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ViessmannVitocal 250-A AWO-M-E-AC 251.A06

Viessmann Vitocal 250-A AWO-M-E-AC 251.A06
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The Viessmann Vitocal 250-A AWO-M-E-AC 251.A06 is an air-to-water heat pump with a SCOP of 4.71 (35 °C) and a sound power level of 47 dB(A). Under permitted development the limit is 37 dB(A) measured 1 m in front of the centre of a neighbour’s habitable-room door or window. Free-standing, the indicative minimum distance is 1.3 m; against a wall 1.8 m.1

Last updated: Technical specifications Rules in the UK ⇄ Compare this model
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SCOP (35 °C)
4.711

Seasonal efficiency: how much heat you get per kWh of electricity across a heating season.

Heating capacity (A7/W35)
4.8kW1
Official source
Outdoor unit sound power
47dB(A)1
Official source
Refrigerant
R2901
Official source
Type (source)
Air-to-water1
Official source
UK

Rules in the UK

Minimum distance to your neighbour

MCS 020(a) (England, permitted development since 29 May 2025)2 · 1 m in front of the centre of a neighbour’s habitable-room door or window

Permitted development (MCS 020(a)) ≤ 37 dB(A) · LAeq,5min
Free-standing 1.3 m
Against wall 1.8 m
In corner 2.5 m

Indicative calculation (hemispherical, no barriers). Not a substitute for an MCS 020 assessment.

Boiler Upgrade Scheme

Check conditions

£7,500 – £9,0003Fixed grant (England & Wales)

Fixed grant in England and Wales, deducted from your installer’s quote. £9,000 when replacing oil or LPG off the gas grid (until March 2027). Scotland: Home Energy Scotland grant instead.4,5

  • Must be MCS-certified (product and installer). Check the Ofgem product eligibility list.
  • Rated output 5.41 kW; the scheme covers systems up to 45 kW.
  • SCOP at 55 °C: 3.65. The installed system needs a SCOP of at least 2.8 (MCS calculation).
Heat pump grants in the UK explained →

Technical specifications

General
Type (source) Air-to-water1
Performance
Heating capacity (A7/W35) 4.8 kW1
Rated output 35 °C 5.41 kW1
Rated output 55 °C 5.11 kW1
Min. outdoor temperature -20 °C1
Efficiency
SCOP (35 °C) 4.711
SCOP (55 °C) 3.651
Seasonal efficiency ηs 35 °C 183 %1
Seasonal efficiency ηs 55 °C 141 %1
Energy label 35 °C A, , , 1
Energy label 55 °C A, , 1
COP A7/W35 5.11
Noise
Outdoor unit sound power 47 dB(A)1
Indoor unit sound power 40 dB(A)1
Refrigerant
Refrigerant R2901
Refrigerant GWP 31
Refrigerant charge 1.2 kg1

Variants

This model is registered in 21 combinations (for example with a different indoor unit or cylinder) with exactly the same performance. All figures on this page apply to each of these types. The part of the type number that differs is in bold; small differences (e.g. cylinder volume or anode) are listed after it:

  • Vitocal 250-A AWO-M-E-AC 251.A06
  • IDU-A Compact 2C AWMIT.A1.19-V056 / ODU 250-A AWMOF-251.A1.06-230-V002
  • IDU-A Compact AWMIT.A1.19-V053 / ODU 250-A AWMOF-251.A1.06-230-V002
  • IDU-A Modular AWMIW.A1.19-V051 / ODU 250-A AWMOF-251.A1.06-230-V002
  • Vitocal 250-A AWO-M-E-AC 251.A06 2C
  • Vitocal 250-A AWO-M-E-AC 251.A06 2C SP
  • Vitocal 250-A AWO-M-E-AC 251.A06 SP
  • Vitocal 250-A AWO-M-E-AC-AF 251.A06
  • Vitocal 250-A AWO-M-E-AC-AF 251.A06 2C
  • Vitocal 250-A AWO-M-E-AC-AF 251.A06 2C SP
  • Vitocal 250-A AWO-M-E-AC-AF 251.A06 SP
  • Vitocal 250-AH HAWO-M-AC 252.A06
  • Vitocal 250-AH HAWO-M-AC-AF 252.A06
  • Vitocal 252-A AWOT-M-E-AC 251.A06
  • Vitocal 252-A AWOT-M-E-AC 251.A06 2C
  • Vitocal 252-A AWOT-M-E-AC 251.A06 2C SP
  • Vitocal 252-A AWOT-M-E-AC 251.A06 SP
  • Vitocal 252-A AWOT-M-E-AC-AF 251.A06
  • Vitocal 252-A AWOT-M-E-AC-AF 251.A06 2C
  • Vitocal 252-A AWOT-M-E-AC-AF 251.A06 2C SP
  • Vitocal 252-A AWOT-M-E-AC-AF 251.A06 SP

Manufacturer documentation

  • Datasheet / specifications — VITOCAL 250-A Luft/Wasser-Wärmepumpen mit Innen- und Außeneinheit – Datenblatt (4/2025) (viessmann.de, PDF)

External links to Viessmann's official website. The manufacturer may change or move documents; where they differ, the manufacturer's latest version applies.

Frequently asked questions

Can I install the Viessmann Vitocal 250-A AWO-M-E-AC 251.A06 without planning permission?

Under MCS 020(a) (England, permitted development since 29 May 2025) the unit must not exceed 37 dB(A) 1 m in front of the centre of a neighbour’s habitable-room door or window. With a sound power of 47 dB(A) that indicatively means 1.3 m free-standing, 1.8 m against a wall or 2.5 m in a corner. Your MCS installer must confirm this.1

How much Boiler Upgrade Scheme grant can you get for the Viessmann Vitocal 250-A AWO-M-E-AC 251.A06?

£7,500 in England and Wales, provided the product and installer are MCS-certified (£9,000 when replacing oil or LPG off the gas grid, until March 2027). The installer applies and deducts the grant from your quote.1

Which refrigerant does the Viessmann Vitocal 250-A AWO-M-E-AC 251.A06 use?

The Viessmann Vitocal 250-A AWO-M-E-AC 251.A06 uses R290.1

Sources

  1. Heat Pump Keymark certificates — EHPA / DIN CERTCO (Heat Pump KEYMARK) · accessed 29 Sept 2026
  2. MCS 020(a) (England, permitted development since 29 May 2025)
  3. Boiler Upgrade Scheme: what you can get — GOV.UK · accessed 27 Sept 2026
  4. Boiler Upgrade Scheme: guidance for installers (V5) — Ofgem · accessed 27 Sept 2026
  5. Boiler Upgrade Scheme product eligibility — Ofgem · accessed 27 Sept 2026