Low Temperature (or Pressure) Hot Water, colloquially better known as LTHW or LPHW, has been the most common form of heating within buildings for a very long time. Traditionally, a centralised boiler or group of boilers would heat water from a Return Temperature of 71DegC up to 82DegC before distributing the heated water to the loads.

An open expansion tank is only relevant for Low Pressured Hot Water - LPHW - systems. The pressure is limited by the highest location of the tank. The volume of an open expansion tank should be the double of the estimated expansion volume in the system. The formula below can be used for a hot water system heated from 7 o C to 100 o C (4%):

e.g. for 35mm copper pipe the design flow will usually be between 0.50 & 0.90 l/s. At the lower flow of 0.50 l/s, the pressure drop will be 118 Pa/m with a velocity of 0.60 m/s. At the higher flow of 0.90 l/s the pressure drop will be 337 Pa/m and the velocity 1.08 m/s. mm

Wet central heating systems are low-pressure hot water (LPHW) systems for distributing heat throughout a building; they are sometimes called ‘hydronic’ systems. The Guide is also intended for practitioners who want to gain a better understanding of the principles and methods underlying the design process, and it offers a method for reaching ...

Providing the same capacity with a lower HWS temperature requires a higher fluid flow rate, which affects the size of pipes, pumps, and valves, and can also increase pumping energy use.

2025年3月2日 · LTHW systems work by heating water to a lower temperature than traditional hot water systems and distributing it throughout a building via a network of pipes. This type of system is particularly useful for large buildings with multiple rooms or floors, as it allows for precise temperature control and energy savings.

ores the development of LTHW heating installations in a progressive manner. This begins with the agreement of client needs and design requirements for a system, continues through the design of layouts, proceeds to the sizing, selection and specification of pipes and equipment, and .

Each temperature range has its advantages when used in particular applications but outwith specialist process industries, LTHW is the most common system in use. Traditionally, a flow temperature of 82DegC and a return temperature of 71DegC (a differential of 11DegC) have been used for the design of heating systems.

The current standards, relating specifically to pipe sizing within buildings, are limiting the efficiency heat networks can achieve, down to losses in translation from old standards and confusion between pipework covering long distances, and internal pipes feeding properties.

2023年1月4日 · A LPHW (which donates Low Pressure Hot Water) heater is fed by a hot water system. A boiler, which can be a gas or oil boiler, biomass boilers or a heat pump, is the external warm water heat source used by these water heaters.