Servicing, filters and repairs for Zehnder ComfoAir MVHR units, from the ComfoAir Q range to older models. Full service from £149, across Bristol, Bath and the South West.
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ZEHNDER COMFOAIR
ComfoAir is Zehnder’s range of MVHR units, often found in eco builds, Passivhaus-style homes and high-spec renovations. Like any MVHR unit, it extracts stale, moist air, recovers its heat, and supplies filtered fresh air.
We service and repair all models, including the ComfoAir Q range (Q350, Q450 and Q600) and older ComfoAir units. They’re built to run efficiently for years, but only if the filters are changed on time and the airflow is set correctly.
Based on Zehnder’s ComfoAir Q user manual. Older models and controls may behave differently, so check your own manual too.
An alert, such as filters due or maintenance mode. Check the display for the message.
An error. Clear it from the menu, wait two minutes, and call us if it comes back.
Both filters are due. Zehnder says to replace them at least every six months.
Fresh air is going around the heat exchanger to help keep your home cool. Normal, not a fault.
In very cold weather the unit reduces supply airflow so the heat exchanger doesn’t freeze. Normal in a cold snap.
Boost runs the highest airflow for a set time. Away runs the lowest until you’re back.
Source: Zehnder ComfoAir Q user manual (Zehnder America edition). View the manual (PDF)
What Zehnder’s manual recommends, and how we fit around it.
Same fixed prices for every make, confirmed before we arrive.
£149
Deep clean, new filters, airflow tested and rebalanced in every room, photo report. 90–120 min.
£80
Full diagnosis, duct and airflow checks, PCB testing, written repair quote.
£200
Room-by-room measurements, balancing and a commissioning certificate.
What customers say after a Ventfix visit.
We service all makes and models, including








A slow flash (about once a second) is an alert, such as filters due or maintenance mode. A fast flash (about four times a second) is an error.
Clear the error from the menu and wait two minutes. If it comes back, note the error code and call us to book a fault-finding visit.
Zehnder says to replace both filters at least every six months, and to refit the covers so they seal properly.
Zehnder recommends a maintenance contract with a ventilation specialist, with a full inspection and clean at least every four years. We service ComfoAir units annually, so filters, airflow and drainage are checked every year.
It sends fresh air around the heat exchanger so it isn’t pre-warmed, useful on warm evenings. It’s normal, not a fault.
Yes, including the ComfoAir Q range and older ComfoAir units.
Ventfix is an independent MVHR specialist and is not affiliated with or endorsed by Zehnder. Brand names are trademarks of their respective owners.
Fixed price, all ComfoAir models, photo report after every visit.
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