Hitachi airH2O 800 R290 (RASM-4TW2E)

Specifications and technical data

Also known as: airH2O 800M / airH2O 800H, indoor HWM-W2E(-B), HWD-W2E-220S(-K), ATW-CBX-01

✓ BUS eligibleAir Source (ASHP)ResidentialR29010 kW

Manufacturer	Hitachi
Model	airH2O 800 R290
Model code	RASM-4TW2E
Heat pump type	Air Source (ASHP) All Air Source heat pumps →
Application	Residential All Residential heat pumps →
Refrigerant	R290 All R290 heat pumps →
Mode	Heating & cooling
Heating capacity	10 kW
Max heating output (low temp)	8.9 kW at A-7/W35
SCOP (heating)	4.53 at W35
Heating flow temperature	up to 75 °C
Electrical supply	380-415V (Three Phase)
SEER (cooling)	3.9 at W7
Dimensions (H×W×D)	1140 × 1220 × 430 mm
Operational Weight	130 kg
Sound power level	53 dB(A) (Sound Power LW(A))
Data added	2026-10-04
Data source	Hitachi airH2O 800 R290 catalogue extract (TCGB0154 rev.1, 12/2025) - ErP data only
Verification	Verified by a human
Boiler Upgrade Scheme	✓ BUS eligible — Listed on the Ofgem BUS Product Eligibility List (24 Sep 2026). Grant also needs an MCS-certified installer and a qualifying system design. Funding guide
PEL certificate no.	041-K002-76 a

Free data sheet (PDF) →

Check noise at a neighbour’s window (MCS 020 a) →

Hitachi airH2O 800 R290 4 HP outdoor unit (RASM-4TW2E), three-phase, for use with airH2O 800 indoor units; leaving water up to 75 °C and an inverter compressor.

Where to buy (UK)

UK Supplier	The Heat Pump Warehouse
UK Supplier	Secon Renewables

✎ Suggest a correction to this data

Data is compiled from manufacturer sources and may contain errors or gaps. Always confirm specifications with the manufacturer before making decisions.