GRUNDFOS PRESSURISATION RANGE

PRESSURISATION RANGE
PRESSURE TOP UP UNITS
AND EXPANSION VESSELS
1 CONTENTS

CONTENTS
Overview 2

Mini Pressurisation Units 3

PHT - Pressure Holding Top-up Range 5

PHT A N-Series Narrow Format Wall Mounted System 6

PHT A D-Series Single Pump Units - Deep Format Wall Mounted System 7

PHT A D-Series Twin Pump Units - Deep Format Wall Mounted System 8

PHT A F-Series - Floor Standing System 9

PHT A T-Series - Floor Standing Twin System 10

PHT A V-Series - Floor Standing System With Glycol Make Up 11

Internal Schematic Diagrams 12

Feature Comparison 13

PHT Range and Dimension Tables 14

Expansion Vessels 15

Grundfos GT-HR 6 Bar Rated Expansion Vessels 16

Grundfos GT-U+ 10 Bar Rated Expansion Vessels 17

Grundfos GT-U+ 16 Bar Rated Expansion Vessels 18

Vessel Selection Calculation 19

Low Temperature Heating Water System Schematics 20

Medium Temperature Heating Water System Schematics 21

Chilled Water System Schematics 22

 OVERVIEW 2

Grundfos Pressurisation Equipment

The demand for having the most efficient circulation systems is steadily increasing and at Grundfos we are always
striving to provide products and solutions that exceed our customers’ expectations. Grundfos’ advanced technological
pumping systems and solutions reduce energy consumption and at the same time provide businesses with real economic
savings and CO2 reductions.
Grundfos pressurisation equipment provides solutions to improve the overall performance and efficiency of heating and
cooling installations. The key benefits of these products are to ensure that the fluid in the system is free from air and that
system pressure is maintained, ensuring that the system runs at maximum efficiency. Our equipment improves reliability,
saves energy, reduces maintenance costs and extends the life of the system.
Pressurisation
There are a number of advantages of using a more modern closed heating/cooling system as opposed to a traditional
open system with a feed and expansion tank. The water used in sealed systems is constantly being reused, as a result the
dissolved air is taken care of and exposed steel in traditional vessels is not subject to continued corrosion. Closed systems
also do not require heavy roof top tanks and the associated pipework; therefore water loss due to evaporation is greatly
reduced.
Closed systems also reduce installation cost. Their higher flow temperatures and greater temperature drops reduce
the systems water circulation needs, enabling a smaller pump and pipes to be used. This combined with replacing the
conventional header tank, associated pipework and lagging, leads to considerable savings.
Range Structure
The Grundfos pressure top-up portfolio offers a choice of formats and pump number and are available to match a variety
of fill pressures.

Type Key

Example PHT A F 1 25

Range
PHT Pressure Holding Top-up

Model generation
[] First generation
A Second generation

Format
N Narrow Format Wall Mounted Unit
D Deep Format Wall Mounted Unit
F Floor Standing Unit
T Twin System Unit
V Glycol (additional valves and tank)

Number of Pumps
1 One Pump
2 Two Pumps

Pressure ID
25 Max Fill Pressure 2.5 Bar
30 Max Fill Pressure 3.0 Bar
50 Max Fill Pressure 5.0 Bar
80 Max Fill Pressure 8.0 Bar
100 Max Fill Pressure 10.0 Bar
3 MINI MONOPRESS & MINI DUOPRESS PRESSURISATION UNITS

Mini Monopress and Mini

Duopress Product introduction
and Description
The Mini Pressurisation Unit is a compact wall mounted
unit housing either one or two small pressurisation pumps
and associated control equipment for connecting to small
heating or cooling installations within large domestic
dwellings or small industrial/commercial installations.

Standard Features
• powder coated casing
• front mounted system pressure gauge
• make-up tank complete with system filling valve
assembly
• 0.7 to 2.5 bar pressure pump
• pressure control switch
• control circuit fuse, terminals and all necessary
wiring to achieve the correct operation
• single (Monopress) or twin (Duopress) pump
versions available

Suitable connections are provided to allow system The Mini Pressurisation unit connection to the mains
makeup, tank overflow and connection to the system water is provided by a WRAS approved filling valve
pipe work as well as electrical terminals for connecting suitable for use with potable water. Complies to WRC
the single phase, live, neutral and earth supply. byelaw 11 regulation.

Operation
The pump is controlled directly by the control pressure switch. The control pressure switch has an adjustment for the
cut-in pressure setting. The differential pressure setting is fixed at approximately 0.4 bar. The pump is stopped when the
pressure is 0.4 bar above the cut-in pressure.

The twin pump Mini Duopress has a manual pump selector switch for selecting the duty pump. The duty pump must be
changed over manually.
 MINI MONOPRESS & MINI DUOPRESS - WEIGHTS & DIMENSIONS 4

Maximum / Minimum Operating Conditions

Electrical Supply: 230 v +10/-6 %
Fuse Protection: 2 A
Noise Level: <65 dB(A)
Liquid Temperature Range: +3°C to +40 °C
Usage: Indoor
Ambient Temperature: up to +40 °C Power LED
Relative Humidity: up to 95 % non-condensing Pressure display

Max Inlet pressure: 6 bar

Generated Pressure: 2.5 bar

Mini Pressurisation Range Table

Max cold fill Power consumtion

Product Name Pressure switch Pump Qty Product Code
(bar) (W) (per pump)

MINI MONOPRESS CONTROL 1 2.5 25 MMP50801

MINI MONOPRESS CONTROL + HI & LOW 1 2.5 25 MMP50802
MINI DUOPRESS CONTROL + HI & LOW 2 2.5 25 MDP50802

3/4" BSP M 1/2" BSP M 1/4" BSP F M20 Mains

Overflow Water System Cable gland
connection connection connection

Dimensions (mm) Connections (mm) Break tank

Product Name Dry weight kg
Width Depth Height System Mains Drain capacity (1)

MINI MONOPRESS 350 200 300 ¹/₄" ¹/₂" ³/₄" 4.5 8.5
MINI DUOPRESS 350 200 300 ¹/₄" ¹/₂" ³/₄" 4.5 11
5 PHT A - PRESSURE HOLDING TOP-UP RANGE

PHT A - Pressure Holding Top-up Range

With a combination of reliable pumps, advanced control and a choice of external communication protocols, the new
PHT A range of pressurisation units from Grundfos delivers peace of mind, energy efficiency and maximum system
availability. Part of the extensive portfolio of packaged pump sets available from Grundfos, these intelligent systems are
suitable for use in a wide range of residential, commercial and industrial applications.
Specifically created to efficiently maintain the required water pressure in sealed heating and cooling systems, the
PHT A range comprises an advanced pressure monitoring system, reliable, energy efficient pumps and a break tank
that incorporates a category 5 A/B air gap, preserving the integrity of the mains water supply while minimising space
requirements.
To ease set-up, management and maintenance, set points and alarms can be changed via a simple but secure user
interface combined with a local status display. This is enhanced by advanced component monitoring and reporting, and a
choice of output communications protocols to provide diagnostic and remote status indication.
Pressure holding top-up units should be combined with a suitable expansion vessel (see page 17)

Selection Location
PHT A top-up equipment is selected against the The PHT A should be installed on the return header of
required top-up pressure and in some cases the the system on the suction side of the circulating pump.
expected delivery flow rate required for top-up.
The point of connection will be treated as the system
For convenience, wall mounted or floor standing neutral point, and the system expansion vessel should
formats can be chosen and in many cases the option also be located at this connection.
to specify a second pump for duty assist and partial
redundancy is available.
When two systems are needed, the twin system T-series
provides the solution with minimal space requirements,
while when glycol is present in the medium being
pumped the PHT A V offers an automatic glycol mixing
solution.

Common Range Data

Unit Rating PN10

Electrical Requirements 230V, 50Hz, 1 Phase

Noise Output <75 dbA

Fluid Category Protection 5 AB Weir Overflow Air Gap

Required access for examination and service:

•  minimum of 50 cm above all units
•  minimum of 50 cm to the system connection side of all units
•  minimum of 100 cm at the front of the units
 PHT A N-SERIES 6

PHT A N-Series
The A N-Series is narrow format wall mounted unit with a 2 litre break tank and is
suitable for large residential or small commercial applications (guide maximum
system volume up to 2500 litres).

Standard Features Maximum Operating Conditions

•  Simple, security coded user interface •  Maximum system temperature 85°C
•  Event logging • Ambient temperature up to 40°C
•  Low water sensor • Relative humidity 95% non-condensing
•  Durable powder coated enclosure

Options
•  Single or twin pump versions 5
240
• High water level sensor 27
• BACnet or MODBUS communications via Grundfos CIM

25
Max Cold Fill Power Full Load
Product Name Pump Qty Dry Weight (Kg) Product Code
Pressure (bar) Consumption (W) Current (amps)

482
PHT A N130 1 3 28 0.12 12 99264904

364
PHT A N230 2 3 28 0.12 13 99264947

315
140
Dimensions Connections
37
152

240 57
27
25

Electrical

Water Supply
Overflow
482
364
315

System
140

37
90
110

Dimensions (mm) Connections

Break Tank Capacity
Width Depth Height System Mains Supply Drain
2 Litre 240 152 482 ¹/₄" ¹/₂" ³/₄"
7 PHT A D-SERIES

PHT A D-Series (single pump units)

The D-Series is a deeper format wall mounted pressurisation unit with a 3.6 litre
break tank.
260
Standard Features Maximum Operating Conditions
• Simple, security coded user interface •  Maximum system temperature 85°C
• Event logging • Ambient temperature up to 40°C

24
• Low water level sensor • Relative humidity 95% non-condensing
• Durable powder coated enclosure

Options
• High water level sensor
• BACnet or MODBUS communications via Grundfos CIM

522
403
353
Max Cold Fill Power Full Load
Product Name Pump Qty Dry Weight (Kg) Product Code
Pressure (bar) Consumption (KW) Current (amps)

249
PHT A D125 1 2.5 0.41 1.83 20 99264948
PHT A D150 1 5 0.9 3.94 21 99264949

Dimensions Connections

260 277
57
27
Electrical
24

Water Supply
Overflow
522

System
403
353
249

42
137
245

Break Tank Pump Dimensions (mm) Connections

Capacity Qty Width Depth Height System Mains Supply Drain

3.6 Litre 1 260 277 522 1/2" 1/2" 3/4"

 PHT A D-SERIES 8

PHT A D-Series (twin pump units)

The D-Series is a deeper format wall mounted pressurisation unit with
a 3.6 litre break tank. Twin pumps for duty and standby with automatic
switchover.

Standard Features Maximum Operating Conditions

•  Simple, security coded user interface •  Maximum system temperature 85°C
•  Event logging • Ambient temperature up to 40°C
•  Low water level sensor • Relative humidity 95% non-condensing
•  Durable powder coated enclosure

440
Options
• High water level sensor

34
• BACnet or MODBUS communications via Grundfos CIM

Max Cold Fill Power Full Load

Product Name Pump Qty Dry Weight (Kg) Product Code

522
Pressure (bar) Consumption (kW) Current (amps)

395
346
PHT A D225 2 2.5 0.41 1.83 29 99264951

280
PHT A D250 2 5 0.9 3.94 30 99264952

Dimensions Connections

302
57
440
27
Electrical
34

Water Supply
Overflow
522

System
395
346
280

41
136
260

Dimensions (mm) Connections

Break Tank Capacity
Width Depth Height System Mains Supply Drain

3.6 Litre 440 302 522 ¹/₂" ¹/₂" ³/₄"

9 PHT A F-SERIES

PHT A F-Series
The F-Series is a floor standing top-up pressurisation unit with a 17.5 litre break
tank, for use in medium sized commercial systems.

Standard Features Maximum Operating Conditions

•  Simple, security coded user interface • Maximum system temperature 85°C
•  Event logging • Ambient temperature up to 40°C
•  Low water level sensor • Relative humidity 95% non-condensing
•  Durable powder coated enclosure

Options
•  Single or twin pump versions
57
• High water level sensor 470
27
• BACnet or MODBUS communications via Grundfos CIM

23
Max Cold Fill Power Full Load
Product Name Pump Qty Dry Weight (Kg) Product Code
Pressure (bar) Consumption (KW) Current (amps)

832
PHT A F 125 1 2.5 0.41 1.83 31 99264963
PHT A F 225 2 2.5 0.41 1.83 38 99264966
57
470 332
PHT A F 150 1 27 5 0.9 3.94 32 99264964
23

PHT A F 250 2 5 0.9 3.94 39 9964967

PHT A F 180 1 8 1.15 5.2 37 99264964
PHT A F 280 2 8 1.15 5.2 46 99264968
832

630

Dimensions Connections
590

Electrical
184

70
57
470 332 125
27
290
23

832

630
590

Water Supply
Overflow
184

70
125
290 System

Dimensions (mm) Connections

Break Tank Capacity
Width Depth Height System Mains Supply Drain
17.5 Litre 470 332 832 ¹/₂" ¹/₂" ³/₄"
 PHT A T-SERIES 10

PHT A T-Series
The twin system T-Series is ideal where space restrictions make it beneficial to locate
two systems in a single enclosure. Floor standing, this system combines two top-up
pressurisation units with a single 17.5 litre break tank.

Standard Features Maximum Operating Conditions

• Simple, security coded user interface •  Maximum system temperature 85°C 470
• Event logging • Ambient temperature up to 40°C
• Low water sensor • Relative humidity 95% non-condensing

25
• Durable powder coated enclosure
• WRAS approved components

Options
• High water level sensor
• BACnet or MODBUS communications via Grundfos CIM

852
650
610
Max Cold Fill Power Full Load
Product Name Pump Qty Dry Weight (Kg) Product Code
Pressure (bar) Consumption (KW) Current (amps)

219
PHT A T225 2 2.5 0.41 1.83 41 99264969
PHT A T250 2 5 0.9 3.94 42 99264970

Dimensions Connections

470 333
57
27
Electrical
25

Water Supply
Overflow
852
650
610

System 1, 2
219

70
95
125
260

Dimensions (mm) Connections

Break Tank Capacity
Width Depth Height System Mains Supply Drain
17.5 Litre 470 333 850 2 x ¹/₂" ¹/₂" ³/₄"
 11 PHT A V-SERIES

PHT A V-Series
The V-Series is a floor standing, glycol mixing top-up pressurisation unit. Each
time the V-Series tops up the system with water, it also automatically adds glycol
from a dedicated tank at a predetermined rate, reducing manual intervention and
maximising system protection.

Standard Features Maximum Operating Conditions

•  Simple, security coded user interface •  Maximum system temperature 85°C 670
•  Event logging • Ambient temperature up to 40°C
•  Low water sensor • Relative humidity 95% non-condensing

24
•  Durable powder coated enclosure
Options
• High water level sensor
• BACnet or MODBUS communications
via Grundfos CIM

852
557
517
229
Max Cold Fill Power Full Load
Product Name Pump Qty Dry Weight (Kg) Product Code
Pressure (bar) Consumption (KW) Current (amps)

PHT A V225 2 2.5 0.41 1.83 56 99264977

PHT A V250 2 5 0.9 3.94 58 99264979

Dimensions Connections

333 333
670 670 57 57
27 27
24

24

Electrical

Water Supply
Overflow
852

852
557

557
517

517
229

229

System

70 70
125 125
260 260

Break Tank Glyco Tank Dimensions (mm) Connections

Capacity Capacity Width Depth Height System Mains Supply Drain
3.6 Litre 17.5 Litre 670 333 852 ¹/₂" ¹/₂" ³/₄"
 INTERNAL SCHEMATIC DIAGRAMS 12

Standard Pressurisation Unit 4

(PHT A N/D/F models) 3 5
2
1. Break tank 11. Drain valve 6
2. Drain overflow 12. Pump 1 1
3. Weir overflow 13. Pump 2 7
4. Float valve
5. Water supply
6. High level float switch 8
7. Low level float switch 13
8. System pressure
9
transmitter
10
9. System isolation valve
10. System connection 11
12

4
Twin System Pressurisation Unit 5
3
(PHT A T models) 2
6
1. Break tank 14. System 1 solenoid valve
2. Drain overflow 15. System 2 solenoid valve 1 7
3. Weir overflow 16. System 2 pressure
4. Float valve transmitter
5. Water supply 17. System 2 isolation valve 8
6. High level float switch 18. System 2 connection
13 14
7. Low level float switch 19. Drain valve 9
8. System 1 pressure 10
transmitter
9. System 1 isolation valve 11
10. System 1 connection
12
11. Drain valve 16
15
12. Pump 1
13. Pump 2 17
18

19

4
Glycol Pressurisation unit
3 5
(PHT A V models) 2
6
1. Break tank 13. Pump 2
2. Drain overflow 14. Water flow regulator 1
7
3. Weir overflow 15. Glycol flow regulator
4. Float valve 16. Glycol tank
5. Water supply 17. Low glycol float switch
16
6. High level float switch 14
7. Low level float switch 17
8. System pressure
transmitter 15
9. System isolation valve 8
10. System connection 13
9
11. Drain valve
10
12. Pump 1

11
12
13 FEATURE COMPARISON

Mini Mini PHT A

Model Monopress Doupress N-Series D-Series F-Series T-Series V-Series
Mechanical Features
Cabinet l l l l l l l
Wall mounted l l l l l
Floor mounted l l l l l
Single pump l l l l
Duty / standby pumps M* l l
Glycol mix l
De- gasser
Twin system l
Pump non return valve l l l l l l l
Common outlet isolation valve l l l l l
Category 5 A/B air gap l l l l l l l
Electrical Features
Pressure transducer control S* S* l l l l l
Password protection l l l l l
LED display l l l l l
Pump trip monitoring l l l l l
System flood detection l l l l l
Service due reminder l l l l l
Adjustable pressure differential l l l l l
Manual run l l l l l
Low water alarm l l l l l
High water alarm
Excessive starts alarm l l l l l
Hours run l l l l l
Pump activation counter l l l l l
Alarm logging l l l l l
Anti seize run (30/60/90 days) l l l l l
Automatic duty rotation (twin pump units) l l l l l
MODBUS (via CIM card)
BACnet (via CIM card)
USB software update port l l l l l
Audible alarm l l l l l
Status LED l l l l l
Volt Free Contacts -8A/230v
System interlock l l l l 1(x2) l
General Fault l l l l l
Programmable outputs 3 3 3 2 3

Key
l Standard Option M - manual switch over S - pressure switch
 PRESSURISATION RANGE TABLES 14

PHT Range Table

Pump Maximum Fill Power Full Load

Product Name Product Code
Quantity Pressure (bar) Consumption (KW) Current (amps)

PHT A N130 1 3 0.028 0.12 99264904

PHT A N230 2 3 0.028 0.12 99264947
PHT A D125 1 2.5 0.41 1.83 99264948
PHT A D150 1 5 0.9 3.94 99264949
PHT A D225 2 2.5 0.41 1.83 99264951
PHT A D250 2 5 0.9 3.94 99264952
PHT A F125 1 2.5 0.41 1.83 99264963
PHT A F150 1 5 0.9 3.94 99264964
PHT A F180 1 8 0.15 5.2 99264965
PHT A F225 2 2.5 0.41 1.83 99264966
PHT A F250 2 5 0.9 3.94 99264967
PHT A F280 2 8 1.15 5.2 99264968
PHT A T225 2 2.5 0.41 1.839 99264969
PHT A T250 2 5 0.9 3.94 99264970
PHT A V225 2 2.5 0.41 1.83 99264977
PHT A V250 2 5 0.9 3.94 99264979

BUS communication and High Level Alarm options:

High water level alarm can be provided as option, must be requested at time of order.
BACnet and Modbus communication modules are available as accessories

PHT Range Dimensions Table

Dimensions (mm) Connections Dry Weight

Product Name
Width Depth Height System Mains Overflow (Kg)
PHT A N130 240 152 482 ¹/₄" ¹/₂" ³/₄" 12
PHT A N230 240 152 482 ¹/₄" ¹/₂" ³/₄" 13
PHT A D125 260 277 522 ¹/₂" ¹/₂" ³/₄" 20
PHT A D150 260 277 522 ¹/₂" ¹/₂" ³/₄" 21
PHT A D225 440 302 522 ¹/₂" ¹/₂" ³/₄" 29
PHT A D250 440 302 522 ¹/₂" ¹/₂" ³/₄" 30
PHT A F125 470 332 832 ¹/₂" ¹/₂" ³/₄" 31
PHT A F150 470 332 832 ¹/₂" ¹/₂" ³/₄" 32
PHT A F180 470 332 832 ¹/₂" ¹/₂" ³/₄" 37
PHT A T225 470 332 832 ¹/₂" ¹/₂" ³/₄" 38
PHT A T250 470 332 832 ¹/₂" ¹/₂" ³/₄" 39
PHT A F280 470 332 832 ¹/₂" ¹/₂" ³/₄" 46
PHT A T225 470 333 850 2X ¹/₂" ¹/₂" ³/₄" 41
PHT A T250 470 333 850 2X ¹/₂" ¹/₂" ³/₄" 42
PHT A V225 670 333 852 ¹/₂" ¹/₂" ³/₄" 56
PHT A V250 670 333 852 ¹/₂" ¹/₂" ³/₄" 58
15 EXPANSION VESSELS

Expansion Vessels
Expansion vessels are small tanks used to protect closed water heating and cooling systems from excessive pressure.
The tank is partially filled with air or nitrogen, whose compressibility cushions shock caused by water hammer and
absorbs excess water pressure caused by thermal expansion.
Traditional expansion tanks were larger and had no rubber diaphragm separating the water from the air pocket. This
meant air gradually dissolved in to the water and transferred to the highest part of the system. As a result vessels
regularly needed to be drained and systems bled of air to avoid corrosion and bacterial growth.
Sealed expansion vessels are divided in two by a rubber diaphragm. One side is connected to the pipe work of the
heating system and therefore contains water. The other, the dry side, contains nitrogen gas under pressure, and a
Schrader valve, similar to a car tyre valve, for checking pressures and adding nitrogen. When the heating system is
empty, or at the low end of the normal range of working pressure, the diaphragm will be pushed against the water
inlet. As the water pressure increases, the diaphragm moves, compressing the nitrogen on its other side.
The rubber diaphragm in expansion tanks prevents the undesirable transfer of air and helps maintain low levels of
oxygen, reducing corrosion in the system and saving on maintenance costs.
 EXPANSION VESSELS 16

GT-HR 6 Bar Rated Expansion Vessels

The GT-HR 6 bar vessel range is suitable for use in sealed heating and
chilled systems.

Features
• low-carbon sheet steel shell
• non- replaceable SBR rubber diaphragm
• liquid compartment with a polypropylene liner (PP)
• threaded connection
• available in a variety of sizes

Installation
To ensure that the temperature at the diaphragm does not exceed
70°C (system flow <90°C), the vessel should be installed on the coldest
part of the system, typically the return pipe to the heat exchanger.
For systems running at elevated temperatures (system flow >90°C),
an intermediate vessel may be required to provide additional heat
dissipation.

Maximum Vessel
Connection Volume Dimensions (mm) Weight Product
Product Name Working Pressure Efficiency
Code
(Bar) % BSP M (L) Diameter Height (Kg)
GT-HR-8 PN6 G3/4 V 6 50 R ³/₄ 8 206 305 1.9 96573376
GT-HR-12 PN6 G3/4 V 6 50 R ³/₄ 12 280 275 2.6 96573377
GT-HR-18 PN6 G3/4 V 6 50 R ³/₄ 18 280 380 3.5 96573378
GT-HR-25 PN6 G3/4 V 6 50 R ³/₄ 25 280 490 4.6 96573390
GT-HR-35 PN6 G3/4 V 6 50 R ³/₄ 35 354 460 5.4 96573393
GT-HR-50 PN6 R3/4 V 6 50 R ³/₄ 50 409 493 12.5 96573395
GT-HR-80 PN6 R1 V 6 50 R1 80 480 565 17 96573396
GT-HR-100 PN6 R1 V 6 50 R1 100 480 670 20.5 96573397
GT-HR-140 PN6  R1 V 6 50 R1 140 480 912 28.6 96573398
GT-HR-200 PN6 R1 V 6 50 R1 200 634 758 36.7 96573399
GT-HR-250 PN6 R1 V 6 50 R1 250 634 888 45 96573400
GT-HR-300 PN6 R1 V 6 50 R1 300 634 1092 52 96573401
GT-HR-400 PN6 R1 V 6 50 R1 400 740 1102 65 96573403
GT-HR-500 PN6 R1 V 6 50 R1 500 740 1312 79 96573404
GT-HR-600 PN6 R1 V 6 50 R1 600 740 1531 85 96573405
GT-HR-800 PN6 R1 V 6 50 R1 800 740 1996 103 96573407
GT-HR-1000 PN6 R1 V 6 50 R1 1000 740 2406 120 96573408
17 EXPANSION VESSELS

GT-U+ 10 Bar Rated Expansion Vessels

Grundfos GT-U+ expansion vessels are suitable for use in sealed heating
and chilled systems.

Features: Installation
•  low-carbon sheet steel shell To ensure that the temperature at
•  replaceable butyl bladder the diaphragm does not exceed 70°C
•  built-in pressure gauge (system flow <90°C), the vessel should
•  threaded connection be installed on the coldest part of the
•  WRAS approved system, typically the return pipe to the
•  available in a variety of sizes heat exchanger.
For systems running at elevated
temperatures (system flow >90°C), an
intermediate vessel may be required to
provide additional heat dissipation.

Vessel
Vessel
Maximum Connections Volume Dimensions (mm) Weight Product
Product Name Efficiency
Working Pressure Code
(Bar) % BSP M (L) Diameter Height (Kg)
GT-U+ 100 PN 10 10 50 1" 100 453 983 76.5 99082696
GT-U+ 150 PN10 10 50 1" 150 504 1056 91.5 99082697
GT-U+ 200 PN10 10 50 1¹/₄" 200 604 1103 123.3 99082698
GT-U+ 300 PN10 10 50 1 ¹/₄" 300 654 1286 148.3 99082699
GT-U+ 500 PN10 10 50 1 ¹/₄" 500 754 1561 195.5 99082700
GT-U+ 750 PN10 10 50 2" 750 756 1834 231 99082701
GT-U+ 1000 PN10 10 50 2" 1000 806 2376 327.5 99082702
GT-U+ 1500 PN10 10 50 2" 1500 958 2435 391.5 99082703
 EXPANSION VESSELS 18

GT-U+ 16 Bar Rated Expansion Vessels

Grundfos GT-U+ expansion vessels are suitable for use in sealed heating and
chilled systems.

Features: Installation
•  low-carbon sheet steel shell
To ensure that the temperature at
•  replaceable butyl bladder
the diaphragm does not exceed 70°C
•  built-in pressure gauge
(system flow <90°C), the vessel should
•  threaded connection
be installed on the coldest part of the
•  WRAS approved
system, typically the return pipe to the
•  available in a variety of sizes
heat exchanger.
For systems running at elevated
temperatures (system flow >90°C), an
intermediate vessel may be required to
provide additional heat dissipation.

Vessel Maximum
Maximum Vessel Connections Volume Dimensions (mm) Weight Product
Product Name Working Pressure Efficiency Code
(Bar) % BSP M (L) Diameter Height (Kg)
GT-U+ 100 PN16 16  50 1" 100 454 983 76.5 99082706
GT-U+ 150 PN16 16  50 1" 150 506 1058 91.5 99082707
GT-U+ 200 PN16 16  50 1 ¹/₄" 200 606 1105 123.3 99082708
GT-U+ 300 PN16 16  50 1 ¹/₄" 300 656 1288 148.3 99082709
GT-U+ 500 PN16 16  50 1 ¹/₄" 500 760 1565 254.5 99082710
GT-U+ 750 PN16 16  50 2" 750 760 1862 297.5 99082711
GT-U+ 1000 PN16 16  50 2" 1000 810 2367 409.5 99082712
GT-U+ 1500 PN16 16  50 2" 1500 962 2443 498 99082713
GT-U+ 2000 PN16 16  50 2" 2000 1116 2511 717 99082714
GT-U+ 3000 PN16 16  50 2 ¹/₂" 3000 1216 2938 1055 99082715
19 VESSEL SELECTION CALCULATION

Vessel Selection Calculation

The following guidance is provided to assist with selection of the correct vessel for your application and uses calculations
that conform to BS 7074. However, if you prefer, Grundfos are happy to assist you with your selection.
Vessel sizing centres around determining the minimum vessel sizing based upon the Expanded Volume of the system
and the lower of either the Maximum Vessel Efficiency (see table on preceding pages) or the Acceptance Factor as below

Minimum system vessel size = +10% Expanded Volume

Maximum Vessel Efficiency OR Acceptance Factor

The Expanded Volume is the volume by which system water expands as it is heated and can be calculated from the water
temperature with the assistance of standard reference tables. To provide a level of safety the maximum flow temperature
should be used, not the average temperature. When the quantity of water in the system is unknown an approximation
can be used: 12 litres of system water per 1kW of thermal input. For chilled systems Grundfos work with 18 litres per kW
of thermal input when the actual volume is unknown.

Expanded Volume = Volume x Coefficient at Maximum Flow Temperature

EXAMPLE
For a system with a 100kW boiler we can estimate the water volume is 1200 litres.
If the max. flow temperature is 82°C, tables give an expansion coefficient of 3.02%

Expanded Volume = 1200 x 3.02% = 36.24 litres

The Maximum Vessel Efficiency is the design specification of the vessel, as shown on pages 16-18, whereas the
Acceptance Factor takes into account the limitations that may be placed on the Maximum Vessel Efficiency by the design
of a specific system. As the lower of the two values must be used in sizing it is important to confirm the Acceptance
Factor for your specific system. This is done using the calculation below:
Acceptance Factor = Maximum System Working Pressure (absolute) - Cold Fill Pressure (absolute)
Maximum System Working Pressure (absolute)

Note the use of absolute pressures ie the requirement to add 1.0 bar atmospheric pressure to measured values.
Cold Fill Pressure is calculated from the static height, plus 0.3 bar to expel air.
Note: Cold Fill Pressure (including 0.3 bar to expel air) must not be less than 0.7 bar ie 1.7 bar(absolute).
EXAMPLE
For a system with Maximum Working Pressure 3.0 bar at the pressurisation set and a static height of 7.0 metres

Cold Fill Pressure = 7.0 metres bar + 0.3 bar = 0.7 bar + 0.3 bar = 1.0 bar (or 2 bar absolute)
10

2
Acceptance Factor = (3.0
+ 1.0) – (1.0 + 1.0) = = 0.5
(3.0 + 1.0) 4

Minimum Vessel Size = 36.24 litres + 10% = 79.73 litres

0.5

Looking at the 6 bar pressure vessel range on page 16, the smallest vessel size is 80 litres. A check shows this vessel has a
Maximum Vessel Efficiency of 50%, which is not smaller than the Acceptance Factor for the example system. This means
an 80 litre vessel is the correct size to select.

We realise using the above calculations can be time consuming and Grundfos is available to
assist you with vessel selection if required.
 SYSTEM SCHEMATICS 20

Low temperature heating water system (Typical Installation)

Air separator with

automatic air vents

Flow to system

Automatic
air vent

Flow header Boiler high and low pressure

Safety valve
cut-out switches
To duplicate system (optional, use PHT A T)
High limit thermostat
Temperature Expansion vessel(s)
controller

DC

Boiler Anti-gravity
loop C.W. main
supply
Over-
flow

DC
Automatic
top-up unit

Return header

System initial
fill connection P.G.
Return from system Removable section
Anti-vacuum valve
Pressure reducing valve
21 SYSTEM SCHEMATICS

Medium temperature heating water system (Typical Installation)

Flow to systems
Automatic
air vent

Flow header Safety valve Boiler high and low pressure

cut-out
To duplicate system (optional) (*use PHT-T)
Temperature control
Temperature limit Expansion vessel(s)
switch

DC
Boiler Anti-gravity
circulation C.W. main
loop supply
Over-
flow

DC
Automatic
top-up unit

Return header
Intermediate cooling
vessel *optional extra System initial
fill connection P.G.
Return from system Removable section
Anti-vacuum valve
Pressure reducing valve
 SYSTEM SCHEMATICS 22

Chilled water system (Typical Installation)

NOTE: The temperatures shown are approximate and vary according to climatic conditions and equipment used.
Beds. LU7 4TL
Tel: 01525 850000

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