Radiator bleeding + Aquastat boiler malfunction

[DC]

Hello everybody

My questions in two parts for clarity.

A) Radiator bleeding

What is the procedure for purging an old oil-fired central heating system (radiators installed in parallel)? I have read various posts on this subject but some seem to contradict each other.

In three rooms of the house, the thermostatic valves no longer let hot water pass even when fully open.
I released the stems of the thermostatic valves with a satisfactory result for two of the three radiators, on the other hand that does not give anything in a room. Hot water seems to pass through the thermostatic valve and heats the 2 1st "rays" of the radiator (in cast iron) but nothing beyond.
Note that an "automatic" vent (at least I think that's it, see photos) is present above the boiler.
Is an air pocket in the radiator obstructing the flow of hot water?

Below are some photos of the boiler and the expansion tank as well as the bleeding procedure that I intend to follow.

1. Run the boiler for 15 min and put all radiators in max position. (to accumulate the air present at the purge valves)
2. Then switch off the heating system for about ten minutes (valves always fully open).
3. Bleed the radiators (open them successively starting with the ground floor then floor by floor)
4. Also bleed the expansion vessel (and the automatic vent if applicable) of the installation.
5. Start the circulator and check on the manometer that the water pressure is correct (min. 1 bar).
NB: The optimum operating pressure varies from one system to another (green zone of the pressure gauge)
6. Open the filling valve and let the water enter the system while checking the pressure (recheck the radiators and possibly top up with water to adjust the pressure again ??)
7. Then switch on the heating system again.

My questions

1. Is it correct and complete?

I have read that it is necessary to first check the pressure of the expansion tank (using a pressure gauge attached to the lower valve?) And not hesitate to fill the installation until it overflows. pressure a little in the red zone because the purge will relapse it

Point 2
Switch off the installation = switch off the "Heating" circulator ET (?) the "Boiler" circulator?
Also close the "Burner" switch (see photos of the control panel) when it stops (T ° reached)?
More drastically cut the power supply gen. of the boiler (see photo of electr. connection)?

Point 4
The expansion vessel indicates a pressure of 0,5 bar, is that too little (1 bar min, no?)?

Point 5
Should the DC circulator be started before each water supply or can it be done only after all the purges?

Point 6
Adjust the pressure by opening the (the 2?) Water filling valve (there are 2 at the ends of the hose upstream of the

expansion vessel) BEFORE (circulator in service), during (circulator off) or AFTER purging (circulator active)?

B) Boiler aquastat malfunction

The domestic hot water remains boiling permanently and the burner switches on far too often in my opinion (hence the 3000L / year consumed for a house with 3 facades of standard size and insulation) in order to maintain the domestic water at a T ° too high in the boiler regardless of the position of the "boiler" aquastat ...

Despite my explanations, the pensioner from St Roch who came to replace the ECR circulator (hot water radiator) last summer, in my absence, did not touch the very scaled T ° probe (bulb) visible at the back of the boiler and connected by a thin copper pipe to the control panel (up to the aquastat boiler control? See photos).
I tried a brief descaling without result.

What ??

Thank you in advance for sharing your experience

[DC]

Hello everybody

To summarize my questions and get to the point since no one is showing up:

1. Should the DC circulator be started before each water supply (if the pressure is too low) or can it be done only after all the radiators have been purged?

2. Adjust the pressure by opening the water filling valve BEFORE bleeding the radiators (circulator in service), during (circulator off) or AFTER (circulator active)?

3. Boiler aquastat malfunction: what to do and in what order?

By thanking in advance the enlightened goodwill

[sicetaitsimple]

I can just tell you that I personally bleed the radiators with the heating system off and restore the water pressure before restarting. No problem.

Are you telling us to have a floor? In this case 0,5 bar seems little to me, especially if your boiler (it is not said) is in the basement? In my case (floor and boiler in the basement) the pressure setpoint at the boiler level is between 1,1 and 1,2 bar. But hey, to see, I do not advise you anything, I just give you my example.

Your aquastat is probably either dirty (temperature sensor) or faulty.

[Ahmed]

The advice of Sicetitsimple seem relevant to me. On point 2, it may be desirable to add water to the circuit during operation (bleeding the radiators) if there is a lack of water, because in this case it is impossible to fill the radiators. It is better to start by purging the radiators from the lower rooms to the upper ones ...

[Macro]

And get to the service pressure (in the green of the mano) when the whole circuit is hot ....

[sicetaitsimple]

On point 2, it may be desirable to add water to the circuit during operation (bleeding the radiators) if there is a lack of water, because in this case it is impossible to fill the radiators.

Indeed, if there is a lot of air to be purged, it may be necessary to make one (or even several) intermediate additions to be certain that the circuit remains under pressure during the purging operation, including at the highest point of installation.
Otherwise, there is even a risk of admitting air into the circuit and not extracting it by bleeding a radiator upstairs!

[DC]

Hello,
Thank you for your suggestions which I will summarize in my case like this (boiler in the cellar, a mezzanine + 1 floor):
1.Add water to the system BEFORE purging
because 0,5 bar instead of 1 bar, start of the colored zone on the pressure gauge?
first cut off the general electrical supply to the boiler or only the circulator or without turning off anything?

2. Add water to the system DURING the purge to compensate for water loss and prevent the admission of air at this time (ideally one person in the cellar and another who is purging).
During purging requires that the circulator (at least him) be stopped?

3. Reset the circulator (or the entire boiler if applicable) after all operations and check again?

Regarding the aquastat, what can be fouled?
How is the thin copper tube starting from the copper "bulb" (see photo, = thermal probe still scaled up in the hole at the back of the boiler?) How is it connected to the control panel at the front?
The expansion of the gas contained in this thin tube actuates what and where in this place?
Is there an electrical contact to check? How to test with a multimeter?

I'm swimming for this important point, an idea

[Ahmed]

Regarding the water supply, it can be done at any time, as long as the air is expelled from the radiators (whistling); 1,5 hot bar is sufficient for this kind of configuration. No need for the circulator to be running and no need to cut off the power supply ...
The control is limited to seeing the water flowing through the purge, a sign that the air is evacuated ...
For the aquastat, no idea, sorry ...

[DC]

OK thank you, in conclusion, I am content to cut the circulator at the level of the control panel but I did not understand why in fact it is necessary to stop the circulation in the circuit of the radiators at this moment ...

[Ahmed]

I do not have a really clear cut answer: I prefer to operate with static water, fearing an air transfer by forced circulation; maybe this is not a necessary precaution, but as it works well like that ...