Diaphragm valve on a combi boiler

[KlondikeMike]

I am having problems with my 3year old Jaguar combi boiler, manufactured by Hepworth Heating Division.
The central heating works ok but the hot water system has become erratic.
There are two small-bore pipes leading from each side of an orifice in the hot water line to detect when there is a flow of water to the hot taps. these lead to each side of a diaphragm differential valve which, in turn actuates a micro-switch to send a signal to the pcb. I have checked the signal from this switch with the tap open and closed and there is no difference. I have taken the switch off and there is nothing wrong with it. Ergo; the diaphragm is bust.
1. How do I take the diaphragm off? There are two grub screws which appear to be holding it in place.
2. Do I need to drain the central heating system?
3. What is likely to go wrong?
4. Where do I get a replacement?
Any advice will be appreciated.
Mike

 

[ChrisR]

1. Undo the 6 or 8 screws to split the housing.
2 No only the CW. Turn it off where it goes into the combi.
3 You'll drop a screw, and forget which way round the diaphragm went
4 Boiler spares boutique.

 

[kevplumb]

3 You'll drop a screw, and forget which way round the diaphragm went

should read you will drop a screw and find the only gap in the boards for 100 ft

 

[gasgeezer]

you have to isolate boiler i.e turn off valves drain boiler i think you remove diaphram housing so it is easier to replace whole unit

 

[ChrisR]

you have to isolate boiler i.e turn off valves drain boiler

Nah.

 

[gasgeezer]

you will get very wet if you remove diverter valve without draining boiler

 

[Paul Barker]

they're talking about a diaphragm in the flow sensor on the hot water pipework.

 

[gasgeezer]

yes I know but you have to remove the diaphram housing from the boiler to access all the screws! And in doing so you will have to drain the boiler because the domestic hot water heat exchanger is attached to the diaphram housing and the central heating system passes through the top section of the DHW heat exchanger. That is why I normally change the whole unit as it has to come out anyway, hope this clarifies the point.

 

[Paul Barker]

Sorry I'm not familiar with the Jaguar. Bad design then.

 

[gasgeezer]

yep cheap throw away boiler fopr the letting market very similar to protherm boiler believe it is eastern european hepworth bought into like the ikon series

 

[ChrisR]

BUt
a) you can split the diaphragm housing in situ if you have boiler menders' tools
a)taking the diaphragm housing off the boiler doesn't involve letting prmary water out. You don't have to remove the dhwhe.

 

[ollski]

I must be getting confused..the only jaguar I have ever seen is the one sold as both protherm and glow worm 4704716 (23kw) and 4704717 (28kw). Bog standard nice easy diaphragm housing on the left hand side. Is it this one?

 

[Agile]

I do wonder if Gas geezer is think of the Celtic where you do get wet for some odd reason?

Unfortunately I dont remember doing a Jaguar but I am virtually certain its the standard diaphragm unit with two square screws?

Tony Glazier

 

[gasgeezer]

diaphram has 6/8 screws at least one not accessible on boiler not rocket science if you do not isolate and drain boiler you get wet

 

[Agile]

I am sure my memory is not that bad!

Six screws holding diaphragm unit together.

Two square screws holding hydraulic unit into diverter manifold.

Two spring clips holding capillary tubes in to manufold unit connections.

As there is a seal in the end of the diverter manifold then where does the water come out from?

Tony