Boiler notes with CAP and solar

[dedeleco]

I just noticed that the sensor which controls the DHW pump in solar mode is burned out. She couldn't stand the heat maybe.

This probe is on which measurement principle, because if identical it will burn out again.
There are a very large number of temperature measurement methods at all prices and some resist very high temperature for no more expensive (600 ° C).
You have to see the necessary precision.
So you have to take a close look at the method and change it.
On conventional bulb thermostats with mechanical deformation by expansion of a gas in a tube which pushes a contact, it happens if too heated or improper welding that the gas is leaking!!
It suffices to put gas back on (like acetone) according to the necessary T (water if T <100 ° C) to regenerate it (I did it on a washing machine) and it works again after a good weld better with the bulb in the cold (liquid acetone) !!

I did not understand everything, but I do use vacuum tube panels.

It would be good to specify us what is not clear in our theoretical views so that we detail them and specify better, because combined with your well thought out concrete realization, one has the theoretical impression that optimization can be improved with no too much work !!!

Thus to see your tubes under vacuum, in full air currents and without parabolic cylindrical reflector under each one, one has the theoretical impression that their output can be improved without much trouble, as for the structure of the circuit and regulation!
Flat collectors are better insulated with more thermal inertia and take longer to cool.

Indeed blocking on the sides by simple rudimentary borders the air circulation around it a little should decrease the cooling speed of the tubes by a factor to be measured according to the wind.
Put a slightly rounded reflector under the tubes which return the light rays in the tubes instead of the sky, must improve by a factor also to measure!
A quick rudimentary test by the sun is to put inexpensive thin aluminum foil (kitchen aluminum bonded to semi-rigid plastic sheet) in half round under and around the slightly flared tubes joining between the tubes, and to see the real gain depending on the sun between summer (too hot) and winter.
Probably the tubes are too tight (especially with a reflector) and the optimum is to be determined experimentally ?????

Otherwise, for heating I think that inexpensive sensors that heat from the bottom outside to 45 ° C followed by some sensors under vacuum which heat higher from 45 ° c to 55 ° C (suppressed by bipass if without sun) can be more effective ??

[bernardd]

So to see your tubes under vacuum, in full air currents
...
Flat collectors are better insulated with more thermal inertia and take longer to cool.

If we put copper sensors under vacuum, it is so that the wind passing on the external envelope has no effect. We can put these sensors on a chalet in the mountains at -20 ° C and they will heat as well, while flat sensors will never thaw.

Otherwise, for heating I think that inexpensive sensors that heat from the bottom outside to 45 ° C followed by some sensors under vacuum which heat higher from 45 ° c to 55 ° C (suppressed by bipass if without sun) can be more effective ??

It is interesting only for curiosity to measure the difference in efficiency, but otherwise I do not see the interest given the current low price of vacuum tubes.

[PITMIX]

Ok I understand the idea better but I don't think I can do the improvement of the panels immediately.

For my probe it is a PTC it is supposed to resist 150 ° C.
It is not out of service. It was the thermostat that released, not the probe.

It must be said that originally I recovered this electronic thermostat during an intervention at a customer when he had taken the water.

Today it is sunny in my house and I am at home to check the operation of the installation.

I realize that at this time of year and with my current system, the temperature of the heat-carrying fluid of the solar panels is not sufficient.
As soon as the DHW pump is authorized to start, the 3-way valve closes because the temperature of the sensors drops suddenly.

This confirms to me the idea of ​​preheating the water in the boiler.
This would save me a little money throughout the year by entering water slightly warmer than the network temperature in the boiler. And in summer 100% solar hot water without using the boiler.

Does anyone of you have a solar system for preheating the water before the boiler? Citro?
What temperatures do you get throughout the year?

[dedeleco]

It was the thermostat that released, not the probe.

It must be possible to repair it if it has not been at 150 ° C too ??
Otherwise, if it is far from the probe, there can be high voltages on the long wires during lightning strikes even from a distance (hundreds of meters) which kill the probe input electronics and it is enough to change it .
I had this several times on my alarms and even VMC motors in attics with long wires, rare but destructive !!
In which case it is better not electronic (good old thermostat with rudimentary bulb) or a powerful protection circuit on the input wires but distorting the PTC measurement !!
I do not like this type of probe which simplifies electronics to nothing but limited semiconductor while many others are also simple in electronics !!
A thermocouple (two welded wires) with very low resistance is much more resistant and protective for electronics.

[dedeleco]

As soon as the DHW pump is authorized to start, the 3-way valve closes because the temperature of the sensors drops suddenly.

Logic since the sun is not very powerful, and therefore the fluid flow in the collectors must be automatically adjusted to the power of the sun by adjusting this flow to the temperature of the fluid exiting the collectors, with a circulating pump with rotational speed controlled by a proportional regulator (PID) with time constant greater than the circulation time of the water, so that this water is always hot at the maximum possible power (different from T).

[bernardd]

I realize that at this time of year and with my current system, the temperature of the heat-carrying fluid of the solar panels is not sufficient.
As soon as the DHW pump is authorized to start, the 3-way valve closes because the temperature of the sensors drops suddenly.

In addition, the water that stayed outside has had time to cool down during the absence of sun, and therefore the first wave that arrives is going to be even colder, before it is water heated by the collectors.

You need a timeout. And that's the point of a self-draining system: the water does not cool outside.

This confirms to me the idea of ​​preheating the water in the boiler.

anyway, as it is the "freshest" source, it is up to it to come first.

You could also go into a CMV if you had one, I don't know.

This is also the reason why I mentioned the idea of ​​several hot water storage tanks: it is better to keep one very hot and one cooler, because when the sensors are not at maximum temperature, they can still heat the coolest.

[dedeleco]

The VMC double flux is obviously worth it to lose nothing independently!
Otherwise, if the collectors heat above the 20 + x ° C return of water from the radiators, it is advisable to heat it with the collectors if they can before returning to the boiler.
So we have an interest in have this x back low enough by slowing the circulation in the radiators to have x low enough and to have a maximum amplitude y of heating to 20 + x + y ° C by the solar collectors before returning to the boiler, which will only have to heat the heating water, leaving the radiators tracked by solar collectors, from 20 + x + y ° C to 55 ° C, temperature of the water leaving the boiler, for example taken at 55 ° C.
Le gain is roughly y / (55- (20 + x)) in energy that the boiler does not have to provide, even if y is weak in weak sunshine, but accumulated over all the values ​​of y over months, the gain (otherwise lost) is significant.

[PITMIX]

I remind that for the moment I use my solar panels only for domestic hot water. I haven't done anything yet to heat the house.

Here is the diagram I think of to preheat the sanitary water.

https://www.econologie.info/share/partag ... omPsDk.JPG

[bernardd]

I remind that for the moment I use my solar panels only for domestic hot water. I haven't done anything yet to heat the house.

I wanted to congratulate you for tinkering in this way and with the desire to go solar,

And thank you for sharing and chatting with us.

Here is the diagram I think of to preheat the sanitary water.
https://www.econologie.info/share/partag ... omPsDk.JPG

I will give you my remarks live, but I will have to think a little more because it is an interesting subject.

I'm surprised because I thought you wanted to put the heat exchanger on cold water, and I imagined it before the ball. Otherwise the tank is no longer useful, it only stores cold water, right? And if you go into the exchanger starting from the top pipe, you send the hottest water ...

By authorizing the boiler with the pressure switch, is it not too short to heat "live" with the boiler?

I wonder if we should not consider 2 circuits, one for "lukewarm" water circulating in the exchanger, and one for hot water circulating in the boiler.

The 2 circuits must be able to share the same tank, putting the cold circuit at the bottom and the hot circuit higher, the flow to the taps being at the top.

[I Citro]

Does anyone of you have a solar system for preheating the water before the boiler? Citro?
What temperatures do you get throughout the year?

This is the operating principle of all solar water heaters, it seems to me.
My 300 liter solar tank has 2 exchangers.
- The lower exchanger is connected to the solar panels
- The upper exchanger (or the electrical resistance) is connected to the boiler and heats only the upper part of the tank.

Today (gloomy weather) the CESI has produced the equivalent of 3,25 kWh in solar energy. The temperature at the solar exchanger is 33 ° C at 23 p.m., and 46 ° C at the boiler exchanger.
Tomorrow morning the boiler should switch on to raise the water temperature in the upper part of the tank to around 50 ° C (around 80 liters).

Note that in summer, we consider that the mains water arrives at around 14 ° C (in Bordeaux). In winter, the water reaches only 7 ° C.

I am therefore very happy that the meager sun of today was able to raise my arrival temperature to 33 ° C ...
That's always the energy that the boiler will not have to provide.