Boiler problems part 2

[kev_off_the_tee]

Thanks of you who responded to a previous post, but I'm needing more help. Still the same problem as before where the heating works no problem but the hot water is cooler the higher you have the tap turned on. The 3 way valve and dhw thermistor was replaced last month to try and rectify the problem but to no avail. I'll say at this point that at no point does the radiators get warm when I run the hot tap as I've had this problem before and know this would mean the diverted.

I had my retired gas fitter come and take a look at the boiler (chaffeteaux britony combi 80) and he said that it could be down to the pcb so to replace that and while I'm at it replace the pressure relief valve as it was slowly loosing pressure. I got the new parts which he fitted and then turned the hot tap on. The water was hot even when the tap was on full flow, job done, or so I though.

I filled the sink and don't the dishes then ran a full bath for my daughter, no problem.

I the went up to wash my daughters hair and the original problem returned and I'm now at my wits end. That's now the diverted, dhw thermistor, pcb and pressure valve replaced. Every time a part gets replaced the dhw works 2 or 3 times then back to the original problem

WHAT ELSE COULD IT BE???

Thanks for any advice guys/gals

 

[markyjee]

Does the water get hotter if you turn the tap off slightly to reduce the flow rate?

 

[kev_off_the_tee]

Got it in one

 

[markyjee]

Get the flow rate checked, combi boilers can only heat upto a certain flow rate. Too much water it will only get lukewarm.

Regards Mark

 

[daymond]

Makes me glad I'm all electric!

 

[kev_off_the_tee]

Just an update, but everything is working perfectly. Strange as the original problem was still there and the next morning (sat) all was fine.

Not sure whether to be happy or worried that it might go at any time

 

[Brookesy]

Hi mate,

The only thing i can think it will be now is that the DHW heat exhanger is scaled up! Replace this and hopefully it will solve the problem, literally cant think of it being anything else :/

I very much doubt its the PCB! Suprised he got you to change the pressure relief valve also unless there was actually water dripping out the discharge pipe!

 

[Mark_G]

Like was said earlier it sounds (in my humble opinion) like a water pressure problem, my wifes grandmother had terrible problems with her boiler due to the variation in water pressure coming through the mains. As the pressure varied it went below a critical point and the boiler shut down. If the cold supply pressure went too high logically there would be no safety issue, except an inability to maintain the heat at full flow. If this is correct, then you could test the theory by when the problem is occurring, turn on all the cold taps to reduce the pressure to the boiler, if the hot taps start to work correctly then you have proven its a pressure issue.

 

[kev_off_the_tee]

Thanks guys, I think I'll run some sentinel x800 then drain and refill with inhibitor

Sorry mark I couldn't help it but.....

my wifes grandmother had terrible problems due to the variation in water

 

[Mark_G]

Thanks guys, I think I'll run some sentinel x800 then drain and refill with inhibitor

Sorry mark I couldn't help it but.....

She did mate, terrible lol

 

[williamalex1]

could be the pressure vessel has burst or needing pumped up.easy job for a heating /plumber

 

[kev_off_the_tee]

Sorry to bring this one up but still having the same problem. Heating is working better than ever but hot water is hit and miss, most of the time only being Luke warm with the tap slightly open. The tap fully open gives cold water only.

Williamalex1 - could this still be the problem if the heating is working perfectly?

After still having problems I have changed the secondary heat exchanger to the newer, deeper model but the old one didn't look too bad. I'll keep it and descale it then its a backup.

I have been advised that the water governer could be the problem. Is this a possibility and is this something I can change myself as money is a little tight given the time of year?

 

[williamalex1]

whats make and model . and i'll ask my mate who is qualified in plumbing / heating, i only do electrics for him.i asked at the moment he says the thermister if its an newish boiler or the diaphragm if an old one. get back to me

 

[kev_off_the_tee]

It's a britony combi 80, around 10 years old

In October it had the dhw thermistor, pcb, and air pressure valve changed

In September it had the 3 way diverter/ diaphragm changed. Don't think this is the problem as there is no hot water getting into the central heating when the hot tap is being run

Thanks again, kev

 

[6inchcup]

sounds like a flow rate problem,but to be honest i would not have spent so much on a 10 year old combi,for what you have paid in parts and labour you could have got a new one fitted with a 5 year warranty.

 

[williamalex1]

my mate said to check your flow rate . it should be no more than 10 litres per minute . so get a 10 litre container and a hose turn your tap on full to fill it , if it overflows in less than a minute then your flow rate is too high, and you will have to reduce it. worth a try, get back to me and i'll ask what else to try . its elimination. but he agrees with 6 inch .should add cold mains tap

 

[kev_off_the_tee]

Thanks guys ill check the flow rate but the strange thing is for 10 minutes there it worked perfectly. Tap on full and red hot water.

6inch - i get all my parts of ebay, new and with warranty and I'm using a neighbour who is a retired gas fitter. He retired well before his 60th which was some time ago but is still handy and very willing to help in exchange for a few beers. Have offered him proper payment but he point blank refuses saying if he got paid he might as well go back to work.

Everything I've swapped up to now has cost less than £100 so it really is worth battling on

 

[Brookesy]

Hmmm suprised its not fixed with the heat exchanger! Does sound like water pressure could be the answer although its quite uncommon!

You wont get any heating when your running the hot water as in combi's hot water takes priority over heating

 

[kev_off_the_tee]

I haven't got a 10 litre container just did an experiment with a 1 litre jug (how scientific).

Water comes into house, through meter then to a t-piece taking water to the boiler and kitchen tap/upstairs taps. Using my highly technical method of filling a jug, very quickly emptying then refilling I got 11 litres in a minute. Allowing for the emptying I'd guess 12 litres per minute.

The strange thing is that it has worked no problem for 4 1/2 years without problem

 

[kev_off_the_tee]

Is there a way I can reduce the flow to the boiler?