FCB 21002Ducting and Piping Network

-Hydronic system types-

PRESENTATOR

• Nur Syafiq bin Halimi(50206209244)

• Saifullah bin Shukeri Jamil(50206209039)

• Mohd Nurul Imran bin Mustaffa(50206209246)

• Mohamad Azizuddin bin Mohd Salleh (50206209283)

TOPIC REVIEW

Hydronic system types :Open and Closed types Direct and Reverse return One-, Two-, Three- and Four- Pipe systems Primary and Secondary looping

PROLOGUEHydronics is the use of water as the heat-transfer medium in heating and cooling systems.

Some of the oldest and most common examples are steam and hot-water radiators.

A hydronic system may include both a chilled and a heated water loop, to provide for both heating and air conditioning.

Chillers and cooling towers are used separately or together as means to provide water cooling, while boilers heat water.

Many larger cities have a district heating system that provides, through underground piping, publicly available steam and chilled water. A building in the service district may be connected to these on payment of a service fee.

Basic Type of Hydronic System

Hydronic System

Hot Water or Steam Chilled Water

Hydronic System

Flow Generation

(forced flow/gravity

flow)

Temperature (low

medium & high)

Pressurization (low

medium & high)

Piping Arrange

ment

Pumping Arrange

ment

Classification of Hydronic System

Hydronic System

Single or One

Pipe

Two Pipe

Three Pipe

Four Pipe

Series Loop

General Piping Arrangement Categories

OPEN AND CLOSED TYPE

• For open system, pipe expose to atmosphere (outside). For example, from cooling tower to condenser.

• The type are black steel. (commonly used)• For closed system, pipe not expose to atmosphere (inside building).

For example, from chiller to AHU or FCU.

• The type are galvanized ion (GI). (commonly used)

The piping materials for various services are shown below:

SERVICE TYPE OF PIPE

Chilled water Black and galvanized steel

Hot water Black steel

Cooling water drains Black

ONE PIPE SYSTEM

The One Pipe Series Loop uses less pipe than any other hydronic piping arrangement therefore it is less expensive to install the piping but you need bigger radiators or longer baseboards at the end of the loop because this part of the loop will have less heat.

The radiators or baseboards at the beginning of the loop use most of the heat thus the reason for the larger radiators and baseboards at the end of the loop.

There is also a larger temperature drop in this type of loop between the supply and the return versus other types of hydronic piping arrangements. The near boiler piping may need to be modified to prevent large delta T between supply and return.

MONOFLOW HYDRONIC LOOP & MONOFLOW TEES

The monoflow hydronic loop is similar to the one pipe series except the main loop uses monoflow tees to divert the water to the radiators or baseboards.

The main hydronic loop maintains a constant flow on a call for and the water temperatures for each zone are more even throughout the hydronic loop than the one pipe series hydronic loop.

The monoflow tee is a special tee which needs to be installed at the supply and the return for each radiator or baseboard.

This loop system is easy to zone but needs more piping and special monoflow tees for each separate circuit. Additionally, if not installed properly flow problems will occur in radiators and/or baseboards.

It is really important that if you have a monoflow system and want to modify it in any way for an addition or other work that you consult a plumbing and heating HVAC specialist for this retrofit.

TWO PIPES SYSTEM

DirectReturnReverseReturn

DIRECT RETURN piping

The Two Pipe Direct Return Loop utilizes more pipe than the one pipe series loop but all radiators and baseboards receive the same temperature of water therefore it is more even heat than in all the radiators and/or baseboards than the one pipe series loop.

Another advantage of two pipe direct return loop over the one pipe series loop is that it can be zoned.

Zoning gives you more control over where and when you want heat and this can save you money on the cost of heating.

As with many hydronic loop systems the two pipe direct return needs balancing valves. The near boiler piping may need to be modified to prevent large delta T between supply and return.

The return piping, as the name suggests, takes the most direct path back to the boiler.

Low cost of return piping in most (but not all) applications, and the supply and return piping are separated.

Advantages

Disadvantages

This system can be difficult to balance due to the supply line being a different length than the return.

The further the heat transfer device is from the boiler the more pronounced the pressure difference.

Because of this it is always recommended to: minimize the distribution piping pressure drops; use a pump with a flat head characteristic, include balancing and flow measuring devices at each terminal or branch circuit; and use control valves with a high head loss at the terminals..

REVERSE RETURN PIPING

The Two Pipe Reverse Return Hydronic Loop uses more pipe than the two pipe direct return hydronic loop but the flow is more balanced and even than the two pipe direct return hydronic loop.

All baseboards and radiators receive the same temperature of water so is the same as the two pipe direct return but an advantage over the one pipe series hydronic loop.

The two pipe reverse return hydronic loop can also be zoned offering you savings on your heating bill by taking advantage of hydronic loop zoning and large pressure drop.

The return piping takes the same basic path as the supply back to the boiler.

This system is often considered "self balancing", however, valves should always be included.

Advantages

DisadvantagesThe installer or repair person cannot trust that every system is self balancing without properly testing it.

Very large scale systems can be built using the two-pipe principle. For example, rather than heating individual radiators, the steam may be used in the reheat coils of large air handlers to heat an entire floor of a building

THREE PIPES SYSTEM

A three-pipe system is usually used with an induction system and will satisfy the variation in load by providing independent sources of heating and cooling to the room unit in the form of constant temperature primary or secondary chilled and hot water.

If it used with an induction unit, it contains a single secondary water coil.

A three-way valve at the inlet of the coil admits the water from the hot or cold water supply as required. The water leaving the coil is carried in a common pipe to either the secondary cooling or heating equipment.

FOUR PIPES SYSTEM

Systems for induction and radiant panel or fan-coil systems derive the name four-pipe systems because of the four pipes to each terminal unit.

The four pipes consist of a cold water supply, a cold water return, a warm water supply, and a warm water return.

The four-pipe system satisfies variations in cooling and heating to the induction units using temperature primary air, secondary chilled water, and secondary hot water.

Terminal units are provided with two independent secondary water coils one served by hot water and the other by cold water.

PRIMARY LOOPING

Primary-secondary variable-flow systems: Water flows through the chiller or boiler primary loop at a constant rate, and water flows through the secondary loop, which serves air handlers or fan coils, at a variable rate.

The decoupled section (shown as common piping in the diagram below) isolates the two systems hydraulically. Primary-secondary variable-flow systems are more energy efficient than constant-flow systems, because they allow the secondary variable-speed pump to use only as much energy as necessary to meet the system demand.

These are chilled-water or heating-water systems with a single variable-flow loop.

A two-way bypass valve is typically used to maintain a minimum specified flow rate through the chiller or boiler.

Primary-loop variable-flow systems are more efficient than primary-secondary variable-flow systems.

SECONDARY LOOPING

Flow Diagram for a Secondary Loop Refrigeration System

Secondary loop systems have all of the refrigeration associated with liquid chilling located within the central machine room of the supermarket.

The chiller system resembles the multiplex refrigeration system since multiple parallel compressors are employed in both systems.

The compressors are utilized based upon suction pressure which controls the supply temperature of the chilled fluid.

The use of multiple compressors allows the refrigeration capacity to conform to changing operating conditions, resulting in better fluid temperature control and lower compressor energy use.

The cooling of the secondary fluid takes place in a heat exchanger whereby the liquid refrigerant of the chiller system is evaporated to provide chilling to the secondary fluid.

Heat rejection for the chiller system is accomplished utilizing a condenser cooled by ambient air. Either a dry, air-cooled condenser or an evaporative condenser may be employed.

The evaporative condenser is favored because of the lower condensing temperature which may be obtained by rejecting heat to the lower ambient wet-bulb temperature.

The lower condensing temperature provides greater compressor refrigeration capacity and lower power draw, both of which result in reduced refrigeration energy consumption.

PIPE SIZING

Open System (Scheduled 40)

Closed System (Scheduled 40)

ANSI Schedule 40

ANSI Schedule 80

ASHRAE Journal - Sizing Pipe Using Life Cycle Costs

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