V3V and boiler temperature

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bnohit77
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V3V and boiler temperature




by bnohit77 » 14/11/17, 11:07

Hello,

I notice a phenomenon that seems quite illogical to me with my heating installation.
I have a pellet boiler with two V3V (control of a PC for circuit 1, and low temperature radiators for circuit 2).

When my V3V close, the temperature of my boiler decreases and vice versa, when they open the temperature of my boiler increases : Shock: ?

If I understood correctly the V3V when opening sends hot water from the boiler to the heating circuit ... the calories lost at the level of the boiler should therefore cause a decrease in its temperature and not the reverse. .. or I'm wrong : roll: ?

Is there not an inversion somewhere? (in the montage?).

Thank you in advance for your advice.
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dirk pitt
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Re: V3V and boiler temperature




by dirk pitt » 14/11/17, 16:01

it is quite possible that there is an assembly error.
the V3V is a mixer which introduces a variable part of the return water (warm) in the starting water (hot). this is the most common assembly.
but one can mount a V3V in discharge or in distribution. everything depends on whether you want to regulate the temperature or the flow and on which branch of the circuit it is located.
a small diagram or a photo would help better understand.
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Re: V3V and boiler temperature




by Christophe » 14/11/17, 16:16

+1 a diagram should help us to help you ...

On a well-designed installation there is a hot loop at the level of the boiler so that the return to the boiler limits condensation and fouling of the heating body, this is especially true in wood heating ... which is your case.

Uh how long has the installation been running?
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bnohit77
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Re: V3V and boiler temperature




by bnohit77 » 27/11/17, 21:59

Hello,

first of all thank you for your answers :) It’s really cool to find nice people here willing to help 8)

After a closer observation of the cycles of my boiler I think that there is not really an anomaly. In fact, the overall temperature of the boiler takes a certain time to fluctuate ... By noting this latency time, I had imagined - I believe - a bad assembly of the 3V valves (we see the evil everywhere sometimes : Twisted: ).

As soon as the boiler opens the valve (and this valve goes "mechanically" into the red at this time), the temperature of the heating circuit1 increases ... On the other hand, the overall temperature of the boiler for its part does not move .
This temperature begins to drop when the V3V is fully open, and, where it begins to close.
It then stabilizes around 59-60 ° C, then starts to rise slowly; the V3V opens again and so on ...

In short, I don't think there is really an anomaly.
FYI, my system has been in place for 5 years soon, but I had never fully observed the complete cycles of my boiler. I have been tweaking my settings lately, and I have taken the time to observe things more. Since then, by reading your very interesting interesting posts, I think I have learned a lot (and it is not finished I think :D ).
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Re: V3V and boiler temperature




by dirk pitt » 28/11/17, 15:14

what you describe is typical of a bad adjustment of the regulation of the V3V.
it should not oscillate but open to the desired percentage then only make small adjustments to guarantee a constant temperature of the heating circuit (downstream.)
pumping as you describe it is not favorable in terms of valve wear, consumption and lifetime of the pellet boiler which turns ON / OFF quite often under these conditions when it is not not planned for that.
you will find on the forum hundreds of pages of these problems.
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bnohit77
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Re: V3V and boiler temperature




by bnohit77 » 29/11/17, 15:08

Hello,

Thank you dirk pitt for these details! 8)

But suddenly, that does not reassure me too much. However, I did not say that my boiler was ON / OFF; the V3V modulates certainly, but it does not systematically pass through the position 0 (fully closed) and 10 (fully open). It modulates more or less according to the requests of my Pelletronic plus regulation.

My operating cycles are currently 73min (average over 5 years), which is pretty honorable I think : roll:
During a comfortable heating period over 6 hours in the morning, and over 6 hours at the end of the day on the underfloor heating (with in addition in the evening, radiators and DHW circuit), the boiler will do between 6-8 starts over 24 hours with the current temperatures ( 8-10 ° C during the day and 0-4 ° C at night).

I settled properly (well, I think : Cry: :!: ) my temperatures (max boiler, pump limit, nominal temp etc ...) according to the long discussions and experiences of this forum, and then refining according to my installation. I adjusted my heating curves as well as the speed and timing of the V3V (opening / pause time) to avoid as much as doing this little, the descent of the boiler below 58 ° C at the start of the heating cycle (in particular when the water circuit returns from the PC and the radiators are cold, which causes the circulators to stop).

That said, in your opinion my V3V could gain more stability? I am a taker in any case : Wink: But on what (s) other parameter (s) can I play?
I admit that I am very attentive to improve the performance of my installation.

I think I understood some things thanks to this forum and other discussions that I have read here and there, but many small details are still very obscure despite everything : Oops: . The operation of a pellet boiler is both simple, but can quickly become complex as the ideal combustion equation remains difficult to balance.

Hoping not to overshoot the initial thread, thanks for the help in advance : Wink:
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Re: V3V and boiler temperature




by Did67 » 29/11/17, 17:07

According to my experience, the "terrible" inertia of a PC leaves little choice to the boiler: it raises the temperature of the circuit in "stages". What happens: the V3V opens, the hot water content of the boiler runs out, the boiler starts up again, often, it is late, to protect the boiler (condensations), the V3V closes, suddenly the temperature boiler rises faster (less cold returns), the V3V opens, etc etc ...

It is very difficult, with a very inertial PC and boilers with low power (compared to the inertia of the PC), to switch to "smooth" mode right away ...

But I reassure you: another month and my installation will be 10 years old. And everything (except an igniter) is original. Including V3Vs which have not stopped opening / closing for 10 years ...
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bnohit77
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Re: V3V and boiler temperature




by bnohit77 » 29/11/17, 21:31

Hi,

Thank you Did67 for your feedback - almost - decennial suddenly 8)

Indeed, I see like you a little the same phenomena of the movements of my V3V which are a little on the move all the time : Lol:

I recently modified the opening / pause / closing time of V3V by reducing the times. They were originally on 8s for open / close and 5s for pause, and I changed everything to 3s to have faster reaction times. I said to myself that closing or opening "the tap" more quickly, would probably prevent the boiler from reaching the maximum limit too quickly (at the risk of stopping and thus restarting the burner for nothing), and vice versa , that it does not fall too far below the 60 ° C threshold at the start of the cycle by cutting the circulation pumps.

Is my reasoning really relevant? ... Suddenly, is there not a perverse effect which ultimately generates more V3V movements during the same heating cycle? ... it would seem logical : roll:

In short, I'm not sure that this approach is really good for flirting with the high and low thresholds of my boiler without exceeding them?

Thanks again for your expert advice : Wink:
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Re: V3V and boiler temperature




by dirk pitt » 30/11/17, 08:21

ok, i skipped the fact that you had a heated floor.
Considering what you say and your average cycle time, you are probably already at the optimum and which is actually quite honorable.
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Re: V3V and boiler temperature




by Did67 » 30/11/17, 09:52

bnohit77 wrote:
a little the same phenomena of the movements of my V3V which are a little on the move all the time : Lol:

I recently modified the opening / pause / closing time of V3V by reducing the times. They were originally on 8s for open / close and 5s for pause, and I changed everything to 3s to have faster reaction times. I said to myself that closing or opening "the tap" more quickly, would probably prevent the boiler from reaching the maximum limit too quickly (at the risk of stopping and thus restarting the burner for nothing), and vice versa , that it does not fall too far below the 60 ° C threshold at the start of the cycle by cutting the circulation pumps.

Is my reasoning really relevant? ... Suddenly, is there not a perverse effect which ultimately generates more V3V movements during the same heating cycle? ... it would seem logical : roll:

In short, I'm not sure that this approach is really good for flirting with the high and low thresholds of my boiler without exceeding them?

Thanks again for your expert advice : Wink:


For my part, unfortunately, I still have the old TEM regulation, which does not allow the closing speeds of V3Vs to be changed (or the rate of change).

That's what I wanted to do, reduce the opening times (at least) ... The closing, I admit I no longer remember what conclusion I had reached ...

I think, like Dirk, that you're on top ...

Regs are not made to lower / raise PCs. The doxa is not to lower the PC!

They should be managed completely differently, like a buffer. Think of your PC as a "water and concrete pad" to be brought up to a certain temperature and then to be maintained. While knowing that this "certain temperature" results from your external temperature and is therefore variable. There should therefore be a double loop: one which manages the buffer, the other which indicates the first at which maximum temperature to stabilize ....
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