Tankless Hot Water Heaters - Review of 5 Tankless Water Heaters
Home hot water circulating systems provide the user with fast
hot water providing a convenience for the user, and saving the water
that would have been run down the drain.
Normal hot water circulating systems form a loop with the hot
water piping that connects from the water heater outlet to the
fixtures, and then back to the water heater. A pump circulates the
hot water through the loop. These systems provide nearly instant hot
water at every fixture, but they are really pricey to operate. They
waste big amounts of energy keeping hot water in the pipe, and
decrease the life of the water heater. They are unbecoming for
tankless water heaters. Standard circulating systems are made by
Grundfos, Taco, Bell & Gusset, and others.
Laing makes a system appropriate for retro-fitting to existing homes that
don't have a dedicated return line, called the Auto Circ. It's a
little pump that mounts under the sink, and pumps water from the hot
water pipe into the cold water pipe, and when hot water reaches 95
degrees, the pump shuts off. When the temperature drops to 85 degrees
the pump turns back on and the cycle repeats. The pump can handle
many fixtures if the plumbing layout is right. This system uses
plenty of energy since it keeps the plumbing full of above background
temperature water, and the cold water line ends up with tepid water
not cold. The Laing autocirc isn't OK for use with a tankless
water heater.
Grundfos makes a similar hot water circulating system for retrofitting
into homes that don't have a dedicated hot water return line. A pump
connects to the outlet of the water heater, and a thermally controlled
valve is placed at every fixture in the home.
The valves are connected between the hot and cold water lines. When each valve is cold water
can flow from the hot line to the cold, and does so as the pump
at the water heater outlet is providing pressure. When hot water
reaches the valve, the valve closes. This keeps hot water near all
the fixtures in the home with just one pump. [**] like the Laing
Autocirc, it doesn't really deliver hot water, just luke warm, and it
replaces the cold water with luke warm. The system is not acceptable for
use with a tankless water heater.
Metlund and Chilipepper make'demand' hot water systems. Demand hot
water systems are home hot water circulating systems designed
to work without a dedicated return, and are appropriate for retrofit to
existing homes. They also use the cold water piping for a return
line.
The demand pumps, like the Laing pump, are placed under a
fixture where they connect the cold and hot water lines. When the
pump is activated by the user pushing a button, it pumps water out of
the hot water pipe and into the cold water pipe, and shuts off when
the hot water reaches the pump. Demand system pumps are far more tough
than the other types of systems to move the water fast.
The demand system has many edges over the conventional system,
and saves an identical quantity of water. One large advantage is the
reduction in energy usage. Since the demand system only runs for some
seconds whenever somebody demands hot water, it uses little energy
for pumpingtypically less than $2.00 a year. It stops running when
hot water reaches the fixture, and so it doesn't use any more hot
water than what you would typically use without a circulating system.
Another advantage is the much smaller installation cost. It's simple and
cheap to retrofit to any house.
Demand systems have stronger pumps than the other systems and so
the Chilipepper pump and one of the bigger Metlund pumps will
work with tankless water heaters. The majority of the circulating pumps will not
pump enough water to turn on the tankless heaters.
