Sabre HE, hot water goes cold

[Brownbridge1981]

Hi, first post on the forum.

My 4 year old Sabre HE (25 I think) has started playing up. The water runs hot for 20-30 seconds then goes cold. It seems to run hot longer if I turn the temp down. The heating works fine. All seems to function as it should, fires up, pressure at 1.2 bar, lights as they should be. Never had any problems till now.
I realise its a budget boiler, but cant afford a better one at the moment.
I'm wanting a pro to fix it just don't wont to get ripped of.

Any idea as to what the issue is ?

Thanks Dave

 

[dcawkwell]

Possibilities without seeing it could be thermistor if it suddenly started
happening.

Does the central heating still work?

 

[picasso]

more likely to be the plate heat exchanger blocked on the primary side.

 

[Brownbridge1981]

Heating works fine.
Would heat exchanger need replacing or just cleaning. I was hoping it would be something simple like a thermostat. What sort of price am i looking at ?.

 

[dcawkwell]

Possible to remove the existing plate heat exchanger and flush out.

But I would have expected if the plate heat exchanger is blocked this
to have happened over a period of time rather than suddenly.

 

[Brownbridge1981]

Thanks dcawkwell.
It has started quite suddenly, would there be any other symptoms. Or checks I could do to say for sure.
And what's an engineer likely to charge to fix.

 

[gasbanni]

Got a restaurant where I change the dhw plate to plate every three months,
buy a new one and clean the old one and keep it as a spare !

Easy fix ! £120 all in ? give or take.

 

[Brownbridge1981]

Thanks. Would this have to be done by a corgi fitter, or could I DIY without having to disconect gas.

 

[gasbanni]

No gas does not need to be touched, turn off the water, open all hot taps and drain the heating and get new washers when you get the new dhwhex.

just depends on your aptitude skills and tools !

 

[Brownbridge1981]

Think i'l give it a go, Just a last note turned the DHW temp down last night and managed to run a bath at a reasonable temp. temp seemed to stay constant, the problem only occurs if i increase temp. Would this still indicate the heat exchanger to be the problem.

 

[gasbanni]

No !

Maybe a sensor thats playing up, if the plate to plate dhw hx is blocked irrespective of dhw temp setting would go to overheat lockout.

Your probably best getting a decent repair engineer to have a look.

 

[picasso]

If the plate is partially blocked the boiler will cut out because it cant loose the excess heat, if you turn the temp down ie less heat being generated then it wont cut out, its a strange fault if it is a sensor.

 

[Brownbridge1981]

So could it be the thermostat.

 

[picasso]

So could it be the thermostat.

if the temperature of the hot water drops when you turn down the DHW dial it aint the sensor, I still reckon its a partially blocked plate heat ex.