Reduced mode problem with gray TEM and Okofen

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Bedouin
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Reduced mode problem with gray TEM and Okofen




by Bedouin » 22/01/10, 22:13

Hi,

I open a new subject although I had already covered the question on the long thread of the monitoring of the operation of the Okofen pellet boiler.

One of the forumthem described exactly the same behavior.

In reduced mode, the boiler continues to heat even if the interior temperature is 21C and the setpoint in reduced mode requires 18C.

I even noted and informed Okofen that according to the settings, in reduced mode everything is stopped (circulators and boiler) on the other hand the V3V of the 2 zones continue to be actuated by the regulation to try in vain to reach the calculated flow temperature according to the slope and the base of the curve with 18C as setpoint.
Suddenly the V3V are always working, it does not seem normal to me.

However, the documentation clearly states that if the reduced mode is active, the circulators work.

other forumthey have their boiler almost stopped all night.

??
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by dirk pitt » 23/01/10, 09:19

First, two things must be distinguished:
regulation with its actions on the V3V and the circulator on the one hand and the boiler on the other.
I already mentioned that the fact that the boiler (the burner) works or not is not directly related to what the regulation requires.

for regulation, since it is it which manages the lowering function (reduced), its purpose is to obtain the required ambient temp (reduced or comfort) depending on the case it may or may not completely cut off the hot water supply to the circuit of heating.
it will depend if the heating limit conditions have been reached.
if the limits are not reached, the regulation simply lowers the water flow temperature according to the new setpoint.

there are two limits that can be reached:
the outside temperature limit (param 3-4) and the flow temperature limit.
the departure temp limit is only reached if the TD calculated according to the water law becomes so low that it falls below the limit T setpoint amb + 2x (1 + slope).
Unless you have a very low curve foot, I think this limit is rarely reached.

the outdoor temp limit, depending on what value it was set to, is more likely to be reached. with the factory setting of -5 °, it is even reached all night very often which means that there is no heating AT ALL, that is to say that the reduced ambient temp is not respected.
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by Bedouin » 23/01/10, 11:42

Hello Dirk,

I have 2 zones and the water laws are respectively 0.5 / 25 and 0.4 / 24
My (3-4) is at + 3C and (3-6) at 2.
At the moment it freezes first so we are always below (3-4) so ​​the lowering mode applies.

When I display the TD calculated by the regulator in lowering mode, it sometimes displays a bizzare value, namely 7.2 which in fact corresponds to the value of the compensation ..... but it is as if this value does not was not added or removed from the initial calculated TD ...... a bug in fact.

On the other hand if I go back for the 2nd circuit the law of water to 0.5 / 25 instead of 0.4 / 24 all the calculations become correct again cad in accordance with the formulas given by the doc of the TEM.

I had never noticed it before because I was not monitoring the boiler in reduced mode.
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by manet42 » 23/01/10, 12:02

The reduction:
-The reduced mode does not seem to work with compensation at 0. Okofen fault ......
False algorithm:
T. dep = T base + slope (15-T.ext) + T. amb.cons. - 20 °. (1)
Instead of :
T.dep = T.base + slope (15-T.ext.) + (1 + slope) x (T.amb.cons.-20 °). (2). Gray regulation already insufficient. In average T., 5 ° drop T. dep. for 1 ° less in the atmosphere
Example, for a reduction from 20 ° to 18 °, formula 2 gives TD = 36,4 °; 1 gives 38 °. While it should be 40 ° -10 = 30 °. (It is written, 5 ° change at the start gives 1 ° difference in the atmosphere, roughly) To have 18 ° you have to ask for 10 °? TD = 30 ° on the white regulation.
Mode reduced to 16 ° without interruption (hysteresis at 7), at 4:19 in the morning, 6 ° 12; at 19 o'clock still 2 ° 4. The TD dropped by 20 ° (0,8 ° -12 °). Return to comfort around 19 p.m .: 6 ° 22 to XNUMX p.m.
Auto mode, reduced to 14 ° without cut-off (hysteresis at 7): 18 ° 6 to 9H; TD decreased by 6 ° (20 ° -1,2 °).
Auto mode, reduced to 18 ° 5 without interruption, practically no change on T. amb.
Auto mode, reduced to 18 ° 5 with cut off of the circulator (hysteresis at 1 °), T. decreases until 17 ° 5 (3 / 4H in the morning), then, long ascent .... 19 ° at 8H; 19 ° 4 at 11H.
Here are calculations. The mini tD is 20 ° at home

https://www.econologie.info/share/partag ... wKggod.xls

JC
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by dirk pitt » 23/01/10, 12:27

excuse me manet42, it may be clear to you but in everything you just wrote, I didn't understand anything.
we don’t know if you’re talking about TEM, white regul, or both.
same for the excel sheet. I did not understand what she is referring to.

bedoin, i'll check on mine if it does too. I never noticed it.
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by manet42 » 23/01/10, 13:38

Well, here, my pedagogy is to review ...
I calculated the starting T. for different room setpoints, in 3 cases:
-1) With the rule of 5 ° of variation for 1 ° of difference of environment as said in the doc Okofen for average temperatures.
-2) When using Pelletronic plus (white) (formula 1).
-3) In the case where TEM is used (formula 2).
This is the table xls, to show that the two rules do not lower the T enough. The worst is the white one.
The examples given in the message are the tests carried out on my installation to obtain the desired reduction with the white regulator.
Either by "tweaking" so that the heating circulator; not be cut.
Either by doing as I usually do (no heating. At night, down to -1 ° set point).
Here, I hope to have been clearer.

Kind regards.

JC
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by manet42 » 23/01/10, 19:04

I will put it differently with a concrete case.
Currently, it is 20 ° in the house (in accordance with the instructions) and TD = 40 °.
I want a reduced to 18 ° 5, for this the TD must decrease by about 7 ° 5 or 32 ° 5. (5 ° rule).
With my white Pellematic, to have 32 ° 5 in TD, I need 12 ° in reduced setpoint. I checked, it works within a "hair".
By calculation, with TEM it would be necessary to program 15 ° 8 for the same reduction.

JC
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by dirk pitt » 23/01/10, 19:43

the 5 ° rule is absolutely not a golden rule but an indicative value when there is no motorized valve and no external probe (old fashioned)

TEM regulates me a correct reduction

I don't have the white regulator but several people have indeed noticed the "bug" in the formula which does not take into account the slope, so the reduction is not important enough.
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by Bedouin » 24/01/10, 20:06

Hi,

The problem occurs when:

- compensation = 0
- early evening, the temperature is balanced and reaches 21C.
- The lowering limit temperature is + 5C
- outside temperature around 0.

When switching to reduced mode:

- The controller calculates the new TD for the reduced mode
- As this temperature is higher than the heating limit and the lowering mode is active, the regulation switches on the circulators and controls the 3-way valves to reach the calculated TD. At this point, the floor is warm and the water flowing through it is warmer than the new TD.

If the compensation was 4 for example, the calculated and compensated TD would be lower than the heating limit and therefore the heating at this temperature does not bring to the building. In this case the circulators and the V3V are cut.
The problems I have seen are when the TDs are close to these limits. The regulation sometimes loses the pedals.
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by Bedouin » 25/01/10, 23:06

Here is a small spreadsheet that takes up most of the gray TEM formula. You can change your parameters and then inform the temperatures of the boiler, tank, room and outdoor sensors.

So you can clearly see the problem I am describing.

https://www.econologie.info/share/partag ... CTIj3G.xls
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