Impossible to fix flow problem? 4 grand down so far...

[Rob Foster]

I am finished with this one - it going around in circles the OP has had loads of help and assistance. I hope he gets it sorted I will just watch now

 

[Old UKPF 99429]

Thanks again all, really useful info and advice, and asnwered lots of questions on bits I had no clue about. Will def post back if I ever get it fixed!! Going to try a boiler powerflush (as mentioned just on HW circuit only), and get that booked in first, and possibly a full powerflush. I agree Flexitflav, the symptoms and history of problems with flow still doesn't quite fully add up together.

 

[Jim Goodenough]

Darryl, did you read my earlier post?

Have you checked pump valves are both fully open. Very basic suggestion but could be a knackered pump valve??

Just you may have missed it as there's been a lot of comments/suggestions.

 

[Old UKPF 99429]

Thanks Jim, will check that.

 

[Murdoch]

I think the £4K is BS and the OP is trying to do it all himself ..... the pipework is not of a time served plumber, that's for sure

Just saying what most people are thinking

 

[Old UKPF 99429]

Good one.

 

[Old UKPF 99429]

Already listed the costs, was just after some advice from some kind people. Gratefully received. Let's leave this here. Thanks again everyone for the things to try etc.

For the record I can't do any plumbing myself and wouldn't try.

 

[fixitflav]

Already listed the costs, was just after some advice from some kind people. Gratefully received. Let's leave this here. Thanks again everyone for the things to try etc.

For the record I can't do any plumbing myself and wouldn't try.

Thinking about this again, it seems odd that everything heated up during powerflush (your #6) but not otherwise. I suppose a powerflush pump has more umph than a heating pump, but still strange. Is it possible there's a spring-loaded valve somewhere in the system?

 

[oilmark]

Probably debris in the flow/return pipes unable to be power flush cleared. I bet its chipboard from a lid on the old header tank. Any evidence of chipboard particles near disused header?

 

[DerekJB]

Hi is it possible you have a check valve on the system somewhere? Have found these hidden in a few places, and I would Powerflush every individual loop and see what happens, you could put a cleaning solution in the system and run for a week then flush it. Fit an primary filter on the return first though or all the crap will go in the heat exchanger.

 

[Viper Gas]

Check direction of your rad valves and make sure flow is concurrent.

 

[Trotter31]

I noticed 2 gate valves in your photos.
Have you checked that BOTH open and close properly?
Just a thought!

 

[Bibbs118]

Bypass could be open.

The return from the cylinder should be the return nearest the boiler.

 

[sammathias]

Clutching at straws!

 

[kris]

If it was me id drain system ' remove gate valves make sure there fully open, if there ok id check zone valves and automatic bypass . If everything seems ok id disconnect flow and return near boiler and blast a compressor down ( shutting every rad apart from 1 and at one by now check airflow going round the flow and return . The fact it had a powerfully should be adequate but was it a machine or someone just pouring in chemicals ) there has to be a simple explanation even if tricky to find but a good engineer will find with out costing thousands .

 

[kris]

Just had a look at the pics of your system and tbh looks very diy ish and unprofessional. Don't take offence but there's a good chance it's simply the way it's piped that's causing issues .

 

[Harvest Fields]

If it were me, like I said before I would put a complete new flow and return in.

 

[doitmyself]

the circulation is not good, although the boiler is looking for 20 deg differential between flow and return rather than measuring flow rate I think.

I don't understand that

It appears that the Viessmann "expert" doesn't understand either.

The installation manual explains it like this:

Flow rate monitoring
Flow switch
The boiler is equipped with a flow switch for monitoring the minimum flow rate. The burner is shut down at a heating water flow rate below 200 l/h. No fault message is shown.
Recording the differential between the boiler water temperature and return temperature
The flow rate through the boiler is monitored by recording the differential between the boiler water temperature and the return temperature. Monitoring of the temperature spread with the boiler water temperature sensor and the return temperature sensor is an additional safety mechanism.
■ At a differential of > 25 K/< 30 K, the burner is operated at the lower heating output.
■ At a differential of > 30 K, the burner is switched off.
In such cases, check whether the heating system is adequately vented and the circulation pump is pumping sufficient
heating water.

200 litre/hr is equivalent to a differential of 35C at minimum output of 7.9kW.

 

[sammathias]

There was not veissmann engineer I'd say.

 

[Everal]

I would Scrap the old flow and return and start again.

SOUND