ᐅ How often should the heating circuit be refilled in a new building with underfloor heating?

Created on: 18 Sep 2019 10:53
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Vega82
Hello everyone,
how often nowadays does water need to be refilled in a new building (built in 2016) with underfloor heating?
We have a Viessmann gas boiler and about 140m² (1507 ft²) of heated area.

Currently, I need to refill water about once a year because the pressure drops from 1.5 bar to around 0.9 bar. The underfloor heating only runs about 7.5 of 12 months, and the rest of the time only hot water is produced.

In your experience, is this still within a normal range, or should I start to be concerned?
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Müllerin
26 Sep 2019 13:06
?? Five people have said that it is not normal to have to refill a floor heating system so often and with so much water.
What would you like to hear?
If your heating technician says everything is fine, then that’s great.
I find it strange.
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Michlhausbauaa
26 Sep 2019 14:01
Heating circuit – it is a closed loop after all – just think about it yourself
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Joedreck
26 Sep 2019 17:39
The best-case scenario would be a broken or undersized expansion vessel.

The worst-case scenario would be a defect in the underfloor heating system.

A middle ground would be a leaking safety valve.
tomtom7926 Sep 2019 17:41
As a plumber, I would also say that everything is fine if it would be expensive to locate and fix the leak.
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Domski
26 Sep 2019 19:38
In my opinion, such a significant drop in pressure is not normal. We used to experience something similar in gravity-fed heating systems when the open expansion tank in the attic eventually emptied due to evaporation.
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Vega82
29 Sep 2019 08:01
The expansion vessel inside the unit has a Schrader valve, and pressure is probably lost through it. With a capacity of 12 liters (3.2 gallons), even a small loss of a few milliliters is noticeable. As far as I can tell, the vessel is airtight. Otherwise, everything in the boiler is dry and sealed.

The automatic air vent was slightly open, so some loss could have occurred there as well.

I have now added around 500 to 1000 milliliters (17 to 34 fluid ounces) and increased the pressure from 0.8 to 1.8 bar.