Combi Boiler problems!?!?!?

[rash_decision]

Hi all. I'm looking for some advice on an issue I'm having with my Boiler, a Biasi Garda HE, I think. Sometimes when the heating comes on, the radiators heat up fine, but when the boiler switches off once at temperature (thermostatically controlled internally for water temp??) and comes back on to maintain the heat, well, it doesn't! The pump is running, but there's no sign of the burners being ignited, and the temperature drops.

I've also had an issue, which may or may not be related, that when the heating is on and working fine, I get no hot water from taps or shower!? Could these be related and pointing to an issue with the diverter valve??

I'm keen to get these issues resolved as we're getting closer to winter!! Hopefully someone can conclude it's something simple! I don't want to be replacing the boiler!!

[shirt]

bookmarked!

i have the same boiler [i think] and have an issue where the boiler fires up when a hot tap is turned on, then once it reaches temp. will switch off and wait a few mins before firing again, makes showering a fun game!

plumber is going to look at it when someone can be there to meet him. i did note that it works fine [or much better] with the cover to the combustion chamber removed.

[Rickyy]

I've discovered the issue.

rash_decision said:

Biasi Garda HE

In all seriousness though, I'm not too familiar with this boiler. But I wouldn't be looking in to the diverter valve unless you are getting symptoms such as radiators warming up when you run the hot tap. Don't rule it out completely though.

Personally I'd be looking at sensors/thermistors. Sounds more like an electronic problem rather than a mechanical one.

Without seeing the boiler, its hard to tell.

[Arthur Jackson]

shirt said:

bookmarked!

i have the same boiler [i think] and have an issue where the boiler fires up when a hot tap is turned on, then once it reaches temp. will switch off and wait a few mins before firing again, makes showering a fun game!

plumber is going to look at it when someone can be there to meet him. i did note that it works fine [or much better] with the cover to the combustion chamber removed.

Most likely a blocked domestic heat exchanger, but might be a CH thermistor.

[rash_decision]

Rickyy said:

In all seriousness though, I'm not too familiar with this boiler. But I wouldn't be looking in to the diverter valve unless you are getting symptoms such as radiators warming up when you run the hot tap. Don't rule it out completely though.

Personally I'd be looking at sensors/thermistors. Sounds more like an electronic problem rather than a mechanical one.

Without seeing the boiler, its hard to tell.

So Biasi aren't very good I assume???

If it's a blocked heat exchanger, or a knackered thermistor, can these problems be rectified??

[rash_decision]

Sorry, I should have said, once I realise that the heating is no longer working, if I switch the heating off, then immediately back on, it fires up fine, in case this helps with diagnosis!!???

[Rickyy]

They're not the best, no.

But shouldn't be beyond repair. Thermistors are relatively cheap and easy to replace.

Heat exchangers are considerably more expensive and more time consuming to replace.

But going on from your description about it working once you've switched it on and off.

I'd still say it is an electronics problem. When the heating is working, how hot does everything get?

Its possible that it is going into overheat lockout. This could be caused by a duff sensor/thermistor, which will not detect the system temperature and continue to heat up until the safety over heat stat kicks in.

When this stat kicks in they normally kill the burner and keep the pump running to dissipate heat. By turning it on and off may act as a manual reset. Just an educated guess.

Overheat can also be caused by poor circulation caused by air locks, faulty pump or a build of sludge in the heating system.

Could also be a circuit board fault. The possibilities are endless!

[rash_decision]

Rickyy said:

They're not the best, no.

But shouldn't be beyond repair. Thermistors are relatively cheap and easy to replace.

Heat exchangers are considerably more expensive and more time consuming to replace.

But going on from your description about it working once you've switched it on and off.

I'd still say it is an electronics problem. When the heating is working, how hot does everything get?

Its possible that it is going into overheat lockout. This could be caused by a duff sensor/thermistor, which will not detect the system temperature and continue to heat up until the safety over heat stat kicks in.

When this stat kicks in they normally kill the burner and keep the pump running to dissipate heat. By turning it on and off may act as a manual reset. Just an educated guess.

Overheat can also be caused by poor circulation caused by air locks, faulty pump or a build of sludge in the heating system.

Could also be a circuit board fault. The possibilities are endless!

There are no lights up to indicate a boiler lock out from overheat, but what you're saying makes perfect sense, and sounds just like what I'm experiencing. When the heating is working it doesn't heat up any more than I would expect in comparison to the temperature setting. Once I switch it off and back on it works no problem for as long as it's left on, which would kind of rule out a "mechanical" issue I guess??

I might drain the system and replace the thermistor for the heating, and whilst it's down give it a flush through, then bleed it all thoroughly. A quick search and the thermistors are around £5, and very easy to replace from what I can gather. In fact, I should do both for the heating and hot water, to see if that helps the issue with the shower running cold when the heating is on?? Although I'm convinced that's the diverter valve!?? The annoying thing is, it's quite random!!

[Rickyy]

rash_decision said:

There are no lights up to indicate a boiler lock out from overheat, but what you're saying makes perfect sense, and sounds just like what I'm experiencing. When the heating is working it doesn't heat up any more than I would expect in comparison to the temperature setting. Once I switch it off and back on it works no problem for as long as it's left on, which would kind of rule out a "mechanical" issue I guess??

I might drain the system and replace the thermistor for the heating, and whilst it's down give it a flush through, then bleed it all thoroughly. A quick search and the thermistors are around £5, and very easy to replace from what I can gather. In fact, I should do both for the heating and hot water, to see if that helps the issue with the shower running cold when the heating is on?? Although I'm convinced that's the diverter valve!?? The annoying thing is, it's quite random!!

Like I said, I'm not too familiar with this boiler, so no idea of any indicator lights or reset buttons.

I know certain boilers tend to play up after a short while if you replace one thermistor without the other, so may aswell replace the pair, especially at that price.

As I said, I'm just making educated guesses, but changing the cheapest things first is always the sensible option if you are unsure.

[rash_decision]

Cheers Rickyy, I'll have a go!