Ariston Eurocombi A23MFFI- Hot water probs

[leezer3]

I'm well aware of which is which in terms of the two diaphrams
DHW diaphram is the larger one with a pushrod attached. The main flow switch diaphram is much smaller and mounted on the three-way valve.

Trouble is that I'm not sure what the main flow switch diaphram & microswitch is doing. I know that its going into the PCB, and that if I remove it the boiler gives a no gas light. I don't know why though- As I understand it, the microswitch should either be operated or not. When its not operated, it ought to be exactly the same state as unplugged.

FWIW, the manuals (Got the service manual, installation manual & user manual) are a waste of space, not even mentioning diaphrams



No, I'm not a boiler engineer, but equally this thing doesn't appear to act through any reasonable laws of logic

-Leezer-

 

[leezer3]

Okies, bump.
Symptons have changed again
Its now working again in DHW only mode, but once more has the crappy hot water issues & the DHW diaphram is moving as opposed to still as it was previously. Only change is that the boiler is warm (Heating has been running for an hour or so).


Also been on the phone to Ariston, & they say if the pump's not coming on & the DHW diaphram isn't moving, then its a fault with that diapham. They've suggested cleaning out the two small pipes going into this before doing anything else.
Thoughts on this- If these two small pipes are clogged, could this be causing the issues seen?

Wondering if its worth getting BG in on the fixed rate jobbie at the moment, its doing my head in!

-Leezer-

 

[Agile]

Also been on the phone to Ariston, & they say if the pump's not coming on & the DHW diaphram isn't moving, then its a fault with that diapham. They've suggested cleaning out the two small pipes going into this before doing anything else.
Thoughts on this- If these two small pipes are clogged, could this be causing the issues seen?


-Leezer-

Its the DHW diaphragm which starts the sequence so then the pump will not run.

The pump then operates the system flow switch and tells the PCB that its safe to turn on the gas.

Unfortunately you are making the same mistake as many diyers that you try to understand how the boilers works rather than concentrating on what is not working.

Its very rare that the two pipes are blocked. If they were then they would stay blocked.

Much more common that the system flow switch does not operate reliably due to dirt or blockages in the system.

Its difficult for me to me more specific because you are not posting consistant situations.

Tony

 

[leezer3]

Its not consistant, although I'm getting a better idea of whats happening

Boiler Cold:
DHW diaphram doesn't move, burner doesn't light. No hot water. If the microswitch operated by this diaphram is pushed, the burner lights but cuts out when the tap is turned on.
Central heating works as expected; IE. 6 mins odd for rads to start warming up properly.
Pump starts if the heating is on only.

Boiler Hot:
DHW diaphram moves when hot water is demanded. Water is relatively hot at trickly, going cold as the tap is turned on. Boiler mode is unimportant, will do this either in HW only/ HW & heat modes.
Central heating works as expected.
Pump starts whichever mode the boiler is in.

Make any more sense to you than it does to me?

-Leezer-

 

[Agile]

Not much but start at the beginning!

If the DHW diaphragm is not moving then the expectation is that the internals of the diverter valve are stiff !

Ideally the whole assembly should be removed, dissembled and boiled in a pan of citric acid and then washed, dried and reassembled with silicone grease on the pins and seals.

Special attention must be paid to the cleanliness of the two pins where they pass through the glands. They must be completely clean and smooth.

Tony

 

[leezer3]

OK, had the whole thing to bits as best I can. Redid the DHW diaphram, cleaned pipes etc. Symptons are better, but its nowhere near as good as I'd like.
Currently:
Hot water works acceptably on low tap settings.
Hot water temperature dial isn't having any effect on the initial water temperature (Temperature lights don't go above 40 on the boiler), but turning it to max as I have currently gives barely acceptable hot water as a whole, going to lukewarm on nearer full flow.
CH pipes are both cold when in HW mode.

Both diaphrams are new, haven't changed the microswitches, although I could, but AFAIK these either work or don't?

Further thoughts, other than junk it

-Leezer-

 

[Gasguru]

Check the temperature control spindles on the knobs aren't broken ie maybe the board is set to a low temperature.

Adjust the hot tap flow rate to fill a standard sized bucket in 1 minute. Look at the burner flames...they should be on maximum and not fluctuating up and down or cutting out, if they do remove the plate heat exchanger and check for blockage on the primary (heating side) as has been suggested several times.

 

[leezer3]

No change
As far as I can tell, spindles are working, but I wouldn't like to be certain. (Boxed in & changing the setting appears to affect the amount of HW given, overall temp doesn't change, but you get a higher rate out the tap so I presume they're working to an extent at least)
Flow rate is already at about that level. (As close to 9l/min as I could get things, as per Ariston's specs)
Boiler pressure is at 1.5 bar cold, 2 bar working, again as per the specs.
Burner flames are on max & don't cut out or anything.
No blockages in the heat exchangers as far as I can tell, water in the system is pretty clean with no gunk.

Cheers

-Leezer-

 

[Gasguru]

If your hot tap flowrate is about 9 litres a minute and the burner is on maximum (and not modulationg down at any stage) the boiler would appear to be working normally. The temperature should be sufficient for bathing.

If the heat is not going to the radiators (ie the diverter is not partially jammed and all the heat energy is going to heat the domestic hot water) and the water is still not getting sufficiently hot there must be a problem with the burner gas pressures.

The next procedure is to measure the gas rate at the meter to check it's burning sufficient gas. Open the hot tap fully ie to get more than 9 litres/min, make sure no other gas appliances are running. Go to the gas meter and time (in seconds) for 1 revolution of the test dial. If there is no test dial on the meter note the reading (3 right hand digits) and start the stop watch. After 2 minutes note the 3 right hand digits again.

Post the results.

 

[ChrisR]

REplace the "CH" Thermistor.
Let CH go cold, run tap and see if Heating flow pipe gets hot while tap is running.

 

[Agile]

CH pipes are both cold when in HW mode.
-Leezer-

I think that he has done that Chris!

Its the gas rate we are waiting for now.

Tony

 

[leezer3]

Apologies for reviving a rather old thread, but I'm back to trying to fix this idiotic boiler
Nothings really changed since my last post. I ignored it over the summer, as hot water wasn't an issue then, and for the most part I've been using the other shower otherwise. Circumstances mean that I may well need hot water in the other shower, and the boiler needs fixing
The central heating works perfectly, it's just hot water thats an issue. (Undersized radiators, but again thats another thing that I'm not changing any time soon)

From the last post, one revolution of the meter test dial takes 36 seconds with the boiler running on full hot water. This produces lukewarm water at best.

Cheers

-Leezer-

 

[Gasguru]

If the flames remain at full height for the full 36 seconds then the boiler is consuming the correct amount of gas. Either the diverter is sticking and heat is being sent to the radiators or you are expecting too much performance from the boiler and you should adjust the flowrate acordingly.

 

[leezer3]

If the flames remain at full height for the full 36 seconds then the boiler is consuming the correct amount of gas. Either the diverter is sticking and heat is being sent to the radiators or you are expecting too much performance from the boiler and you should adjust the flowrate acordingly.

No heat going to the radiators & the flames remain constant (I can only presume this is full flame), so maybe I am expecting too much from it
The specfied flow rate is 9L/ min, surely I should be getting better than lukewarm water out of it for this though?

Cheers

-Leezer-