Presentation on theme: "Hydronic System Balancing and Building Commissioning"— Presentation transcript:
1 Hydronic System Balancing and Building Commissioning Chapter 8Hydronic System Balancing and Building CommissioningTesting, Adjusting, and Balancing of Chilled and Hot Water Hydronic Systems • Commissioning of Commercial Buildings’ HVAC Systems
2 Hydronic System Balancing and Building Commissioning Chapter 8Hydronic System Balancing and Building CommissioningTesting, Adjusting, and Balancing of Chilled and Hot Water Hydronic Systems • Commissioning of Commercial Buildings’ HVAC Systems
3 Circulation pump testing is required when a new system is installed. To properly test, adjust, and balance a hydronic cooling and/or heating system, the circulation pump or pumps in the system must first be tested. A poorly operating circulation pump affects the operation of the entire hydronic system. Circulation pump testing is required when a new system is installed. Electrical measurements are taken off the motor for the pump. See Figure 8-1. Both the motor current and voltage for each leg of the three phases are measured under normal operational conditions. The readings are then checked to ensure that the readings match the motor nameplate and system characteristics.
4 Variable-frequency drives need to be tested and adjusted to fit the correct operating requirements. When a variable-frequency drive is being used, the drive operation and sequence must be verified. The variable-frequency drive for the pump may need to be adjusted to meet the proper operating parameters. Pump variable-frequency drive adjustments are done in accordance with the manufacturer’s procedures, using either the front panel keypad menu or a computer connected to the drive. See Figure 8-2.
5 Electronic tachometers measure the speed of a moving object. An electronic tachometer is a test instrument that measures the rotational or linear speed of a moving object. Rotating speeds are displayed in revolutions per minute (rpm) and linear speeds are displayed in feet per minute (fpm). Electronic tachometers optically measure a mark made out of tape or chalk as the mark revolves or travels with the motor or pump shaft. See Figure 8-3. Some electronic tachometers also contain a contact tachometer on one end that can be applied directly to a shaft to measure RPM.
6 The speed of a rotating shaft can be measured by an electronic tachometer. The reflective tape must first be attached to the shaft being measured before any readings are taken. Once the shaft of the piece of equipment is rotating, the electronic laser tachometer is pointed at the reflective tape to determine the speed (in revolutions per minute) of the shaft. See Figure 8-4.
7 Digital multimeters record measurements of electrical properties. A digital multimeter (DMM) is a test instrument that can measure two or more electrical properties and displays the measured properties as numerical values. Digital multimeters can record measurements, and the digital display makes it easier to read displayed values. See Figure 8-5.
8 Digital multimeters are relatively easy to use to measure the line voltage of an variable-frequency drive.To measure the line voltage to an variable-frequency drive with a digital multimeter (DMM), the test leads must be in the proper jacks and the function switch must be set to AC voltage. See Figure 8-6.
9 Clamp-on ammeters measure current in a circuit. A clamp-on ammeter is a test instrument that measures the current in a circuit by measuring the strength of the magnetic field around a single conductor. See Figure 8-7. A clamp-on ammeter is typically used to measure current in circuits with over 1 A of current and in applications where the jaws of the ammeter can be placed around one conductor.
10 The procedure for using clamp-on ammeters to measure current involves several steps. To measure the current from a variable-frequency drive to a 3-phase motor with a clamp-on ammeter or a multimeter with a clamp-on attachment, it is important to ensure that only one conductor at a time is in the center of the jaws and aligned with the alignment marks. See Figure 8-8.
11 Hydronic manometers measure water pressure to help balance a hydronic system. A hydronic manometer is a test instrument that measures water pressures (differential and gauge) to determine the flow rate and to balance a hydronic system. See Figure 8-9. Facilities that use hydronic systems for heating and/or cooling are usually balanced for terminal flow using differential pressures. Hydronic manometers are used to check pump performance and verify terminal flow and the flow through balancing valves, venturis, and orifice plates.
12 Hydronic manometer procedures are used to check pump performance and verify terminal flow. To measure pressures in a hydronic system with a hydronic manometer, the two hoses of the manometer are connected to the low- and high-pressure test ports. See Figure 8-10.
13 Mechanical gauges measure pressure and are available in a variety of ranges. Mechanical gauges (Bourdon tubes and Schrader-types) are available in various numerical pressure ranges such as 0 psi to 10 psi, 0 psi to 60 psi, or 100 psi to 600 psi. See Figure Bourdon tube gauges are the gauge design with the highest accuracy, but Bourdon tube gauges are susceptible to pressure surge damage. Schrader gauges are not as accurate as Bourdon tube gauges, but Schrader gauges are not damaged by pressure surges. Pressure gauges are also available in various units of measurement such as pounds per square inch (psi), absolute pressure (psia), inches of water (in. WC), or inches of mercury (in. HG).
14 Flow-balancing valves often have a manual valve with an indicator to show how much the valve is open.A flow-balancing valve is a special valve that is usually attached to the output side of individual heating and/or cooling coils (terminal units) in the main piping runs in order to control flow. Flow-balancing valves usually consist of a manual valve with an indicator that shows the percentage that the valve is open. See Figure Flow-balancing valves are also known as balancing cocks and have a Schrader-type pressure tap on both sides of the valve. Hydronic manometers or mechanical pressure gauges are attached to the pressure taps on both sides of flow-balancing valves and provide either an electronic or analog readout of the pressure.
15 The flow rate through balancing valves can be determined using charts and graphs. The readout in differential pressure is compared to a chart, usually provided by the valve manufacturer, indicating the pressure measurement versus the percentage that the valve is open. This chart provides readouts in gallons per minute (gpm) at a specific pressure difference and at the percentage that the valve is open. See Figure 8-13.
16 If the gallons per minute of flow and the temperature differential of the water in a coil are known, the amount of British thermal units removed can be determined.A coil is balanced to obtain 50 gpm at full flow. The temperature of the water entering is 42°F and the temperature of the water leaving is 52°F. See Figure 8-14.
17 The water flow rate through a valve can be determined if the flow coefficient and pressure drop are known.An automatic control valve has a flow coefficient of 50. The pressure drop across the valve is 5.25 psi. Find the water flow rate through the valve. See Figure 8-15.
18 While building commissioning can be expensive, often the cost is less than 1% of the total construction costs.Building owners often object that the process of building commissioning costs too much. However, final costs vary depending on the project size and the number and complexity of the systems involved. Building systems to be commissioned may include HVAC/mechanical, lighting, life safety, electrical, and plumbing systems. A general industry rule of thumb is that equipment commissioning costs 2% to 5% of the equipment cost. Commissioning an entire building is often less than 1% of the total costs involved in the construction of the building. See Figure The added cost may seem to be a burden, but there are direct and indirect costs resulting from the decision to not commission these systems.
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