Why Does My Tankless Water Heater Go Cold ?

We all need water heaters to heat the water used for bathing and other purposes in cold weather conditions. These have become an essential part of our day to day life. There are two types of water heaters as below.

Tank Type Water Heater

Tankless Water Heater

The Basic Working Of Tank Type Water Heater

As the name suggests, this type of water heater will be consisting of a tank for the storage of water. The process of heating takes place once the tank is filled with water.

This heating process is done either by electric coils powered by a power supply or by a Gas-powered system. It will take up to 30 minutes for the tank to get the water heated depending upon the size of it. Then the hot water can be circulated for further use.

why does my tankless water heater go cold

The Basic Working Of A Tankless Water Heater

In this advanced version of water heaters, the storage tank will be absent. These tankless water heaters works with the principle of instant heating as done by the copper coils in a heat exchanger.

The storage tank is replaced by a small tank that hosts an electric coil or gas system that heats the water flowing through it. Since it heats the water flowing through it all the time, there won’t be any time lapse for the heating of stored water.

Temperature Fluctuations In Tankless Water Heaters

  1. Low water pressure:– Due to lower flow rate.

  2. Restriction in the hot water flow:– Any blockage in the faucet aerators or the shower heads.

  3. Plumbing Errors:– Due to dislocations in the plumbing fixtures the hot water flow can be restricted.

  4. Problem with Recirculation system:– The recirculation pump should be operating well and the pump sizing should be matching the requirement for the flow rate needed.

Tankless Water Heater Going Cold

Although tankless water heaters have many advantages over tank-type water heaters, there are some disadvantages in using it. One such disadvantages is the cold water sandwich effect.

are electric tankless water heater worth it

What Is A Cold Water Sandwich Effect And Why Does It Happen?

In the case of successive showers using a tankless water heater, you may notice that the second person taking bath in the same shower just after the first person has taken the shower, will be exposed to warm water initially and then he will be blasted with cold water from the heater till it gets heated up again slowly.

This effect is called as Cold Water Sandwich Effect. This is because, when the first person is done with his shower, some hot water will be trapped in the faucet and the other opening areas.

water heater not heating

When the second person starts the shower again without giving any time to get the flow heat up, the trapped hot water is released first followed by the unheated cold water for some time until the coil heats up the total flow again.

Although a tankless water heater is an instant heater, it needs at least a little time to heat the water flowing through it. This issue is more common in electric powered water heaters since gas-powered and hybrid water heater takes very little time to heat the water to the needed temperature.

Some Solutions To The Coldwater Sandwich Effect

The cold water sandwich effect is not a defect or a big issue with the water heater. Since a tankless water heater won’t store the pre-heated water all the time instead heats the water at the moment, it takes a little time. So, by knowing this,

  • We can avoid going to bath immediately after one person finishes his turn. This is a simple solution to the problem.

  • We can use recirculation loops that bring the cold water back to the heater.

  • We can employ a mini tank-type heater to create a loop with the tankless heater.

Advantages of a tankless water heater

  • Heats water only when you are in need of it thus saving Energy.

  • Provides instant hot water instead of waiting for 30 minutes to get it.

  • Less space is enough since there is no need for a large tank to store 50 gallons of water.

  • Constant stockpile of hot water is possible.

  • They are cheap to maintain.

  • They have easy control system and operation.

  • They are portable.

  • They provide high energy efficiency and save maintenance costs.

  • They can provide hot water for multiple appliances simultaneously.

Disadvantages of a tankless water heater

  • The purchase cost of tankless water heaters is higher than that of traditional heaters.

  • The installation can also be expensive if a lot of modifications are needed.

  • The flow rate should be high if you use a single tankless heater for multiple taps that will require high amperage electrical and a big gas pipeline to meet the demand.

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