A building automation system or BAS is a network of controlling and monitoring devices mainly responsible for the heating, ventilation, and air conditioning (HVAC) control system in large facilities and commercial buildings. Building automation systems are most commonly implemented in large facilities such as healthcare facilities, schools, universities, hotels, residential buildings, and data centers. A BAS network allows building operators to supervise and control the HVAC systems from a centralized location known as the Building Management System or BMS. VAV system, the air handling unit (AHU) and the VAV boxes are physically separated from each other, and each one has its own controller, also distanced from one another. However, for a VAV system to operate effectively, the VAV Boxes and the AHU have to talk to each other; in other words, they need to share information to properly adjust their setpoints based on zone heating or cooling demand.
Chiller & Boiler Pump Location – Upstream or Downstream? Let’s Settle This Debate
One of the recurring questions I hear from engineers, operators, and even contractors on site is:
👉 “Should pumps be located upstream or downstream of chillers and boilers?”
At first glance, it feels like a simple “rule-of-thumb” answer. But in reality, it’s a nuanced design decision guided by hydronic principles, ASHRAE handbooks, and equipment manufacturer limits.
Let’s break it down 👇
🌡️ Chilled Water Systems
Low- to Mid-Rise Buildings:
Pumps are often placed upstream of the chiller evaporator (on the return side).
✅ Benefits: Pump heat is absorbed by the chiller, positive NPSH margin, and evaporator stays flooded.
🔎 Backed by: Trane Engineers Newsletter & ASHRAE guidance.
High-Rise or Pressure-Limited Plants:
Pumps are placed downstream of the chiller evaporator (on the supply side).
✅ Benefits: Prevents adding pump head across the chiller tubes (protects pressure rating).
❌ Drawback: Pump heat goes directly into supply water → chiller has to work a bit harder.
🔥 Heating Hot Water Systems
Primary-Variable Plants (no dedicated boiler pumps):
Pumps are located on the boiler outlet (supply side).
➡️ This ensures we “pump away” from the expansion tank (point of no pressure change).
Primary–Secondary Plants:
– Primary (boiler) pumps are placed on the boiler inlet (return side).
– Secondary (system) pumps are located on the boiler outlet (supply side).
🔎 This arrangement keeps boilers happy (positive pressure at inlet) and still respects air management and expansion tank rules.
💡 Golden Rule: Pump Away from the Expansion Tank
This isn’t just tradition—it’s hydronic science.
The expansion tank defines the point of no pressure change (PoNPC).
Locating the pump discharge away from that point ensures stable pressure, proper air elimination, and avoids cavitation.
Referenced in ASHRAE Handbooks, IAPMO, and Bell & Gossett hydronic design manuals.
📖 References for Deeper Reading
ASHRAE HVAC Systems & Equipment Handbook – Hydronic Systems
Trane Engineers Newsletter: Chiller Pumping Arrangement Trade-offs
Bell & Gossett / Xylem – Pump Away & Expansion Tank Guidance
IAPMO: Point of No Pressure Change
🗣️ Let’s Collaborate!
I’d love to hear from fellow engineers, operators, and designers:
How do you arrange your pumps in different projects (especially tall buildings)?
Have you faced challenges with cavitation, pressure ratings, or air elimination due to pump location?
Do you follow the upstream rule, downstream rule, or always “pump away” rule?
Drop your insights in the comments. Let’s turn this into a living knowledge base for our community.
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👉 “Should pumps be located upstream or downstream of chillers and boilers?”
At first glance, it feels like a simple “rule-of-thumb” answer. But in reality, it’s a nuanced design decision guided by hydronic principles, ASHRAE handbooks, and equipment manufacturer limits.
Let’s break it down 👇
🌡️ Chilled Water Systems
Low- to Mid-Rise Buildings:
Pumps are often placed upstream of the chiller evaporator (on the return side).
✅ Benefits: Pump heat is absorbed by the chiller, positive NPSH margin, and evaporator stays flooded.
🔎 Backed by: Trane Engineers Newsletter & ASHRAE guidance.
High-Rise or Pressure-Limited Plants:
Pumps are placed downstream of the chiller evaporator (on the supply side).
✅ Benefits: Prevents adding pump head across the chiller tubes (protects pressure rating).
❌ Drawback: Pump heat goes directly into supply water → chiller has to work a bit harder.
🔥 Heating Hot Water Systems
Primary-Variable Plants (no dedicated boiler pumps):
Pumps are located on the boiler outlet (supply side).
➡️ This ensures we “pump away” from the expansion tank (point of no pressure change).
Primary–Secondary Plants:
– Primary (boiler) pumps are placed on the boiler inlet (return side).
– Secondary (system) pumps are located on the boiler outlet (supply side).
🔎 This arrangement keeps boilers happy (positive pressure at inlet) and still respects air management and expansion tank rules.
💡 Golden Rule: Pump Away from the Expansion Tank
This isn’t just tradition—it’s hydronic science.
The expansion tank defines the point of no pressure change (PoNPC).
Locating the pump discharge away from that point ensures stable pressure, proper air elimination, and avoids cavitation.
Referenced in ASHRAE Handbooks, IAPMO, and Bell & Gossett hydronic design manuals.
📖 References for Deeper Reading
ASHRAE HVAC Systems & Equipment Handbook – Hydronic Systems
Trane Engineers Newsletter: Chiller Pumping Arrangement Trade-offs
Bell & Gossett / Xylem – Pump Away & Expansion Tank Guidance
IAPMO: Point of No Pressure Change
🗣️ Let’s Collaborate!
I’d love to hear from fellow engineers, operators, and designers:
How do you arrange your pumps in different projects (especially tall buildings)?
Have you faced challenges with cavitation, pressure ratings, or air elimination due to pump location?
Do you follow the upstream rule, downstream rule, or always “pump away” rule?
Drop your insights in the comments. Let’s turn this into a living knowledge base for our community.
Activate to view larger image,
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