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Condensing Tankless Water Heater 101

Condensing Tankless Water Heater
Condensing Tankless Water Heater

Condensing Tankless Water Heater vs Non Condensing Tankless Water Heater

Water heaters have a variety of distinctive features that we use to categorize them. For instance, we categorize water heaters into electric ones and gas-powered ones. Then, there are tankless water heaters and tank-style water heaters. Residential water heaters or commercial water heaters. The list goes on. In this article, we will be looking at the categorization of condensing vs non-condensing water heaters. Followed by that, we will understand the pros and cons of condensing water heaters. Finally, we will understand whether a condensing tankless water heater might be a better choice for your property. 

Condensing water heaters use condensing technology to absorb additional heat from exhaust gases while heating water.

First, we will take a look at the categorization itself. We will understand the basis on which water heaters are divided into condensing water heaters and non-condensing ones. Then, we will look at four different types of water heaters to further realize this categorization: non-condensing tank-style/storage water heaters, condensing tank-style water heaters, non-condensing tankless water heaters and condensing tankless water heaters.

Table of Contents

Water Heater and Condensing Technology

So, now that we know that water heaters can be condensing or non-condensing, let us try and understand this categorization further. To begin with, this categorization deals with what a water heater does with its exhaust gases. Here is how most gas-powered water heaters work:

Non-condensing Water Heaters Workflow:

  1. Natural gas/propane is combusted to create enough heat energy required to heat the water.
  2. The exhaust/flue gases are vented to the outside.

However, condensing water heaters have an additional step in this process:

Condensing Water Heaters Workflow:

  1. Natural gas/propane is combusted to create enough heat energy required to heat the water.
  2. The water heater uses “condensing technology” to absorb additional heat from the exhaust gases.
  3. The additional heat is also used to heat the water.

Since condensing water heaters deal with the treatment of flue gases, the categorization is only applicable to gas-powered water heaters since electric water heaters do not combust a fuel to release energy (and exhaust/flue gases). Essentially, condensing water heaters can absorb some of the heat from exhaust gases after the combustion process which would have been wasted in a non-condensing water heater.

What is Condensing Technology?

Condensing technology is essentially the process with which a condensing water heater absorbs additional heat from exhaust/flue gases. The way in which this additional heat is used to heat water differs for tank-style and tankless water heaters. We will be looking at the working of both these types of water heaters shortly.

When natural gas/propane is combusted to heat water, the process releases a lot of gaseous byproducts like steam. Instead of venting these gases out directly, a condensing water heater facilitates the condensation of these gases. That is, it helps the exhaust/flue gases turn into liquid. The process of condensation (which turns gas products into liquid) releases heat. This heat is trapped by the condensing water heater and used to heat water (in addition to the primary heat energy created).

In the above process, the exhaust/flue gases are converted to their liquid state called condensate. The condensate is usually neutralized and disposed in a condensate drain. Neutralization and careful disposal of the condensate, in accordance with local regulations, is important to avoid flammable or unsanitary byproducts from re-entering the building’s HVAC system.

Condensing Tank-Style Water Heaters | Condensing Storage Water Heaters

As mentioned earlier, condensing water heaters utilize the additional heat that they absorb by the condensation of flue gases differently based on their design. Let us look at how condensing technology is used in a tank-style water heater.

A condensing storage water heater makes use of better insulation to trap the heat from combustion. Some models also have a secondary heat exchanger through which the hot, combusted gases are flown. This secondary heat exchanger uses the excess heat from the exhaust/flue gases to assist primary water heating. Enough heat is absorbed from the exhaust gases to turn them into condensate liquid which is then neutralized and drained.

Condensing Tankless Water Heaters | Condensing On Demand Water Heaters

Condensing tankless water heaters heat water on demand without the need for storage and use condensing technology to absorb additional heat from exhaust/flue gases post-combustion for higher efficiency. All tankless water heaters use a primary heat exchanger to heat water on demand. The way in which a condensing tankless water heater uses the absorbed heat from exhaust/flue gases differs with each model.

Some condensing tankless water heaters have two heat exchangers. The primary heat exchanger combusts natural gas/propane to heat the water. The heat from the exhaust/flue gases is reabsorbed in a secondary heat exchanger. The incoming water gets heated by the standard, primary heat exchanger first, followed by the secondary heat exchanger.

On the other hand, some tankless water heaters use the absorbed heat from the exhaust/flue gases in the primary heat exchanger itself. For instance, Intellihot’s tankless water heaters route the combusted flue gases close to the water pipe in the heat exchanger. The heat from the flue gases also contributes to the water heating process in the primary heat exchanger, as opposed to this excess heat being wasted in a non-condensing tankless water heater. Here is a video of how Intellihot’s condensing tankless water heaters work:

Condensing Water Heaters Pros and Cons

Now that we know what condensing water heaters are, you might be wondering what the purpose of condensing technology is. Are condensing water heaters better than non-condensing water heaters?

The purpose of condensing technology is the absorption of as much heat energy as possible from the combustion process to avoid energy wastage. Here are some of the pros and cons of condensing water heaters:

  • Condensing water heaters are more energy-efficient and reduce utility bills: Condensing water heaters can absorb more heat from the combustion process than non-condensing water heaters. Hence, they need lesser energy to heat the same amount of water, helping customers reduce their operational expenses.
  • Condensing water heaters allow customers more choice in venting: Since condensing technology cools down the exhaust/flue gases, venting pipes do not need to be capable of handling high temperatures. Hence, condensing water heaters can be vented using PVC pipes.
  • Condensing water heaters usually cost more than non-condensing water heaters: Condensing water heaters typically cost more to purchase than a non-condensing water heater. Hence, customers ought to evaluate whether the amount of money that they can save due to the efficiency of a condensing water heater can make up for the additional upfront cost of purchasing a condensing water heater.
  • Condensing water heaters need a separate condensate drain: Condensing water heaters require a separate drain to safely dispose of the condensate. Hence, customers need to consider this installation requirement before considering a condensing water heater.

Condensing Tankless Water Heaters vs Non-Condensing Tankless Water Heaters

Tankless water heaters are more efficient than tank-style water heaters. They reduce operational expenses, decrease the risk of pathogens like Legionella, and save space. Condensing tankless water heaters are even more efficient than non-condensing tankless water heaters. Hence, customers enjoy the efficiency and cost-saving advantages of tankless water heaters even more with condensing ones. However, tankless water heaters typically cost more upfront than tank-style water heaters. Condensing tankless water heaters are even more expensive to buy than non-condensing tankless water heaters.

Condensing Storage Water Heaters vs Non-Condensing Storage Water Heaters

Storage water heaters are usually less efficient, less safe, and bulkier than tankless water heaters. However, condensing storage water heaters help increase the efficiency of tank-style systems. Hence, a condensing storage water heater might offset the energy inefficiency of tank-style system.

The Most Efficient Choice

Among all the options mentioned, a condensing tankless water heater would be the most energy-efficient type of water heater. Hence, a condensing tankless water heater would result in the lowest utility bills when compared to a condensing storage water heater, a non-condensing tankless water heater, and a non-condensing storage water heater.

Condensate Draining | What is a Condensate Neutralizer?

As mentioned earlier, condensing tankless water heaters cool down the exhaust/flue gases, turning them into a liquid called condensate. The condensate needs to be safely disposed of. It cannot be released directly into the drainage system since it can be unsanitary and explosive and can re-enter the building’s HVAC system.

Before the condensate is released, it needs to be neutralized to make it safer to be released. To do so, the condensate is passed through a condensate neutralizer. The condensate neutralizer needs to be changed routinely – usually once every year.

You can order a condensate neutralizer using Intellihot’s online water heater parts store. You can purchase varying levels of condensate neutralizer depending on your water heater: a smaller quantity for units under 1 million BTUs/hr. and a larger quantity for units above 1 million BTUs/hr. Watch the following video to understand how to understand the proper condensate disposal inspection for Intellihot units:

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