The hydrobox is a wall-mounted cabinet roughly the size of a boiler, or it can be built into a combined cylinder unit. It holds the heat exchanger, circulating pump, valves and controls. Outdoor units for split systems can be more compact than monobloc units of similar output, which helps where outdoor space is limited.
In County Down homes where the clearest unit position is away from the plant cupboard, a split system allows a longer route indoors. In County Down, a hydrobox often goes in an utility room or garage, with the cylinder alongside. Flats and terraces in County Down with a small yard or flat roof can suit a compact split outdoor unit.
Who it suits
- Owners who would rather not use glycol or anti-freeze valves
- Houses with indoor wall space for a boiler-sized hydrobox
- Homes where the outdoor unit must sit some distance from the plant space
- Exposed or frost-prone sites where outdoor water pipes would be a risk
Grants and rules for heat pumps in Northern Ireland
The Boiler Upgrade Scheme covers England and Wales only, and there is currently no dedicated heat pump grant for homeowners in Northern Ireland. Our quote for a home in County Down is therefore shown without a grant deduction; if support becomes available we will tell you how it applies.
Installing heat pumps has been zero-rated for VAT in Northern Ireland since 1 May 2023, in line with the rest of the UK, until 31 March 2027. Northern Ireland has its own permitted development rules and building regulations, and we confirm what applies to your property at survey.
Split system heat pumps prices in County Down
These are guide prices for County Down, installed and including VAT. Your final price is fixed in a written quote after the survey and depends on the heat loss of the house, the radiators that need changing and where the unit goes.
| Home | Typical size | Installed guide price |
|---|---|---|
| 1–2 bedroom flat or small terrace | 4–5 kW | £9,200–£12,150 |
| 2–3 bedroom terrace or semi | 5–7 kW | £10,200–£13,100 |
| 3 bedroom semi or small detached | 6–9 kW | £11,650–£15,050 |
| 4 bedroom detached | 8–12 kW | £13,600–£17,450 |
| 5+ bedroom or larger older house | 11–16 kW | £16,000–£21,850 |
Installed, inc VAT: unit, cylinder, controls, minor pipework and commissioning. No dedicated heat pump grant currently applies in Northern Ireland.
Towns we cover in County Down
We cover 13 towns in County Down for split system heat pumps. Each links to local guide prices and the grant position for Northern Ireland.
| Town | Postcode district | Nearest town | Midwinter daylight |
|---|---|---|---|
| Bangor (County Down) | BT20 | Newtownards | 7 h 14 min |
| Newtownards | BT23 | Comber | 7 h 15 min |
| Newry | BT35 | Warrenpoint | 7 h 20 min |
| Banbridge | BT32 | Dromore | 7 h 18 min |
| Ballynahinch | BT24 | Downpatrick | 7 h 17 min |
| Comber | BT23 | Newtownards | 7 h 15 min |
| Donaghadee | BT21 | Bangor (County Down) | 7 h 14 min |
| Downpatrick | BT30 | Ballynahinch | 7 h 18 min |
| Dromore | BT25 | Banbridge | 7 h 17 min |
| Holywood | BT18 | Newtownabbey | 7 h 14 min |
| Kilkeel | BT34 | Warrenpoint | 7 h 21 min |
| Newcastle | BT33 | Downpatrick | 7 h 20 min |
| Warrenpoint | BT34 | Newry | 7 h 21 min |
Split system heat pumps questions
Is a split system eligible for the Boiler Upgrade Scheme?
Yes. A split air-to-water heat pump counts as an air source heat pump under the scheme, so in England and Wales eligible owners of existing homes can receive £7,500, or £9,000 when replacing oil or LPG within the published dates. The MCS-certified installer applies for you. Scotland's Home Energy Scotland funding is separate, and Northern Ireland has no dedicated homeowner grant at present.
Do I need an F-gas engineer for a split heat pump?
Yes. Split systems usually use a fluorinated refrigerant such as R32, so installing, servicing or repairing the refrigerant circuit must by law be done by an F-gas certified engineer. That covers joining the refrigerant pipes, testing them for leaks and charging the system. Your quote sets out who carries out each part of the installation, including the refrigerant work.
Is a split system more efficient than a monobloc?
Not inherently. Efficiency depends far more on design, meaning correct sizing, low flow temperatures and good controls, than on whether the unit is split or monobloc. A split system can avoid the heat loss and glycol of a long outdoor water run, which helps in certain layouts. The survey estimates seasonal efficiency for the specific units proposed, so you can compare like for like.
How far apart can the outdoor unit and hydrobox be?
It depends on the model: each manufacturer sets a maximum refrigerant pipe length and height difference, and longer runs may need extra refrigerant. In practice a split system allows more flexibility than a monobloc's water pipes, so the outdoor unit can often sit on the far side of a house, on a flat roof or round a corner. The survey measures the actual route.