Voglio sapere a riguardo di…

Federal Register / Vol. 86, No. 87 / Friday, May 7, 2021 / Proposed Rules or redesign an existing motor in order to improve a pumps motor efficiency.
c. Ability To Operate at Reduced Speeds Circulator pumps with the variable speed capability can reduce their energy consumption by reducing pump speed to match load requirements. As discussed in Section II.B, the PERCIRC
metric is a weighted average of input powers at each test point relative to BEP
flow. The circulator pumps test
procedure agreed to by the CPWG
allows: PERCIRC values for multiand variable-speed circulator pumps to be calculated as the weighted average of input powers at full speed BEP flow, and reduced speed at flow points less than BEP and PERCIRC for single-speed pumps to be calculated based only on input power at full speed. Due to pump affinity laws, variable-speed circulator pumps will achieve reduced power
24529

consumption at flow points less than BEP by reducing their rotational speed to more closely match required system head. As such, the PERCIRC metric grants benefits on circulator pumps capable of variable speed operation.
Specifically, the pump affinity laws describe the relationship of pump operating speed, flow rate, head, and hydraulic power as shown in Equations 11, 12, and 13.

11

12

This means that a pump operating at half speed will provide one half of the pumps full-speed flow and one eighth of the pumps full-speed power.11
However, pump affinity laws do not account for changes in hydraulic and motor efficiency that may occur as a pumps rotational speed is reduced.
Typically, hydraulic efficiency and motor efficiency will be reduced at lower operating speeds. Consequently, at reduced speeds, power consumption is not reduced as drastically as hydraulic output power. Even so, the efficiency losses at low-speed operation are typically outweighed by the exponential reduction in hydraulic output power at low-speed operation;
this results in a lower input power at 11 A discussion of reduced-speed pump dynamics is available at https www.regulations.gov/
document?D=EERE-2015-BT-STD-0008-0099.

VerDate Sep<11>2014

17:32 May 06, 2021

Jkt 253001

low speed operation at flow points lower than BEP.
Circulator speed controls may be discrete or continuous, as well as manual or automatic. Circulator pumps with discrete speed controls vary the pumps rotational speed in a step-wise manner. Discrete controls are found mostly on circulator pumps with induction motors, and have several speed settings that are can be used to allow contractors greater installation flexibility with a single circulator model. For these circulator pumps, the pumps speed is set manually with a dial or buttons by the installer or user and operate at a constant speed once the installation is complete.
Circulator pumps equipped with automatic speed controls can adjust the circulators rotational speed based on a signal from differential pressure or temperature sensors, or an external input signal from a boiler. The variable frequency drives required for ECMs makes them fairly amenable to the addition of variable speed control logic.
Currently, the vast majority of circulator pumps with automatic continuously variable speed controls also have ECM
motors. However, some circulator models with induction motors also come equipped with automatic
PO 00000

Frm 00017

Fmt 4702

Sfmt 4702

continuous variable speed controls.
Automatic controls can reduce energy consumption either by allowing circulator speed to dynamically respond to changes in system conditions or simply by reducing speed to a single value optimal for the specific application. Automatic controls can be broadly categorized into two groups:
Pressure-based controls, and temperature-based controls.
Pressure-based controls vary the circulator speed based on changes in the system pressure. These pressure changes are typically induced by a thermostatically controlled zone valve that monitors the space temperature in different zones and calls for heat i.e., opens the valve when the space/zone temperature is below the set-point, similar to a thermostat. In this type of control, a pressure sensor internal to the circulator determines the amount of pressure in the system and adjusts the circulator speed to achieve the desired system pressure.
Temperature-based controls monitor the supply and return temperature to the circulator and modulate the circulator speed to maintain a fixed temperature drop across the system.
Circulator pumps with temperaturebased controls are able to serve the heat
E:FRFM07MYP1.SGM

07MYP1

EP07MY21.008 EP07MY21.009

Where:
Q1 and Q2 = volumetric flow rate at two operating points H1 and H2 = pump total head at two operating points N1 and N2 = pump rotational speed at two operating points P1 and P2 = pump hydraulic power at two operating points
EP07MY21.010

13