Bit of a strange combi boiler problem

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12 Mar 2008
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Cheshire
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Hi all,

This one has got me stumped!

Running a Main 30 HE combi fitted in the kitchen and it was fitted before we moved in 5 years ago, worked fine til last the last couple of weeks.

The problem I have is with the DHW not kicking in properly upstairs. Both downstairs hot water taps work fine.

When the upstairs bath tap is opened the hot water comes on fine but if you put the cold on as well the hot water tap runs cold, If you turn on the sink tap in either the main bathroom or the en suite it stays cold, same goes for the en suite shower.

To take a shower we have had to turn the heating on full to get hot water and its not good! :mad:

I've asked a friend for advice and he suggested the pressure diff but the rod pushes out and activates the microswitch fine, but it is not touching it when the taps are closed, it is level with the housing.

It just seems to me that there is not enough pressure going upstairs to activate the pressure diff correctly but water pressure is fine throughout the whole house.

Anyone got any ideas before I melt with the heating on full to get clean every day? :?:
 
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Diverter valve is jammed.

A renewal kit will have everything required, wouldn't hurt to change the diaphragm as well.
 
Thanks Tom but if the valve is opening fine for the downstairs DHW how can it be jammed? Is it that there is more pressure when the downstairs hot water is on?

Cheers
 
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Thanks Andy

I had suspected this earlier today when I read other peoples similar problems with the 30 HE but had discounted it as its only the upstairs where its not hot.

I'll give this a try mate as £7 is nothing compared to the moaning from the missus with the heating on!

Cheers
 
Before you buy, take off the white case (not the combustion case) run the tap and get the boiler into it's fault condition then check that the pin isn't making the switch correctly. This way you can be 100% positive it's the diaphragm.
 
Just tried it and the rod slides out but not far enough to push the microswitch to make the circuit.

Looks like I'll be on ebay and a bit busy later this week!

and buying the missus flowers for waking her up to turn the taps on upstairs while I was 'p*ss*ng about again!'

Thanks Andy
 
Thanks Andy changed the diaphragm earlier and cleaned up the housing inside, cleaned the rods and greased them and now the hot water kicks in lovely!

Bled the pump with the bleed screw at the top and pumping away nicely.

Only problem now is that it still sounds like there's air in the pump. Will that just run through the system now or do I need to bleed it again? Had the screw right out and pushed the pressure up to 2bar but got no water coming out of it
 
Am trying that at the mo mate, got a load of air out upstairs so guessing it will blow round eventually!

Thanks loads mate - you is a star!
 
Well got up this morning and jumped in the shower - all nice and hot then turned the temp down a bit and the hot water went cold again!

Diaphragm replaced yesterday and flushed out the plate heat exchanger as well just in case and it was clear.

Anyone got any ideas?
 

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