Ariston Eurocombi A23MFFI- Hot water probs

[leezer3]

Hiya,
Got an Ariston Eurocombi A23MFFI here (Can post the GC number if that becomes necessary). Got a problem in that hot water is only being provided at low speeds; Turn the tap on more than a small trickle & it goes cold.
So far I've changed the DHW diaphram & the thermistor with no change in symptons. Operating the microswitch the DHW diaphram pushes isn't doing anything either.

The radiators remain cold when in hot water only mode.
Boiler is firing fine in HW mode, and central heating works nicely.

From what I know, this leaves the main flow switch as the only real culprit?

Anyway, would appreciate anyone with any more knowledge of this precise model.

Cheers

-Leezer-

 

[Agile]

Have you done a thermal survey of the boiler and concluded the domestic heat exchanger is blocked???

Tony

 

[possum_jenkins]

plate heat exchanger ? dont see very many aristons up my way but seems like you've ruled out every other possibilty.

 

[leezer3]

Not a real boiler man, and no qualifications as such.
Have also been consulting with a friend in Cornwall (Corgi fitter), & his opinion was diaphram/ thermistor. Have obviously changed both of these with no change, and so his opinion without seeing the boiler was now main flow switch, which agrees with whats on the faultfinder flowchart (This makes no mention of diaphram whatsoever though )

If it is a blocked heat exchanger, how easy is this going to be to clean?
I'm presuming that its a case of systematically dismantling the boiler & acid or similar to clean out the crud?

(No idea how to conduct a thermal survey of the boiler, all I can really say is that the burners are going when hot water is in demand)

Cheers

-Leezer-

 

[possum_jenkins]

beat me to it!

 

[possum_jenkins]

yes, remove the heat ex and remove all the loose debris from it. Use a descaler on the primary side (connected to the main heat ex) , as this will be the side that is blocked. Wouldn't hurt to drain and cleanse your htg system as well, as this is probably dirty too.
I think what Tony ment by a thermal survey was checking the difference in temperature between the primary and secondary pipes connected to the heat ex.

 

[leezer3]

Right, what would be a suitable descaler? Kettle stuff? Also got a large bottle of bleach floating around, would this be suitable?

Heating wise, there's a Sentinel X100 sticker on the side of the boiler (Dated 1997) I don't know how regularly things have been serviced/ renewed, but water out of the rad bleed valves/ when draining from boiler is pretty clean, so I hope things on this front are OK

Advice much appreciated, total spend on this so far is just over £12, would love to keep it this way!

Cheers

-Leezer-

 

[possum_jenkins]

Yep that would do the trick, although i would steer clear of the bleach.

Would still advise to drain and clean the system tho, as the blockage suggests theres a good bit of rubbish in there. Has the system been drained since 1997? Even so, would recommend draining, filling and adding X300 and running for a couple of days, draining again then adding X100.

 

[leezer3]

Don't ask me
Owned this house for 9 months, HW has been getting worse for a while now, but I've never got round to doing anything because there's an electric shower.
All I can say is that the boiler was serviced relatively regularly for at least the two years before I got the house, as this is the only paperwork I have.

I'd much rather avoid draining the whole system if I can help it, thats far more hastle than I can do with at the mo, especially as I have a nasty suspicion that a large amount of bodging went into things (Removed a set of metal spotlights from the downstairs bathroom right next to the shower was among a quite large list of electrical faults).


Final point (I hope!)- There's only thing that I recognise as a shutoff valve (On the heating flow)- The return has an odd 90 degree brass thing, which I can't find a way to close off. There's also one for the cold water. The boiler drains fine, and as far as I'm aware this isn't going to be a problem, but I'd like confirmation that this isn't going to cause a waterspout or something!

Cheers

-Leezer-

 

[Agile]

The plate has to be cleaned on its own.

To clean the system you need X800 but not X300 which is only for claning newly installed systems.

But for anyone who must use X300, we have about 20-30 bottles to many if amyone wants to put in an offer!

Tony

 

[possum_jenkins]

i'll give a crisp 20 for the lot. cash mind then again not sure if my notes are accepted widely down your end, had a lot of funny looks at my scottish notes in london!

 

[leezer3]

I think I need a wall to beat my head on
I've now changed both diaphrams & the temperature probe in this wretched thing. Secondary heat exchanger is clean as a whistle.

The symptons have now either changed though, or I may have been wrong in the first place. I can't get any HW at all when the boiler is in HW only mode, burner doesn't even bother lighting (The switches may well be dodgy, power button is totally ratted)

This is pointing to a broken 3-way valve I think?
If so, can anyone point to one at a decent price (Under £80 would be good )

Cheers

-Leezer-

 

[possum_jenkins]

so the boiler doesn't light when hw is opened? faulty flow switch most likely. wont be the diverter valve as the boiler would light when hw is demanded, but you wouldnt get and hw thru. think you were right in your first post, i didnt read it properly!

 

[leezer3]

My poor head
There's a 3-way valve, with two microswitches attached.
Microswitch 1 is on the right hand side, and is operated by the DHW diaphram. When the boiler is on DHW mode only, this diaphram doesn't even move. Turn the boiler to heating/ DHW mode, this diaphram operates, pushing the microswitch.
Pushing the microswitch when boiler is in DHW only mode causes the burner to light, either until the tap is turned on, when it cuts off instantly with the overheat light or until the boiler shuts down with an overheat warning.

Not sure what microswitch 2 is doing, this is what Ariston call the main flow switch & is operated by a smaller diaphram on the 3-way valve. Unplug the microswitch & the boiler doesn't even fire, with the no gas indicator coming on.

Is there any useful way to test the second microswitch- I can probably find a spare switch or bridge the two terminals, but as I'm unsure of what this switch is supposed to be doing testing blind isn't going to help things
It strikes me though, that as unplugging this second switch causes the boiler to die altogether it must be working in some way or another?


I really need someone who's seen this precise issue I suppose, doesn't help that the boiler is cheap tat. Will try ringing Ariston tomorrow and see what they have to say for themselves, but I suspect that will be a futile excersise.
If nothing else, I know how to strip this dratted thing down extremely quickly now

Cheers

-Leezer-

 

[Agile]

I think that you dont know which diaphragm is which and the same with the microswitches.

Dont you have a manual which can tell you?

Tony