Hot water not working please help

[simonwright91]

Hello everyone

My boiler has developed a fault and I'm sure it an easy fix.

When I turn 1 hot tap on the boiler does not start but if I turn the sink, bath and shower on the boiler fires up....

In the kitchen we don't get any hot water. Sometime if you out the tap on full whack till you hear the boiler fire and then turn the tap slower it works?

I haven't got British gas cover any more as we had everything replaced.... Board, pump, new switch assembly thing.

The boiler is a Halstead high ace.

Thank you very much

 

[picasso]

Worn diaphragm, easy fix if you know what your doing.

 

[simonwright91]

yeah i watch the guy do it last time, where do i get the parts from tho?

si

 

[simonwright91]

does it matter that BG replaced the diaphragm last year so it would be a bit of a crappy if its gone all ready...

 

[MANDATE]

Daughter had same problem about five years back, halstead diaphragms about £12 if I remember correctly.
However I was advised that the 'vokera diaphragm code 0870 would be OK for less than £4 at the time, and thats what I fitted.
I understand that british gas did replace it about one year ago.

 

[simonwright91]

http://www.ebay.co.uk/itm/VOKERA-DO...arden_Hearing_Cooling_Air&hash=item415e361fb7

is that one ok?
what steps do i need to do to fit it?turn water off etc.
cheers

 

[MANDATE]

Yes thats the one!
I take it you know that mains cold water enters the boiler and goes through a heat exchanger and comes out hot, turn off the inlet valve at the back of the boiler or your mains stop cock. You don't need to drain the system water.
The instructions suggested the shelf holding the pcb be removed but I found there was no need for that.
Also the two pipes have to be detached from the housing at the right hand side. I had slight problem there and found it much easier to detach the pipes at the left hand side, leaving the right hand side still attached to the housing.
Can't remember if housing screws were 'cross head' or 'torq' or 'hexagon'

 

[simonwright91]

nice one thank you, ive just ordered it now hopefully tuesday night we will have hot water again..

is there any temp fix till then?

cheers

 

[simonwright91]

is the diaphragm located in the round bit on the left or right in the round bit that sits on the top?

si

 

[ianmcd]

the large bit on the left

 

[picasso]

The hot water diaphragm is in the large bit on the left, the bit on the right also has a diaphragm for the pump proving switch.

 

[simonwright91]

nice one thank you, so the part ive ordered is for the large bit on the left

si

 

[simonwright91]

Is there anything else it can be if this does not fix it?

 

[MANDATE]

When you select HW the diverter moves across from right to left (well its supposed to) when it reaches the end of its travel it triggers a micro switch so I suppose the micro switch (having contacts) could be a problem.
But from what you say its got to be the diaphragm.
The diaphragm has water pressure on both sides of it.
Opening a hot tap reduces the pressure on one side, so the pressure on the other side forces the valve across.
If there is a hole or split in the diaphragm water will pass through the hole and valve will either not move at all or it may move but not to the full extent.
Opening a hot tap fully or more than one tap is somtimes sucessful, whereas opening a hot tap partially has little effect if diaphragm faulty.

 

[simonwright91]

right well i have just been up and had a look ready for the part coming tomorrow and the boiler is very rusty on the surface! its not shiney like it used to be!!

this has got to be down to BG not cleaning up after them and even arround the pump they fitted there is crap. my phones about dead so ill take some pics tomorrow! (tuesday)

also that last screw at the back (bottom of the pic above) looks a pain to get to?? any tips on that one?

si