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Heating Ventilation and Air Conditioning Full Course - HVAC Course (Part 39)


                In this part of the full HVAC course, we will learn about Hydronic System in HVAC.

Hydronic System in HVAC

What is Hydronics?

Hydronic systems are heating/cooling systems that use water rather than electricity to transfer heat or cold throughout a house or building. These types of systems were originally invented to prevent damage to a home caused by freezing pipes, but they have become increasingly popular over time due to their efficiency, reliability, durability, and cost savings.

How do Hydronic Systems Work?

In a typical hydronic system, water passes through pipes inside of a radiator known as a boiler or condenser. A pump circulates the water back and forth between these two components, creating a loop of continuous circulation. In order to keep the temperature consistent throughout the entire system, the water flows past radiators that are constantly changing direction and moving air.

Why Use a Hydronic System?

Water-based systems are both environmentally friendly and reliable. They don’t rely on power generators that may malfunction or go out of service at any moment, making them highly dependable. Water-based systems also work much faster than traditional AC systems. While the average electric furnace takes 30 minutes to kick on, a hydronic system may only take 10 seconds or less. Finally, unlike traditional AC units, hydronic systems are cheaper to run over long periods of time. Because the pumps and radiators are powered by the same water circulating through them, a single unit can last longer and require fewer repairs in comparison to other methods.

How do Hydronic Units Work?

A hydronic system consists of three basic parts. There are the radiators, pumps, and valves. Each radiator contains a series of tubes where hot and cold water circulate around each other. Pumps pressurize the water and send it through the radiators, while valves regulate the flow of water through the different sections of the system.

Are Hydronic Systems Less Efficient Than Electric Heating?

Not necessarily. Many people think that using a hydronic system means having less efficient heating. However, this is not true. In fact, many times hydronic systems are more efficient than traditional AC systems. One reason is that they use less energy to compress gases, and therefore create less noise. Other reasons include the fact that they utilize the heat produced by the combustion of natural gas instead of trying to convert natural gas to electricity, which requires additional equipment and consumes fuel.

Types of Hydronic Piping systems in HVAC

Hydronic systems can be divided into following types:
* Single or one-pipe Hydronic System
* Two pipe Hydronic System ( Direct return or Reverse return)
* Three pipe Hydronic System
* Four pipe Hydronic System
* Series Loop Hydronic System

* Single or one-pipe Hydronic System

In case of single pipe hydronic system, the water supply pipes are connected directly from the city mains to the radiant coil unit without any intermediate valves. There is no need of isolation valve at the point where the cold water feeds to the radiator. On the contrary, there is a separate hot water return line to the domestic hot water service (DHWS). Therefore, if the DHWS fails, then there would not be any direct supply of hot water to the radiators.

One drawback associated with such systems is that they do not have any safety mechanism for shutting off the flow of water under pressure in times of emergency. This may result in serious injury to people who get trapped inside these units. One advantage of such systems is that it does not require any plumbing work. However, if the temperature of the incoming water is different than the desired temperature, then the efficiency of the heating system decreases. In addition, the cost involved in installation of such systems is high.

The easiest to install, single pipe relies on only one heated line. In order to provide an adequate flow rate, the diameter of the tubing should be sized appropriately. Single pipe units tend to be economical since they can use smaller copper piping.

* Two pipe Hydronic System ( Direct return or Reverse return)

In case of two pipe system, a water pump circulates water from the city mains through both the hot and cold water piping systems separately. When the flow rate of either of the water supply pipes is less than the set limit, the circulating pumps automatically switch over to the other pipe until the flow ceases completely. Such systems can shut down in extreme conditions due to low temperatures and/or excessive pressures.

However, the major disadvantage with these systems is their higher operation costs. Further, the complexity of installing such systems makes them expensive. Also, the capacity of the system in terms of the number of radiators that can be installed is restricted. There is always a risk of contamination of the hot water due to leakage of cold water into the hot water ducting.

A double pipe consists of two parallel lines of tubing with a small gap in between them. This design provides a slightly higher flow rate than single pipe units, but still maintains an acceptable level of comfort. Double pipe units are often installed in larger rooms.

* Three pipe Hydronic System

Three Pipe Hydronic System (TPS) is an example of how a home heating system is being used to provide hot water. TPS uses two pipes, one returns chilled water back to the boiler while the second pipe circulates heated water throughout the house. These pipes are connected at the top of the boiler where they meet, forming three separate water circuits. These three pipes are called the return piping, circulation piping, and distribution piping.

Return piping supplies cold water to the boiler. Circulation piping supplies hot water to various devices in the house; these could include showers, sinks, tubs, etc. Distribution piping supplies hot water to the house via radiators, spas, etc. In general, the system works much like a typical centralized heating system with some major differences. The most obvious difference between a TPS and a traditional central heating system is that it does not require any ductwork or vents. Due to having no air movement in the piping, the temperature remains constant throughout the entire unit.

To start using a TPS, take out the old boiler and connect the new one. There are several different types of boilers that can be connected to a TPS. The most popular type of boiler for TPS is a baseboard furnace. The furnace is placed in the basement or garage and heats the house. Baseboard furnaces are the same size as a standard furnace without any modifications. These units run off gas or electric power and usually have a fan to circulate warm air. Gas-fired baseboard furnaces have a venting blower to pull smoke away from the chimney. Electric baseboard furnaces do not require a blower. If you want to use an oil burner, make sure to get one that has a pilot light. To install a TPS, simply replace the flue cap over the existing chimney. Then add the new boiler, install the distribution piping, and hook everything together.

* Four pipe Hydronic System

A four-pipe hydronic heating/cooling system is similar to a forced air furnace or A/C unit except instead of using hot combustion gas (air) to transfer heat, they use water. Water contains less than 1% thermal conductivity compared to air at about 0.04%, making it an excellent insulator. Also, pipes containing cool water have very low thermal mass, meaning they take time to reach equilibrium temperature after being turned on. When the pipes are filled with hot water, however, the water’s thermal capacity increases dramatically, allowing quick warming of rooms. In addition, the pipes can be installed underground or under floorboards without disrupting any existing plumbing systems.

What Is Four Pipe Hydronic System in HVAC?

A four-pipe hydronic system is comprised of two primary components: a boiler and a radiator/condenser coil. Both elements are located inside of the building's exterior wall. In addition to providing heating to the interior space, these systems generally have some sort of circulation loop (e.g., water pipes) running through them. A thermostat connects to the boiler via a control valve to regulate temperature, while the radiator/coil serves as a heat exchanger. By using a single radiating surface instead of individual sections of copper tubing, the four-pipe hydronic provides even distribution throughout the room, resulting in less hot spots. Because each section in the system is fully enclosed, they're easier to install than open-loop units.

 Components Of Four Pipe Hydronic System

Boiler - The boiler contains pressurized water and generates steam at high temperatures. The boiler is often referred to as a heat pump because it uses electric power to heat the water. In many cases, the actual heating device is mounted outside of the building since it requires less wiring.

Condensing Coil - The condensing coil is where the steam is condensed into liquid water. If there isn't enough air in the room, the coil may need to be vented outside of the building.

Radiator/Coil - The radiator/coil consists of coils of metal tubing covered with insulation and connected to the floor, ceiling, and walls of the room. The coils transfer heat between the circulating water and the room. Condensation produced in the coil is drained away.

Thermostat / Valve - This controls the amount of steam generated by the boiler. Usually, the thermostats are set to maintain a uniform temperature throughout the room.

Circulation Loop - Circulating water flows through the system to allow the radiator/coil to conduct heat out of the room. To prevent leaks, piping should be insulated and securely attached to the structure.

* Series Loop Hydronic System

Series Loop Hydronic System - A Series loop hydronic heating and cooling system requires hot water to circulate throughout the building. This type of HVAC system is commonly referred to as a “loop” system. In a traditional heating and cooling system, warm air flows from a furnace or boiler. As it travels through ductwork, it warms up before being distributed to rooms or spaces in the house. Air conditioning units work similarly, except they remove heat from the air instead of adding it. When a person turns on the thermostat in their home, the temperature setting is selected and the unit automatically adjusts accordingly.

Series Loop Hydronic Systems – While these systems were first developed in Europe, they are now widely popular in North America. Their distinguishing feature is that they are closed loops with no outside air transfer of heat or cold. Instead of a traditional furnace or boiler that heats or cools air, the system uses an electric heater and compressor that heats or compresses refrigerant gas. The resulting high-pressure refrigerant is then circulated through pipes running throughout the house. The system maintains a constant temperature inside the house by adjusting the flow of refrigerant. These systems have become increasingly popular over the years due to their efficiency, low maintenance costs, and long lifespan.

A series loop hydronic heating and/or cooling system consists of three basic components:

1) Circulating water (a pump supplies water to the system)

2) Pipes that connect the hot water to the rooms

3) An electronic controller that regulates the amount of heat or cold that goes into each room

The circulating water provides the heat or cold to the rooms. The pipes run throughout the building and carry the heated or cooled water to the various places where the people live. There is one outlet valve per room, which controls how much heat or cold enters the room. The valves, located at the top of the pipe, open and close based on the desired temperature set by the thermostat.

There are two types of series loop hydronic systems: indirect and direct. Indirect systems use the air around the building to keep the temperature regulated. In direct systems, the room’s temperature is controlled by the circulation of water directly through the pipes. These systems are becoming less common today because of the space they take up and the additional cost involved. Another disadvantage to direct systems is that they require the installation of vents on the roof of the building. These vents allow cool air to enter the building causing the temperatures to drop.

The advantages of using a series loop hydronic heating system include:

• No outside air is necessary to regulate temperature.

• The system does not produce noise as an air conditioner does. Because the refrigerant is circulated throughout the building, it creates a steady stream rather than a loud wind blowing across the area.

• Unlike many traditional heating and cooling systems, the system does not need to be connected to an electrical outlet. All heat or cold is generated from electricity. The only thing that runs off the power supply is the pump that circulates the water around the building.

• Since the system operates off electricity, there are few moving parts in the system. This makes the system reliable and durable.

• The unit can be placed anywhere in the building since it doesn’t depend on air movement.

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Heat Load Calculation Guide 1

Heat Load Calculation Guide 2

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