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• Operate pump with system configuration set for maximum flow.

• Measure pump capacity.

• Measure motor RMS power input.

• Change system configuration to reduce flow and repeat measurement steps 2 and 3.

• Calculate pump and energy characteristics.

Method #4: Multiple Point Test with Imposed Loads at Zone

Measure: i) volumetric flow rate and ii) coincident RMS power for a range of building or zone thermal loads as prescribed in the test procedures.

Applications: Variable volume systems. The loads are imposed on the building or zones such that the system will experience a broad range of flow rates. The existing pump variable speed control strategy is allowed to operate. Pump differential pressure and rotational speed may also be measured for more complete pump system evaluation.

Steps:

• Operate pump with system configured for maximum flow rate.

• Measure pump capacity.

• Measure motor RMS power input.

• Change system configuration and repeat measurement steps 2 and 3.

• Calculate pump and energy characteristics.

Method #5: Multiple Point Test through Short Term Monitoring

Measure: i) volumetric flow rate and ii) coincident RMS power for a range of building or zone thermal loads as prescribed in the test procedures.

Applications: Variable volume variable speed systems. A monitoring period must be selected such that the system will experience a broad range of loads and pump flow rates. Pump differential pressure and rotational speed may also be measured for more complete pump system evaluation.

Steps:

• Choose appropriate time period for test.

• Monitor pump operation and record data values for pump capacity and motor RMS power input.

• Calculate pump and energy characteristics.

Method #6: No-Flow Test for Pump Characteristics

Measure: i) differential pressure at zero flow conditions (shut-off head) and compare to manufacturer's pump curves to determine impeller size.

Applications: All types of centrifugal pumps (not recommended for use on positive displacement pumps) Steps:

• Run pump at design operating conditions and close discharge valve completely.

• Measure pump suction and discharge pressure, or differential pressure.

• Calculate shut-off head.

• Compare shut-off head with manufacturer's pump performance curve to determine and/or verify impeller diameter.

the pump and motor data (i.e., manufacturer, model and serial number), fluid characteristics and operating conditions. The first two methods (i.e., single-point and single-point with a manufacturer's curve) involve testing at a single operating point. The third and fourth procedures involve testing at multiple operating points under imposed system loading. The fifth method also involves multiple operating points, in this case obtained through short term monitoring of the system without imposed loading. The sixth procedure operates the pump with the fluid flow path completely blocked. While the sixth procedure is not useful for generating a power versus load relationship, it can be used to confirm manufacturer's data or to identify pump impeller diameter. A summary of the methods is provided below. Additional details can be found by consulting ASHRAE's Guideline 14-2002.

A-1. Constant Speed and Constant Volume Pumps

Constant volume pumping systems use three way valves and bypass loops at the end-use or at the pump. As the load varies in the system, pump pressure and flow are held relatively constant, and the pump input power remains nearly constant. Because pump motor speed is constant, constant volume pumping systems have a single operating point. Therefore, measuring the power use at the operating point (i.e., a single point measurement) and the total operating hours are enough to determine annual energy use.

A-2. Constant Speed and Variable Volume Pumps

Variable pumping systems with constant speed pumps use two-way control valves to modulate flow to the end-use as required. In constant speed variable volume pumping systems, the flow varies along the pump curve as the system pressure drop changes in response to the load. In some cases, a bypass valve may be modulated if system differential pressure becomes too large. Such systems have a single possible operating point for any given flow, as determined by the pump curve at that flow rate. In such systems the second and third testing methods can be used to characterize the pumps energy use at varying conditions. In the second procedure, measurements of in-situ power use is performed at one flow rate and manufacturer's data on the pump, motor, and drive system are used to create a part load power use curve. In the third testing method in-situ measurements are made of the electricity use of the pump with varying loads imposed on the system using existing control, discharge, or balancing valves. The fourth and fifth methods can also be used to characterize the pump electricity use. Using one of these methods the part load power use curve and a representative flow load frequency distribution are used to determine annual energy use.

A-3. Variable Speed and Variable Volume Pumps

Like the constant speed variable volume system, flow to the zone loads is typically modulated using two-way control valves. However, in variable speed variable volume pumping systems, a static pressure controller is used to adjust pump speed to match the flow load requirements. In such systems the operating point cannot be determined solely from the pump curve and flow load because a given flow can be provided at various pressures or speeds. Furthermore, the system design and control strategy place constraints on either the pressure or flow. Such systems have a range of system curves which call for the same flow rate, depending on the pumping load. 827-RP provides two options (i.e., multiple point with imposed loads and short term monitoring) for accurately determining the in-situ part load power use. In both cases, the characteristics of the in-situ test include the pump and piping system (piping, valves, and controllers), therefore the control strategy is included within the data set. In the fourth method (i.e., multiple point with imposed load at the zone), the pump power use is measured at a range of imposed loads. These imposed loads are done at the zone level to account for the in-situ control strategy and system design. In the fifth method (i.e., multiple point through short term monitoring), the pump system is monitored as the building experiences a range of thermal loads, with no artificial imposition of loads. If the monitored loads reflect the full range of loads, then an accurate part load power curve can be developed that represents the full range of annual load characteristics. For methods #4 and #5, the measured part load power use curves and flow load frequency distribution are used to determine annual energy use.

A-4. Calculation of Annual Energy Use

Once the pump performance has been measured the annual energy use can be calculated using the following procedures, depending upon whether the system is a constant volume or variable volume pumping system. Savings are then calculated by comparing the annual energy use of the baseline with the annual energy use of the post-retrofit period.

Constant Volume Constant Speed Pumping Systems. In a constant volume constant speed pumping systems the volume of the water moving through the pump is almost constant, and therefore the power load of the pump is virtually constant. The annual energy calculation is therefore a constant times the frequency of the operating hours of the pump.

annual where:

T = annual operating hours

P = equipment power input

Variable Volume Pumping Systems. For variable volume pumping systems the volume of water moving through the pump varies over time, hence the power demand of the pump and motor varies. The annual energy use then becomes a frequency distribution of the load times the power associated with each of the bins of operating hours. In-situ testing is used to determine the power associated with the part load power use.

Eannual S (Ti Pi)

where: i

Ti Pi

B. Fans

= bin index, as defined by the load frequency distribution = number of hours in bin i = equipment power use at load bin I

Most large HVAC systems utilize fans or air-handling units to deliver heating and cooling to the building's interior. Such air-handling systems use different types of fans, varying control strategies, and duct layouts. Therefore, the characterization of fan electric power depends on the system design and control method used. Fan systems can be characterized by the three categories shown in Table 27.8.84

In a similar fashion as pumping systems, ASHRAE's Research Project 827-RP developed five in-situ methods for measuring the performance of fans of varying types and controls. To select a method the user needs to determine the system type and control, and the desired level of uncertainty, cost, and degree of intrusion. The user also needs to record the fan and motor data (i.e., manufacturer, model and serial number), as well as the operating conditions (i.e., temperature, pressure and humidity of the air stream). The first two methods (i.e., single-point and single-point with a manufacturer's curve) involve testing at a single operating point. The third and fourth procedures involve testing at multiple operating points under imposed system loading. The fifth method also involves multiple operating points, in this case obtained through short term monitoring of the system without imposed loading. Additional details about fan testing procedures can be found by consulting ASHRAE's Guideline 14-2002.

B-1. Calculation of Annual Energy Use

Once the fan performance has been measured the annual energy use can be calculated using the following procedures, depending upon whether the system is a constant volume or variable volume system. Savings are then calculated by comparing the annual energy use of the baseline with the annual energy use of the post-

retrofit period.

Constant Volume Fan Systems. In a constant volume system the volume of the air moving across the fan is almost constant, and therefore the power load of the fan is virtually constant. The annual energy calculation is therefore a constant times the frequency of the operating hours of the fan.

annual where:

T = annual operating hours

P = equipment power input

Variable Volume Systems. For variable volume systems the volume of the air being moved by the fan varies over time, hence the power demand of the fan and motor varies. The annual energy use then becomes a frequency distribution of the load times the power associated with each of the bins of operating hours. In-situ testing is used to determine the power associated with the part load power use.

Table 27.8: Applicability of Test Methods to Common Fan Systems from the ASHRAE Guideline 14-2002.85

Test Method:

Fan System:

Constant Speed, Constant Volume

Constant Speed, Variable Volume

Variable Speed,

Variable

Volume

1. Single Point Test

0 0

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