How to Operate

A – Provide sufficient fresh & filtered air to the occupant’s health & wellbeing.

B –  Extract excessive moisture and polluted air, prevent the build up of pollutants and minimize the risk of mould growth and house dust mite proliferation.

C – Recover heat: Minimising the ventilation heat losses that are associated with other forms of ventilation. These can mount up to over 30% of your heating costs.

(D – For some systems: Provide or supplement heat distribution, space heating or cooling, if this has been explicitly designed to do so)

The system is there for you, to create a healthy indoor climate and to protect the building structure from decay of moisture build-up.

UK MVHR systems have typically two fan speed settings:

– Nominal/ trickle = base ventilation level for the health & wellbeing of the occupants
– Boost: When smells or excessive humidity need to be extracted. This setting sometimes automated with humidity sensors.

European systems are normally operated on four levels:

– Level 1 = reduced: When the dwelling is un-occupied for a couple of hours.
– Level 2 = nominal: Whenever the house is occupied.
– Level 3 = boost level: When smells or excessive humidity need to be extracted. This setting is limited to normally 15 min after pressing a boost switch.
– Away or Un-occupied: holiday mode. The ventilation is operated on the lowest level for 15min. per hour.

MVHR systems are normally commissioned on level 2, as the nominal ventilation level. Level 1 is set at 70% of level 2 and level 3 typically at 130% of level 2. The away mode is often the lowest setting of the fan speeds.

There are two filters in the MVHR unit: One intake filter and one extract filter. Older systems sometimes have a filter in the defroster box. MVHR units have got a timer which counts down for the next filter check.

Better installations have a filter element on the kitchen extract, that protects the ductwork from grease.

All of these filters need to be inspected regularly (every 3 to 6 months) in order to prevent mal-ventilation and increased energy use. If the filters are visibly stained – up to the point that the filter medium is fully covered – they should be exchanged or cleaned. Depending on the pollution levels, filters usually last between 4-12 months. They can be cleaned with a vacuum cleaner once, but need to be exchanged for new ones at least once per year.

The maintenance of the system is mostly low-tech house-keeping and can be done with your annual spring clean:
– Check all filters
– Please remove any dust on your room terminals
– Check your external terminals for dust and blockages.
– Take out the heat exchanger and rinse it in a bath tub with warm water and wash-up liquid. Do not scrub it or poke into it.
– Check if all ducting in cold loft spaces is still properly covered by loft insulation.

Please refer to the user manual for your MVHR unit for more information.
If you don’t want to engage in such work yourself, please arrange for a maintenance contract with PAUL Heat Recovery or another provider.

At least every 4 years the system should be serviced by an MVHR technician. Contact us or look at our webpage for service partners in your area.

Yes, that is possible with active charcoal filters, which bind organic particles. They need to be replaced in regular intervals when the active medium is used up. Most of them last for one year.

If you have a Zehnder ComfoAir Q MVHR, you are lucky, as there are active charcoal filters available for the air intake. Otherwise charcoal filters can be installed in a filter box in the supply air duct run. These can sometimes be retrofitted, if there is enough space for them available.

As part of the heat recovery process, condensation will fall out within the heat exchanger and is drained away through the condensate connection. The higher the heat recovery rate ans the greater the temperature difference between inside and outside, the more condensation will appear.

If accidentally water leaks out of the housing, please check following things:

1. The MVHR unit is not straight (sideways and back to front). It should rather tilt backwards, than forward.
2. The heat exchanger of Paul units has a plastic tray underneath with two holes on one side. The holes should face towards the same side as the condensate connection.
3. Please also check that the dry-trap is not blocked.

The myth that all windows need to be kept close with MVHR system stems from the operation of air conditioning systems, which actively (electrically) heat or cool with re-cycling of air. With each air cycle heat or cold is introduced. The opening of windows breaks this cycle and renders the system useless, whilst all the kWh’s of energy used for heating or cooling are being lost.

MVHR operates in a completely different way, as the air is not re-cycled and is heated or cooled passively, without heating or cooling elements (unless a post heater is installed).
So, feel free to open windows and doors. In summer you can then turn down the MVHR. In the cold time of the year, you will want to limit the opening of windows to retain the heat inside.

Again this myth originates from some of the experiences with air conditioning systems, which had not been maintained properly. As air conditioning is based on the (re-)cycling of air, bacteria that are being picked up can be distributed around. Also it is important to clean A/C systems and change filters regularly, to avoid the germination & growth of mould, harmful bacteria and pathogens inside the system, as these will be re-introduced into the building.

MVHR in contrast does not re-cycle air. In high-quality systems, all contaminated extract air is completely exhausted and is not in contact with the fresh air which is being supplied to the house. Thus it helps creating a healthy environment.