Baxi Instant 80HE not detecting Hot Water Flow

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Have have just renovated a house for my In-Laws and the last job (why did I put this off??) is the boiler.

I am coming here as Baxi give me snippits of help, but keep refusing to talk any more as I am not "Gas Safe", so I hope someone here might be able to help.

It has an Baxi Instant 80HE, which only intermittently detects HW flow... It works when I turn on the bath tap (lots of water), but not the sinks..

I have looked at the mechanism which detects flow, and its obvious what the issue is.. When I turn on the tap, the "pin" that presses the microswitch comes out long and hard.. But when I turn on the sink taps, it only comes out 1/2 way and I can easily push it back.

At the weekend I had a look at the diaphragm and associated mechanism and it was sound.. I cleaned of a bit of scale and it made little difference.

So then I moved onto the "Venturi" which was something that Baxi told me to look at. They said that sometimes the splines come off of the cage. So I removed the cartridge, and to my surprise, the Venturi was missing. I checked inside the opening with a mirror/torch and its not there. The Venturi is awol.

So I would hope this could be the cause.. But a call to Baxi today resulted in them telling me that it WAS there as teh boiler wouldn't work at all without it. They refused to accept that in my case the venturi was missing.. And the boiler works some times and simply refused to speak to me.

Does anyone with Baxi knowledge know why my venturi is missing? And why the boiler still works??.

How confident are you that if I simply replace the venturi is will solve my problem?

Thanks in advance for any advice.. I need to get this fixed quickly now as they have moved in and have no reliable hot water, so don't have time on my side.

Jon
 
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Here is my cartridge... I am not missing something? Would you agree the venturi is missing?
 

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think the fairies must have taken it :) you want to try looking in the manifold or plate heat exchanger ;) also inspect the diaphragm
 
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First of all, thanks for your reply.. I got properly caned on another forum for even asking as I am not qualified to open the boiler.. Whilst I know this to be true, I am not paying someone £100s to fix something as easy as this.

The Diaphargm is fine.. Checked that first.. I only looked at the Venture as Baxi told me too "off the record".

I looked inside the aperture where the cartridge lives and its not in there, and there is no where else it could go, so I can only assume that due to another fault, someone removed it as perhaps it was broken.

I just have to hope that a replacement Venturi/Cartridge fixes it, as this is about as deep as I want to go myself.

Jon
 
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How confident are you that if I simply replace the venturi is will solve my problem?

Thanks in advance for any advice.. I need to get this fixed quickly now as they have moved in and have no reliable hot water, so don't have time on my side.

Jon

I am never very confident of any DIYer doing boiler repairs.

This is mostly because they are unable to recognise when parts are missing or just not correctly fitted.

For example you are talking about replacing the venturi. But any professional would replace the whole brass assembly.

Tony
 
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I am never very confident of any DIYer doing boiler repairs.

This is mostly because they are unable to recognise when parts are missing or just not correctly fitted.

For example you are talking about replacing the venturi. But any professional would replace the whole brass assembly.

Tony

No I am not.. I am replacing the whole thing.. Just replacing the Venturi was temping (And not unreasonable, as it has its own part number and is easily installed onto the end of the cartridge), but I figured the whole cartridge was better and it only cost £3 more so it was a no brainer.

I understand the negativity towards DIYer and Boiler repairs.. But I am an engineer of 30 years and consider myself pretty competent... At the end of the day, someone got there before me who was probably "Gas Safe" and he left it in this shocking state (i.e no venturi), so what does THAT say about the legislation.

I do all my own repairs.. My own electrics.. my own plumbing.. And I believe I do it to a higher standard than a professional as I can take my time and make sure its done right. The only thing I won't touch is gas!

You are comparing ME, who is replacing the necessary parts to a "professional" who basically removed the venturi and put the cartridge back incomplete... No words!

Oh yes.. And your implication that I can't recognise when a part is missing is preposterous.. I have shown a photo of my cartridge and can easily find photos of what it SHOULD look like and any fool can see the venturi is not there!
 
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Venturi will sort it. Baxi tech are talking rubbish. He has probably never worked in the field and seen these boilers work without the venturi intact. The venturi is probably in little bits in the plate heat exchanger.
Take no notice of Agile. The venturi is all you need.
 
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If, and we don't know, any professional intentionally removed the venturi, then it was probably done to increase the water flow through the boiler as they do cause a big restriction.

Just possibly he was being dishonest but in this instance I doubt it. Misguided perhaps!

Tony
 
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Venturi will sort it. Baxi tech are talking rubbish. He has probably never worked in the field and seen these boilers work without the venturi intact. The venturi is probably in little bits in the plate heat exchanger.

Cheers John... That would certainly explain it.. Do you think the bits can just live in the heat exchanger forever? Or should they be removed? And if they should is this something that i should leave to an expert as I assume its on the "gas" side of the boiler?
 
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If, and we don't know, any professional intentionally removed the venture, then it was probably done to increase the water flow through the boiler as they do cause a big restriction.

Just possibly he was being dishonest but in this instance I doubt it. Misguided perhaps!

Tony
Agreed.. And I am wrong to assume that a "professional" did this.. But equally, please understand when I take offence because someone questions my competance.. Rest assured, if its humanly possible (And safe) for a DIYer to do something, I have the tools, the means, the time and the willingness to do it.
 
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A Baxi advert in Leamington asked for "technical advisors, no experience needed"!
 
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Cheers John... That would certainly explain it.. Do you think the bits can just live in the heat exchanger forever? Or should they be removed? And if they should is this something that i should leave to an expert as I assume its on the "gas" side of the boiler?
I would just leave it. They break up in to tiny pieces so it's unlikely to cause an issue.
 
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Just to give an update and closure.. Replaced the cartridge today. Before doing it I spent a while to check the chamber and it was completely empty.

And now the problem is entirely solved.. The taps trigger the boiler as soon as they are switched on.. And I checked the push rod into the microswitch and where as before it was "limp".. Its now shoots out like a dog on heat.

Thanks for your help

Jon
 
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