Is it Better to Use a Condensing Steam Boiler?

When it comes to choosing the type of boiler for your business, there are a few things you need to consider. One such factor is whether to use a condensing steam boiler. Here we look at the pros and cons of using this boiler to help you make an informed decision.

What is condensing steam boiler?

A condensing steam boiler is energy-efficient and draws heat from fuel as it burns. This heat is transferred through a heat exchanger to water, baseboards, and radiators. While no fuel-burning system operates at 100%  efficiency, some heat escapes through the exhaust. As a result, you must choose between a condensing and a non-condensing boiler.

A condensing boiler uses special heat exchangers to recover the latent heat of vaporization and extract additional heat from waste gases. The result is an efficiency boost of 10 to 12%, but the effectiveness of the condensing process depends on the temperature of the water recirculated in the boiler. However, a condensing boiler is always as efficient as a non-condensing boiler.

The difference between a condensing and a non-condensing boiler is the type of secondary condensing heat exchanger in the boiler. A non-condensing boiler does not have this secondary condensing heat exchanger and is known as a standard boiler.

The latter is more energy-efficient, however, and many older industries, businesses, churches, and even Penn State University use steam heating in some capacity.

A condensing steam boiler has many benefits, including being more efficient and energy-efficient than conventional ones. First of all, it’s safer for your house. Traditional boilers release water vapor and waste heat as exhaust.

A condensing boiler recovers this water vapor and puts it back into the heating system, putting more heat into the industry’s heating system. Secondly, a condensing boiler doesn’t waste fuel. Using this energy-efficient technology, a condensing boiler can significantly lower your heating bill.

Working process of condensing steam boiler

Condensing boilers are designed to take advantage of the energy contained in water vapor that escapes the exhaust flue gases. A heat exchanger is installed between the boiler and the exhaust gas, extracting heat from the air and pre-heating the water entering the boiler.

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This water is typically discharged to a convenient floor drain. Because of its energy-efficient design, condensed water is expected to have a generous flow rate in the spring and fall seasons.

The flue gases must exit the boiler at a low temperature to achieve this efficiency. This temperature is limited by economics, equipment, and corrosion issues. The boiler should be configured, so the flue gas temperature is between 150 and 200degC.

The temperature of the flue gases is not too high for the flue gases to escape, as the reaction heat is considered incombustible. Thermodynamics also limits the progress of combustion. In any case, the combustion reaction always produces hydrocarbons, CO, and H2.

The condensing process of a steam boiler reduces the overall temperature by removing heat from the flue gas. The resulting vapor is converted to water, with only a slight temperature difference. This means that condensing boilers can be set to meet the heating requirements of a building and return water temperatures below 130degF. Ultimately, condensing boilers can achieve maximum efficiency by utilizing heat in the boiler instead of heat.

Pros & Cons of condensing steam boiler

It can maximize energy efficiency by utilizing condensing technology to reduce combustion gas temperatures. This type of boiler produces less heat and requires less air to operate. Typically, the flue gases are about 150 to 200 degrees Celsius, which is well within limits set by thermodynamics and economics.

Hydrogen, carbon monoxide, and water are produced during the combustion process. This combustion waste is incombustible, and it’s important to avoid this waste by following proper boiler maintenance.

However, this type of boiler has a drawback. They produce condensate in great quantities, about one liter per cubic meter of gas. A capacity of 25 kW boiler releases three liters of condensate per hour and nearly 70 liters per day.

The pros of condensing boilers are that they are ideal for various factories. They can efficiently heat a larger house. Their main disadvantage is that they are not designed to fit into small spaces but can be placed strategically to heat multiple rooms simultaneously.

Cost of condensing steam boiler

In addition to operating costs, installing a condensing steam boiler requires drain and vent installation, which can increase the total cost. The boiler may also require HVAC personnel or plumbing work, including modifications to the pipe system, expansion tank, air separator, and circulation pump. When installed with an air separation system, a combi-boiler also has an increased price tag, as the boiler may require retrofitting existing plumbing.

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The calculations for AFUE are more accurate than those made for commercial-sized boilers. This is because AFUE only takes into account the efficiency of a boiler when it is running at maximum capacity.

However, boiler usage varies over time and fluctuates with demand. In-service efficiency, on the other hand, reflects the response of the boiler system to fluctuating demands, including standby and low output conditions.

The thermal efficiency of a condensing steam boiler depends on two factors: the temperature of the return water and the percent of firing rate. At lower temperatures, efficiency is enhanced by the process of counterflow heat exchange with flue gas and condensing water vapor in the flue gas.

The condensing process recovers the latent heat of vaporization and reduces water and energy consumption. In some cases, using oil-burning boilers may be the only option available.

An efficient condensing steam boiler is highly energy-efficient. The efficiency of a boiler is measured as the ratio of useful heat output over the total energy input. This reflects the efficiency of the fuel conversion and the efficiency of steam that goes to the turbines.

While most of the efficiency loss is due to the sensible heat lost as hot flue gases leave the boiler, other losses are caused by convection or heat radiation to the surroundings. The latent heat of vaporization of steam within flue gases must also be included in the gross efficiency calculation.

Design of condensing steam boiler

The overall efficiency of a boiler is a measure of its performance. This efficiency is measured in terms of fuel-to-steam ratio and heat loss due to radiation and convection. Typically, the efficiency of a condensing steam boiler is greater than its non-condensing counterpart. Listed below are some of the main benefits of condensing steam boilers.

High-efficiency heat exchangers are used in condensing boilers to capture the latent heat energy of water vapor. In conventional boilers, this energy is lost, but the boiler uses it to recover the sensible heat energy of flue gases. Because the water vapor is highly corrosive, a condensing boiler must be constructed with materials that can withstand high temperatures.

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Variable-primary-flow systems are also available, allowing the system to operate at a lower flow rate during low load times. The variable-primary-flow design promotes a lower return water temperature, increasing the boiler’s efficiency.

It also allows the boiler to operate constantly to maximize efficiency. Its variable-primary design allows less water to flow into the boiler at low loads while increasing the available surface area in the condensing mode.

The BL Controller is an important safety component. It simplifies monitoring steam pressure, flue gas temperature, feed water temperature, conductivity, and blowdown time. It also helps maintain the boiler’s efficiency by minimizing heat leakage from the combustion air. When the pressure in the boiler is low, the safety door will spring back, preventing any explosion dangers. We can see below the types of condensing boilers–

  1. Oil-Fried condensing boiler
  2. Gas-Fried condensing boiler
  3. Biomass Pallet condensing boiler

Maintenance of condensing steam boiler

Operation and maintenance (O&M) personnel must keep records of services and metering data. These records should include time spent on the boiler system, alarms that caused a corrective action, and equipment downtime.

This information will help prevent recurring issues and ensure proper maintenance and warranty coverage. In addition, periodic evaluations of components are needed for boiler system health. They should be evaluated for their age, repair history, and criticality to the overall system operation.

During the process of installation and maintenance, the pipe design of a boiler has only minimal impact on the boiler’s efficiency. The type of control valves used on the loads affects the boiler efficiency. A condensing boiler uses oxygen to operate at optimum levels.

Every pound of water vapor that is condensed contains 1,000 BTUs of latent energy. This energy is extracted from the exhaust gas during combustion and converted into heat, increasing boiler efficiency.

Proper condensing steam boiler maintenance requires regular inspections and adjustments to keep it in peak performance. A certified technician can adjust the fuel/air mix ratio and ensure peak performance. Antrim technology, for instance, monitors the oxygen level in the combustion chamber and auto-adjusts to maintain the optimal level of oxygen. Moreover, it can maintain the condensing mode even without load changes.

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