6 minute read -
Preparing a Heat Pump Installation: What You Do and What the Installer Does
You cannot install a heat pump entirely by yourself. On a split heat pump, only an F-gas certified engineer may connect the refrigerant circuit, and the electrical connection to a dedicated circuit is also a job for a qualified electrician. What you can do is the groundwork for a heat pump installation: choosing the location, laying a base or fitting a wall bracket, drilling the wall penetration and preparing the condensate drain.
Agree with your installer in advance which jobs you will take on, so the sizes, diameters and positions are right.
What will you learn in this article?
- How does a heat pump work?
- Monobloc or split: what does it mean for the installation?
- Which jobs can you do yourself?
- What does the installer need to do?
- Where should you put the outdoor unit?
- Which tools do you need for the groundwork?
- Laying a base or fitting a wall bracket
- Drilling the penetration through the outside wall
- Draining condensate
- Frequently asked questions about preparing a heat pump installation
- In short: preparing a heat pump installation
How does a heat pump work?
A heat pump takes heat from the outside air, the ground or exhaust air and uses a refrigerant and a compressor to raise it to a higher temperature. That heat goes into the water of your central heating for radiators or underfloor heating, and often into your hot water as well. There are fully electric heat pumps and hybrid heat pumps that work together with a boiler.
Monobloc or split: what does it mean for the installation?
| Monobloc | Split | |
|---|---|---|
| Refrigerant | Sealed inside the outdoor unit | Runs through pipes between outdoor and indoor unit |
| Pipes into the house | Water pipes | Refrigerant pipes |
| Who connects it | Installer, some groundwork possible yourself | Refrigerant work only by an F-gas certified engineer |
| Frost risk outside | Yes, insulate water pipes well | Lower, no water outside |
With a monobloc unit the installer has less refrigerant work to do, but the water side and commissioning still require professional knowledge.
Which jobs can you do yourself?
- Choosing and preparing the spot for the outdoor unit
- Laying a base of paving slabs or concrete pads, or fitting a wall bracket
- Drilling penetrations through the outside wall
- Fitting cable trunking or pipe covers
- Preparing a condensate drain, for example a gravel soakaway or a connection to a drain
- Clearing space for the indoor unit or hot water cylinder
What does the installer need to do?
- Connect, evacuate and charge the refrigerant circuit on a split system
- Size the system for your home: output, flow temperature and balancing
- Connect it to the central heating system and the water side of the installation
- Add a dedicated circuit from the consumer unit if the heat pump needs one
- Commission and test the system
If you want to apply for a grant, such as the Boiler Upgrade Scheme, check the current conditions on the government website first. They may include requirements for the installer and the installation.
Where should you put the outdoor unit?
- Noise: do not place the unit under a bedroom window or right next to the neighbours' boundary. Noise limits can apply, so check the sound level of your unit in its specifications and ask your installer how it affects the position.
- Airflow: the unit needs clear space all around it. The minimum clearances are in the installation manual.
- Distance to the indoor unit: the shorter the pipe run indoors, the better.
- Access: the installer must be able to reach it later for servicing.
- Rules: an outdoor unit often counts as permitted development, but different rules can apply to listed buildings, front elevations and conservation areas. Check with your local council.
Which tools do you need for the groundwork?
- A rotary hammer for plug holes for wall brackets and clips
- A diamond core drill for the pipe penetration, in the diameter the installer specifies
- A cordless drill driver for cable trunking and brackets, for example from the Maxxpack 18V range
- A spade, spirit level, rubber mallet and possibly a plate compactor for the base
- A cable and pipe detector
- Dust mask, safety glasses, ear defenders and work gloves
Laying a base or fitting a wall bracket
Stand a ground-mounted outdoor unit on a flat, firm base that will not sink. Dig out the soil, add a layer of compacted sharp sand and lay paving slabs or concrete pads on top. Use a spirit level, because the unit must be level. Keep the unit raised a little above ground level, so there is room for condensate to drain away in snow and frost.
If you hang the unit on the wall, use a bracket rated for the weight of the unit, along with anti-vibration mounts. Fix the bracket into solid masonry or concrete with chemical anchors or heavy-duty fixings as the bracket instructions specify. A cavity wall with a thin outer leaf, aerated concrete blocks or a timber-clad wall is often not suitable. Discuss this with your installer.
Drilling the penetration through the outside wall
- Agree the position and diameter with the installer.
- Use a detector to look for pipes and cables.
- Drill with a diamond core drill sloping slightly down towards the outside, so rainwater cannot run in.
- Use dust extraction or drill wet when core drilling.
- Fit a sleeve and seal the penetration properly against draughts and moisture afterwards.
Draining condensate
The outdoor unit produces condensate when heating, and during defrosting that can be a fair amount of water. Make sure it can drain away, for example into a gravel soakaway or a drain. Water left standing on paving turns into a slippery patch of ice in winter.
Frequently asked questions about preparing a heat pump installation
Can I connect a split heat pump myself?
No. The refrigerant circuit of a split heat pump may only be connected by an engineer with the right F-gas certification. You can do groundwork such as the bracket, penetrations and cable trunking yourself, in agreement with the installer.
How much space does an outdoor unit need?
That depends on the model. The installation manual lists the minimum clearances to walls, fences and other obstacles. Too little space means lower efficiency and more noise.
Does a heat pump need its own circuit?
Often it does, depending on the output and the type. The installer decides this based on the specifications. Always have a new circuit from the consumer unit installed by a qualified electrician.
Can a heat pump hang on a cavity wall?
That depends on the wall and the weight of the unit. The outer leaf of a cavity wall is not always strong enough, and vibration can travel through the wall and be heard indoors. A ground-mounted unit on a solid base is often the quieter choice.
In short: preparing a heat pump installation
A heat pump installation is a job for a certified installer, but you can save time by doing the groundwork yourself. Choose a good spot, lay a level base or fit a suitable bracket, drill the penetration and plan the condensate drain. Agree every step with your installer beforehand.
