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Piping Systems
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Piping Systems
•
•
•
•
•
•
•
SERIES LOOP
MONOFLO SYSTEM
DIRECT RETURN
REVERSE RETURN
PRIMARY/SECONDARY SYSTEM
BASIC PRIMARY SYSTEM
SYSTEM SYZER
3
4
Hydronic System
Water
Heater
and Tank
Open System
• Static Head Loss
• Friction Loss
• Valve and Fitting Loss
• Atmospheric Pressure
• NPSH(a) vs. NPSH(r)
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Hydronic System
Cooling
Tower
Open System
• Static Head Loss
• Friction Loss
• Valve and Fitting Loss
• Atmospheric Pressure
• NPSH(a) vs. NPSH(r)
Chiller
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Open System Pressures
Pipe Friction Loss
(Varies with flow)
Total
Static
Head
Total
Suction
Head
Basin Water
Level
Condenser
(Known head loss)
Pump
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Backflow
Preventer
Water
Heater
Cooling Tower
Storage
DHW System
HW
CW
HW
Water
Heater
City
Main
Water
Meter
Backflow
Preventer
PRV
Pump
CW
HW
Water
Heater
CW
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Hydronic System
Hot Water Coil
Closed System
• Friction loss
• Valve and Fitting Loss
• NO Static Head Loss
• Pressurized System
Hot Water
Boiler
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Closed System Pressures
Hot Water Coil
Multi-Level Building
1 PSI = 2.31 Feet
Head (ft) = head (psi) x 2.31
specific gravity
Hot Water
Boiler
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Closed System Pressures
Example: 4-Story Building
Hot Water Coil
•60 feet to top of system
•26 PSI of Static Pressure
Static Pressure (26 PSI)
+Minimum Pressure (4 PSI)
30 PSI
Hot Water
Boiler
PRV setting = 30 PSI
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Closed System Pressures
Hot Water Coil
Example: Single Story Building
12 PSI fill pressure
System can be 18 feet tall
Hot Water
Boiler
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Series Loop Piping
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Monoflo System
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Direct Return
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Direct Return Piping
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Reverse Return
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Reverse Return Piping
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Primary-Secondary Direct Return
Supply
Secondary Pumps
Primary - secondary
Common
Return
Primary Pumps
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19
Primary-Secondary Reverse Return
Terminals
Terminals
Terminals
Supply
Supply
Return
Secondary
Pump
Primary
Chiller
Pumps
Return
Common
Pipe
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Primary-Secondary-Tertiary
Zone C
Zone A
Zone B
Tertiary Pumps
Common
Pipe
Secondary Pumps
Modulating
Control Valves
Optional Variable
Speed Pump
DP Sensor
Common Pipe
Primary Pumps
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Primary-Secondary-Tertiary Hybrid
Zone C
Zone A
Zone B
Tertiary Pump
Secondary Pumps
Supply
Common Pipe
Primary
Pumps
Return
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Primary Variable Speed
Two-position Control Valves
Flow Meter
DP Sensor
Modulating
Valve
VFD
VFD
VFD
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Primary / Secondary
Terminology:
“Pump #1 can be referred to as the source
or primary pump and pump #2 as the load
or secondary pump.”
– 2004 ASHRAE Systems and Equipment Handbook, page 12.7
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Law of the “T”
The flow rate entering a tee must
equal the flow rate leaving the tee!
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Law of the “T”
50 GPM
100 GPM
50 GPM
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Law of the “T”
50 GPM
100 GPM
150 GPM
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Law of the “T”
50 GPM
50 GPM
100 GPM
100 GPM
50 GPM
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Law of the “T”
100 GPM
100 GPM
100 GPM
100 GPM
0 GPM
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Law of the “T”
175 GPM
175 GPM
100 GPM
100 GPM
75 GPM
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Prim. / Sec. -- Basics -Common Pipe
SECONDARY
PRIMARY
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Prim. / Sec. -- Basics -Common Pipe Flow
Pump OFF
100 gpm
A
100
B
100
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Prim. / Sec. -- Basics -Common Pipe Flow
Pump ON - 100 gpm
100 gpm
A
0
B
100 gpm
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Prim. / Sec. -- Basics -Common Pipe Flow
Pump ON - 50 gpm
100 gpm
A
50
Mixing @ tee
B
100 gpm
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Prim. / Sec. -- Basics -Common Pipe Flow
Pump ON - 200 gpm
100 gpm
A
100
B
Mixing @ tee
100 gpm
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Primary / Secondary --Bridge
SUPPLY
PRIMARY / SECONDARY
COMMON
RETURN
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P/S bridge - Front Loaded
Common
Load = Production
HWS TEMP. - 180F
(flow in gpm)
500
SECONDARY
PUMPS
500
O
F
F
O
N
COMMON -- NO FLOW
0
500
500
EHW TEMP.
150 F
HWR TEMP. - 150
F
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P/S bridge - Front Loaded
Common
Load > Production
HWS TEMP. -
(flow in gpm)
171 F
500
SECONDARY
PUMPS
700
O
F
F
O
N
MIXING (500 @ 180) + (200 @ 150)
0
COMMON -- 200
500
EHW TEMP.
150 F
HWR TEMP. - 150
F
700
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Bridge Check Valve
SUPPLY
COMMON
RETURN
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P/S bridge - Front Loaded
Common
Production > Load
HWS TEMP. 180F
(flow in gpm)
1000
SECONDARY
PUMPS
800
O
N
O
N
COMMON -- 200
500
500
Equally Loaded
MIXING (800 @150) + (200 @ 180)
EHW TEMP.
156 F
HWR TEMP. - 150
F
800
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Primary-Secondary System
Relationship
SUPPLY
Step
Function
Linear
Function
PRIMARY /
SECONDARY
COMMON
RETURN
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T3
HWS
T1
Boiler
T2
3-10 pipe
diameters
between Tees
T4
HWR
Single Boiler - Primary / Secondary
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Boiler
Control
T5
HWS
T3
Boiler
T4
T7
T1
Boiler
T2
T6
HWR
Dual Boiler - Primary / Secondary
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T5
HWS
T3
Boiler
T1
Boiler
T7
T4
T2
T6
HWR
Dual Boiler - Primary / Secondary
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Four Boiler Primary Secondary System
.
.
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Low Temperature Application
Water Source Heat Pump
or Radiant Heating
Problems:
Boiler Condensation!
Fire tube: 160
Water tube: 140
Copper fin tube: 105
Version #1
B&G balance valves w/
bypass line to
provide high temp inlet
water to boiler
T3
HWS
T1
Boiler
T2
3-10 pipe
diameters
between Tees
T4
HWR
Single Boiler - Primary / Secondary
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Low Temperature Application
Water Source Heat Pump
or Radiant Heating
Problems:
Boiler Condensation!
Fire tube: 160
Water tube: 140
Copper fin tube: 105
Version #2
FPE Valve w/
bypass line to
provide high temp inlet
water to boiler
T3
HWS
T1
Boiler
T2
3-10 pipe
diameters
between Tees
T4
HWR
Single Boiler - Primary / Secondary
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Low Temperature Applications
• Alternate: Condensing Boiler
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Primary Only Piping
• For boilers that can handle variable flow
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System Syzer Calculator
•Circular Slide Rule
•Analog Calculator
•Extremely Helpful Tool
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Explanation
• Non-product
specific
• Water Use
Only
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Heat Transfer Formula
Q = m CP (T2 - T1)
Energy = mass flow x specific heat x Delta T
lb
1 Btu
°F
Btu / Hr =
Btu / Hr = X Gal
Min
Hr
lb
8.34 lb
°F
60 Min
1 Btu
1 Gallon 1 Hour lb
Btu / Hr = 500 GPM T
°F
°F
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Scale 1: Heat Transfer / Flow
1 MBH = 1000 Btu/hr
Δt from 1 to 200º F
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Scale 1 - Example Problem
• Determine flow required for 150,000 Bth/hr
using a 300T.
10 gpm
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“Tons” of refrigeration
One ton  12,000
BTU
hr
therefore
12,000
BTU
hr
20 tons X
ton
 240 , 000
BTU
hr
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Scale 1 - Example Problem
Determine flow required for 20 tons cooling using a 100Dt.
20 tons x 12,000 BTUH/ton = 240,000 BTUH or 240 MBH
48 gpm
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Scale 2: Pipe Sizing
Window
• Milinch
• Ft/100ft
• ASHRAE
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Scale 2: Example Problem
Determine pipe size for 70 gpm in a typical hydronic
system.
2½” Pipe
3.5’/100’
3” Pipe
1.2’/100’
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Scale 3: Flow Velocity
Works with Scale 2
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Scale 3: Example Problem
What is the velocity of 1600 gpm through an 8” pipe?
Problems?
10+ fps
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Scale 3: Example Problem
What is the velocity of 1600 gpm through an 8” pipe?
Problems?
7 fps
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Pipe Sizing / Fitting Pressure Drop
• System Syzer
Jacket
• Based On
Hydraulic Institute
Standards
• One Method,
There Are Others!
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Equivalent Lengths Table
11’
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Scale 4: Description
• Pipe Length - TEL - 50% rule
• Friction Loss
• Total Pressure Drop
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Scale 4: Example Problem
What is the total pressure drop in a pipe with a TEL of 130’ and
flow rate of 200 gpm?
Scale 2
2.3’/100’
Or….
2.3’/100’ x 130’ = 3’
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Scale 4: Example Problem
The TEL of the longest circuit is 1500’. The head loss rate in the
system piping is 3.4’/100’ at design flow. How much head does
the pump have to provide to overcome the piping head loss?
1500’
3.4’/100’
50’
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Scale 5: Flow/Head Relationship
2
 Q2 
h2

 
h1
 Q1 
Q1= Known (design) flow
Q2 = Final flow
h1 = Known (design) head
h2 = Final head
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Scale 5: Example Problem
A chiller has 12’ head loss at 100 gpm. What is its head loss
at 150 gpm?
27’
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Scale 5: Example Problem
A closed system has a flow rate of 200 gpm and a head loss of
30’. Plot the system curve.
Flow vs
Head
100 7.5
150 17
200 30
250 46
300 67
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Plotting the System Curve