Last reviewed: by the MVHR Expert engineering team
We repair all major brands and fault-find the whole system, not just the box: ducting, valves, controls, condensate and electrical supply.
Faults we diagnose and repair
- Fans not running, stuck on boost or cutting out
- Rattling, humming, whistling or vibrating units
- Condensate leaks and blocked traps or drains
- Poor or no airflow at valves
- Failed or unresponsive controllers and sensors
- Fault codes and filter-warning lights that won't reset
- Bypass damper and summer bypass faults
- Disconnected, crushed or leaking ductwork
Common symptoms we're called out for
- Unit completely silent or display dead
- Water dripping from the unit or ceiling below
- Loud noise that was not there before
- One room has no airflow at all
- Fresh air feels cold in winter (bypass stuck open)
- Unit constantly on boost or permanently on low
How it works
- Describe the fault. Tell us the symptoms and, if possible, the unit make and any fault code showing.
- Diagnose on site. We test power, fans, controls, bypass, condensate and airflow to find the real cause.
- Quote before work. You get a clear price for the repair before anything is touched.
- Repair & verify. We fix the fault and re-measure airflow so you know the system is performing again.
Why is my MVHR noisy?
Noise usually comes from one of four things: dirty or unbalanced fan impellers, worn fan bearings, loose mounting or duct connections transmitting vibration, or airflow forced through a restricted filter or valve. Whistling at valves often means the airflow is set too high for that terminal.
A deep hum or rattle that has appeared recently is typically a fan imbalance or a loose fixing. A grinding sound suggests bearing wear, and the fan or motor may need replacing.
Why is my MVHR leaking water?
MVHR units produce condensate as warm, humid extract air cools across the heat exchanger. This drains away through a trap and pipe. A dry trap, blocked drain, kinked pipe or unit that is not level will cause water to leak out of the unit and into the space below.
Don't ignore a small drip — it often means the drain is partially blocked and will get worse.
Repair or replace?
Most MVHR faults — fans, controls, filters, condensate and balancing — are repairable at a fraction of replacement cost. If a unit is very old, parts are obsolete or the heat exchanger is damaged, we will say so and discuss replacement, but only after a proper diagnosis.