Tankless Coil Water Heater
Buying Tips

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Take advantage of using tankless coil water heater when utilizing hydronic boiler, gas or oil-fired furnace for home heating. Check out the tips on buying the tankless coil systems for residential heating, pros and cons.

Tankless coil water heater is designed to perform as the heat exchanger to heat domestic water.
tankless coil water heater Tankless coil unit has a coil type heat exchanger as part of the main heating system, and it is found in oil-fired and gas fired boilers or furnaces.

Coils are immersed in the hydronic boiler. The purpose is to transfer the heat from the boiler's hot water to the water that is running through the tankless coil exchanger and further to the tap.

Tankless coil devices are designed to provide an optimal heat transfer. If the cold water flows too quickly through the coil the result is the lower outgoing hot water temperature. By installing a flow regulating valve on the incoming cold supply you can regulate this temperature.

Tankless coil water heaters are integrated and combined systems, installed in the home space heating system that are using a hydronic boilers and for the tank-less heating needs, while saving money on the total installation cost.

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Pros and Cons

Tankless coil system advantage is the absence of the storage tank and no stand-by heat loss, eliminating the need of purchasing a separate heating system and resulting in money savings. Water is heated on demand, as it flows through the heat exchanger whenever the hot tap is open. Tankless coil can also work as the supplemental heater.

Home heating has to work to be able to produce the hot water. This is the main drawback, as the system is less efficient during the summer when space heating is not required. If there are colder days during the year, home heating is more used and water heating is more efficient.

This is why tankless coil water heaters are primarily seen in cooler climates.

To help tankless coil water heaters to overcome problems with the low efficiency during the warmer months, the coil system is combined with the storage tank. Now, the whole system has to be upgraded with the pump and other controls. The boiler will not operate all the time, only when there is a call from the thermostat for heating.

The pump will run the cooler water near the bottom of the storage tank through the tankless coil and moved to the top of the storage tank providing a stable temperature. The circulation will stop when the temperature on the thermostat is satisfied.

One of the reviews or studies done by " Consumer Guide to Home Energy Savings" is that in non-winter months, tankless coil water heaters can consume three BTU's of fuel for every one BTU of hot water these units provide.

Problems and how to solve them

If you notice that the flow is lower than usual, mineral deposits or rust might have built up in the coil exchanger. This is one of the frequent problems as the tankless coils are built from the small size pipes, which are subjected to clogging. To avoid further problems the unit needs to be flushed.

Use white vinegar, citric acid or any other available solution for the heat exchangers, and pump it through the tankless coil, to flush out mineral deposits. It is important to have the isolation valves installed, to isolate it from the potable water supply. This is not a simple DIY project, the project needs a specialized pump, so the recommendation is to call a plumber.

If the coil leaks you might have potable water contaminated with the boiler water, or even worse it might damage the boiler. Leaks are caused due to the failed connection in the coil tubing or where it joins the plumbing. The pressure and the amount of hot water will be reduced.

Mineral deposits and improperly adjusted mixing valve can be the cause for the insufficient hot water production.

According to the above overview of the tankless coil water heaters, these systems work great during the winter time when taking advantage of the home heating, but due to its inefficiency during the warmer days, and other problems, conclusion is that this is not a preferable way for water heating.


Picture is courtesy of energysavers.gov

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