Flexit SL4R filters

We supply filter sets for Flexit's most widely used residential lines — Nordic S2/S3, S4 and CL2/CL3/CL4, UNI 2, UNI 3 and UNI 4, Econordic W4/WH4 and SL4R — common across Norway and the other Nordic countries. For Nordic and UNI units you can choose between Flexit originals and our house brand. The model designation is usually printed on the label on the front panel.

Our house brand Flexit sets are F7+F7 — a fine F7 (ePM1) filter on both the supply and extract side — and the Econordic W4/WH4 and SL4R originals are F7+F7 as well. That protects the heat exchanger and gives strong filtration of fine dust and pollen in the incoming air.

Yes, we handle bulk orders for:

• Owners' associations and apartment buildings
• Property managers looking after several buildings
• Landlords with multiple Flexit installations

Volume pricing applies above four filter sets, and a valid VAT identification number gives 0% VAT at checkout with invoices e-mailed automatically. Send us your unit models and quantities and we can put together a consolidated order and delivery schedule.

More than most people expect, though not in a way you can put a single figure on. Two things happen as the filter loads. The fan has to work against a higher pressure drop, so in a unit that holds a constant air flow it simply draws more electricity, continuously, all year. And if the unit cannot compensate, the air flow falls below what the house was designed around, so less warm extract air passes through the heat exchanger and the recovery you paid for delivers less. In a tightly built house where the ventilation unit is the main route for fresh air, keeping to the filter interval is one of the cheapest ways to protect the efficiency the building was designed for.

Flexit's heat exchangers are optimised for sub-zero climates, and units often run at higher, more consistent airflow through cold months to maintain heat recovery efficiency. That steadier airflow can mean filters reach saturation a little sooner than in milder seasons, so a mid-winter check is worthwhile.

No, standard filters are fine. The F7 filter media in our Flexit sets handles the temperature and humidity swings of Nordic installations, so no special low-temperature filter is needed. What matters more is checking the filters a little earlier in winter, when higher sustained airflow can bring the change forward.