Danfoss Training Module 3 v1 Understanding Pressure Control Valves

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Transcript of Danfoss Training Module 3 v1 Understanding Pressure Control Valves

Introduction

Danfoss Training Module-3 ******

Understanding DifferentialPressure Control Valves

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Introduction

Hello and welcome to the Danfoss training module Understanding Differential Pressure Control valves The purpose of this training module is to give you the knowledge required to select, specify, and understand Danfoss products.

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IntroductionWe will examine the types of valves used to balance hydronic systems...and how we select the correct product for the application they are to be used in.

This module takes around 20 minutes and forms part of a Continuous Professional Development training course.Once 3 modules are complete you can apply to Danfoss for a certificate of your achievement. Now let us begin.

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The History of Danfoss Balancing Valve1989In 1989 Danfoss produced its first series of MSV commissioning and ASV automatic balancing valves.

2003

2009

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The History of Danfoss Balancing Valve1989In 2003 Danfoss was the first major valve manufacturer to introduce a combined control and automatic balancing valve, the AB-QM.

2003

2009

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The History of Danfoss Balancing Valve1989The LENO MSV-O, unique commissioning valve was launched by Danfoss in 2009. By choosing Danfoss you have over 75 years of expertise behind you

2003

2009

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Modernising Heating & Cooling SystemsAs clients look to improve the efficiency of heating and cooling systems, building services designers are increasingly looking at ways to reduce energy.Poor control and in-efficient system design are contributing factors to high building energy usage. By providing the correct temperature, using the least amount of energy possible, we can make heating and cooling systems comfortable for users, and run at a lower cost.

A common way to improve a systems energy efficiency is to use variable speed pumps.Let us look at how variable speed pumped systems operate

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Modernising Heating & Cooling SystemsVariable speed pumps work by matching the pumps flow with the requirement of the system at any one time. As parts of the system reach temperature, and the control valves close, the pump senses a change in pressure. This pressure sensor is linked to a variable speed drive which matches the pump speed with the system requirement.

Variable Speed Drive

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Modernising Heating & Cooling SystemsPrior to variable speed, pumps ran at either 0% or 100%. Controlling the pump speed means we can provide enough flow to achieve the comfortable temperatures, and at the same time dramatically reduce the energy used to get it there. However this modulation of the pump, makes the system pressure and flow variable. This variable pressure means traditional static balancing (commissioning) valves cannot operate effectively in this type of system. In variable flow systems we need dynamic balancing valves which react to the changes in system pressure. Danfoss ASV Differential Pressure Control Valves will provide the dynamic balance required in variable flow systems.

Variable Speed Drive

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ASV Differential Pressure Control ValvesThe use of Differential Pressure Control Valves is essential in modern hydronic systems.

They provide dynamic balancing to react to pressure changes from the pump and to keep constant pressure in the circuits.This constant circuit pressure enables the system to balance and be accurately controlled.

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ASV Differential Pressure Control ValvesThe outcome of using DPCVs is: -Good control whether the system is running at full or partial capacity -High control valve authority -Improved user comfort -Maximised pump energy savings To understand how we achieve these benefits, we first need to examine how ASV Differential Pressure Control Valves operate

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Operation of Differential Pressure Control ValvesDanfoss ASV-PV DPCVs are installed on the return pipe of the circuit. Danfoss ASV-I partner valve are used on the flow pipe. An impulse tube is installed from the partner valve to the DPCV and allows the flow pressure to act upon the top of the valve diaphragm.DPCV

Partner Valve

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Operation of Differential Pressure Control ValvesThe return pressure acts upon the underside of the diaphragm. The spring within the valve is set by the installer, using an allen key, to deliver a set circuit pressure loss. The diaphragm along with the spring act together to react to system changes and to keep this constant pressure loss. So as the system pressure rises, the diaphragm moves the valve cone down, to keep a controlled circuit pressure.

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Operation of Differential Pressure Control ValvesThe commercial radiator heating circuit shown below demonstrates this process in action.

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Operation of Differential Pressure Control ValvesThe pressure in the system (P1) is variable as the pump modulates to match the systems requirements. As the Differential Pressure Control Valve detects a change in the variable system pressure it reacts to keep a constant circuit pressure (P2). This constant pressure in the circuit gives the radiators a controlled flow. The controlled flow to the radiators allows the Thermostatic Radiator Valve to achieve a controlled temperature. This controlled temperature improves comfort for the users.P1 P2

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Benefits of using Differential Pressure Control ValvesWhilst the operation of Differential Pressure Control Valves demonstrate the benefits of improved temperature control, we should not end there. Comfort is not just about temperature. A common problem for variable flow systems without pressure control is noise. Here is why

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Benefits of using Differential Pressure Control ValvesSystem Noise As parts of our variable flow systems close down (this state is called partial load), the open circuits without pressure control see an increase in pressure. This increase in pressure results in a higher differential pressure across the radiator valves. If the differential pressure across the radiator valve becomes too high it will cause noise and this noise will be uncomfortable for users,

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Benefits of using Differential Pressure Control ValvesDifferential pressure control ensures the pressure over the radiator valve will not increase at partial loads. Thus excess noise emissions caused by the radiator valves will be eradicated.

DpPnom

Without ASVs

DpPnom

With ASVs

Dp supply system

Pressure Drop

5x0%50% 100% Flow

0%

50%

100% Flow

The system without Danfoss ASV DPCVs allows the excess pressure to be lost across the radiator valve (shown in red). By installing DPCVs we remove the excess pressure in the balancing valve (yellow) giving the TRVs a constant pressure. This eliminates noise.

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Benefits of using Differential Pressure Control ValvesWhen looking for improved efficiency we should recognise the importance of the cost of installing the system. Danfoss Differential Pressure Controls Valves give clear cost savings by reducing the time taken to balance and commission. The traditional proportional balancing method requires each balancing valve to be visited at least twice to complete commissioning. This is because the setting of each commissioning valve affects others in the system.

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Benefits of using Differential Pressure Control ValvesThis is not the case when using DPCVs. By installing ASV Differential Pressure Control Valve Sets you can divide the system into pressure independent zones. This means once the DPCV has been set, the flow balance in this circuit is unaffected by any other changes in the rest of the system, e.g. Other circuits opening or closing down, pump speeding up or slowing down. Each valve is only visited only once. By reducing the number of visits to each valve by more half, we more than half the cost of water system commissioning.

Heat Interface Unit Application

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Benefits of using Differential Pressure Control ValvesTo achieve the perfect balance Danfoss recommend the installation of ASVs on all branches. When used on every branch, DPCVs ensure accurate control and noise protection throughout the system. Time savings during commissioning are also best realised with complete DPCV coverage.

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Benefits of using Differential Pressure Control ValvesCommon applications for DPCVs are to balance: -Under-floor heating manifolds (as pictured) -Radiator circuits -Heat interface units -Circuits with radiant panels DPCVs can also be used in cooling systems to balance fan coils, chilled beams and air handling units. However Danfoss recommend utilising the additional benefits of Pressure Independent Control Valves in cooling applications.

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Selecting ASV-PV Differential Pressure Control ValvesSizin