Problem with Biasi boiler?

[fobes77]

Hello, been having a few problems with a 24s Biasi Boiler in a flat I recently moved into. Just thought I'd check on here first to see if this is something real simple.

The main problem is that the central heating doesnt come on unless I press the Overheat Thermostat Reset Button, which then lights the boiler and everything is good. This sometimes applies to the hot water too but not always.

I notice from the Biasi brochure that reset button should have some kind of cover on it, which might keep the small red button depressed, would this be the problem?

Picture -

We do not have this black cover over the Thermostat Button - is that a problem?

Thanks for any help!

 

[Nixt]

From your picture you have no system pressure hence the overheat problem. Look up filling in FAQ's.

 

[fobes77]

Thanks but that is not my boiler in the picture - that is from the Biasi brochure - it shows the Thermostat Reset Button with a black screw-on cover on it. We dont have this (there is just a small red button exposed, which the missing cover should fit over). But we definitely do have system pressure!

 

[gas4you]

Black cover won't affect anything.

To overheat you must have lack of circulation somewhere with a faulty stat or a faulty overheat stat.

 

[fobes77]

Ah ok I see, thanks.

I'll keep an eye on it and see if the problem persists, it seems to be ok since the last reset this afternoon.

 

[Agile]

Its most likely to be a blocked plate heat exchanger or a scaled main HX.

Does the overheat happen DURING boiler usage and if so on CH or DHW?

Or does it happen a few seconds AFTER heat use?

Tony

 

[fobes77]

Cheers.....it's only started happening since we tried the CH, but now the HW will cause the temp gauge to rise steeply too.

It's currently on around 40 deg with just HW, I think if I leave the CH on it will continue to rise - or is that the correct kind of temperature?

I'm pretty sure before messing with the CH the temp was around 20-25.

I could try putting the CH on again and seeing what happens to the temp?

This boiler's heating wouldnt have been used since early this year I guess, I was hoping it was just something to do with that.....

 

[Agile]

At normal settings the temp will be 50-60 on DHW and 60-80 on CH.

At those temperatures the oveheat stat will not trip.

It MIGHT be tripping just AFTER using DHW. Is that when its tripping?

What position have you got the two control knobs at?

Tony

 

[fobes77]

Thanks Tony, it's stopped tripping now - it hasnt gone above those temps.

Might it be possible it was a temp problem caused by lack of use?

The temp control knobs are at about 5 oclock (CH) and 6 oclock (HW).

 

[gas4you]

I have had faulty stats that only fail when you turn them up above a certain point, so if you keep them in the working lower area it will cut off as normal so it won't overheat.

Not had it on Biasi's but on Ravenheats. I wish I knew why though

 

[Agile]

I have had faulty stats that only fail when you turn them up above a certain point, so if you keep them in the working lower area it will cut off as normal so it won't overheat.

Sometimes low calibre engineers put the 24S knob spindles in at 180 degrees out and the control is not operating as expected.

Tony

 

[blooto]

Its most likely to be a blocked plate heat exchanger or a scaled main HX.

Does the overheat happen DURING boiler usage and if so on CH or DHW?

Or does it happen a few seconds AFTER heat use?

Tony

Hi,

My biasi 24s oh stat sometimes activates after use, could you please explain what this could mean?

 

[Rick79]

Hi,

I also have the same problem but the boiler trips/overheats and needs resetting only AFTER the dhw is used for a long time e.g. running a bath. it does not do it during operation but a few seconds afterwards. Please can you suggest what this may be.

Agile, you seemed to have an idea in your posts, thanks.

 

[Agile]

Re. the last two posts. ( Never got to see the 2009 one! )

If the o/h stat tripps AFTER a DHW useage then that indicates a scaled up main heat exchanger.

[ To engineers, this is because the boiler does not have a pump over run to hide the fault. ]

That can either be fixed by replacing it ( needs gas engineer ) or by chemical treatment in situ. At a pinch that can be done as a DIY job, BUT is messy and involves using acidic chemicals.

We always deal with it as a clean in situ as we can do it on the one initial visit but as its time consuming and messy then we charge about £160-£180 for the job.

Tony