Heating
Installing and balancing water-based underfloor heating
From laying the loops to balancing the circuits at the manifold
Water-based underfloor heating is low-temperature heating that is perfectly suited to heat pumps. A well-functioning system requires both correctly laid loops and subsequent balancing so each circuit gets the right flow. The guide covers planning, laying, pressure testing before casting and balancing with flow meters.
Plan circuits and c/c spacing
Size according to the room's heat loss. With 16 mm pipe and c/c 200 mm, allow approx. 5 m of pipe per m² as a guide. Max. flow temperature is 45 °C (BR18 / DS 469); with a heat pump, max. 40 °C is recommended to keep the SCOP high. Average floor surface max. approx. 27 °C.
Material consumption~5 m/m² (16 mm, c/c 200)Max. flow temperature45 °C (40 °C with heat pump)Floor surface, avg.~27 °CLay the loops with equal circuit lengths
Lay the pipes according to the drawing and keep the circuits on the same manifold roughly equal in length, so the water is distributed evenly. For 16 mm pipe, a guideline maximum of approx. 100 m per circuit applies — circuits that are too long cause excessive pressure loss and uneven heating. Verify against manufacturer data.
Max. circuit length16 mm: ~100 m (guideline)Mount the manifold cabinet and connect circuits
Mount the manifold and connect flow and return for each circuit. Ensure the correct direction of fall and air separation, so the system can be bled. Max. differential pressure across the manifold is a guideline of approx. 20 kPa (0.2 bar).
Max. differential pressure~20 kPa (guideline)Pressure test before casting
Pressure test the circuits BEFORE the floor is cast or screeded, and document it in a record. Damage or leaks must be found while the pipes are accessible — after casting, a fault is very expensive to put right.
Cast, dry out and run the heating curve
After screeding, the floor must dry and be brought up to temperature following a controlled heating-up curve before the floor covering is laid. Check the floor surface temperature once the floor is dry so that the comfort and floor covering limits are met.
Set the flow on each circuit
When balancing, each circuit is set to the calculated flow rate using the flow meters on the manifold. Most circuits are, as a guideline, between 0.8 and 1.5 l/min; if a circuit falls below approx. 0.5 l/min, it must be turned up or the circuit split. Circuits on the same manifold should have equal flow relative to their length.
Flow per circuit~0.8–1.5 l/min (guideline)Minimum~0.5 l/minCheck ΔT across the circuits
Check the temperature difference between flow and return on each circuit. A practical rule of thumb is a ΔT of approx. 5–10 °C: if the difference is smaller, the flow can be reduced; if it is larger, the flow must be increased. The aim is an even floor temperature without cold and warm zones.
ΔT (guideline)~5–10 °C per circuitHand over with heating instructions
Complete the QA form and hand over the system with instructions on the heating curve and operation. Note that loop lengths and c/c spacings are design/manufacturer rules of thumb — the final sizing follows the manufacturer's calculation tool and DS 469 / EN 1264.
Circuits on the same manifold should be of roughly equal length — large differences create cold and warm zones.
Source
Based on the worktree article «Underfloor heating» + the template «Checklist: water-based underfloor heating» (DS 469:2013 / DS/EN 1264, temperature and material figures) and evb.dk and handyhand.dk on balancing (flow per circuit, ΔT) — balancing figures are indicative.