heating problem to solve, low on return

[cily35]

Hello,

 

recently our boiler stopped working properly, causing a lack of heat in our 14-radiator splitter in 3 storeys. having only one boiler at time it kind of working, only for one at time, and depending on the the priority on the system.

 

We contacted Valliant for assistance, and they replaced the PCB and pump, that the pump had burned out. However, the issue persisted, with the engineers pointing to a problem within the heating system, even though it had been functioning correctly before the boiler failure. 

 

A second technician reiterated the same diagnosis after flushing the system for 8 hours, there was still no improvement. They now intend to break through the floor to inspect the pipes' route. In the meantime, they applied some chemicals and left it to work for three weeks.

 

 the Boiler is a Valliant ecotecPlus  837 r1, the system is running 30 sec just to heat the water then it goes for 3, 4 mins to S7 (pump heat overrun), where it drops the heat then start again the ignite for few sec etc... 

 

Today, I removed two radiators on the ground floor and cleaned them. During this process, some dark liquid came out (nothing solid or viscous, only dark fluid). We tested the tubes, and the flow was strong and hot, but the return remained cold. we run the system opened with the radiator out and the in water open to the boiler. It's likely that there's a blockage in the return, but my question is, after the flushing is still there?, what could be causing this issue? and where and how to identify it? 

 

it could be the pump or the boiler still have problem?

 

I really hope some one can help us

 

thanks, simo

Edited October 29, 2023 by cily35

[cily35]

some picture of our small clean, I've a magnetic filter which I cleaned as well today (after 3 weeks with the chemical)

Edited October 29, 2023 by cily35

[markocosic]

Can you sketch the pipe layout?

 

Auto bypass failed open perhaps; so water short-circuiting?

[cily35]

hi, I didn't find any bypass valve near the boiler and before the first T pipe, from the image attached the bolier is on the right and the top t is the flow and bottom the return wich goes on the ground to the first floor

 

is it normal for the primary exchange to be always hot when running only the radiator and the boiler most of the time in S7?

does it compromise the circulation?

 

 

Edited November 1, 2023 by cily35