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Hot Water Heating Systems - Online Design Application

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This tool can be used to design hot water heating systems.

How to Use

  • Make a sketch of the system - something similar to the default sketch below. Custom drawings can be linked to the application - any global (http://..) or local (file://..) url should work
  • Tag the sections and add them to the hierarchical application structure below (after reset)
  • Add input data - power, preliminary dimensions, lengths, minor coefficients, temperature drop, and so on for each section
  • Modify the piping dimensions to achieve reasonable values for velocities and pressure drops
  • Select pump - the pump pressure must be larger than the highest accumulated pressure loss in the system
  • Balance the system - start with the endpoints - add balancing pressures until the pump pressures in the end points equals zero. Add balancing pressure in other sections if required.
  • Save the data file to your computer/network
  • dimensions, minor loss coefficients, viscosity, density, roughness, specific heat

Important! - this calculation is for the flow OR the return piping system. If the flow and return piping systems are more or less identical - as in the default example above - the total pressure loss through the system for the pump to handle is 2 times the calculated (as indicated in the graph).

If the flow and the return system are different - like with a reversed return system - then the flow and the return systems must be calculated separately. The total pressure loss for the pump to handle will be the summarized pressure loss for the flow and return system.

  • Note! - Since only half of the system is calculated - use only half the minor loss coefficients specified by suppliers in connection points between flow and return systems - typical in heating elements and/or in the central heater and pump.
  • When selecting balancing valves - keep the flow but double the calculated balancing pressure drop for systems with identical flow and return piping - and summarize if the piping is different.

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Related Topics


Heating systems - capacity and design of boilers, pipelines, heat exchangers, expansion systems and more.

Related Documents

ASME/ANSI B36.10/19 - Carbon, Alloy and Stainless Steel Pipes - Dimensions

Pipe sizes, inside and outside diameters, wall thickness, schedules, moment of inertia, transverse area, weight of pipe filled with water - U.S. Customary Units.

ASME/ANSI B36.10/19 - Carbon, Alloy and Stainless Steel Pipes - Dimensions - Metric Units

Pipe sizes, inside and outside diameters, wall thickness, schedules, weight and weight of pipe filled with water - Metric Units.

BS 2871 Copper Tubes Table X, Y and Z - Working Pressures vs. Size

Working pressures of metric sized copper tubes according the BS (British Standard) 2871.

Domestic Hot Water Service Systems - Design Procedures

Design procedures for domestic hot water service systems.

EN 10255 - Non-alloy Steel Tubes for Welding and Threading - Dimensions

Dimensions and weights of steel tubes according BS EN 10255.

Ethylene Glycol Heat-Transfer Fluid Properties

Properties like freezing point, viscosity, specific gravity and specific heat of ethylene glycol based heat-transfer fluids, or brines.

Fittings and Minor Pressure Loss

Minor pressure loss with fittings in piping heating systems.

Gravity Heating System

The density difference between hot and cold water is the circulating force in a self circulating gravity heating system.

Heating Systems - Safety Valves Size vs. Boiler Power

Safety valves with boilers ranging 275 to 1500 kW.

Hot Water Heating System - Design Procedure

Hot water heating system design procedure with heat loss, boiler rating, heater units and more.

Hot Water Heating Systems - Flow Temperatures vs. Outside Temperatures

Seasonal effects on hot-water heating systems flow temperatures.

Hot Water Systems - Equivalent Length vs. Fittings Resistance

Equivalent length of fittings like bends, returns, tees and valves in hot water heating systems - equivalent length in feet and meter.

Hot-Water Heating Systems - Classification

Hot-water heating systems can be classified by temperature and pressure.

NPS - 'Nominal Pipe Size' and DN - 'Diametre Nominal'

The size of pipes, fittings, flanges and valves are often given in inches as NPS - Nominal Pipe Size, or in metric units as DN - 'Diametre Nominal'.

Piping - Recommended Insulation Thickness

Recommended insulation thickness for heating systems like hot water and low, medium or high pressure steam systems.

Piping Materials - Temperature Expansion Coefficients

Temperature expansion coefficients for materials used in pipes and tubes like aluminum, carbon steel, cast iron, PVC, HDPE and more.

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