When installing an inverter-driven heat pump, the consumer unit isn’t just a box to hang off the wall - it’s the backbone of compliance. Get it wrong and you risk nuisance trips, inspection failures, or worse, damage to the inverter. This checklist gives professional installers a straight-talking run-through of what to confirm before, during, and after fitting a heat pump consumer unit.
Jump to: Pre-Install Checks | Compliance Requirements | Installation Steps | Post-Install Checklist | Recommended Products | FAQs
Pre-Install Checks
Before you even lift the lid on the board, confirm:
- Load & supply capacity: Verify the incoming supply and DNO approval. Many ASHP/GSHP units draw high start-up current.
- Breaker allocation: Heat pumps typically need a dedicated MCB or RCBO.
- RCD type: Inverter-driven units require Type B RCDs for smooth DC leakage, or high immunity Type A RCBOs if specified.
- Consumer unit space: Ensure the board has enough usable ways for surge, isolator, and any future hybrid additions (battery/PV). See Enclosures & Consumer Units.
Compliance Requirements
Every heat pump board must align with the 18th Edition Amendment 2:
- Surge protection: SPDs are mandatory unless a documented risk assessment rules otherwise. Browse Surge Protection Devices.
- Isolation: Fit an accessible 100A main switch or isolator.
- Earthing & bonding: Confirm compliance with PME/TN-C-S rules. If PME risk exists, a PME fault detection unit may be required.
- Certification: Record disconnection times and protective device ratings in the EIC.
Installation Steps
During install, follow this checklist:
- Mount the enclosure securely (IP-rated if outdoors).
- Fit the main switch/isolator.
- Wire in the heat pump’s dedicated protective device (MCB/RCBO).
- Add SPD as close as possible to incoming supply tails.
- Terminate neutrals/earths clearly, using terminal blocks if required.
- Verify clear labelling for future maintenance.
Post-Install Checklist
Before sign-off:
- Confirm correct tripping of RCD/RCBO devices.
- Test SPD connection (shortest possible earth link).
- Run insulation resistance tests with inverter connected.
- Complete and issue the Electrical Installation Certificate (EIC).
Recommended Products
If you’re fitting a new heat pump, these ready-built options save time on site:
- Heat Pump Consumer Unit – SPD + B Type RCD
- B Type RCD – Heat Pump Compatible
- Surge Protection Devices
FAQs
Installers often have the same compliance questions crop up on site. To save time, here are the most common queries around heat pump consumer units answered clearly and to the point.
Does a heat pump need its own breaker?
Yes. Heat pumps must be on a dedicated circuit, normally protected by a correctly rated MCB or RCBO.
Do heat pump consumer units require surge protection?
Yes, unless a risk assessment proves otherwise. In practice, most installs will include an SPD as standard to comply with the 18th Edition.
Which RCD type is best for a heat pump?
Inverter-driven heat pumps typically need a Type B RCD to detect smooth DC leakage. In some cases, high-immunity Type A RCBOs can also be suitable.
Do I need to upgrade the main consumer unit for a heat pump?
Not always. If your existing board has spare ways, capacity, and SPD/RCD compliance, you may not need an upgrade. Otherwise, a dedicated Heat Pump Consumer Unit is often the cleanest solution.
Are PME fault detection units required with heat pumps?
Not usually - PME fault detection is more common in EV charger installs. But if the heat pump is part of a hybrid system with EV or solar, PME protection may be needed.
Conclusion
Heat pumps are unforgiving on the electrics. By following this installation checklist, you’ll avoid nuisance trips, protect the inverter, and sail through inspection with a board that’s fit for purpose.
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