HIU Repair London
HIU repair in London covers no hot water and no heating faults in flats on communal or district heating. We test the plate heat exchanger, PICV, actuators, sensors, strainers and controls, then fix the root cause.
Commercial rate: £75+VAT per half hour, minimum 1-hour charge
No hot water in your flat? Common HIU causes
Most “no hot water flat HIU” calls trace back to a handful of faults. A blocked primary strainer starves the unit of flow; a scaled or fouled domestic hot water plate heat exchanger cannot transfer enough heat; a failed flow switch or sensor means the unit never calls for heat; or the actuator on the control valve has stuck.
Sometimes the unit is healthy and the problem is upstream: low differential pressure on the primary circuit, a closed isolating valve in the riser, or network flow temperatures that have dropped. We check both sides before recommending parts.
- Blocked or partly blocked primary strainers
- Scaled or fouled plate heat exchangers
- Failed actuators, motorised valves or PICV heads
- Faulty flow switches, temperature sensors and controllers
- Secondary circuit pressure loss, expansion vessel and pump faults
No heating or poor heating from the HIU
On the space-heating side we look at the secondary circuit pressure, the heating plate heat exchanger, the pump, the expansion vessel, the room thermostat or programmer and any zone valves. Air in the secondary system and low pressure are common after radiator work or a leak.
How a repair visit works
We record the unit make and model, primary and secondary temperatures and pressures, and the condition of strainers and valves. You get a clear written note of what we found, what we fixed and anything that needs a follow-up visit or a part order. Parts are quoted before fitting.
Common Questions
Why do I have heating but no hot water from my HIU?
Usually the domestic hot water side of the unit is at fault: a scaled hot water plate heat exchanger, a failed flow switch or sensor, or a stuck diverting or control valve. The primary strainer can also be partly blocked.
Can a blocked strainer stop my HIU working?
Yes. A blocked primary strainer reduces flow from the communal network, so the unit cannot deliver enough heat for hot water or heating. Cleaning it is a routine part of a repair or service visit.
Is a no hot water fault my responsibility or the building’s?
It depends on your lease and the heat supply agreement. We can attend on behalf of the managing agent, the heat network operator or the resident, and our report shows whether the fault is in the flat or on the network.
How much does an HIU repair cost?
Labour is charged at £75+VAT per half hour, minimum 1-hour charge. Any parts are quoted before fitting.
