Combi boiler problem- advice please.

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
Flossie

Flossie

Well-Known Member
Posts
11,051
Location
Shropshire
Sisters gaff. Her usual boiler guy has gone AWOL and she has been the victim of cowboys in the past so she's rung me:rolleyes:.
7 yr old baxi neta Tec combi GA range.
Had a problem with a braided hose around 2 yrs ago, goes to the expansion vessel, twas blocked, unblocked and has been fine since.
New problem symptoms are, CH works fine but opening a HW tap slightly gives some hot water(boiler does fire up) but opening a HW tap further and the water goes cold:(
This is her description and I hope to pop over later to confirm although she isn't stupid so trust what she says is accurate.
Any ideas you lot :D
 
I'm not a plumber but maybe it's like a turbo hose collapsing under pressure, the braided hoses are easy to replace tho.
 
When that hose blocked there was no heating or HW and the boiler shut down soon after firing up and threw up a fault code. Can't see it being that again on this fault.
Galladog said:
I'm not a plumber but maybe it's like a turbo hose collapsing under pressure, the braided hoses are easy to replace tho.
Click to expand...
 
Usual suspects would be the plate heat exchanger or the diverter valve, you need to follow the checks in the fault finding part of the manual
i cant see how the blocked pipe to the expansion vessel stopped it before.
looks an easy one to change the plate heat exchanger or remove and descale
let us know when you have more info.
manual if it helps
https://mediacdn.baxi.co.uk/-/media...i-neta-tec-install.pdf?v=1&d=20191003T080308Z
 
Flossie said:
boiler shut down soon after firing up and threw up a fault code. Can't see it being that again on this fault.

Doesn't the fault code indicate the current problem ?
Usually a explanation of the codes on the drop-down panel.

I have a Baxi running on LPG, the only fault so far has been the expansion vessel seal failing, leading to water ingress
Click to expand...
 
No fault codes she said.
Never managed to get up there in the end, something unexpected turned up.
That braided pipe to the EV was definitely the problem resulting in no CH or HW last time.
She has text me this morning and has got hold of her usual boiler guy and he will attempt to call round this afternoon. I've got to let him in as sis is at work .
I'll update later.
 
He's just left, diverter valve seized and diverter motor duff.
Lots of that black cr@p in the valve so I'm getting him to fit a filter thing too and replace that braided hose whilst the system is down. Glad I'm not paying:cool:.
 
Flossie said:
He's just left, diverter valve seized and diverter motor duff.
Lots of that black cr@p in the valve so I'm getting him to fit a filter thing too and replace that braided hose whilst the system is down. Glad I'm not paying:cool:.
Click to expand...

It would be worth cleaning or replacing the plate heat exchanger if there is lots of black cr@p in the valve it can only make the boiler work better there about £50, if you swap it you can clean the old on ready to swap out again if needed.
 
What's the best way to clean them Brian? Reverse flush with a hosepipe and maybe a descaler poured in for good measure?
 
Flossie said:
What's the best way to clean them Brian? Reverse flush with a hosepipe and maybe a descaler poured in for good measure?
Click to expand...

I have removed them taken them outside ( do not do indoors) put on an old baking tray and used heavy duty descaler ie killrock but wear gloves and mask and try not to be over it when you pour it in, let it do it thing whilst moving it around so the stuff gets in all the spots then flush out with hosepipe and refit.
 
Hi @Flossie

Plus 1 what @brianp38dse has mentioned

Ref the black stuff, indeed air must be getting in, if the EV pipe was blocked it stops any expansion and will then allow the pressure relief to open and dump the water , that will then cause a hard fault because of the pressure sensor will detect low water pressure

Every time it’s filled up more oxygen is introduced , also as said never ever try and clean items that contain black water indoors, if that gets on carpet it’s tremendously difficult to remove

black water can also be caused if the rubber membrane failing inside the expansion vessel

As mentioned needs a good flush, also would be tempted to fit a new EV , flat plate and a pressure relief valve as once they open they can and do let by , must admit gave up trying to clean flat plates

once the system is empty just put a tyre pressure gauge on the EV, see what the pressure is, if it’s zero , don’t bother pumping it up but replace it

also worth fitting a magnaclean and keel checking it , is easier as well as u can turn the valves off on the magnaclean, fill it with cleaner , let the system run for a few days , then flush the system again and finally after the parts have been fitted , out some inhibitor in
 
Last edited:
We live in a hard water area & have always had a filter, plus the system is de-scaled with an inhibitor added every 5 years.
Boiler is serviced every autumn, it all costs money but worth it for the peace of mind. The guy who fitted our current Baxi & looks after it only lives a few doors away.

We don't get many long term power 'outages' these days, but my attempt to provide a battery/inverter back up stalled at the last post because I can't figure out how to fool the safety device into still thinking the boiler is running off grid power ... this is despite the employment of a pure sine wave inverter. The pump will start, the boiler will attempt to fire up but throw an error code after 2 or 3 attempts.
It's maddening, so near but so far :mad:
 
norseman said:
I can't figure out how to fool the safety device into still thinking the boiler is running off grid power ...
Click to expand...

Ok, I'll bite ..... How on earth does the boiler know where the power is coming from ?

All our power here goes through power conditioners and UPS'. The current boiler is a B*sch, 8 months old, and of the problems we have had with it, none have been input power related .....
 
Plus 1 with regards to power , what pure sine wave inverter are u using plse, trying to think why it would lock out, maybe the power is fluctuating or bad earth , or maybe the wattage is too low ??

don’t inverters have a power saving mode , wonder if the boiler isn’t pulling enough wattage for it to come out of that mode , best to see what wattage the boiler is pulling , particularly when the central heating pump comes on

May i also ask what inhibitors do u use please , assume u drain it out and renew it,

have seen in the past that if it’s a central heating inhibitor where it keeps getting added the system won’t heat up properly and in the header tank u get like a frog spawn across the surface of the water

personally haven’t found a filter that completely stops scale , only a water softener , of course there’s claims magnets etc work but are rubbish
 
Last edited:
Disco1BFG said:
Ok, I'll bite ..... How on earth does the boiler know where the power is coming from ?

All our power here goes through power conditioners and UPS'. The current boiler is a B*sch, 8 months old, and of the problems we have had with it, none have been input power related .....
Click to expand...

hiya

also been racking my brain of why , only thing I can think of is I wonder if the inverter has some kind of power saving mode, so if it goes into that state and boiler fires the voltage is to low , alas don’t know a lot about the inverters
 
You must log in or register to reply here.
Back
Top