CH still blocking even after flush, HW prob also. Any ideas?

[Elmo's_world]

Hi all,

I have a baxi 105e combi.
I posted here about a month ago and got some good advice as to flushing my CH as my downstairs rads were not heating up. This problem then got worse as over a few days as all the rads went cold. After I had performed a manual flush as detailed in the wiki the CH was working fine and I was well impressed with the advice - Thanks everyone.
However, after about 3 weeks the same problems started to return, so last weekend I repeated the flush and all was fine again. I also added so System Cleanser (not sludge remover) as I figured that the whole system probable needed a clean through and I planned to repeat the whole flush thing for a final time. Now just 3 days after the last flush all rads have suddenly gone cold. - Yesterday morning piping hot, yesterday after work stone cold!
The flow pipe is red hot, but the return is barely warm. I'm finding it hard to believe that every rad has suddenly blocked as I would expect the return to be hotter, and am thinking that it may be the heat xchanger that is clogged and slowing the whole flow around the system. I am also having a problem with my HW repeatedly going hot and then cold after 20 seconds or so. I need to have the HW temp on min. or the pressure valve will trip and after a few bangs the boiler shuts off.
Does this sound like a heat xchanger problem? If so how would I fix it? Does anyone have any other ideas, if so I would like to hear them, as I was hoping not to spend every other weekend flushing my CH!


Thanks
Martin

 

[corgiman]

sounds like it to me

you need the systme cleansed properly with a machine etc no good just whacking a few chems into it

 

[Elmo's_world]

Thanks corgiman. Do you think this is the only way to clean the xchanger propaply so that it will not clog up again, after a few weeks? I have used the method listed in the wiki to flush the system.

Also do you think the system cleanser would have had any effect after just 3-4 days? It said on the bottle to leave it in for 21 days for established systems. Its just that I'm a bit peved that it will all be lost, as I will have to try and get some kind of heat back.

Martin.

 

[corgiman]

well unless its agitated you cannae get all the carp out

imagine a bottle half full of sand

pour water into it and allow the sand to settle.

then slowly pour the water out

how much sand do you get out ??? not a lot

now shake the bottle like a bas tard and pour it out, how much sand do you have left now?

my case is rested

 

[ChrisR]

Also do you think the system cleanser would have had any effect after just 3-4 days? It said on the bottle to leave it in for 21 days for established systems.

Which one did you use?

Whether you use plain water or some noxious elixir there's always a risk that you'll disturb, rather than dissolve, some humungous grollies which will give you grief. If your HW is going hot then cold there's a good chance the secondary heat exchanger is clogged. They're relatively easy to remove and clean, though it would mean draining the boiler to that level, which means losing your system cleaner. If it was a mild one like X400 though, don't expect a lot in a couple of weeks.

Solution - even Fernox claim powerflushing is "up to " 80% effective, so you get 20%+ left! If you hire a powerflushing machine (about £50 a day) and use chems like Fernox DS40 or Kamco FX-2, that's your best chance for thorough cleaning.
It's always useful to remove the worst rad, and hose it and invert it several times in the garden to see what's in there. Can be more effective than powerflushing sometimes.

 

[Elmo's_world]

Very good picture corgiman. It reminds me when I go to the beach and I get sand in my shoes. I always have to shake them like mad to get the sand out again!

Martin

 

[Elmo's_world]

Thanks ChrisR.
I used kilrock system cleanser. It stated something like 14 days new systems, 21 days existing systems and 28 days for something else. I think I am resigned to losing the solution now.

Can I just be clear that the secondary heat exchanger is the same as the Plate Heat exchanger. As I don't see an mension of a secondary heat exchanger in the instalation and servicing book. Also this would be a separate problem from the CH as this is not part of the CH circuit.

I guess I should add that I have boiler breakdown insurance, even though I like to sort problems out myself, but this does not cover the CH rads etc. Which is why I have been flushing the rads myself. However, if it is looking like the problem is in the boiler, I may well give the insurance a call and see what they say. Though I'm not sure my cover would pay for a powerflush.

Martin

 

[Softus]

well unless its agitated you cannae get all the carp out

 

[Slugbabydotcom]

Does anyone have any other ideas,

I'm finding it hard to believe that every rad has suddenly blocked

Me too!
I'd be checking the efficacy of the pump.
If its got settings then set it to 3 or use a screwdriver as a listening stick to get it on the fastest speed.

Baxi people on here can tell you precisely where to look but I'd be sniffing about for a filter somewhere on the return that might be blocked.
[{EDIT} Just found it on inlet return manifold See Manufacturers instructions Page 27]

I have other ideas but there's your starter for 10 Check that and post back

 

[Agile]

Your plate HE is blocked and should be removed and cleaned or replaced.

I also suspect the pump. The head should be removed and the impeller inspected. If all is well the torque should be checked. You should hardly be able to stop it start with a small finger.

If you use chemicals then you need to use the right ones for the job and the best ones NOT cheap shed copies. Fernox or Sentinel ( or Camco to keep Keith happy ! ).

Tony

 

[Elmo's_world]

Thanks everyone for your replies.

I too had suspected the pump, but it always works fine after I have flushed things through. Although I haven't taken the head off yet, so I guess it could still be working when the system is clear, but start to slow quickly when things start to build up. No speed setting on mine, although the installation guide says it should have, so not sure how I can up the rate.

slugbabydotcom - Good idea to clean the filters, though the inlet return maifold filter in under the DHW instructions, though it can't hurt to clean them out anyway.

Agile - Excuse my ignorance, but is the HE the unit which sits directly above the burner and is the secondary HE also called the plate HE? Which I belive is under the burner unit near the pump unit. Just checking as I was going to take the HE out a few weeks back to clean, but decided not to, but looks like I should give it another look.

Martin