worcester 24i

[ambrosia]

Old style worcester combi with the twin pass heat exchanger, no plate heat exchanger or diverter valve

works fine on heating and also works fine for the majority of the time on the water
however every so often when you run the hot tap (while heating is on) after you turn it off and it switches back to the heating its starts banging as if its got a blockage, presure guage goes mad and then very quickly boiler locks out and red light flashes.

Thing is it cant be a blockage as most of the time it works fine on water or heating, it cant be the diverter valve sticking because it doesnt have one.

The tenants had become so used to pressing the reset button theyve now broken the button and cant reset it anymore
Landlord was only willing to pay for half and hour fault finding which i spent going through all the faults as the boiler has been thrown in, 15mm gas pipe which does cooker, boiler and range fire, push fit on PRV, etc etc. so i've just left it capped/safe, not going back and its now someone elses problem

But now i've got the frustration of never knowing what was wrong with the boiler

 

[bigads28]

It could be the pump not kicking in quick enough when it changes from DHW to heating. It might just be a bit sticky

 

[ambrosia]

It could be the pump not kicking in quick enough when it changes from DHW to heating. It might just be a bit sticky

as i was writing the above i was thinking 'i wish i'd checked to see how consistant power to the pump was as it changed over from water'

tenant was convinced problem was most likely to occur when the hot tap had been running for awhie, ie a shower or something

 

[dancinplumba]

Twin pass heat ex, no need for pump on dhw? Is there check valve on cold main ? Sounds like boiler overheating, nowhere for heated expanded water to go once tap turned off. Just a thought

 

[ambrosia]

Twin pass heat ex, no need for pump on dhw? Is there check valve on cold main ? Sounds like boiler overheating, nowhere for heated expanded water to go once tap turned off. Just a thought

no check valve, but pushfit right up to the boiler on everything except for the gas, sure the blockage if thats what it was is on the heating side as pressure guage goes mad

flow turbine was leaking

 

[townfanjon]

Half hour and you have to get there and back, is the landlord for real.

 

[Atouchofgas]

Boiler still thinking there's a demand for hw? Possibly dirty flow turbine sending a signal to pcb

 

[dancinplumba]

no check valve, but pushfit right up to the boiler on everything except for the gas, sure the blockage if thats what it was is on the heating side as pressure guage goes mad

flow turbine was leaking

Boiler kettling causes gauge to go mad

 

[Mike Jackson]

My first port of call would fault on the flow switch. No hot water flow, boiler carries on firing but pump not running because the boiler is registering a hw demand. Localised boiling causes pressure spikes and sends gauge mad.

 

[Nostrum]

I've had some really weird faults on these and the boilers been replaced before finding out the cause (including running through fault finding with Worcester technical more than once) Was the hot water very hot?

 

[Leo21]

I've had some really weird faults on these and the boilers been replaced before finding out the cause (including running through fault finding with Worcester technical more than once) Was the hot water very hot?

That,d be a first on an old 24i

 

[arran197]

The pump should kick in occasionally when the DHW is running anyway, no matter if there is ch on or off. It does sound like a flow switch problem, although I would also check the Ntc sensor.

 

[Millsy 82]

The pump should kick in occasionally when the DHW is running anyway, no matter if there is ch on or off. It does sound like a flow switch problem, although I would also check the Ntc sensor.

As far as I'm aware the pump should only come on when the flow switch goes back to off to get rid of the heat in the heat exchanger.

I would of been looking at the flow switch myself sounds like it's sticking open.

But I probably wouldn't of gone if the landlord said I'm only paying for the first half hour!

 

[arran197]

I believe the pump comes on very very briefly during DHW, literally 1 second, but if it's someone else's problem now then no worries.

 

[gassafe]

Just charge the landlord the minimum 1 hour anyway... Since when do they start dictating the way we operate... Thats like travelling there & diagnosing the fault for 25 quid...!

 

[ambrosia]

for some reason my boss thinks being able to book an engineer for min half an hour is a selling point but dont tell Thermological our minium charges start at £55 per half hour

 

[Millsy 82]

for some reason my boss thinks being able to book an engineer for min half an hour is a selling point but dont tell Thermological our minium charges start at £55 per half hour

I'm surprised you can shoehorn £55 out of a landlord! Lol.