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

[Darryl Pullen]

Thanks again for taking time to respond. Got Viessmann coming out today to check the boiler.

Will check the pump arrow direction, and will confirm if there are any pipes and connections at the bottom of the boiler from memory just one, plastic pipe?

 

[sammathias]

Ohh hopefully they don't condemn that boiler then. Let us know how you get on and weather they resolve the problem.

 

[fixitflav]

connections at the bottom of the boiler from memory just one, plastic pipe?

That's probably to be the condensate drain.

Consensus is it's likely to be low or no flow causing the problem. Re-reading your original post, I would guess the system has never worked, and the old boiler would have been fine if the flow issue had been sorted.
Assuming it is low flow, it could be due to a blockage or maybe the way the piping is installed. A sketch of the complete system would be useful, but not easy to prepare as much of the pipework will be out of sight. On a working system you can get some idea by following rising temperature round the system, but that's catch-22 in your situation.
Keep us posted about how you get on with Viessmann.

 

[Darryl Pullen]

So, Viessmann came and went. He was adamant (obviously) that it was a flow problem! In his opinion, it is a blockage in the heat exchanger. This is because it does indeed behave exactly the same on just HW as CH. Possibly caused by powerflushing the system with the new boiler connected (as was mentioned), so has flushed some gunk down in to the heat exchanger.

His suggestion, get the boiler powerflushed, or just heat exchanger removed and cleaned fully. Put a magnaclean or some kind of filter on the return...

 

[Darryl Pullen]

He only determined it by measuring flow and return temps. But was sure.

 

[Rob Foster]

so no result thats boring and AUTUMN is approaching. You will have to get someone in and maybe pay. See what the collective wisdom here says again. And then who ? cause you have done that ! hmmm

 

[Rob Foster]

I was again going to offer to look 'at cost' if you are not too far away cost wise and give you a contact no but your settings are precluding this -

 

[Darryl Pullen]

Not shy of paying if that is what the implication is? Already had two plumbers/heating engineers out, approx 8 visits, maybe 4 days of work. Cost of 3.5k to 4k so far (900 initial investigations, new 3 port valve, air release valve, more diagnostics, 2.2k on new boiler and installation, further 900 ish on conversion to sealed system, new pump fitted, another new pump (bigger)) etc. etc. etc....

It's been "broken" for two years, hence I thought I would see if people had any ideas, just might have unearthed something. And it is clear it is a flow problem, needs a heating engineer to come and look again. Darn it.

 

[sammathias]

You had 2 plumbers out, one being the one who installed boiler...then you payed £900 to seal the system which judging by the pictures would have cost next to nothing for materials. I cant see how you have had so many incompetent people to look at it. Things just don't add up. I'm starting to think it's not even a legal install. Did the veissmann engineer not even bat an eyelid over the shoddy pipework/installation?

 

[fixitflav]

His suggestion, get the boiler powerflushed, or just heat exchanger removed and cleaned fully.

Sounds like the original powerflush was done after the new boiler was installed, if it's suspected that the powerflush drove muck into the h/ex. But I'm still puzzled why the flow was low enough to give those symptoms with the original boiler. I don't think we can rule out yet the blockage being elsewhere in the system.
Also if powerflushing is going to shift it, I wonder why on the original powerflush the muck wasn't swept through the h/ex and discharged.
I had a similar problem a few years back after powerflushing, I didn't know at the time not to powerflush through the boiler. We live and learn! No obvious flow problem, but very noisy (there were other issues which didn't help - gas pressure too high, and pump output down due to clogged impeller). I cured it by chemical cleaning, just through the boiler and HW cylinder, to make sure the boiler got the full benefit.

 

[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

 

[Darryl Pullen]

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.

 

[Darryl Pullen]

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

 

[Darryl Pullen]

Good one.

 

[Darryl Pullen]

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

 

[Everal]

Sounds like a circulation issue, pump could be at fault, causing boiler to overheat and cut out especially where so few radiators are getting warm

 

[gmartine]

Sounds like a circulation issue, pump could be at fault, causing boiler to overheat and cut out especially where so few radiators are getting warm

You resurrected a three month old, seven page thread for that? Congrats and see page 1.

 

[Everal]

You resurrected a three month old, seven page thread for that? Congrats and see page 1.

 

[rpm]

You resurrected a three month old, seven page thread for that? Congrats and see page 1.

Frustrating as it is, they are new, all excited and jumped in without reading the whole thread, better than a 7yr old post though

 

[Rob Foster]

Frustrating as it is, they are new, all excited and jumped in without reading the whole thread, better than a 7yr old post though

Agree I am a worn out 60 year old post, ultimately the more the merrier in my opinion , gmartine rocks for having a go
Rob Foster aka centralheatking