Vokera Linea 28 Combi boiler issue

[Madrical]

New to this, looking for some advice...

Combi boiler radiators (7 in total, upstairs/downstairs house) were not heating up some not at all. System always topped up with "inhibiter". Hot water great. So

- all radiators removed and flushed clean. (Some black water, to grey to clear)
- pipework at each radiator point the same. (same)
- new lock shield valves and tvr's fitted where need be.
- New Grundfos Pump head fitted.
- Domestic Heat Exchanger removed and cleaned with Sentinel 800.
- Auto Air vent cleaned as it had white deposits at the vent.
- Additional Sentinel 800 added to system. System flushed and drained again.
- Re-filled downstairs first then upstairs. Inhibiter added. Radiators bled of air. same with Pump. Refilled to 1.3 pressure. Before system switched back on.
- Boiler holds its pressure at 1.3. Bypass gate valve very slightly open. Feed pipe gets very hot and return pipe gets hot however clear difference in temperature to feed pipe.
- Thermostat works in that the gas burner engages when turned up, same for hot water.
- Main burner looks clean when fired up.

However only one radiator closes to boiler upstairs goes to temperature and a little in the next one in the upstairs hall..the other 5 nothing. LSV set at half up stairs and one downstairs. Radiators bled again till water drips out. When heating on I still get hot water. I have left the boiler on timer and the pump at setting 2 to see if this make a difference so far no change.

I have had a professional look at this and was not impressed with bill and he only changed the filling loop tap as he advised had a leak. He advised none of the above though stated pump perhaps needed replacing. The boiler is over 8 years old however would like to repair than replace if possible.

Any advice most welcome. Thanks.

 

[Hot&Cold]

For testing reasons. Have you run the heating with all the lockshield valves fully open,trv's on full or with the heads removed and the bypass closed ?

if still poor circulation check the boiler flow&return valves are fully open. There could be a fault in the boiler diverter valve mechanism preventing full flow to the radiators or other faults,now its get more involved

 

[ianmcd]

Pump must be at speed 3, try closing all the radiators and only open one at a time, if the radiators heat individually then you have a balancing problem

 

[Madrical]

For testing reasons. Have you run the heating with all the lockshield valves fully open,trv's on full or with the heads removed and the bypass closed ?

if still poor circulation check the boiler flow&return valves are fully open. There could be a fault in the boiler diverter valve mechanism preventing full flow to the radiators or other faults,now its get more involved

Thanks yes however not with the bypass closed..will try that. Also will check to make sure boiler valves fully open too...enjoy your holiday

 

[Madrical]

Thanks Ian..pump speed at setting 2. Tried that re-radiators individually..no change there..

 

[DP]

Circulation issue is what comes to mind
Some of the bits replaced seems excessive
x800 is going to kill the pump unless system has been thoroughly flushed

There is a need to carry out temperature checks on the system to ascertain what is going on
If system plumbed in plastic, that could be a cause too

Where are you, a regular here might be able to fix the problem.

 

[Hairymelon]

Yes circulation restriction. I would drain off and check the flow/ return cocks are fully open. The lines on the cocks can be vertical indicating fully open but a valve may be partially closed internally because the fixing bolt or whatever is wrung off

 

[endecotp]

Diverter valve stuck in DHW position?

(I have the same boiler... I’ve not had this particular problem though.)

 

[ianmcd]

Thanks Ian..pump speed at setting 2. Tried that re-radiators individually..no change there..

As I have already told you the pump MUST be set at position 3 on your boiler and its nothing to do with the radiator problem you are having.

 

[Madrical]

Thanks, it copper pipes

Pump must be at speed 3, try closing all the radiators and only open one at a time, if the radiators heat individually then you have a balancing problem

Sorry misread your message..changed setting to 3.

 

[Madrical]

on advice from above:

- removed motorised valve and checked diverter valve..pin moved in and out all looked okay.
- Inside the motorised valve there are two plastic clips one blue and one green. The green one was fitted correctly however the blue one was out of its slot spring intact etc..strange but true. Re-fitted correctly now waiting to see if all radiators heat up also with pump setting at 3.

 

[Madrical]

Yes circulation restriction. I would drain off and check the flow/ return cocks are fully open. The lines on the cocks can be vertical indicating fully open but a valve may be partially closed internally because the fixing bolt or whatever is wrung off

I assume they are coz the flow and return pipes get hot from the boiler to the floor. Also in not properly switching off the return when removing end cap further along the pipeline the water gushed out. There has never been a problem..re-filling the system and radiators when flushed and drained down etc. However I am thinking of changing the type of valve from screw turn to a handle of some sort..any suggestions? thanks

 

[ianmcd]

stop constantly putting x800 in your system it will kill your pump

 

[Hairymelon]

Water under pressure will gush out even if a valve is partially closed. The ch pumped flow won’t force its way past a restriction like pressurised water will. I have had it happen to me after turned of the flow and return valves. the one which has the fill loop check valve fitted has a design that allows system dirt to lodge around the ball jamming it , I assumed it was open and lost a lot of time figuring it out. Just a suggestion as you have checked /replaced many parts.

 

[Madrical]

Thanks..will check this further too.

Update:

- with pump setting at 3 I went round to open rads individually and some success this time some heat went to five though rads not hot like the temp gauge on the boiler...at 85 rads just warm.
- Started on the last two however this morning although the boiler engaged a couple of times during the night and this morning there was an error code 7 primary thermistor circuit open.
-PTCO temperature overheat?
-I switched off boiler and checked individually rads not holding air...only one very little.
-Boiler switched on code gone now finishing checking the last two rads get some heat with pump at 3.
-This time there is noise coming from boiler which sounds like crackling.