boiler coupling wood and oil: map and diagram

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Philippe Schutt
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by Philippe Schutt » 12/02/11, 17:57

stoa wrote:2. The 50L is the volume of the heating core. The DHW is still other 140L which are heated in a water bath by the heating core.

So these 140 L participate in the inertia of the fuel system

stoa wrote:4. There should not be a thermosiphon at the insert level. The insert is fitted with the factory prerequisite kit.

Most connection kits do not have a non-return valve. This point is to be checked to be sure because if there is a thermosiphon, the loss would be significant.

stoa wrote:Me, I believe that the pump C gives a too high flow.

In position 1, this should not. Pump references?
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loop
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by loop » 13/02/11, 09:31

Hello everyone,

What I don't like about the existing operating principle is that to be usable, the water in the buffer tank must be at least 70 ° C. As the tank is loaded at 80 ° C, the usable delta T ° is 10 ° C.
I am astonished that nobody has noticed this detail which makes the buffer tank almost useless (at the limit, it must be deleted if you stay in series)

On my installation (which gives me satisfaction), I completely empty the calories from my buffer tank (500L loaded at 60 ° C) in the heating circuit (radiators) at night.
In the early morning the water in the tank is at room temperature (pretty much) and the oil boiler has not tripped.

I would like to know what is the principle of regulation of the heating part. What controls circulator A of the radiator circuit?
Does it run continuously? is the mixing valve at the start of the circuit motorized.
Circulator A is not enough, the good question is why? is it not the passage through the boiler which increases the pressure losses? If it is necessary to add a circulator for circulation in the radiators, this is certainly not where it is placed, but indeed in series with A.

When this part is cleared up, we can move on.
The DHW part is different. There you need a parallel installation with a circulator or dedicated sector valve (maybe there is a circulator integrated in the boiler?).
The operating conditions in DHW mode must be conditioned by a thermostat:
If buffer tank T °> 70 ° C, then the fuel oil boiler and its DHW can be "reheated".
Otherwise the buffer is only used for heating and the oil boiler maintains its temperature, including the DHW tank, with its burner.

A+

Gérald
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by stoa » 13/02/11, 16:03

Hello,

Some answers:

The pump reference C: Altech CPS 180-4. It gives 0.8 m3 / h at speed 1 under 2 bar (2 m in height) = ~ 14 l / min. That would indeed make that 150L will last only 10 min? The difference with pump A is that A at the same flow rate would only take part of the water in the boiler (via 3-way valve), the other part coming from return recycling. When pump C pushes it pushes at 14 l / min, whether there is this valve or not.

Circulator A runs permanently.

The 3-way flow valve is not motorized. I set it manually according to the T outside. It doesn't take a lot of effort. Pump A was not powerful enough to provide circulation in the presence of a balloon. I could try with a more powerful pump A and without pump C. Does that make sense? Do I not risk that when the tank is exhausted that the new pump pushes too fast compared to the oil boiler alone and that I would consume more fuel?

Arthur
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Philippe Schutt
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by Philippe Schutt » 13/02/11, 17:59

A little more than 10 °, because it is 80 ° - (T ° of cut of C). But this is a drawback of series circuits. We can save a bit by cutting C and tilting the valve at 51 °, just before the boiler ignites.
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by stoa » 13/02/11, 19:53

Philippe, I did not understand your last remark.
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loop
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by loop » 13/02/11, 21:59

Good evening,

The difference with pump A is that A at the same flow rate would only take part of the water in the boiler (via 3-way valve), the other part coming from return recycling. When pump C pushes it pushes at 14 l / min, whether there is this valve or not.


And yes, adding a circulator completely unbalances the flow rates upstream and downstream of the mixing valve.
Circulator C makes the sampling flow in the buffer tank too large for the overall thermal balance of the installation.

Circulator A runs permanently.
The 3-way flow valve is not motorized. I adjust it manually according to the T outside


The manual adjustment of the mixing valve OK, I do the same.
On the other hand, the circulator of the radiator circuit should normally stop when the heating need is zero.
Hence my room thermostat in circulator cutout, shown in my diagram. If the drawing is continuous, whether in the boiler or the tank, the calories unnecessarily overheat the ambient air.
It is basic, but with an oil boiler (which keeps its T ° constant) and a buffer tank, it is this mode of regulation which it is necessary to choose.
Now it's up to you whether you want a gas plant or save money on heating.

A+

Gérald
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Philippe Schutt
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by Philippe Schutt » 14/02/11, 15:23

stoa wrote:Philippe, I did not understand your last remark.

Well, the boiler thermostat switches on at 70 ° and switches off at 51 °, just before the boiler turns on. It still has to be adjustable ...

For the regul, it would be necessary to know the rest:
thermostats on all radiators or 1 radiator without?
outdoor probe?
Day-night programming?
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by stoa » 14/02/11, 20:14

Philippe, I still haven't understood what thermostat you are talking about.
Otherwise, there is 1 radiator without thermostats; there is no outdoor sensor or day / night programming.

Arthur
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by loop » 14/02/11, 21:31

Good evening,

Arthur,
Philippe is talking about the thermostat which activates the valve V2 (tank / oil sector) and which starts the circulator C.

I pointed out that because of this thermostat, switching from one heating mode to another is conditioned by a very small temperature difference.
Buffer tank loaded at 80 ° C, as soon as one draws a few calories from it, cooled to 70 ° and there we go back to the oil boiler.
In short, the buffer tank is underused, and moreover it generates much more losses by being hot than lukewarm.

Your radiators have thermostatic valves, it's already more information.

A+

Gérald
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by stoa » 16/02/11, 19:38

Hi,

In fact, I would like to be able to send the water between the buffer tank and the boiler up to 45C, for example. As soon as this water is hotter than the return of the radiators (~ 30C) it should be interesting, no?

Arthur
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