Ariston microGenus combi Boiler

jennifernil

Our daughter has an Ariston microGenus combi boiler in her flat. It is about 6 years old, she has owned the flat for 4 years now. The flat is on 2 levels with the lounge and kitchen on the upper level. The boiler is situated on the lower level. Generally the boiler has worked quite well until now.

She had it serviced after she moved in and the guy topped up the water in it. There is a permanent filling loop, this seems to be common up here in Scotland, I have see similar on several other boilers. It then started making a vibrating in the pipes when the thermostatic valves started closing off. The pressure in the system was also much higher than before.

The engineer returned and let some water out again, but the only way to let water out seems to be to open a joint and hope you catch the water. Surely this cannot be right?

He also said she had to keep one radiator with the top of the TRV removed as the automatic bypass in the boiler was insufficient. This she has done.

All was fine until about 3 months ago, then it started making the vibrating in the CH pipes again. This was relieved by turning up the TRV in the lounge. She also found (after that) that there was a lot of air in the lounge radiator, which was not very warm, this was solved by bleeding it.

Then she started having problems with the hot water from the shower, which is a thermostatic one over the bath. There is plenty hot water from the kitchen and bathroom taps, but the shower is now decidedly chilly. The only way to get a hot shower is to reduce the flow, and this causes the pipework to the shower to judder and there is a sort of clattering noise in the boiler. If the flow is turned up the juddering and noise stops but the water gets too cool again.

At about the same time, she also noticed that the water pressure dial on the boiler was showing 3, rather than the usual 1.5. She was frightened to run the boiler so her dad went down and let out some of the water and made sure the filling tap was properly turned off.

So far the pressure has stayed normal, but she still cannot get a hot shower and the juddering and noise is still happening when she turns down the flow.

Her dad is good with electrics and plumbing and is going to look at it again, but he will certainly not be touching anything to do with the gas connections. We just want to get some idea of what the possible problem could be, whether this is a common fault, will it be straightforward to fix. Perhaps it is something her dad can fix.

We do not have any recommendations for heating engineers so want to have as much knowledge as possible before calling someone in if it is something complex. She is now a PhD student on a limited income so she cannot afford to give anyone carte blanche to just replace parts till it works. (previous family experiences with heating problems have not been good!!!)

She has the Ariston Installation Instructions which have a lot of detail, but, unlike in our boiler manual, there is no fault finding guide.

Any help/advice/experience of similar faults most welcome.
Thank you! And sorry it was so long!

Canucklehead

Hi

Which model of micro genus is it?
Some do not have a drain point under the boiler.

I would suspect the diverter and or diaphragm
Just to rule them out have a look on the trv and see what direction the arrow points.It sounds like they are on the 'wrong' end.
Not only should there be a rad with no trv on it , it should have a room stat in that room or area as well.

Your description of the system gives the impression of a poorly maintained one and maybe a poor original installation as well. IMO you will need to spend some money on it now , or more in the future.

Corgi Guy.

PS What about the original 'engineer'?

jennifernil

Thank you for taking time to reply.

It is the 23MFFI according to the instructions. It is the one with the mechanical 24 hour timer, but her dad fitted it with an external electronic 7 day controller.

If there is no drain point then how are you supposed to drain the system?

Her dad suspected the diverter valve, it seems to be "fluttering" when she turns down the flow on the shower. Presumably replacing the valve will require the system to be drained? Is replacing it something he could do himself? Is the diaphragm available on its own if that is the problem?

When the shower is on full flow the water is tepid, presumably this is because it is running through the boiler too fast to get heated enough being very cold at this time of year? But could this indicate a second fault? Should the boiler not be able to cope with this?

There is no problem with getting plenty hot water at the taps in the kitchen, upstairs toilet whb and bathroom whb, and drawing water from these taps does not bring on the noise in the boiler. It only happens with the shower. Hot water to the bath taps has never been great, but that seems to be common with combis. The radiators are piping hot.

I was not impressed by the first guy who serviced it, he did not seem to be very knowledgable, but that was only my impression. And it was OK before he touched it! So we decided not to use him again.

Since then it has been checked over every January by a different company who seemed better, and everything was OK for those 3 years. They also did the Gas Safety Certificate as she had a room rented out. Now she is on her own she doesn't need one so she was hoping not to need him to visit this January.

Her dad says he would agree it was a poor original installation! A lot of the work in the flat is poor, especially the plumbing, she has had a lot of trouble.

We will check the TRVs tonight when we visit, but 99.9% of the time the CH is fine, so the problem with the HW seems to be unconnected. It was however worrying that the pressure in the system rose so much, but maybe she did not have the tap on the filler 100% tight.

Is the microGenus a decent boiler? Is it worth spending a bit on? We have 2 Potterton conventional boilers in our house and they have been running for almost 20 years now with absolutely no problems, there seems to be a lot of problems with the newer boilers.

Sorry for so many questions, but we do not want her to be wasting her money.

Canucklehead

Hi

There are three diaphragms but I would look to the diverter, it has a motorised head (p 14 in the book) it might be the push rod assembly inside it. not moving smoothly . Try using the hot water when the heating is cold and see if the c/h flow gets hot, also see where the noise is at it's loudest.
Looks like a fiddle to get out and service.
The system would normally have a drain off somewhere on the lower floor. Quite often I take off a small rad and drain from the valve, much less mess as drain off valves can be a pain.
Your boiler is only 9.2 litres a min for hot water so at the lower end of the market in that regard.(the 27 will give 11.5)
Boilers are more complicated and will therefore have more to go wrong ,not much to be done about that except that if it's fitted to a clean system and looked at regularly certain parts will last longer.
If the pressure is not stable between 1 and 2 bar then it was probably not turned off 100% as you say.


Corgi Guy.

jennifernil

Thank you for that, we will see what's what this evening and maybe have a few more questions!

KPNUTZ666

Hi,

I've got the microgenus 24 , i've had it for 18 months.. in the past few months i have experienced the following :-

1. Whether the heating is on or off , when i'm washing or having a shower in the last few months i have experience the water goes from HOT TO COLD even though on the bolier panel the LED DISPLAY FOR THE TEMPERATURE SHOWS THE CORRECT TEMPERAUTRE THE WATER HAS REACHED. ( i live on my own - therefore no chance of anyone else turning the taps on.


2 . error code A94 .. i've checked the service manual etc ..it does'nt tell you the exactly what the error is . I have re-set the boiler several times , i noticed it goes away ..it comes up when you least expect it.

3.I notice the fan comes on 5-7 times a day for a few minutes , this is when the timer is not set .. Is this normal ?

it's becoming a nusinace , because when my young daughter comes and stays with me , she is having a shower , the hot and cold flushes occur.

Please can some one advice why i experience these problems.

The engineer who installed the boiler has gone AWOL .. he promised to send me my guarantee ..he hasn't .. thats why i'm on here for advice.

I got a quote from ofew corgi reg chaps .. they say its going to cost me well over £150 for the part + labour ex vat .. i think they trying to pull a fast one.
They say the divertor valve is faulty .... hmmm


Sorry for the long post..

Hope to hear from some-one ..

Cheers

K

gasmanmartin

KPNUTZ666 wrote: »

2 . error code A94 .. i've checked the service manual etc ..it does'nt tell you the exactly what the error is . I have re-set the boiler several times , i noticed it goes away ..it comes up when you least expect it.

Code a94 is the overheat thermostat, top left of the boiler inside the combustion chamber. You will need an engineer to look at this.

Usually if you take the leads off and give the probes a clean and re-fit it will cure the problem, It's not the stat that's at fault, its the boiler having problems sensing it correctly.