Tankless Hot Water Heaters

Tankless compact water heater systems are more efficient in delivering hot water, and it helps the homeowner save on energy and utility costs over the use of traditional tank heaters.  

Tankless Hot Water Heaters
By Pierre Mouchette | Bits-n-Pieces

Tankless compact water heater systems are more efficient in delivering hot water, and it helps the homeowner save on energy and utility costs over the use of traditional tank heaters.  These systems are available for propane/natural gas and electric. 
Using a tankless hot water heater, you can have hot water whenever you need it.  These systems instantly heat water as it flows through the device and does not retain any water internally except for what is in the heat exchanger coil, making these heaters highly efficient and safe.  With today’s technology, an endless supply of hot water is available when needed.
Unlike standard units, which continuously heat and reheat the water to be always hot, tankless heaters generate hot water instantly using high-powered gas burners or electric coils. Yes, this instant heating requires more power, but because the water does not have to be reheated again and again, like in a standard tank model, tankless systems use less energy overall. 
 
Pros and Cons of Compact Water Systems
Does the system provide instant hot water at a uniform temperature?
Pro:     After running (wasting) the cold water from the pipes out of the faucet, tankless water heaters can instantly provide an unending stream of hot water.
Con:    Inconsistent water temperatures due to the heater’s inability to simultaneously send enough hot water to multiple outlets.  It has also been noted that the faucets must be opened fully to activate the heater.
                       
What is the expected life of a tankless water heater?
Pro:     Most tank heaters have a life expectancy of ten years, whereas tankless models function for twice as long.
Con:    A more extended lifespan equates to a more expensive unit, with the tankless unit costing more than twice as much.  They are also more costly to install, so labor fees must be factored into the overall price tag.
 
Pro:     While these systems are more expensive, they are also more efficient.  Consumer Reports indicate that tankless water heaters are 22% more efficient than standard models.  The monthly savings might be nominal, but homeowners can expect to save hundreds of dollars annually.
Con:    Tankless water heaters supply a steady stream of hot water, but the supply is not unlimited.  Standard models heat several gallons of water at once, perfect for a single person taking a shower or washing the dishes.  But if an individual is running the dishwasher or washing machine while someone else is taking a shower (or two people are taking showers in two different bathrooms at the same time), a tankless heater is not equipped to keep up.  A traditional water heater, which can store between 30 and 80 gallons, will not have a problem providing hot water to multiple outlets at the same time.
Electronic ignition means no standing pilot light that constantly uses energy in gas-fired systems.  When purchasing a system, use an ENERGY STAR certified tankless water heaters for additional savings.
 
Tankless Hot Water Heaters Have a Compact Design

• Maximum output, minimum space - these wall-mounted units can be installed on the interior or exterior walls and in tight areas to free up valuable floor space.
• Flexible installation - the small size allows for installation in non-traditional spaces such as crawl spaces and attics, making it perfect for any size home.

 
Advantages and Disadvantages of Tankless Hot Water Heaters
Advantages - the main advantage of a tankless water heater system is the continuous flow of hot water as compared to the limited flow of continuously heated hot water from conventional tank water heaters, and 

• Long-term energy savings - a tankless water heater costs less to operate because of lower energy use.
• Unlimited hot water - though the flow rate determines the amount of hot water the heater can produce, it can indefinitely deliver that flow rate. 
• Less physical space - most tankless water heaters can be mounted on a wall, leaving more physical space. 
• Reduced risk of water damage - no stored water means there is no risk of water damage from a tank failure or rupture.
• Temperature compensation - most new generation tankless water heaters stabilize water pressure and temperature by a bypass valve and a mixing valve incorporated in the unit.  Modern tankless is not inversely proportional because it regulates the amount of water they heat and discharge and stabilizes water temperature using a flow control valve.  Temperature change, not flow speed, is the issue the water heater must address.  The wider the temperature rise, the less flow from the unit; the smaller the temperature rise, the greater the flow.  In conjunction with thermistors, the flow control valve maintains a stable temperature throughout the use of the unit.
• Safety - tankless water heaters precisely control water temperature, which means dangerous temperature levels and spikes are less likely. 

Disadvantages - the main drawback of tankless hot water systems is their high initial costs (equipment and installation).

• Startup costs - a tankless water heater costs more than a conventional storage unit, and installing a tankless system comes at an increased cost, especially in retrofit applications (increased size of the electrical wiring or gas pipeline, and the replacement of the existing vent pipe.
• Power outage - in case of a power outage, electric tankless heaters cannot supply hot water.

 
Operation of a Tankless Hot Water Heater
The heater is usually turned off but is equipped with flow sensors that activate it when water travels through them, and a negative feedback loop is used to bring water to the target temperature.  Water circulates through a copper heat exchanger (copper heat exchangers are preferred because of their high thermal conductivity and ease of fabrication) and is warmed by gas or electrical heating.
 
Tankless heater controls
Tankless water heaters can be further divided into two categories according to their heating capability: "full on/full off" versus "modulated."  Full-on/full-off units do not have a variable power output level; the unit is either entirely on or off.  This can cause an annoying and possibly hazardous variation of hot water temperature as water flow through the heater varies.  Modulated tankless water heaters change their heat output in response to the flow rate of water running through the unit.  This is usually done using a flow sensor, a modulating gas valve, an inlet water temperature sensor, and an outlet water temperature sensor-choke valve.  A properly configured modulating heater can supply the same output temperature of water at differing water flow rates within their rated capacity.
 
 
A wise investment for now and the future - increase your home’s value with a tankless water heater.  You will obtain an improved Home Energy Rating System (HERS) Index Score and optimized LEED certification.   Additionally, available energy efficiency rebates and tax credits offer the opportunity to help make your purchase more affordable.