Lowering t ° at night with underfloor heating: useful or not?

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logredudon
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Lowering t ° at night with underfloor heating: useful or not?




by logredudon » 08/09/10, 13:16

Hello,

I have a pellet boiler with 2 heating circuits.

Ground floor: underfloor heating (set at 20 ° C during the day, 18 ° C at night)
attic: radiators (regulated 19 ° C during the day, 17 ° C at night).



My former heating engineer (and installer) has just retired.

The new one, who just did the maintenance, checking my settings, told me that for the underfloor heating part, you shouldn't lower the temperature at night because it was not at all economical.
For him, the amount of granules used to warm the slab in the morning after lowering at night is greater than the amount used by keeping the temperature constant throughout the day.

Is it true or not? What should I do ?

Goods.
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tigrou_838
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heating at night




by tigrou_838 » 08/09/10, 13:47

Hello,

I can't answer your question, but share my experience with you.

on my floor heating with buffer tank heated by the sun, the heating thermostat is always set to 18,5 day and night, this allows to maintain a house temperature without temperature difference between day and night which for me and my low reserve of heat will make too much consumption of hot calories in the morning (when the day program is started).

for you it's different since you can just press a button to raise your temperature by a few degrees.

the best of one or the other, I don't know, maybe the heating professionals will answer you more clearly.

tigrou
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by dedeleco » 08/09/10, 14:42

It all depends on the thermal constant of the house and the heating, ie the time it takes for the house to cool down after the heating stops.
If very short one or two hours (unlikely for a slab), we certainly save !!
So long one or more days you save nothing !!
But theoretically we don't lose much, since the house does not cool quickly.
We can lose the heating energy of the boiler, but there is something to discuss endlessly !!

Instead of believing the assertions, mine and that of the new heating engineer, measure the consumption of pellets, with a little more difference in temperature, 15 to 20 ° C, in very cold weather. !!
In my opinion, the difference should be small !!

In any case, with long absence, weeks, reducing the heating sharply, is a huge saving, I had personal experience at home !! Basic common sense.
So as soon as the absence is much greater than the characteristic cooling time of the house, we gain a lot !!
http://fr.wikipedia.org/wiki/Constante_de_temps
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Re: lowering t ° at night with underfloor heating: useful or




by dirk pitt » 08/09/10, 14:43

logredudon wrote:For him, the amount of granules used to warm the slab in the morning after lowering at night is greater than the amount used by keeping the temperature constant throughout the day.

Is it true or not? What should I do ?
.


it can't be.
any reduction in temperature is a NET gain in energy, the energy expended being a function of the temperature difference between the interior and the exterior. The two diagrams below are fairly clear.

on the other hand there can be inconveniences of comfort due to the inertia and to the maximum "flow" of energy supplied by the boiler to return to the comfort temperature.
also drawbacks induced on the disturbance of the regulation during the rise in temperature.
it is therefore necessary to carry out tests in order to determine both the judicious lowering schedules and the lowering value. for a heated floor, a room setting lower by 2 to 3 ° maximum is recommended.

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by dirk pitt » 08/09/10, 14:46

dedeleco wrote:It all depends on the thermal constant of the house and the heating, ie the time it takes for the house to cool down after the heating stops.
So very short one or two hours (unlikely for a slab), we certainly save!!
So long one or more days you save nothing !!
...

.....
In any case, with long absence, weeks, reduce heating strongly, is a huge economy, I had personal experience at home !! Basic common sense.


I do not understand very well :?: :?: :?:
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by chatelot16 » 08/09/10, 14:47

lowering the heating at night is only useful if it lowers the room temperature, so decreases all heat loss by insulating the walls and roof

but the underfloor heating has a big inertia: therefore the temperature variation of the room will be very small, therefore derisory economy

and if in addition it causes the regulation to go wrong, and then go higher in temperature, profit = loss
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by logredudon » 08/09/10, 20:08

So, chatelot16, if I understood you correctly, you advise me not to do a lowering at night, is that correct?
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by dirk pitt » 08/09/10, 21:14

but if!
the lowering saves energy but it is necessary to test the limits of the system by going slowly and by failing the adequate hours.
start by setting a setpoint of 2 ° lower than the comfort value and anticipate the triggering by 2 hours to start and refine as you go.
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by dedeleco » 08/09/10, 21:50

Measure and trace the dirk pitt curve, interior T, exterior T, setpoint T, and measure the consumption of pellets, as a function of time!
Only way to know !!
The dirk pitt curve, in demo, shows a response time of 3 to 4 hours, but a massive slab with house can have a lot more, one day and then almost more variation on this curve !!!!
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by sspid14 » 09/09/10, 00:46

I agree with dirk pitt .. Energy consumption is a function of the difference in temperature between the outside and the inside. So lowering the temperature at night is economical!
In addition, a boiler has a better performance when it runs as long as possible (that is to say in the morning when it warms up). And in the evening it stops entirely.
As here the inertia is great, it is necessary to lower the temperature earlier than expected (one hour before going to sleep for example) and to make it rise also faster (one hour before waking up for example).

PS for septic tanks: we must compare this case with a bucket of water pierced in the bottom. If the level is above and it is constantly filled to the bottom, the pressure is high and the water flows quickly (max flow). If "at night" we wait a little for the bucket to empty and then we constantly fill it halfway, the flow will be less. "In the morning", it is then possible to refill the bucket with the water saved when we waited for the bucket to empty halfway and the gain (saving) will be at the level of the lower flow rate due to a pressure less !!
(hoping that there is no more "???" after that ...)
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