Mikrofill Pressurisation Unit’s
Mikrofill MAXI AP 280 Twin Pump Pressurisation Unit 47724
- Established 1975
- Trusted by thousands of customers
The Mikrofill MAXI AP 280 is a twin pump (duty/standby) high pressure digital pressurisation unit for sealed heating and chilled water systems of up to 300,000 litres. It fills the system, maintains a set pressure by topping up automatically, and raises an alarm if pressure falls or the unit runs dry.
Floor standing, with an 18 litre break tank, bronze peripheral pumps and Category 5 backflow protection. Cold fill pressure up to 8 bar, for tall buildings and high static head. Made in the UK by Stuart Turner, with a two-year warranty.
More about this product
Product overview
The Mikrofill MAXI AP 280 is a twin pump (duty/standby) pressurisation unit for sealed LTHW heating, chilled water, refrigeration and industrial cooling systems. Connected to the mains cold water supply and the system, it fills the system to the set cold fill pressure, tops it up automatically as the system loses water through venting or small leaks, and signals a fault if pressure drops below the low limit or the break tank runs dry.
The MAXI AP is the top of the Mikrofill range: a floor-standing unit for sealed systems of up to 300,000 litres with Ai100 microprocessor control. The AP 280 is the high pressure twin pump model, with a cold fill pressure of up to 8 bar for tall buildings and plant with a high static head, and duty/standby changeover so the system keeps running if one pump fails. Bronze peripheral pumps.
Key features
Typical applications
Technical specifications
| Brand | Mikrofill (Stuart Turner Group) |
| Model | Mikrofill MAXI AP 280 |
| Part number | 47724 |
| Range | MAXI AP |
| Pumps | 2 — duty / standby |
| Pump type | Bronze peripheral pump |
| Maximum cold fill pressure | 8 bar |
| Maximum flow | 16.5 l/min per pump |
| Sealed system capacity | Up to 300,000 litres |
| Connections | Cold water inlet ½″ BSP male, system outlet 22 mm compression, overflow 20 mm |
| Break tank | 18 litres, polyethylene |
| Backflow protection | Fluid category 5, type AB air gap with weir overflow and warning pipe |
| Mounting | Floor standing |
| Power supply | 230 V / 1 ph / 50 Hz |
| Power consumption | 1400 W |
| Full load current | 8.4 A |
| Enclosure | IP55 powder-coated steel |
| BMS | Modbus RTU and 4 volt-free relays |
| Dimensions (W × D × H) | 505 × 405 × 805 mm |
| Weight | 54 kg |
| Warranty | 2 years |
| Certification | UKCA / CE |
Frequently asked questions
When do I need the 8 bar version?
When the cold fill pressure needed is above 3.9 bar. As a rule of thumb, cold fill pressure is the static height of the system in metres divided by 10, plus 0.3 bar. A system 45 m tall needs around 4.8 bar, so the AP 280 rather than the AP 240.
Single or twin pump?
The AP 280 runs two pumps duty/standby, so if one fails the other takes over and the controller alarms. Specify it where the system must not go down. For the same 8 bar performance with a single pump, see the MAXI AP 180.
Does it need a separate expansion vessel?
Yes. The unit maintains pressure; the expansion vessel absorbs the expansion of the heated water. Size the vessel to the system volume and cold fill pressure. Ask us if you need help sizing it.
Is it WRAS compliant?
Yes. It has Category 5 backflow protection with a type AB air gap, weir overflow and warning pipe, so it can be connected directly to the mains.
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Data Sheet PDFDownload
Standard delivery:
Standard delivery is free on most orders. Some items may incur a delivery charge depending on weight, size or value. Any applicable charge will be displayed at checkout.
Deliveries will typically be made between 7am and 6pm, Monday to Friday (excluding public holidays).
Next day delivery:
Next working day delivery is available for a £16.50 + VAT delivery charge.
Orders must be placed before 12 noon to qualify for next working day delivery. Orders placed after 12 noon on Thursday but before noon on Friday will be delivered the following Monday. Orders placed after 12 noon on Friday will be delivered on Tuesday.
Pallet/Large/Difficult items:
Some large, heavy or difficult to transport items may incur an additional delivery charge. Please contact us for a delivery quote before ordering.
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Frequently Asked Questions
Quick answers to common questions about the Mikrofill MAXI AP 280 Twin Pump Pressurisation Unit 47724. For technical specifications, see the product details above; for sizing or installation advice, contact our team. If you have any other questions, we're happy to help.
What is a mains pressure boosting system?
A mains pressure boosting system increases the pressure and flow of water from the incoming mains supply into a property. It typically combines a pump and a storage or expansion tank, drawing water from the mains and delivering it to taps, showers and appliances at a stronger, more consistent pressure. They are used where the incoming mains is too weak to serve modern outlets reliably.
When do I need a mains booster pump?
You normally need a mains booster if static mains pressure is below 1.5 to 2 bar, if showers run weakly when other taps are open, or if combi boilers struggle to deliver hot water. Anglian Pumping recommends checking static pressure at the stop tap before specifying a system, then choosing a model rated for the number of bathrooms and outlets in the property.
What size mains booster do I need for my home?
Sizing depends on the number of bathrooms, the type of fittings and the static mains pressure. As a guide, a 1 to 2 bathroom property with combi boiler or single shower often needs 1.6 to 3 bar boost. A 2 to 3 bathroom property typically needs 3 to 4.5 bar with an integral break tank. Larger homes need a tank-and-pump system such as the DAB Esybox with Esytank or a Powertank set.
What is a water booster pump?
A water booster pump increases the pressure of an existing water supply to give stronger flow at taps, showers and appliances. It can be a small inline pump fitted to the incoming mains, or a larger pump and tank set that draws from a break tank to feed the whole house. Boosters do not create water – they raise the pressure of the water already coming in.
What is the difference between an inline booster and a tank-and-pump booster?
An inline booster connects straight onto the incoming mains and is limited to 12 litres per minute under UK water regulations – examples include the Salamander HomeBoost and WaterBoost WB-Compact. A tank-and-pump booster, such as the Grundfos Home Booster or DAB Esybox with Esytank, draws from a break tank and can deliver much higher flow rates for larger homes with multiple bathrooms.
What is a variable speed booster pump?
A variable speed booster uses an inverter to adjust pump speed in real time to match demand. It maintains constant pressure as outlets open and close, runs more quietly than a fixed-speed pump and typically saves up to 50 per cent of the energy a fixed-speed equivalent would use. The DAB Esybox, DAB Esybox Mini 3 and Grundfos Scala2 are common variable speed examples.