biasi combi boiler m96 24sm/b

[rayplane]

I have a biasi combi boiler approx 2 years old we seem to be having trouble with the hot water first of all the hot water during operation runs hot then cold about every 10-15 seconds i read on the forum a simalar problem, and they suggested it could be the diapram in the diverter valve i have changed this and there did not seem to be anything wrong with the one i removed, now i can only get hot water when the heating is on but it is not as hot as it should be if the heating is off i can no longer get hot water
Anybody got any advise

 

[ChrisR]

Which one is that - Garda, Riva...?

Do the pins come out to hit their respsctive microswitches? HW one on HW diaphragm, main system flow one on smaller diaphragm.

 

[rayplane]

i cans see the one switch working that pushes the diaphragm i changed but the other one inside the 3 way diverter valve i can not see is it ok to remove the switch out of its housing and operate the boiler to see if it works , ithinck is the garda HE?

 

[ChrisR]

Oh it's this one.... http://www.biasi.co.uk/pdf/GARDA_HE/SERVICE/3704_EDITION.PDF

Probably the problem is a blocked secondary heat exchanger. But check:

You only have one diaphragm
It checks the pump's running, not the hw tap.

HW tap operates a flow switch on the right reear which I think has a light on it when water runs - yes?
Then diverter head on left should operate the pin (slide out U clip to remove motor) - yes?
ANy sign of leaking in there?
Vertical pin inside you can feel but not see should spring up and down. Hard to push - use a 2 inch stub of pencil or summat.

--------
Reassemble.
slide out U clip which holds switch on the housing where you removed the diaphragm
Turn on CH. Does the pin come out and it is HARD to push back? (boiler won't run cos switch not attached)
Turn on HW. Does the pin come out and it is HARD to push back?

 

[rayplane]

yes found the other switch it lights red when operating the DHW
i removed the diverter head and when i oparate the CH the pin does come out the diverter head or do you mean the pin in the diverter valave
hot water works but still keeps switching on and off

 

[rayplane]

there is no leakage in the head also i pushed in the pin with a scredriver and it does spring back

 

[Agile]

You do seem to be getting very mixed up with what you read and what your boiler has.

Just as not all ford cars are the same, similarly not all Biasi boilers are the same.

Your problem is quite simply that the plate heat exchanger is blocked and needs to be replaced or cleaned!

Thats obvious from your initial description.

Tony

 

[rayplane]

cheers tony do i need a plumber to do that

 

[Agile]

You dont need a plumber! You need a boiler engineer or you might be able to do it yourself if you are clever with technical ( and wet ) DIY.

There have been lots of discussions if you search for cleaning plate HEs.

We charge about £136 in our local area for fitting a ready cleaned one. So if you could do it yourself there is a saving to be made. But then you might risk messing the boiler up or flooding the house!

Tony

 

[ChrisR]

No you don't, if you've got ball-ended allen keys.
Takes about 20 minutes to remove clean and replace- all within a £60 or whatever call-out.
As I said, Probably the problem is a blocked secondary heat exchanger. But a couple of minutes on checks of other things to make sure they aren't half-working is worthwhile. Owners' descriptions aren't always as clear-cut as Tony implies!

 

[Agile]

Takes about 20 minutes to remove clean and replace- all within a £60 or whatever call-out.

High speed Chris!

What do you use to clean it within that time scale? 100% HCl ?

It took me about three days to clean a completely lime scaled plate from Berkshire!

Tony

 

[ChrisR]

This one wouldn't be lime scale as it's on the primary side of the heat exchanger.

(You asked for that!)
I think 100% HCl would fume a bit orribly.

I had to do one recently in a hurry, and it was a baddie, diverter had flakes in it too so I squirted from the top while the plate was cooking and poked about with a pick-up tool end.
Still have the cuts on my fingers - some of them HE's are sharp! ANd the acid stings a bit.

If access is bad or draining is hard it takes much longer.

 

[rayplane]

you guys are loosing me i dont mind having a go but which is the secondary heat exchanger

 

[rayplane]

i would just like to thank chris i took your advise done a bit of research and cracked it i removed both heat heat exchangers desacled them along with all removable pipe work although i must admit what i got out chris i thought you where wrong, i also removed the diverter valve replace all the o ringgs and removed the crud put it all back together and we are all queing for the shower once again many thanks if you ever have problems with drainage or subcidence shire piling or need your house underpinning give me a shout
once again many thanks chris
Regards
a clean subsidence engineer