
Separate water heaters can provide more hot water than a tankless coil in most cases and choices among water heater types by fuel, size, recovery rate, etc. can make a big difference in the hot water quantity, pressure, flow, and cost at a building. Here we discuss some alternative water heating methods.
Use Instantaneous Water Heaters for Increased Hot Water Supply
Installing an instantaneous water heaters are usually installed as a 'point-of-use' hot water system. You can see the basic appearance of a point-of-use instantaneous water heater in the sketch at left, provided courtesy of Carson Dunlop.
For example an instantaneous water heater, electric or gas fired, may be installed at a single kitchen or bathroom.
In the U.S. and Canada, this is an approach to providing hot water that is usually applied where the total hot water delivery rate needed is modest or where only a limited number of fixtures need to be supplied with hot water.
Higher-capacity instantaneous water heaters are available, and in countries where people use water more modestly, these systems are sometimes installed as the only hot water supply.
How to connect multiple water heaters in parallel to increase total hot water quantity
Where hot water volume requirements are high, in addition to installing a single larger-capacity water heater, one can install a several water heaters connected in parallel. You can see this design in our sketch at left, provided courtesy of Carson Dunlop.
Parallel water heaters means that all of them are "on" and heating water at the same time, providing a very large quantity of hot water to the building.
We see this installation most often when building occupants find that they do not have enough hot water but their present water heater is in good condition.
Rather than scrapping a perfectly good water heater to install a single larger unit, a second water heater is simply added, installed in parallel to the first one.
How to increase hot water quantity using multiple water heaters in series for lower hot water cost
Some buildings use water heaters installed in series to handle variations in hot water demand more economically. Unlike the illustration of parallel water heaters shown above, water heaters connected in series means that incoming cold water flows first into heater #1, then out of heater #1 into heater #2, then out of heater #2 into the building hot water supply piping (or into additional water heaters if more than two are used.)
A synonym for water heaters connected in series is a cascaded water heater design. Cascaded or in-series water heaters is an economical way to handle large variations in hot water demand in a building.
When the anticipated hot water demand is low, only water heater #2 may be running.
When the anticipated hot water demand is high, water heater #1 is turned on as well, doubling the volume of hot water available (if the heaters are of the same capacity in gallons or liters).
Water heater controls can be adjusted so that the "upstream" water heater, (water heater #1 in our example), is left turned off or perhaps set to a very low temperature. In either of these cases, the upstream water heater or tank functions as a "booster water warmer" reducing the energy use by water heater #2 by pre-warming water entering the active heater#2.
Use of a Side Arm Coil to Make Hot Water from a Heating Boiler
As the sketch at left shows (courtesy of Carson Dunlop), a side arm coil is a variation on the tankless coil (inside the boiler) discussed at TANKLESS COILS where we explain how these work and what goes wrong, and further at Tankless Coil for Hot Water where we discuss how to get more hot water from a tankless coil.
A side arm coil is quite similar to an in-boiler tankless coil except that it is located outside of the the heating boiler itself.
We found this system common on older home heating systems such as those using a GE down-fire heating boiler or other boilers whose original design did not include an opening and fittings to mount the tankless coil right into the boiler itself.
Also see WATER SOFTENERS - how to install and adjust a water softener to avoid hot water piping or tankless coil clogging due to hard water and minerals - since a side arm coil can also become clogged by the minerals in hard water.
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Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
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