Condensing vs Non – Condensing tankless water heater in 2022 – Complete Guide

You should be acquainted with both tank and tankless water heaters, but everyone is talking about condensing and non-condensing tankless water heaters these days. So, what are these water heaters? And how are they different from regular tankless units? We will go over all the everyday things you need to know about them to be familiar with their work.

What are condensing and non-condensing tankless water heaters?

A condensing tankless type water heater is a variant of a gas tankless water heater. There is no condensing variant for an electric tankless water heater because electricity doesn’t form any byproduct waste. But before we go over what they are? Let us first see why they are named so.  So, typically when gas, propane, or any other fuel-based tankless water heater kickstart into action. It burns the hydrogen content of the fuel to heat the water. While the remaining parts are released using exhaust or vent in the form of steam or vapors. When this steam or vapors get cooled, they condensate to form acidic water.

Condensing tankless water name comes from the fact that it cools the steam or vapor inside the unit. In comparison, a non-condensing tankless water heater releases the vapors directly before they can cool down.  The most common models of tankless water heaters are non-condensing water heaters.

Why a Condensing tankless water heater?

Condensing tankless water heaters have gained a lot of popularity due to their extreme energy efficiency. A regular or non-condensing tankless water heater gives an energy factor of 0.80 or 80% energy efficiency. While the rest of 20% of the energy gets lost in the form of vapors. On the other hand, a condensing tankless water heater gives you an energy factor of 0.90 or above 90% energy efficiency. It also utilized the hot vapor to heat water and only released them when they are no longer helpful.

Structural differences

Although it may not look any different, there are three significant structural differences between condensing and non-condensing tankless water heaters. Condensing tankless is more efficient than a non-condensing tankless water heater.

1.  Heat Exchanger

A condensing tankless water heater has two heat exchangers instead of one where one heat exchanger works like a normal one by getting heat from the burning gas or propane fuel. At the same time, the second heat exchanger uses the stream or vapors produced as a byproduct of the burnt fuel. A condensing tankless water heater loops the hot steam and vapors from one heat exchanger to the other heat exchanger instead of releasing them through the vent.

The second heat exchanger is made of non-corrosive stainless steel as hot steam and vapors upon cooling can condensate into acidic water, which is highly corrosive and can damage a typical heat exchanger.

2.  Concentric Venting

The second significant structural difference between a condensing and a non-condensing tankless water heater is the vent. Both of these use centric venting where two pipes are used, one pipe being over the second.

For a non-condensing tankless unit, the inner pipe is made of stainless steel. As it is through this pipe that the hot steam and vapors will be vented. It is done so as when the steam or vapor cools, they form acidic water, which is highly corrosive and can damage the vent, so a non-corrosive stainless steel material is used. While the outer pipe is made of PVC through which air will come in the tank to cool it.

In condensing tankless water heater, both the outer and inner pipes are made of PVC. The only difference is that internal pipes are made of PVC schedule 40. It doesn’t need a stainless steel pipe as the second heat exchanger has already used the hot steam and vapors to heat the water. After this, the temperature of the vapors is only 38°C, and the condensed acidic water is drained through a condensate drain.

3.  Condensate Drain

A condensing tankless water heater needs a condensate drain as it doesn’t release the steam or vapors directly through the vent but also uses them to heat the cold water. By doing this, the vapor passes their heat to the cold water and get cold very fast. When vapors cool down, a part of these form acidic water, which is highly corrosive that remain in the unit and damages it. A condensate drain drains this water and protects the unit while the unit saves your energy cost.

So be sure to check for these to know whether you are buying a condensing or a non-condensing tankless water heater.

Working:

Being a tankless water heater, the working of both Condensing vs Non – Condensing tankless water heater units is similar. Coldwater is brought into the unit, where the heat exchanger heats the water. Hot water is sent to the outlet.  But the difference between them is that a non-condensing water heater heats the water by burning natural gas and byproduct formed during this, like steam or vapors that can be as hot as 300 °F.

The non-condensing units exhaust these through the vent using the stainless inner pipe. In contrast, the outer PVC pipe brings in fresh air to cool the unit and to bring out the steam and vapor with them on their way out.

The working of condensing tankless water heater is a little different. The byproduct of burning natural gas are similar to non-condensing but instead exhausting them through the vent. A condensing unit loops them to a second heat exchanger, which is present before the primary heat exchanger. What this heat exchanger does is that it draw heat from the extremely hot vapors and use that heat to pre-heat the cold water coming into the unit before sending it to the primary heat exchanger. As these hot vapors heat is drained, some cool down enough to form acidic water, which gathers in the tank and is drained through the condensate drain. At the same time, the still vapor part is exhausted through the vent.

This is why non-condensing only has a UEF(Uniform Energy Factor) or energy efficiency of 80% while condensing gives a UEF or energy efficiency of above 90%.it is because it also uses the energy present in the steam or vapors to heat the water.

Frequently Asked Questions

Do I want to condense or non-condensing tankless water heater?

If you are keen on buying a gas tankless water heater that gives the highest energy savings and is willing to pay a little extra to achieve higher returns in the future. Then the condensing tankless water heater is the one that you need.

Are condensing water heaters worth it?

A condensing tankless water heater is an upgraded form of a gas tankless water heater. They give ultra energy efficiency, which reflects on you in the form of savings. However, they do cost more than a tankless unit; hence in the short term, you won’t be seeing any returns.

Is condensing better than non-condensing?

The thing that makes condensing better than a non-condensing tankless water heater is its energy efficiency. The energy efficiency of condensing can be as high as above 90%, while non-condensing only gives around 80% energy efficiency. This may not look like much, but in the long term, condensing gives you more considerable savings.

Do tankless water heaters need a condensate drain?

The condensing tankless water heater needs a condensate drain as it drains the acidic water, condensate when steam and vapors are produced as a byproduct of burning gas, condensate upon being drained of heat. This acidic water is highly corrosive and can damage your unit if left unnoticed. A condensate drain drains this liquid before it can damage the tankless unit.

Conclusion

Condensing vs Non – Condensing tankless water heaters both have their own merits. A condensing water heater is an excellent choice to buy if you are looking for a gas tankless water heater. They reduce the ventilation requirements and have less operating costs. They also use hot vapors to heat water, giving an energy efficiency of more than 90% and can significantly increase your savings. But they are a little more costly than a non-condensing water heater. So, in the short term, you won’t get much, but they give a lot of savings in the long term. They are the smart choice and are trending, which makes them worth considering.


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