1½″ Male ASHP Antifreeze Valve
Automatic Heat Pump Frost Protection
Outdoor water-filled heat pump pipework can become vulnerable during freezing weather.
If circulation stops during a power cut or system fault, water inside the exposed circuit may begin to freeze.
The antifreeze valve reacts automatically as the water temperature approaches freezing.
Therefore, it provides an additional mechanical layer of frost protection without relying on the heat pump controller.
1½″ Male Threaded Connection
This version uses a 1½″ male threaded connection.
The ZL-7201 threaded range covers 1″, 1¼″ and 1½″ male sizes.
Therefore, installers can select the valve size that matches the primary heat pump pipework.
Always check the adjoining fittings before ordering.
Exact Product Code ZL-7201-11/2M
The manufacturer product code is:
ZL-7201-11/2M
This identifies the 1½″ male version within the Bastion ZL-7201 antifreeze valve range.
Using the exact code also makes replacement identification easier during servicing.
Designed for Air Source Heat Pumps
The valve suits compatible water-based heat pump installations.
Typical applications include:
- Air source heat pumps
- Monobloc heat pumps
- 1½″ primary pipework
- Heat pump flow circuits
- Heat pump return circuits
- External ASHP pipework
- Renewable heating systems
- Heat pump service work
- Heat pump replacement projects
- New ASHP installations
Always follow the heat pump manufacturer’s frost-protection requirements.
Opens Automatically at 3°C
The valve monitors the temperature of the system water.
When water temperature reaches approximately 3°C, the valve opens and begins to discharge water.
This helps prevent ice from forming inside exposed hydraulic components.
Closes Automatically at 4°C
As the system-water temperature rises, the valve automatically closes again at approximately 4°C.
Therefore, manual resetting is not normally required.
The published temperature sensitivity is ±1°C.
No Electricity Required
The antifreeze valve operates mechanically.
Therefore, it does not require:
- Mains electricity
- Batteries
- Control wiring
- Wi-Fi
- External sensors
- A room thermostat
This is especially useful during a winter power failure, when normal circulation and electronic frost protection may stop.
Ideal for Monobloc Heat Pumps
Monobloc air source heat pumps contain water-filled components within the outdoor unit.
As a result, part of the heating circuit remains outside the building.
If circulation stops during very cold weather, the exposed system water can freeze.
A correctly installed antifreeze valve helps protect the external hydraulic circuit where the heat pump manufacturer permits this method.
High-Flow 1½″ Connection
Larger heat pump systems may require increased primary flow rates.
The 1½″ connection provides a larger connection option for compatible systems.
Published Bastion data gives a Kv value of 55m³/h for the ZL-7201 antifreeze valve range.
However, always size the complete hydraulic circuit according to the heat pump manufacturer’s requirements.
10 Bar Maximum Inlet Pressure
The valve has a published maximum static inlet pressure of 10 bar.
Therefore, it covers the operating pressures used by many domestic and light-commercial heating systems.
Always confirm system pressure before installation.
0°C to 65°C Water Temperature Range
The published working temperature range is:
0°C to 65°C
The ambient operating range is:
-30°C to 60°C.
Therefore, the valve suits exposed heat pump pipework in cold outdoor conditions.
Brass Valve Body
The ZL-7201 threaded antifreeze valve uses a brass body.
This provides a robust construction for professional heating and renewable-energy installations.
Suitable for Water-Based Systems
The Bastion antifreeze valve is specified for water-based systems.
If the heating circuit contains glycol or another heat-transfer fluid, check the heat pump manufacturer’s requirements before installation.
Different heat pump systems use different frost-protection strategies.
Protection During Power Cuts
A power failure can stop both the heat pump and circulating pump.
During freezing conditions, this can leave water stationary within outdoor pipework.
Because the antifreeze valve operates mechanically, it does not rely on electrical power.
Therefore, it can continue to respond to falling water temperature during a power outage.
Install on Flow and Return Where Required
Many monobloc ASHP installations use antifreeze protection on both the exposed flow and return pipework.
This helps the outdoor circuit drain correctly if freezing conditions develop.
However, the exact number and position of valves depends on the heat pump design.
Always follow the manufacturer’s installation instructions.
Correct Installation Is Important
Install the antifreeze valve where it can sense cold system water correctly.
In addition, discharged water must be able to escape freely.
Avoid pipe arrangements that create trapped sections because these can prevent effective drainage. Manufacturer guidance specifically warns against pipe configurations that create a trap effect.
Keep the Discharge Route Clear
The valve protects the heating circuit by releasing water.
Therefore, never cap or obstruct its discharge route.
Also consider where the discharged water will go.
During freezing weather, discharged water can itself freeze once it reaches the ground.
Antifreeze Valve or Glycol?
Some heat pump systems use mechanical antifreeze valves.
Others use a glycol-based heat-transfer fluid.
The correct method depends on:
- Heat pump manufacturer
- System design
- Outdoor pipework
- Local conditions
- Water-treatment requirements
- Installer specification
Therefore, never change the frost-protection method without checking the heat pump manufacturer’s requirements.
1½″ vs Smaller Antifreeze Valves
Choose the connection size according to the hydraulic system.
Smaller domestic heat pump installations may use 28mm, 1″ or 1¼″ connections.
Meanwhile, larger primary circuits may use 1½″ connections.
The antifreeze valve should match the actual pipework and system design rather than simply the heat pump’s nominal output.
Ideal for Replacement Work
Antifreeze valves may eventually need replacement.
Common reasons include:
- Valve leakage
- Temperature cartridge failure
- Physical damage
- Frost damage
- System alterations
- Heat pump replacement
- Primary pipework upgrades
- Routine servicing
- Renewable heating refurbishment
The ZL-7201-11/2M provides a replacement option where a compatible 1½″ male connection is required.
Part of the Kudos ASHP Antifreeze Valve Range
Kudos Trading is expanding its range of antifreeze valves for heat pump installers.
The family includes different threaded and compression connections.
Therefore, engineers can select a valve that closely matches the original installation instead of adapting an unsuitable connection.
Technical Specifications
| Specification | Details |
|---|---|
| Brand | Kudos Trading |
| Product | ASHP Antifreeze Valve |
| Product Code | ZL-7201-11/2M |
| Connection Size | 1½″ |
| Connection Type | Male Thread |
| Thread | G 1½ Male / ISO 228-1 |
| Medium | Water |
| Body | Brass |
| Maximum Inlet Pressure | 10 Bar |
| Working Temperature Range | 0°C to 65°C |
| Ambient Temperature Range | -30°C to 60°C |
| Opening Temperature | 3°C |
| Closing Temperature | 4°C |
| Sensitivity | ±1°C |
| Kv Value | 55m³/h |
| Electrical Supply | Not Required |
| Application | Air Source Heat Pumps / Water-Based Heating |
Published technical data confirms the ZL-7201-11/2M model, 1½″ connection and operating specifications.
Why Choose the 1½″ Male ASHP Antifreeze Valve?
Key benefits include:
- Automatic frost protection
- 1½″ male threaded connection
- Opens at approximately 3°C
- Closes automatically at approximately 4°C
- No electricity required
- No batteries required
- Works during power failures
- 10 bar maximum inlet pressure
- High-flow 55m³/h Kv rating
- Brass construction
- Suitable for compatible monobloc heat pumps
- Ideal for larger ASHP primary circuits
- Suitable for replacement work
- Designed for exposed heating pipework
Why Buy From Kudos Trading?
Kudos Trading supplies professional air source heat pump, plumbing and heating components throughout the UK.
Our expanding Air Source Heat Pump Parts & Spares range includes antifreeze valves, flexible hoses, flow setters, balancing valves, filters and air separators.
Therefore, installers can source more ASHP service and replacement components from one supplier.
We have supplied underfloor heating products to the UK since 2001.
Frequently Asked Questions
What Does a 1½″ Heat Pump Antifreeze Valve Do?
It automatically releases water when system temperature approaches freezing.
This helps prevent ice from forming inside exposed heat pump pipework and hydraulic components.
What Connection Does This Valve Have?
This model uses a 1½″ male threaded connection.
The manufacturer identifies the model as ZL-7201-11/2M.
Is the Thread BSP?
The manufacturer specifies a G 1½ male threaded connection to ISO 228-1.
At What Temperature Does the Valve Open?
It opens at approximately 3°C.
At What Temperature Does It Close?
It closes again at approximately 4°C.
Does the Valve Need Electricity?
No.
It operates mechanically and does not require an electrical supply.
Will It Work During a Power Cut?
Yes.
Because the valve does not rely on electricity, it can still respond to falling water temperature during a power failure.
Is It Suitable for a Monobloc Heat Pump?
Yes, where the heat pump manufacturer permits mechanical antifreeze valves within the frost-protection design.
Should I Install One on Both Flow and Return?
Many monobloc installations use frost protection on both exposed flow and return pipework.
However, always follow the heat pump manufacturer’s installation requirements.
Can I Use It Instead of Glycol?
Some systems use mechanical antifreeze valves instead of glycol.
However, the correct approach depends on the heat pump manufacturer and hydraulic design.
Never alter the frost-protection method without checking those requirements.
What Is the Maximum Working Pressure?
The maximum published static inlet pressure is 10 bar.
What Is the Working Temperature Range?
The system-water range is 0°C to 65°C.
The ambient range is -30°C to 60°C.
What Is the Kv Value?
The published Kv value is 55m³/h.
What Other Antifreeze Valve Sizes Are Available?
The same Bastion family includes:
- 1″ Male
- 1¼″ Male
- 1½″ Male
- 1″ Male x Female Swivel
- 1¼″ Male x Female Swivel
- 28mm Compression
The published product range confirms these connection options.
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