Worcester combi HW problem

Simon1506 · 9 Feb 2004

Hi everyone
I've got a Worcester Bosch Highflow 400 RSF combi boiler, 4 years old, very hard water area. One of the thermostats (not sure which one) cuts out after about 10 mins. regardless if any HW is used, and then there is no more HW until I let the system cool down and reset the thermostat. A moderate-high HW flow rate will result in a loud whining noise from the boiler. CH is fine. We called Worcester-Bosch who inspected it and said we had a blocked water-water heat exchanger, which was not his responsibility, but charged us £210 for the diagnosis

. My questions are: would a power-flush cure this, should I get the whole house CH circuit flushed (£500), and would a water softener be a good investment? Also if I hired a power-flusher, how easily could I do it myself?.
Many thanks, Simon

ChrisR · 9 Feb 2004

"would a power-flush cure this"
Depends how it's done. Still would need to descale the secondary (tap) side.

" should I get the whole house CH circuit flushed (£500),"
Only if you have a general sludge problem. Cold rad bottoms would indicate.

"and would a water softener be a good investment"
Would only affect the tap water side of the heat exchanger in question. A "conditioner" is a lot cheaper and should help at least some. Possible you'll have to accept descaling the h/e every few years.

"if I hired a power-flusher, how easily could I do it myself?.
"
You could do the rads ok, but the boiler bits take a good understanding of how it works, and some fiddling.

Post the same question on PlumbingPages forum - more specialists there.

COG · 10 Feb 2004

Get WORCESTER BACK. they charge £94 to service or inspect £160 to reapair most faults with spares and £210 to repaire any fault including heat exchanger replacement SO GET THEM BACK to replace your heat exchanger you have paid for it. The warenty wont cover you against lime scale but you can pay to have the heat exchanger replaced if you want or have to. As a pointer once replaced fit a lime scale preventer as you cant de scale the 400 it just blocks the heat exchanger tottaly and once the circulation is stopped the de scaleing machine cant work,most plate heat exchangers wont de scale,and a powerflush is for the primary side of the heat exchanger (boiler/rad water) .

ChrisR · 10 Feb 2004

Primary side of secondary heat exchangers can be cleaned on combis generally by circulating appropriate chemicals within the boiler, but no it isn't part of what a powerflush does. Never tried it on a HF400.

Simon1506 · 10 Feb 2004

Many thanks for all your replies.

I will contact Worcester again to get them to change my heat exchanger, and will ask about a secondary circuit water conditioner.
Since my rads are all working fine (top & bottom) then a flush sounds to be a waste of money.
Thanks again.

COG · 11 Feb 2004

CHRIS ,just a note if the heat ex is blocked on a 400 you can set a cleaner away and sometimes its ok but generaly because its a tall plate sitting upright the scale can just drop down like a door,then the circulation just stops dead,it seems best to try just sentinel on its own first and use a more jentle action from the boiler pump.

ChrisR · 12 Feb 2004

Thanks. Have made a note of that. I guess you mean X400 though it's really slow on anything dense?. Doing the descaling in a bucket of warm DS40 + DS3 could be one way to go. Pricey one to replace!

COG · 12 Feb 2004

Chris , not just a pricy one to replace its b**** to do first time,got a scaled up one in the van will try what you sugest to see if it works, from an area with750ppm limescale.

zutman · 30 Mar 2006

Ive done one of these, you will find the HW heat exchanger is scaled up dont try and clean it replace it !!! then fit a scale master to your cold water inlet on the boiler and change it every three years, with the boiler drained down fill system with X400 and leave it in. Job Done

P

chrishutt · 30 Mar 2006

Zutman, that thread is over TWO YEARS OLD! There are enough zombies hanging out on this forum without you digging more out.

ollski · 30 Mar 2006

chrishutt said:
Zutman, that thread is over TWO YEARS OLD! There are enough zombies hanging out on this forum without you digging more out.

Ah be fair chris, when you've done your first one you deserve to be able to shout it from the rooftops

Just as an addition if it is sludged / scaled I always replace both manifolds aswell.

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Worcester combi HW problem

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