Unreliable Worcester Bosch Highflow 400's x 2

[Lightman]

Hi there

I have 2 Worcester Bosch Higflow 400's in 2 rented houses which have been an absolute nightmare. Both boilers were new about 4 years ago and in that time I have had perhaps 10 breakdowns on each boiler.

Research on "the net" reveals reliability problems with that model and it seems they are very sensitive to any rubbish at all in the central heating system. My boilers were installed on clean (new) systems of HEP2O pipe and new radiators and the system was well flushed proir to installation

It seems the diverter valve often goes wrong and there is a little 1 way non return valve which often sticks. The plate heat exchanger has been removed and descaled at least once on one boiler and the high temperature trips have often "popped out" even when brand new on both (these trips are not counted as a breakdown in my statistics!!)

There is also little plastic filter (on the heatbank?) which clogs and even the electronic timer clocks have gone wrong once on each boiler. Why should an electronic timer go wrong for goodness sake?

I'd apprecaire replies on 2 things

1. Any experiences you have had on this Worcester model (only) I know Worcester generally are supposed to be good for reliability

1. Comments on my plan is to install a stainless steel Megaflo (or similar pressurised tank like the Telford stainless tanks) asap to supply hot water and junk the Highflows for a system boiler when the tenants move out next summer. I know this "stored water solution" is a better solution for me purposes as I have used it in other properties. One huge advantage is that the immersion heater can be turned on as a "back up" as boilers will always break down every so often.

Ideally I would like to convert the Highflows to a boiler which is stuck in "heating mode" but the electronics apparently go into a routine (even if the hot water is off) which instructs the boiler to fill up the storage tank with hot water when first turned on.

I'll install an external 2 port valve and S plan or Y plan to heat the megaflo

Can anybody suggest a clever way to rewire or fool the boiler to think the hot water tank is up to temperature so it could be used as a conventional boiler? (ie change the sensing thermister for a fixed value resisitor or something?)

Thanks for any help - Lightman

[John Stumbles]

Sorry can't help with 1, but if you're DIYing remember unvented are notifiable and need annual servicing to ensure safety so I'd suggest thermal store/heat banks instead.

[jack]

I had one of these highflow 400's fitted 3 1/2 years ago. Worked fine until 2 weeks ago, until I noticed water coming through the kitchen ceiling. the Highflow upstairs had sprung a leak on the plate exchanger. Called a service engineer out from Worcester Bosch (no one else would touch it(not even the company who installed it) on one of their repair plans. Cost a set fee of £245 due to a new plate exchanger being fitted. Also changed were a diverter valve (supposedly sticking), a braided hose to the pressure vessel and a pressure valve. The fault I was told was caused by the braided hose becoming blocked with sludge, which in turn caused the other problems. On checking the braided hose later, looks more as though it has collapsed internally as there seems to be a kink in it.

The system had been cleaned prior to fitting the boiler

I currently have Fernox super concentrate restorer circulting around the system, due to be drained out later this week..

[Tony Bryer]

You might consider installing a Magnaclean - traps a lot of crud but unlike a filter doesn't clog up