Biasi HE hot water goes cold

[thegoose]

Can anybody help? I changed my boiler to a Biasi Garda HE 28 fitted about 6 months and everything worked as it should. Now for some reason when I run the shower the hot water heats up and works fine for about 2 minutes and then goes stone cold. After about 30-40 seconds the water heats up again and works for about 2 mins then goes cold again. This repeats itself all the time the shower is on.

I have noticed that when the shower is turned on the temperature gauge that is sensing the temperature of the primary circuit starts to rise from about 30 degs and reaches about 75 degs then cuts out the burner, the water runs cold, the temp drops to around 30 degs and then the burner fires.

The burner on the boiler only seems to have two setting they are full on or off. Is this normal? Or should the flame size vary in size.
Does modulation mean turning the flame steadily up and down appropriately or just on and off

To complicate things further if I turn the bath tap on full I have lots of flow and pressure, the water only get warm not hot. Looking at the temp gauge it reads about 60 degs with the burner on full. If I turn the tap down slightly the water gets hotter and the temp gauge rises. If I turn the tap down some more (still ok flow though) the water gets that hot that the gauge reads about 75 degs and the burner goes out, temp drops to about 30 degs and the water gets hot again just like the shower.

I’m pulling my hair out now. Any ideas please help.

 

[Agile]

Can anybody help? I changed my boiler to a Biasi Garda HE 28 fitted about 6 months and everything worked as it should.

Do you really mean that YOU changed it yourself?

If so the you probably did not bother to power flush the system before fitting the boiler.

The plate HE is now badly blocked and needs replacing or cleaning! Best after the power flushing has been completed otherwise it will just block again.

The boiler does modulate down to a lower power setting although that will not happen unless a CORGI installer has checked the gas valve settings are correct.

If you did not fit it yourself then you employed a cowboy who did not clean the system and should be called back to sort it out at NO extra charge as its his fault entirely.

Tony Glazier

 

[thegoose]

Yes fitted it myself but did power flush the system.
The pressure are set correctly but i apprciate the point your making.

The central heating works perfect, would this not demonstrate that the system was clear as its the same circiut used to heat the rads as it is to heat the water? the cold supply is filtered, softend however the supply pressure maybe high i'll get a pressure reading later.

the hot water has a temp setting from 0 to 7 if i have the setting set to 5 the temp of the primary circuit does not reach 75 deg therefore does not shut down but the water temp is not really hot enough.
My first thought were like yours that the matrix was blocked or reduced on the water supply circuit of the matrix but the flow and pressure are fine.

real puzzler

 

[ChrisR]

would this not demonstrate that the system was clear

No!

Not a puzzler at all. If you do a search you'll find it's a common scenario.

 

[mehran]

Your boiler is displaying classic 'I am too cheap to get it fitted correctly' or the more technical reason is that your dhw plate heat exchanger is blocked.
Your boiler can modulate just fine. Please Phone biasi so some one can come out and charge you for your cheapness

 

[Agile]

The central heating works perfect, would this not demonstrate that the system was clear as its the same circiut used to heat the rads as it is to heat the water? the cold supply is filtered, softend however the supply pressure maybe high i'll get a pressure reading later.

Thats a common missake by people who dont understand how a combi works.

How do you know the GAS pressures on the gas valve are set up correctly????

Did you just read the word pressure ans assume it was water pressure?

Tony

Tony

 

[thegoose]

Mehran, great help?.

ChrisR, Still puzzled. looked over the forum but struggling to find the answers. your right i probably is on here but i cannot find it.
do you think it is the heat exchanger?

Merhan thinks its the heat exchanger thats blocked but which side the heating side or the heated side.
The heating side works fine for the central heating and its the same circuit for the hot water just diverted by divertor valve?

is it really a case that cheap is nasty and this is as good as can be expected.

 

[mehran]

Ok... do you think biasi have a guy at the factory where your boiler is made putting crap in to the heat exchanger? Or the vastly more likely thing that crap from your central heating which has not been cleaned correctly has blocked the water ways in your dhw plate heat exchanger?

Now, is it a case of:
'i was too cheap to pay some one to fit your boiler correctly'
Or as you put it
"a case that cheap[boiler] is nasty and this is as good as can be expected"

Of course you there may be a slim change that something has really gone wrong with your boiler but I doubt it

If you phone biasi for a warranty job they will charge if it is a blocked dhw heat exchanger for wasting their time. If you feel that your system is clean then phone them in to fix your boiler

 

[thegoose]

first things first. why the atitude?

I fitted the boiler but the set and conection was made by my brother Corgi registered plumber.

Agile: the pressure setting were set by corgi they were max/min burner pressure plus gas flow and flue temp and pressure if i remember correctly.
i appologies if i mislead or upset any plumbers but to keep cost down i fitted the boiler and my borther (the proffesional fitter of 20+ years) did the tricky stuff.
He has tried all he know and suggested trying this forum.

The system was proffesionally flushed and evewrything that should be done has. But it would appear that we have done something wrong or missed something.

Again sorry for affending anyone but i still need help.

 

[tonymaloan]

Before the Corgi scaremongers frighten you to death, have you checked xxxxxx fan xxxxxxxxx

It is worth a try, the Biasi is a good little budget boiler

[Sorry, please don't advise DIY work in gas/air/controls parts of boilers.
Secondary heat exchanger is OK & that's where this problem probably lies.
Mod 10]

 

[thegoose]

Tonymaloan:

Thanks for your help i was thinking i'd upset everyone here.
makes me laugh a bit the web site is a do it yourself site.
Obviously somethings you've got to get the tradesman in, and i have for the setup but once there stumped its onto the forums.

Could you explain in a little more depth
Thanks.

 

[Agile]

Before the Corgi scaremongers frighten you to death, have you checked the venturi in the fan housing, it is a 15 minute job, take the flue elbow off the top

You encouraging a non competent person to do work on the gas train! Thats inappropriate advice!

You are also showing up your lack of knowledge of condensing boilers! Only non condensing boilers have a venturi accessable from the flue elbow!

Tony

 

[Agile]

Agile: the pressure setting were set by corgi they were max/min burner pressure plus gas flow and flue temp and pressure if i remember correctly.
i appologies if i mislead or upset any plumbers but to keep cost down i fitted the boiler and my borther (the proffesional fitter of 20+ years) did the tricky stuff.

He has tried all he know and suggested trying this forum.

Its is a pity that after 20 years of being CORGI registered he still cannot diagnose simple boiler faults!!!

Your blocked plate HE is the most common fault during the first few months after a boiler is installed ( badly ). Its so easy to diagnose, you only need two hands or even just one if you like.

In my experience less that 2% of CORGIs ever check the min/max gas valve settings when they install a boiler and hardly many more check them when they do a service.

Presumably he is just a simple installer?

Tony

 

[thegoose]

Agile: Still not sure whats getting you offside.

Any answer that i get from this forum will be tried by my brother (corgi registered)
He set the boiler up as per the instructions and all was well.
The faults has developed reciently and he has gone to town onthe setup now checking everything he can but still got the problem.
The system was power flushed as you said it should be and then some time later i think it was drained or a fernox additive added (cost a lot for a little small tube) and the matrix has been checked again so pretty shore its not that.
Can we now move on from the matrix idea?

 

[Agile]

Any answer that i get from this forum will be tried by my brother (corgi registered)
He set the boiler up as per the instructions and all was well.
The faults has developed reciently and he has gone to town onthe setup now checking everything he can but still got the problem.
The system was power flushed as you said it should be and then some time later i think it was drained or a fernox additive added (cost a lot for a little small tube) and the matrix has been checked again so pretty shore its not that.
Can we now move on from the matrix idea?

What is this "matrix" ? Is that the plate heat exchanger? If so then how was it checked?

All your evidence is that the plate HE is blocked!!! That convinces me that its blocked.

There are a couple of simple checks that YOU can do yourself though.

You need to measure the flow and return temperatures on the two 22 mm pipes under the combustion chamber. You can just use your hands!

The flow running across the back will be pretty hot on DHW delivery but feel it to get an idea. We know it measures 75°C on the gauge.

Then feel the return which is the copper pipe above the pump. It should only be about 15°C less than the flow and at 60°C far too hot to touch for long.

I am expecting the return to be at about 40°C as a result of the reduced flow rate from the blocked plate HE and cool enough to keep your hand on it.

That should convince you that the plate HE is blocked!

Now the modulation! At the top of the gas valve is a green solenoid with two wires connected. They are push fit spade connections. Pull off just one of them and the flame should reduce to about 6 mm high, quite small compared with the 45 mm when its on full! That proves the boiler can modulate if that happens.

If removing the wire does not give a small flame then the gas valve setting is wrong!!! Would need a competent CORGI to set up the gas valve!

Tony