OSO ACCU A60
60 Litres
Stainless Steel
NANOPUR Insulation
SKU 11009165
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Stainless Steel
EVERLAST⢠titanium alloy
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NANOPUR Insulation
Class-leading heat retention
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Dual Connections
Flow + return both sides
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Anti-Clocking
Protects heat pump
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Compact: 60L
Ă434 Ă 741mm
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Wall Brackets
Included
OSO ACCU A60 â 60L Stainless Steel Buffer Tank for Heat Pumps (SKU 11009165) â 60L (57L actual volume) stainless steel buffer tank  | NANOPUR insulation  | Dual flow/return connections  | Hydraulic coupling & balancing  | Anti-clocking protection  | Cool storage function  | G½" air vent + drain  | Wall brackets included  | Ă434 Ă 741mm  | 18 kg  | ErP C
âšď¸ Why does my heat pump need a buffer tank?
Most air source heat pumps require a minimum flow rate to operate correctly â without sufficient water volume in the system, the heat pump can "clock" (short-cycle on and off repeatedly), which reduces efficiency, increases wear and can shorten compressor life. A buffer tank adds volume to the system so the heat pump always has adequate water to heat, allowing it to run in longer, more efficient cycles. A buffer tank is also essential for defrost mode â the tank provides the heat energy the pump needs to defrost its evaporator â and for cooling/heating systems where the buffer stores cooled water during summer operation.
The OSO ACCU A60 is a 60-litre stainless steel buffer tank designed for use with air source heat pumps and solar thermal systems. Built from OSO's EVERLAST⢠titanium-alloyed stainless steel and welded using the ULTRAWELD⢠process, it is inherently corrosion-resistant â unlike mild steel buffer tanks, it requires no sacrificial anode and no periodic re-pressurisation of protective coatings. NANOPUR insulation ensures minimal standby heat loss (44W) to keep the buffer volume at the right temperature with minimal energy input.
The A60 is the most compact tank in the OSO ACCU range, suited to smaller heat pump installations or where space is limited. Its slimline Ă434mm footprint allows it to fit alongside most domestic heat pump units in standard plant rooms, cupboards or utility spaces. Wall brackets are included, allowing the tank to be mounted on a wall where floor space is at an absolute premium â though it can equally stand on the floor.
Key Features
Hydraulic Coupling & BalancingActs as a hydraulic separator between the heat pump's primary circuit and the heating distribution circuit â decoupling the two so the heat pump can maintain its minimum flow rate independently of the variable demand from the heating zones.
Anti-Clocking ProtectionAdds essential system volume so the heat pump runs in longer, more efficient cycles rather than short-cycling repeatedly. Protects compressor longevity and keeps COP consistently high.
Defrost Mode Heat ReserveProvides the thermal mass the heat pump needs to complete a defrost cycle without drawing energy from the heating distribution circuit â critical for reliable operation in colder ambient conditions.
Cool Storage FunctionFor heating-cooling heat pump systems, the buffer tank stores cooled water for space cooling while the heat pump simultaneously heats a DHW cylinder â enabling both functions without conflicting demands on the refrigeration circuit.
NANOPUR⢠InsulationClass-leading insulation technology with thermal performance far surpassing standard Pentane foam â keeps the buffer volume at temperature with minimal standby losses (44W), reducing the energy cost of maintaining system readiness.
EVERLAST⢠Stainless Steel & ULTRAWELDâ˘Titanium-alloyed stainless steel provides class-leading corrosion resistance. The ULTRAWELD⢠welding system and passivation process ensure a sealed, durable tank construction â over 40% lighter than equivalent enamelled steel tanks.
Dual Flow/Return ConnectionsDual sets of flow and return connections on opposite sides of the tank provide flexible connection and installation options for a variety of primary and secondary circuit configurations.
Wall Brackets & Air Vent IncludedCorrosion-resistant wall brackets for vertical wall mounting are included. A separate G½" female connection for an automatic air vent, plus a drain connection, are factory-fitted for installation convenience.
Technical Specifications
| Specification |
Detail |
| Brand / Range |
OSO Hotwater / ACCU |
| Model |
ACCU A60 |
| SKU / Product No. |
11009165 |
| Actual Volume |
57 litres |
| Nominal Capacity |
60 litres |
| Energy Rating (ErP) |
C |
| Standby Heat Loss |
44W |
| Tank Material |
EVERLAST⢠titanium-alloyed stainless steel |
| Construction |
ULTRAWELD⢠â no enamel, no anode required |
| Insulation |
NANOPUR⢠|
| Diameter (Ă) |
434mm |
| Height (H) |
741mm |
| Weight (empty) |
18 kg |
| Freight Volume |
0.18 dmÂł |
| Placement |
Floor-standing (wall-mountable with included brackets) |
| Flow/Return Connections |
Dual sets â flexible configuration |
| Air Vent Connection |
G½" F (separate) |
| Drain Connection |
Yes â factory fitted |
| Sensor Pocket |
1Ă for 6â8mm sensor |
| Wall Brackets |
Included (corrosion-resistant) |
| Typical Applications |
Air source heat pumps, solar thermal, heating-cooling systems |
Frequently Asked Questions
What size buffer tank do I need for my heat pump?The required buffer volume depends on the heat pump output, the number of heating zones, the minimum flow rate of the heat pump and the minimum on-cycle duration specified by the manufacturer. As a general guide, 20â50 litres per kW of heat pump output is a commonly used rule of thumb, though the correct sizing must be calculated for each installation. For a typical 5â10kW domestic heat pump with 2â3 zones, a 60L buffer is often sufficient; larger systems or fewer zones may require 100L or 200L. Always consult the heat pump manufacturer's guidance or MCS documentation for your specific system.
Does a buffer tank replace the need for a hot water cylinder?No. A buffer tank stores heating system water (the circuit fluid) at heating temperatures â it is not a domestic hot water (DHW) cylinder. It is used in the primary heating circuit to stabilise heat pump operation. A separate unvented or vented DHW cylinder (or thermal store) is still required to provide hot water to taps and showers.
Can the OSO ACCU be wall-mounted?Yes. The A60 comes with corrosion-resistant wall brackets so it can be mounted vertically on a wall â useful in plant rooms or cupboards where floor space is restricted. The tank can equally stand on the floor; both installations are supported.
Is this tank suitable for underfloor heating systems?Yes. The OSO ACCU A60 is suitable for use with heat pumps connected to underfloor heating, radiators, fan coil units or any closed heating distribution system. Its dual flow/return connections make it compatible with a wide variety of primary/secondary piping configurations.
