Halstead ACE still overheating

[wanleg]

Having cleaned the DHW exhchanger as recommended in previous posts my ACE is still puffing steam after running a bath or shower. The exchanger was quite junked up and I was hoping a clean would sort it but it hasn't. The CH runs fine and does not cause any steam output when turned off so it looks like I may still have some sort of water flow restriction in the DHW circuit...but where ?

The boiler got so bad yesterday that it actually started to vibrate loudly and spit steam when the hot water was actually running.

Had BG out today......young guy who saw the problem with his own eyes then called his boss as he hadn't seen anything like this before.....his words not mine......a few minutes later the good old powerflush quotation for £440 was produced followed by a sharp embarrassing exit.

Bearing in mind that the CH does not seem to be affected...does anyone know of any obvious places on these boilers where the flow could be restricted by junk ?

£440 is expensive for the flush but I think BG have a pay only once policy where if the system needs flushing again it will be foc for the life of the boiler......a friend of mine recently paid £300 for a flush by a local recognised firm who specialise in combi's.

If the flow is restricted would a flush be of any use ?

 

[Agile]

Many people who do power flushes only flush the radiators whereas in reality the problem is often within the boiler.

It takes someone with considerable skill to be able to diagnose the problem and treat it without changing lots of parts.

Tony

 

[meldrew's_mate]

Have you had the diverter valve out, scale often sits inside this, though it mainly affects the CH output.
I suggest you strip the main H/E as well as the DV, not forgetting the pump itself. If you do get a powerflush done make sure the operator uses an adapter which replaces the boiler pump, then it will descale the primary side of the DHW H/E, the main H/E, and the DV.
Hope this helps.

 

[ChrisR]

Have you checked that the pump overrun is working -?? Bypass/trv's all round??
Have you checked /changed the thermistor(s).??
Gas rate??

 

[ItsOverFlo]

Often when bg offer powerflush, they are aware there may be other faults.
Most customers want to know approx how much the fault will cost.
Basically when bg quote £440 for pf it gives them plenty of time to find the real fault, ie, gas rate, bypass etc. you need a competent service engineer to find the fault. BG employ some top techs, but unfortunately even they employ alot of chancers who ain't got a clue.
Chrisr sounds like hes giving sound advise, a shame bg cant afford him.))

 

[wanleg]

Many thanks to all who replied......I'll give all your suggestions a try. Could BG afford ChrisR ? be a hell of a trek to a call out from Antartica !!

 

[ChrisR]

Call out - you mean go to a boiler? Heavens no, I just sit with the penguins and a terminal copying other people's answers to the same old questions...

Gas rates are in the manual though the cu ft figs aren't right obviously:
Gas rate 2.81 cu m/hr for an Ace and 3.6 cu m/hr for an Ace high, +10% / -20%, with Hot Water on full.

(1 cu meter = 35.31 cu feet)

These aren't in the manual -
Pump overrun should be about a minute, it's timed, not dependant on temperature.
Thermistors should be about 10k Ohms cold reducing to about 4k at 70º.