What is the differance between primary secondary pump and variable primary in the chilled water system ? pump

AfreenAli Subscribe my Channel

What is the difference between primary secondary pump and variable primary in the chilled water system ? pump

Well, we can say that there are a lot of chilled water distribution systems as an Examples:

Primary pump - constant Flow Piping, Single Chiller,

Primary pump - Only Variable Flow Piping, Single Chiller,

Primarily pumps - Only Variable Flow Piping, Multiple Parallel Chillers

Primary/Secondary Variable Flow Piping, Multiple Parallel Chillers

 Primary/Secondary Variable Flow Piping, Multiple Chillers, Multiple Coils, Multiple Series Chillers

For constant Flow Piping ----> Primary constant speed pumps

For Primary / Secondary Variable Flow Piping ----> primary pump is constant & secondary is variable

For Primary pump - Only Variable Flow Piping ----> the pump is variable speed

As a comparison:

Configuration --- Load Valves --- Installed Cost --- Pumping Cost

Const. Primary Flow ---3-way           --- Lowest          --- Highest

Primary/Secondary  ---2-way           --- Highest         --- Medium

Var. Primary Flow     ---2-way           --- Medium         --- Lowest

* Constant Flow Primary

    Advantages

Lowest installed cost

Less plant space than P/S

Easy to Control & Operate

Easy to Commission

    Disadvantages

Highest Plant Energy Cost (must run all, even at low loads)

* Primary (Constant) / Secondary (Variable)

    Advantages

Easy to Control

Easy to Commission

Loop separation

Easier trouble-shooting

Separating isolated loads/buildings for lower total pump energy

Lower Plant Energy (can sequence chillers and ancillary equipment) Primary (Constant) / Secondary (Variable)

Versatile – multi-circuit capability

   Disadvantages

Medium Pump Energy Cost

Highest Installed Cost (Sec Pumps, Piping, etc.)

Potential for higher plant energy loss because of Low Delta T syndrome

* Variable Primary Flow (VPF) System Arrangement

    Advantages

Lower Installed Cost (approx.5% compared P/S)

No secondary Pumps or piping, valves, electrical, installation, etc.

Offset somewhat by added2W Bypass Valve and more complex controls Less Plant Space Needed

Best Chilled Water Pump Energy Consumption (most optimeady configuration)

VSD energy savings Variable Primary Flow (VPF) System Arrangement

Lower Pump Design Head