Ideal Heating 25L Buffer Tank - AH700436 (BT25)

Description

The Ideal Heating 25 Litre Buffer Tank (AH700436, BT25) adds vital system water volume to heat pump and heating installations, helping to prevent short-cycling on systems with low water content, multiple zones, or variable heating demand. By storing a reserve of heated water, the buffer tank smooths flow temperature, supports better defrost recovery, and reduces mechanical strain on the compressor.

Built for flexible wall-hung installation in either horizontal or vertical orientation, the BT25 is compatible with Ideal Logic Air and HP290 air source heat pumps, as well as biomass and conventional gas or oil boilers. Its insulated shell limits standing heat loss, keeping the tank efficient as a passive thermal store in both domestic and light-commercial systems.

25 L

Storage Capacity

6 bar

Max Working Pressure

-10 to +110°C

Operating Temperature

Class C

Energy Efficiency

1″ / 1″¼

Connections

12.5 kg

Gross Weight

Important: Wall Loading & Expansion Vessel Sizing

The tank must be fixed to a load-bearing wall of adequate strength — this is the installer's responsibility. The system's expansion vessel must also be sized to account for the buffer tank's water content, in addition to the rest of the heating circuit.

Please Note: 25L vs 50L — Check System Sizing

This is the 25 litre (BT25, AH700436) variant. A 50 litre (BT50, AH700437) version is also available with larger physical dimensions and connections in the same sizes — confirm the required buffer volume against the heat pump manufacturer's system design guidance before ordering.

Good to Know: Compatible Heat Sources

Suitable for use with Ideal Logic Air and HP290 heat pumps, biomass boilers, and traditional gas or oil boilers — making it a versatile addition to renewable and conventional heating systems alike.

Reduces Short-Cycling

Added system volume stops the heat source switching on and off too frequently, which improves efficiency and extends compressor or burner lifespan.

Flexible Wall Mounting

Can be installed horizontally or vertically on a wall bracket, helping it fit into plant rooms, airing cupboards, or garages where floor space is limited.

Insulated Shell

The tank body is insulated to minimise standing heat loss, so stored thermal energy isn't wasted between heating demand cycles.

Supports Multi-Zone Systems

Provides a stable hydraulic buffer point for systems serving multiple heating circuits or zones with differing flow requirements.

Improves Defrost Performance

The stored water reserve helps maintain heat output to the property during an air source heat pump's defrost cycle.

Dual Connection Sizing

Fitted with both 1″ and 1¼″ connections, giving installers flexibility to match existing pipework without extra reducers.

Product Identification
Manufacturer	Ideal Heating
Product	25 Litre Buffer Tank (BT25)
Manufacturer Part Number (MPN)	AH700436
GTIN / Barcode	3410537004360
Compatible With	Ideal Logic Air and HP290 air source heat pumps; biomass and conventional gas/oil boilers
Technical Specification
Storage Capacity	25 litres
Energy Efficiency Class	C
Waste Heat Loss	41 W
Maximum Working Pressure	6 bar
Operating Temperature Range	-10°C to +110°C
Connections	1″ and 1″¼
Mounting Orientation	Horizontal or vertical, wall-hung
Colour	Blue
Dimensions
Diameter (ØA)	220 mm
Overall Height (I)	785 mm
Body Height (H)	166 mm
Width (E)	450 mm
Depth (F)	290 mm
Wall Bracket Centres (J)	40 mm
Gross Weight (inc. packaging)	12.5 kg

What's the difference between the 25L and 50L buffer tanks?

The 25L (BT25, AH700436) and 50L (BT50, AH700437) share the same connection sizes and pressure/temperature ratings, but differ in physical dimensions, energy class figures, and heat loss — the 50L is taller and wider to accommodate the larger water volume. Sizing should be based on the heat pump manufacturer's minimum system volume requirement.

Which heat pumps is this buffer tank compatible with?

It's designed for use with the Ideal Logic Air range and the Ideal HP290, and is also suitable alongside biomass boilers and traditional gas or oil boiler systems.

Can the buffer tank be mounted horizontally?

Yes, the tank supports both horizontal and vertical wall-hung installation, giving installers flexibility depending on available plant room space.

Do I need to resize my expansion vessel when adding a buffer tank?

Yes. The additional water volume of the buffer tank must be included when calculating the system's total expansion vessel requirement, in line with the manufacturer's installation guidance.

What connection sizes does the buffer tank use?

The BT25 is fitted with 1″ and 1¼″ connections, allowing it to be plumbed into most domestic heat pump and boiler circuits without additional adaptors.

BTU Calculator

BTU & WATT Calculator

Room Dimensions

Length (in m):

Width (in m):

Height (in m):

Room Type

Living Room

Bedroom

Kitchen

Bathroom

Conservatory

Hallway

Glazing Type

Single Glazed

Double Glazed

Triple Glazed

External Walls

0 Wall

1 Wall

2 Walls

3 Walls

4 Walls

Insulation Level

Poor

Average

Good (New Build)

Calculate

Required Heating

0

Watts

0

BTUs