ᐅ Hydraulic balancing of the underfloor heating system

Hello forum,

I am about to have my house (new build KFW70) officially handed over and still have some issues with my underfloor heating. I hope you can help shed some light on them.

For testing the underfloor heating system (district heating), I set all the room thermostats (manufacturer Berker) to the maximum setting (scale from 1 to 6). While the house is not cold, it is not as warm as I expected at full power. The temperature seems to vary between rooms. I have ordered a laser thermometer to measure the floor temperature, but it has not been delivered yet.

I opened the manifold boxes on the floors for inspection (see photo). The actuators are all positioned in the return line. The flow rate is controlled by valves in the supply line. However, all valves are set between 0 and 0.5 liters per minute (0-0.5 L/min). I suspect that no hydraulic balancing has been performed.

How can I, as the buyer, properly test the heating system? Which documents and certificates should I request when taking over the house? How is balancing carried out for an underfloor heating system?

Thank you in advance!

I have to ask a counter-question. Is the photo current? I’m not a heating specialist, but in my setup, electrically disconnected actuators would block the heating circuit. That means no heat output would be available.
Can you remove the actuators? That way, at least full flow should be possible.

Perlenmann schrieb:
I have to ask a counter-question. Is this photo recent? I’m not a heating specialist, but in my case, actuator motors that aren’t electrically connected would block the heating circuit. So, there would be no heat output at all.
Can you remove the actuators? Then at least full flow should be available.

No, the photo is not recent. Sorry for the confusion! All the actuators are electrically connected. The picture was meant to provide an overview only.

Perlenmann schrieb:
but in my case, the electrically disconnected actuators would block the heating circuit.

Then they are configured to be normally closed without power! Usually, normally open is also possible.

Best regards.

Hello,

lubu0815 schrieb:
... I ordered a laser thermometer to measure the floor temperature, but the delivery is still pending.

The surface temperature of the floor is completely irrelevant since the room temperature is the target and control parameter.
The supply temperature or surface temperature used to achieve this depends on the sizing of the heating surfaces!

lubu0815 schrieb:
... I suspect that no hydraulic balancing was performed.

The suspicion is fully justified!

lubu0815 schrieb:
... Which documents and proofs can I request during handover?

Heating load calculation including room heat loads according to DIN 12831; if there is a controlled ventilation system: air volume plan according to DIN 1946-6 and commissioning protocol; heating surface sizing according to DIN 1264 (underfloor heating) and hydraulic balancing documentation!

lubu0815 schrieb:
... How is the balancing carried out for an underfloor heating system?

By adjusting the flow rates based on the calculation (heating surface design). Whether the appropriate flow meters were used should be clarified by the building services engineer (TGA planner).
For district heating, there is a transfer station. The energy delivered is measured on the primary side to ensure that transmission losses remain on the supplier side.

Best regards.

€uro schrieb:
Hello,
The surface temperature of the floor heating is completely irrelevant since the room temperature is the target and control variable.
The supply temperature required to achieve this depends on the sizing of the heating surfaces!

OK, thank you. As a non-expert, what options do I have to check if the heating system is functioning correctly?

My Berker room thermostats have a setting range from 1 to 6, which is supposed to correspond to 5-30°C (41-86°F). Currently, the temperature throughout the house is just under 20°C (68°F) when all the controllers are set to 6.
Is there a maximum room temperature that the heating system is supposed to reach?

The builder gave me the heating protocol for the screed because I had doubts about it. From my understanding, the hydraulic balancing should have been carried out before the screed’s functional heating. The supply temperatures now confirmed only seem to have occurred in my basement; the heating circuits were probably hardly warmed due to the partially closed flow restrictors.

Thank you very much for the expert advice!