Grundfos Magna1 50-120 F N 280 240V Stainless Steel Circulator Pump 99221361 Model C #4913

Grundfos MAGNA1 50-120 F N 280 Model C – 240V Stainless Steel High-Efficiency Circulator Pump (99221361) #4913

This listing is for a Grundfos MAGNA1 50-120 F N 280 Model C high-efficiency single-head canned-rotor circulator pump with DN50 flanged connections, a 280 mm port-to-port length and a stainless steel pump housing. The MAGNA1 range is designed for clean heating, cooling and building-services circulation systems where simple high-efficiency variable-speed control is required.

The N version has a stainless steel housing, making it the preferred MAGNA1 housing option where domestic hot-water compatibility or improved corrosion resistance is required, subject to the full system design, water quality and local installation requirements.

Condition: supplied in as new surplus condition – the unit has not been installed or used but may show minor cosmetic markings from storage and handling. Guarantee: supplied with a 2-year guarantee.

• Pump type: MAGNA1 Model C single-head canned-rotor circulator
• Grundfos product number: 99221361
• Connection: DN50 flanged
• Port-to-port length: 280 mm
• Pressure rating: PN6/10 connection class
• Electrical connection: terminal connection
• Electrical supply: 1 × 230 V / 240 V class, 50/60 Hz
• Power input: P1 approx. 20.2–533 W
• Current: approx. 0.22–2.37 A
• Maximum head class: 12 m
• Maximum flow: approx. 30 m³/h / 8.3 L/s
• Maximum operating pressure: 10 bar
• Liquid temperature range: -10 °C to +110 °C
• Pump housing: stainless steel
• Control: proportional pressure, constant pressure and constant curve / constant speed
• Factory setting: PP2 proportional-pressure curve
• Design: glandless canned-rotor pump with no conventional mechanical shaft seal

Need help confirming suitability?
Call us on 01803 220416 for technical advice.

Manufacturer product page

Full technical specifications, curves and documentation can be viewed on the official Grundfos product page:
View Grundfos MAGNA1 50-120 F N (99221361) – Product curves and specifications

Technical documentation

MAGNA1 Model C technical data can be viewed here:
View Grundfos MAGNA1 Model C technical data PDF

Typical applications

• Heating systems and boiler circuits
• Main circulation pumps
• Zone pumps and mixing loops
• Commercial building-services circulation
• Air-conditioning and chilled water systems
• Domestic hot-water circulation systems, subject to water quality and installation requirements
• Ground-source heat pump and solar-heating systems
• Replacement of matching DN50 flanged circulators

Frequently Asked Questions

What does the model number mean?

• MAGNA1 – Grundfos high-efficiency circulator range
• 50 – nominal diameter of inlet and outlet ports, DN50
• 120 – maximum head class, 120 dm / approximately 12 m
• F – flanged connection
• N – stainless steel pump housing
• 280 – port-to-port length in millimetres
• Model C – MAGNA1 pump version shown on the nameplate

What connection does this pump have?

This pump has DN50 flanged connections with a 280 mm port-to-port length. Please check the flange size, pressure rating and pipework gap against your existing pump before ordering.

What does the N version mean?

The N in MAGNA1 50-120 F N indicates the stainless steel housing version of the pump. This is selected where stainless steel is required for corrosion resistance or media compatibility.

For domestic hot-water applications, Grundfos strongly recommends stainless steel pumps to help avoid corrosion. Suitability still depends on water quality, temperature, local regulations and the complete system design.

What control modes are available on MAGNA1 Model C?

MAGNA1 Model C offers straightforward high-efficiency control without the more advanced monitoring features of MAGNA3. Available operating modes include:

• Proportional pressure: PP1, PP2 and PP3
• Constant pressure: CP1, CP2 and CP3
• Constant curve / constant speed: Speed I, II and III

The factory setting is PP2. The correct setting should be selected during commissioning to suit the system duty and valve arrangement.

What does Model C add?

MAGNA1 Model C includes simple electronic control, LED operating indication, digital start/stop input, fault relay output and Grundfos GO Remote communication when used with the appropriate Grundfos MI 301 infrared interface.

Why choose MAGNA1 instead of MAGNA3?

MAGNA1 is usually chosen where you want a reliable high-efficiency circulator with simple proportional-pressure, constant-pressure and constant-speed control. It is a good option for straightforward heating, cooling and circulation duties where advanced system monitoring is not required.

MAGNA3 is the more advanced option, with additional control, monitoring and communication features such as built-in differential-pressure and temperature sensing, energy monitoring and more advanced commissioning options. If those extra functions are not needed, MAGNA1 can be a simpler and more cost-effective choice.

Is this suitable to replace other DN50 circulators?

This model uses DN50 flanged connections with a 280 mm port-to-port length. Where dimensions and duty are comparable, it can replace other DN50 in-line circulators from brands such as Wilo, Lowara and KSB, subject to hydraulic duty, flange standard, electrical supply and control compatibility.

The advantage of an electronically controlled circulator is that it can often be adjusted during commissioning to better match the required duty of the pump being replaced, rather than being locked to one fixed-speed curve.

What liquids can this pump be used with?

MAGNA1 is suitable for thin, clean, non-aggressive and non-explosive liquids that do not contain solid particles, fibres or mineral oils. Typical uses include heating water, chilled water and clean circulation duties.

Water/glycol mixtures may be used up to 50%, but glycol concentration and temperature affect viscosity, performance and pump selection. The system should be cleaned and flushed before glycol is added, and the glycol mixture should be maintained according to the supplier’s instructions.

Not suitable for:

• Liquids containing solid particles or fibres
• Flammable, combustible or explosive liquids
• Diesel, petrol or mineral oils
• Acids or aggressive chemicals
• Sea water or aggressive saline solutions
• Dirty water, wastewater or drainage applications

Can this be used on domestic hot-water systems?

Yes, this is the stainless steel N version, which is the correct MAGNA1 housing choice where domestic hot-water compatibility is required. Suitability still depends on the full system design, water quality, operating temperature, local regulations and Grundfos installation guidance.

Grundfos recommends stainless steel pumps for domestic hot-water systems to reduce corrosion risk. Grundfos also recommends keeping domestic hot-water hardness below approximately 14 °dH and keeping the liquid temperature below 65 °C to reduce the risk of lime precipitation.

What minimum inlet pressure is required?

The required minimum inlet pressure depends on liquid temperature. For the MAGNA1 50-100 / 50-120 F family, the relevant guidance is:

• 75 °C: 0.10 bar
• 95 °C: 0.50 bar
• 110 °C: 1.00 bar

The inlet pressure and system pressure should always be checked against the installed duty, liquid temperature and manufacturer documentation before commissioning.

Does this pump have a mechanical shaft seal?

No. MAGNA1 is a canned-rotor circulator, meaning the pump and motor form an integrated wet-rotor unit without a conventional mechanical shaft seal.

Does this pump need external motor protection?

No external motor protection is normally required. The pump incorporates overload protection, but electrical installation must still be carried out correctly and in accordance with local regulations.

Can this pump be controlled or monitored externally?

Yes. MAGNA1 Model C includes a digital input for external start/stop and a relay output for fault signalling. It can also communicate with Grundfos GO Remote when used with the appropriate Grundfos MI 301 infrared interface.

Is this a new pump?

This listing is for as new surplus stock. The unit has not been installed or used but may show cosmetic marks from storage and handling.

About Our Stock

Stock code: #4913
We specialise in supplying new and unused surplus pumps. This unit is inspected prior to dispatch and supplied with a 2-year guarantee.