Baxi 80 eco GC 4707505

Hi all.

I'm new to this so I'll do my best to explain myself correctly.

I recently had the Venturi pressure sensing (part #247417) twice as it had melted due to intense heat, i also had it serviced at the same time.

Anyway, as of two days ago the system keeps shutting it down and after several attempts at resetting it the fan kicks in and it fires up, but only stays on for a matter of minutes.

Everything looks in good working order, clean, pipes in good condition and unblocked, no loose wires etc.

No fault lights illuminate.

I thought the fan might have had it but when it does work it works as per normal.

Can anyone offer any advice?

Thank you in advance,
Jon

Ps. Great forum!

You have written a lot but not told us the interesting bits!

WHO replaced the venturi?

What did he say the cause of the problem was?

Melting the venturi is usually a result of dry firing ! Did this occur and why?

It sounds as if there is another fault on a protective device!

Tony

Hi Tony,

A Corgi registered engineer fitted the venturi.

It was the first time he had seen one so melted and deformed so could not conclude the cause.

I have no idea what dry firing is (please elaborate) so am not aware as to whether this occured?

What kind of protective device?

Thanks for replying.

Jon

Under normal conditions the temperature at the venturi is about 130°C because the heat from the burnt gas is reduced by transfer into the primary heat exchanger.

This will not happen if either there is NO water ( dry firing! ) or the flow rate is too slow and the water overheats or turns to steam.

On your model water and pump flow are checked by a system water flow switch on top of the diverter valve before the gas valve is opened.

Its difficult to immagine what situation can cause the venturi to melt unless the flow switch is failed unsafe but it does happen! I saw one a couple of weeks ago and the parts supplier had three in stock so its a common part to be sold.

I could not find any cause on my example so I am particularly interested in this situation.

Tony

So it looks as though I'll have to call the engineer back in does it?

Could what you are talking about relate to the fan cutting out or are these two not related?

The enigma to me is that the fan does actually work, albeit for limited periods of time, so it must be something else that is causing it to cut out. Have you any idea what this could be?

Thanks,

Jon

The fan is driven by relay contacts on the PCB. A faulty PCB will cause the fan to cut out, often for a few seconds at a time.

If the fan stops the venturi could overheat. The APS should shut the burner down within a short time though and I would not expect that to destroy the venturi but it might!

The ignition sequence which starts with the fan is enabled by the system flow switch.

Tony

Sorry Tony, but what you have just has gone straight over my head.

Although I accept it difficult to explain and/or diagnose through text alone, would you or anyone else have an idea why the fan keeps on cutting out?

It's cold in here.

Jon

I have a Baxi 80e and I've had a problem with the CH; but not the HW !

When i turn the CH on it starts as normal, but after a few seconds the burner light starts flickering. It does this for a minute or two then the boiler shuts down with the pilot light flashing.

If i fill up the kitchen sink to do the washing up just after turning the heating on, after im finished filling the sink, the CH seems to work fine.

I've tried a new pressure switch, have inspected the flue and now i've identified that a new PCB was released by Baxi for the 80e (and some other models). The model no of the new PCB is 5112380. Other forums have mentioned a dodgy relay switch on the old model PCB. If you electronically savvy you could have a go at identifying the dodgy component and replacing it with a different relay. I'm competent electronically but i havent got time to do that sort of stuff so i've just parted with £40 for a new PCB - from ebay.

I have a detailed the problem and troubleshooting steps in my own post:
//www.diynot.com/forums/viewtopic.php?t=154462&highlight=
...Check it out

Cheers

Mark

P.S. I am not Corgi registered, if my problem related to directly to gas interfacing components I'd get a Corgi guy to look into it.