Question about heat demand determination and flow temperature

  • Erstellt am 2016-05-16 17:56:14

tecker2010

2016-05-16 17:56:14
  • #1
Hi,

we will start construction soon and regarding the underfloor heating and supply temperature I received a note from an expert and wanted to ask for your opinion here.

A brief profile of the house: city villa 152 sqm with underfloor heating, 30 cm Ytong exterior walls, 3 solar collectors and heating via gas boiler.

The said expert suggested that we should have the underfloor heating laid more densely throughout the entire house and thus design it for lower supply temperatures (35° instead of 40°). Initially, there are additional costs for the effort and material, but in the long term you save money because the gas boiler has to reach a lower temperature and therefore needs less heating. The costs are apparently recovered after a few years. In addition, this does not preclude a later switch to an alternative heating system (heat pump, etc.) since these probably cannot achieve the required 40°, and you never know what other affordable alternatives to gas may exist in the future.

This sounded logical to me as a layman at first. What is your opinion?

Regards
 

nordanney

2016-05-17 09:48:51
  • #2
Always operate with as low a flow temperature as possible. Closer spacing should be a minor cost. Flow temperature with us (with heat pump) in winter has not exceeded 28 degrees in the last two years.
 

Mycraft

2016-05-17 09:57:33
  • #3
whereas for the gas boiler it is relatively indifferent whether it is 35 or 40... nevertheless, I would also design it as low as possible.
 

tecker2010

2016-05-17 10:32:52
  • #4
Ok, thanks. That's what I wanted to hear :) Then I will have it interpreted accordingly.
 

krussi

2016-06-13 20:36:07
  • #5
Since there is already such a post, I will continue here.

We are also facing the choice whether the underfloor heating should be installed at a distance of 15-20cm or 10-15cm, additional costs for the closer spacing amount to €640 /net.
House data: 117m² minus utility room, 107m² living area to be equipped with underfloor heating, sand-lime exterior walls + clinker brick (approx. 45cm total thickness), 3 solar panels, 300L hot water storage, the gas condensing boiler (model ?) comes from Vaillant.

According to calculation, the following data apply for closer spacing:
38.2° C supply temperature
31.2° C average return temperature
6062 watts total heat load
5882 watts underfloor heating output
1143m pipe length
13 heating circuits

Since this is all Greek to me and the advice from the plumbing company is inconclusive, except "both can be done," I am asking here whether it makes sense to lay the heating loops closer together or if I should save the extra cost and have the regular spacing (15-20cm) installed?

Unfortunately, I do not have the data for the standard installation spacing.
 

Sebastian79

2016-06-13 20:44:23
  • #6
I find the pipe length quite high for the small area - we have a laying distance of 10-15cm depending on the room and laid just under 1300 - with 22 or 23 heating circuits and around 240m2 heated area...
 

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