Tankless Water Heaters

Tankless water heaters—also called instantaneous, continuous flow, inline, flash, on-demand, or instant-on water heaters are water heaters that instantly heat water as it flows through the device, and do not retain any water internally except for what is in the heat exchanger coil. Copper heat exchangers are preferred in these units because of their high thermal conductivity and ease of fabrication.


Tankless heaters may be installed throughout a household at more than one point-of-use (POU), far from a central water heater, or larger centralized models may still be used to provide all the hot water requirements for an entire house. The main advantages of tankless water heaters are a plentiful continuous flow of hot water (as compared to a limited flow of continuously heated hot water from conventional tank water heaters), and potential energy savings under some conditions. The main disadvantage of these systems are their high initial costs (equipment and installation) and low GPM hot water production.


Most newer homes is where you will see tankless water heaters installed. The reason being is that cost to upgrade older homes electrical systems outweigh the benefits provided by tankless systems. Most older homes have 200 amp service total. You will need about 150 AMP for most whole home tankless water heater systems. The cost to upgrade your homes electrical service can range from $1500.00 to $5000.00 depending on where you live and level of upgrade you need.


The most important thing to consider when purchasing Tankless water heaters is the flow rates. If you buy a system that has a flow rate of 4 GPM then you will not be able to use hot water anywhere else besides your shower simutaneously. This could be problomatic for people who have large families. Below is a graphic to give you an idea of the flow rates of most fixtures.



Tankless Water Heaers and Scale Accumulation

Tankless water heaters are not immune to hard water problems. As water moves through the heat exchanger, the minerals will precipitate out of solution, some of the minerals will be cleared out with the water flushing through. Unfortunately, because the system is designed to heat water quickly and it passes through smaller tubes in the heat exchanger to increase pressure. As the water heats the calcium carbonate precipitates out of the water and the build up of scale can happen quickly.


As the scale builds up it will cause the heat exchanger to overheat. Every tankless water heater on the market has a safety shut off when a heat exchanger overheats. This prevents damage to the unit and safety to the homeowner. If the unit is reset without the problem being corrected, it will only function for a very short time before the unit shuts itself down. It is also not fail proof and should not be relied on as a signal to maintenance your system. This can cause permanent damage to the system and will not be covered by warranty.


Most tankless water heaters require a yearly maintenance. the primary purpose of this maintenance is to flush the unit of any scale build up. a vinegar-like solution is run through the unit to clean out any scale build up. The time between cleanings depends on how hard your water is and how much the unit is used. the general guideline is once a year for maintenance. This will not be adequate in hard water areas. If you dont have access valves installed then cleaning your unit of scale will be nearly impossible unless a plummer comes and installs access valves to the tankless water heater. Using a HydroFLOW water treatment device will help you avoid this expensive installation of access ports and provide your tankless sytem with hard water protection.


Some manufacturers such as Rinnai has built in scale detection, which will alert the homeowner on when the unit needs to be flushed. The scale detection for Rinnai is only available on their ultra and luxury series. These warning sytems shouldnt be used as a signal to maintenance your tankless water heater. This can cause permanent damage to your very expensive tankless water heater system.


The manufacturers suggest you maintenance these sytems at least once a year. If left untreated scale will accumulate fast in these units and cause them to become ineffiecient and quite possible permanetly damage them. In hard water areas once a year may not be suffecient. Protecting these units from scale accumulation shouldn't be ignored. Using a HydroFLOW water treatment device is highly reccomended to protect these very expensive units.


Here is a list of manufacturers and the various warranties they provide and installation types




Scale Problem areas  


Tankless Water Heater Munufacturers

Manufacturer

Warranty

General Warranty

Electric

Natural Gas

Propane

Indoor

Outdoor

A.O. Smith

15

5

No

Yes

Yes

Yes

Yes

Bosch

15

5

Yes

Yes

Yes

Yes

Yes

ECOSMART

N/A

N/A

Yes

No

No

Yes

No

Drakken

1

1

Yes

No

Yes

Yes

Yes

Eccotemp

10

5

Yes

Yes

Yes

Yes

Yes

EcoSmart / Eemax

Lifetime

Lifetime

Yes

No

No

Yes

No

Marey

5

5

Yes

Yes

Yes

Yes

Yes

Navien

8-15

3-5

No

Yes

Yes

Yes

Yes

Noritz

12

5

No

Yes

Yes

Yes

Yes

Rheem

12

5

Yes

Yes

Yes

Yes

Yes

RINNAI

12

5

No

Yes

Yes

Yes

Yes

Ruud

12

5

No

Yes

Yes

Yes

Yes

Seisco

10

10

Yes

Yes

Yes

Yes

Yes

Stiebel Eltron

3

3

Yes

No

No

Yes

No

Takagi

10-15

5

No

Yes

Yes

Yes

Yes

Titan/Niagara

10

10

Yes

no

no

Yes

no

Hybrid Water Heaters

Innovation continues in the Tankless water heater markets. Just starting to enter the market is a new product called a Hybrid Water Heater. This new variation of the on demand water system addresses the low GPM flow rates that most tankless water heater suffer from. The Hybrid systems have a small tank to provide a buffer of hot water so the units can keep up with hot water demands better than the tankless water heater. Most commercial applications that use tankless water heaters are moving twords the Hybrid systems due to cost and efficiency. Even though Hybrid systems have addressed many of the issues of the Tankless Water Heater,.Niether system handles scale accumulation by itself both tankless water heaters and hybrid water heaters suffer from scale accumulation. If left unchecked it can damge these very expensive systems.Some of the Luxury variations of these models have a scale warning system but they don't self maintenance.