Water not heating consistently

[merton69]

I own a Ariston Euro Combi A23 MFFI and when I turn the hot water tap on in the bathroom, the water heats but not to what I think is hot enough.

The tap is very slow running to gain a decent heat but as soon as you turn it just a little more, the water runs cold.
It's very difficult to obtain a decent flow that will have a hot temperature.

It's not much better with the kitchen tap either and the tap is only 7ft away from the boiler.

Any suggestions for a remedy please?

 

[merton69]

I have turned up the temperature dial and no real change in the flow/heat ratio.

Any ideas please?

 

[oilhead]

You have a combi. If you look at the specifications, it will state a rise in temperature for a given quantity. This time of year, your incoming mains will be pretty close to 5 degrees, so if you have a 40 degree lift, then it will only get to 45 degrees at the tap. Your bath will have a 3/4" tap, and probably 22mm supply pipework, so it will very easy to exceed the optimum flow rate, delivering a cooler temperature than expected.
To test the performance, identify the temperature from your boiler spec book, run your tap into a measured container, and check the temperature. I suspect you will have to get used to running your bath slowly.

 

[merton69]

Thank you oilhead.

I will have a look and see what I can test with.

We have had the boiler for a fair number of years and can never remember having such a poor flow rate with a low temperature.

 

[oilhead]

Now we geta bit more of the story. Do the tests, and you may find you need a new DHW heat exchanger. Irrespective of temperature, how does the hot water flow rate compare with the cold water flow rate. Easy enough to gauge with a watch and a 2 litre pop bottle.

 

[merton69]

Sorry if I didn't give enough history to the system or problem.

Is there anything else I should give oever please?

Also, is it worth giving the DHW heat exchanger a clean out as suggested with a YouTube clip?
(

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Many thanks.

 

[merton69]

 

[merton69]

I see myself as a confident and competent DIYer, so I would like to know if I am in a position to remove the Heat Exchanger myself and clean it out or is it a job that can only be done by a gas registered engineer please?

Thanks.

 

[MeldrewsMate]

Read the manufacturer's instructions.
Changing the secondary heat exchanger is not in itself a registered gas fitter only job, but if at any point you have to either disturb a gas carrying component or open the combustion chamber door (is considered part of the flue system) then it MUST be done by a competant and qualified (Gas Safe Registered) gas fitter.
Prepare to catch water dripping from the boiler, and protect all the electric parts too.

 

[merton69]

Thanks MeldewsMate.

So I feel I can do it. I presume the order to fix this situation is to:-
• Turn of the electrical source.
• Drain the system.
• Remove the DHW heat exchanger.
• Clean throughly.
• Reinstall DHW heat exchanger.
• Fill system to correct pressure.

Is there anything else I should be doing or looking out for please?

 

[ianmcd]

isolating the cold water supply might be a good idea

 

[merton69]

Yes, of course, forgot to add that in.

Thanks.

 

[merton69]

Hello.

I am waiting on my order of Spirit of Salts to be delivered (bl*ody Christmas) so I can flush out my DHW Exchanger.

I presume the metal used for the Exchanger will cope with the acidic strength SoS is?

I won't corrode and damage it please?

 

[John D v2.0]

I presume the metal used for the Exchanger will cope with the acidic strength SoS is?

aluminium wouldn't, but anyway that's horrific stuff isn't that what they used for acid attacks? if you did a risk assessment you'd realise at 55 quid it's the only option to replace the thing!

 

[merton69]

Thank you for your reply. Right now £55 is alot of money. If I had that sort of money right now I would probably get an engineer to do the whole job.

I saw this excllent YouTube video showing how to clean a Exchanger with SoS......