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Heat pumps · Error codes · Worcester Bosch
H7Worcester Bosch · Bosch Compress 2000 AWF (R32 all-in-one monobloc)

H7 on a Worcester Bosch Bosch Compress 2000 AWF: Alarm table: Abnormal power supply voltage / Troubleshooting table: Main circuit voltage fault

Short answer

On a Worcester Bosch heat pump, H7 means: Alarm table: Abnormal power supply voltage / Troubleshooting table: Main circuit voltage fault. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.

Reviewed 23 September 2026 · 1 source

What it means

The manual says: Alarm table: Abnormal power supply voltage / Troubleshooting table: Main circuit voltage fault.

Part involved: supply voltage.

When it shows: Abnormal power supply voltage.

Likely causes:

  • Supply outside range; unit switched on/off repeatedly at short intervals (keep off at least 3 minutes); faulty main control board circuit.

Is it safe?

Switch the heat pump off at its isolator and call an engineer.

Does the heat pump stop?Yes
SeverityFault — clears by itself when the condition goes
Engineer needed?Yes

The heat pump stops until the fault clears or is reset.

Resetting itself: yes.

Manual reset: Manual 13.2: switch the unit off and on again to reset the safety device; if reset fails contact dealer. Manual 11.4 warns repeated resets can cause irreversible damage.

What you can check

  • Read and note the full code (and sub-code) shown on the controller and pass it to your installer.
  • Check the heat pump isolator and consumer-unit breaker(s) are switched on; if a breaker has tripped more than once, leave it off and call an engineer.
  • Manual 13.2: one off/on restart may be tried; if the code returns, stop and call an engineer - repeated resets can damage the unit.

What the engineer will check

  • Measure supply voltage; replace main PCB if faulty.

Who to ask for: heat pump installer / electrician.

Certification: Electrical work to BS 7671 by competent person.

What you might notice

What owners and engineers report

1 owner and engineer report mentions this.

  • Heat pump will not start on the Bosch Compress 2000 AWF (R32 all-in-one monobloc): 1 report

Sources

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026