Ariston MicroGenius 27 DHW Problem

[Ziggy]

Hi Guys

I've been having problems with the DHW which fluctuates between hot and warm.

A British Gas contractor came round yesterday to look at the boiler and without opening it at all diagnosed a sludge problem and would benefit from a 'powerflush' or possibly a new boiler due to cost of 'powerflush'.

Anyway he's ordered some thermistors (I think) and said he'll be back in 2 weeks to fit the part but isn't confident it will fix it as he's adamant about a 'powerflush'.

I've read many alarming articles on the internet about BG's practices regarding 'powerflush' and getting the engineers to promote this service and although I'm not an expert on boilers (just a guy with common sense) it seems to me to be an expensive and intense way to rectify the problem especially as he didn't even take the casing off the boiler to take a look.

He also commented on that there's probably never ever been any inhibitor added to the system which I commented on and said that everytime I drain down the system I add more.

From a central heating point of view everything is working fine with no cold spots on the radiators at all and the house is nice and warm.

So could sludge be a problem?

As I previously stated the problem was that the hot water was fluctuating between hot and lukewarm with the pilot light going out for a few seconds then lighting up again this was happening with the DHW setting on 4 or higher.

After the BG engineer went I experimented more with the DHW and have discovered some more info.

I've now turned down the setting to 3 and now I have constant hot water.

Any help or comments would be most appreciated.

Regards

 

[ChrisR]

Your problem is usually caused by sludge in the boiler side of the heat exchanger which heats the tap water. It doesn't take much. Faulty temperature sensors are cheap and can cause similar symptoms so can be worth a try, but yours sounds like classic for sludge. New sensors = 20 mins work, and van stock.

Most CH systems have some sludge in them. If you replace a boiler , you need to check and get rid of as much as possible, though a powerflush isn't a 100% clean. Fernox who make the kit and chemicals say 80%.

You boiler is a few years old, so it has taken a while for sludge to be an issue. If you keep the level of inhibitotr up as you do, then if the heat exchanger is cleaned or replaced, it should take about the same amount of time for the problem to recur. I think a new hex is about £60 and they're quick enough to change.

This is hogwash:

would benefit from a 'powerflush' or possibly a new boiler due to cost of 'powerflush'.

A powerflush would clean the system (80%), but not the hex.
If you had a new boiler you'd need a flush anyway.

Deal with the hex now, and enjoy a few more years service from the boiler. Sack BG.

 

[Ziggy]

I think a new hex is about £60 and they're quick enough to change.

Many thanks for the quick reply Chris.

Excuse my ignorance but would the HEX be the primary or secondary or I'm I barking up the wrong tree.

Going back to the the powerflush issue, is it worth it in your opinion?

 

[gas4you]

Powerflush can be a good thing, but it is the biggest, overhyped 'cure' for all heating system problems

 

[Ziggy]

... but it is the biggest, overhyped 'cure' for all heating system problems

That was my initial thought, thanks for your input

 

[Ziggy]

I think a new hex is about £60 and they're quick enough to change.

The BG guy came back and fitted new sensors but the problem still remained, his diagnosis is that the HEX is partially blocked and advises on fitting a new one.

He looked up the part on his laptop and came back with a price for the part of £78 but isn't sure if that's the 'fitted' price.

 

[Ziggy]

Not heard anything else from BG so I've decided to sort out the problem myself.

I'm going to soak the HEX in Fernox DS3 and while that's working away I'll fit a Magnaclean and hopefully that cures the problem.

 

[bengasman]

you would do well to first run the system a couple of weeks with cleaner in it, and rinse thoroughly before you do this as that would reduce the chance of the problem coming back

 

[Ziggy]

you would do well to first run the system a couple of weeks with cleaner in it .....

Good advice, thanks bengasman.

Would this product be suitable http://www.calmagltd.com/calchem

 

[bengasman]

sounds okay, though i don't know it personally.
have had good results with kemko hyperflush and fernox f3

 

[Ziggy]

sounds okay ....

Certainly does according to this page

http://www.calmagltd.com/chemical_inhibitor_comparisons

 

[waterworks]

This model is prone to plate ex blockages, remove and clean easy job two screws.

 

[Ziggy]

This model is prone to plate ex blockages, remove and clean easy job two screws.

Thanks waterworks, that's what I intend to do

 

[Ziggy]

Still no word from BG so this morning I drained the system completely and removed the HEX (had to remove the divertor valve actuator first) and soaked it in Fernox DS3, whilst that was doing it bit I fitted a Magnaclean which was easier than I thought (I did notice inside the piece of pipe I cut out there was a very thin film of black debris).

I was expected some sort of reaction from the DS3 on the HEX but just had the odd bubble so I left it for around one and half hours then decided to rinse it through with cold water and then black flakes began to appear.

Then I used a drill pump attachment on it to clean it further and eventually was satisfied that most if not all the black flakes had been removed, hoping the Magnaclean will pick up any residual.

I refilled the system and added some Calchem and everything now seems to be OK.

The DHW is back to how it should and no problems from the CH side but I did get a red light appear after around an hour after bringing the system back and cleared that by turning the power of from the boiler off for a while.

I would like to thank everyone for their input on this matter and hope it helps others.

 

[BigBurner]

Run the system for a day or so and clean the magnaclean filter. Then after a week and a every week until clean. Then every year.