Hi

I am not too clued up on boilers, but thought I would post a message
to see if anyone had any ideas.......

We have a Vaillant Combi (not sure on model at the moment) It is
relatively old, the Vailant phone number is missing the 01 so I
presume it is older than 9 years (i think BT changed the numbers in
1995)

Last week I woke to find the hot water not working, the heating was
working fine. We called out a repair man who thought it was the
'diaphram' that hits the switch when enough water pressure flows over
it. (apologies for not having the technical term for it!)

However, when he arrived later that day the ho****er was working. He
decided to take it apart to check it and found it wasn't broken. He
also noticed that the size of it was only a 1 inch rather than a 2
inch 'diaphram'. He said this would be the reason that we nearly
always have to turn on the tap full before the boiler kicks in.

So 100quid later he had replaced nothing, but it appeared to work,
until ...... this morning when the same thing happened, but by the
time I left for work, it was all back to normal.

My questions a

Could this be caused by a combination of occasional low mains pressure
and this smaller 'diaphram' that causes the boiler to never kick in?

Is this a known issue with older Vaillants?

How can I rectify it?

Is the 'diaphram' answer from our bolier man fact or fiction?

Any help will be appreciated

Regards

Simon

"Dave Clark" wrote in message
om...
Hi

I am not too clued up on boilers, but thought I would post a message
to see if anyone had any ideas.......

We have a Vaillant Combi (not sure on model at the moment) It is
relatively old, the Vailant phone number is missing the 01 so I
presume it is older than 9 years (i think BT changed the numbers in
1995)

Last week I woke to find the hot water not working, the heating was
working fine. We called out a repair man who thought it was the
'diaphram' that hits the switch when enough water pressure flows over
it. (apologies for not having the technical term for it!)

However, when he arrived later that day the ho****er was working. He
decided to take it apart to check it and found it wasn't broken. He
also noticed that the size of it was only a 1 inch rather than a 2
inch 'diaphram'. He said this would be the reason that we nearly
always have to turn on the tap full before the boiler kicks in.

So 100quid later he had replaced nothing, but it appeared to work,
until ...... this morning when the same thing happened, but by the
time I left for work, it was all back to normal.

My questions a

Could this be caused by a combination of occasional low mains pressure
and this smaller 'diaphram' that causes the boiler to never kick in?

Is this a known issue with older Vaillants?

How can I rectify it?

Is the 'diaphram' answer from our bolier man fact or fiction?

Any help will be appreciated

Regards

Simon

Is it a VCW 242 and is this "diaphragm" in a black plastic enclosure at
the bottom centre of the combi, operating a red microswitch via a little
mechanism coming from the black plastic enclosure? I think that there
may be some metalwork directly below the black plastic actuator, a valve,
from which a shaft going to a temperature dial emerges ( calibrated 0-9 I
recall )? I shan't go on in case it ain't the model I'm thinking of, le me
know,

Andy.

In message , Dave Clark
writes
Hi

I am not too clued up on boilers, but thought I would post a message
to see if anyone had any ideas.......

We have a Vaillant Combi (not sure on model at the moment) It is
relatively old, the Vailant phone number is missing the 01 so I
presume it is older than 9 years (i think BT changed the numbers in
1995)


Is this a known issue with older Vaillants?

Any help will be appreciated

Well, you need to find out the model of your boiler. Is it a Sine 18 or
a 242E (H) for example? They're completely different boilers
--
geoff

On Wed, 03 Mar 2004 05:22:38 -0800, Dave Clark wrote:

Hi

I am not too clued up on boilers, but thought I would post a message
to see if anyone had any ideas.......

We have a Vaillant Combi (not sure on model at the moment) It is
relatively old, the Vailant phone number is missing the 01 so I
presume it is older than 9 years (i think BT changed the numbers in
1995)

Last week I woke to find the hot water not working, the heating was
working fine. We called out a repair man who thought it was the
'diaphram' that hits the switch when enough water pressure flows over
it. (apologies for not having the technical term for it!)

However, when he arrived later that day the ho****er was working. He
decided to take it apart to check it and found it wasn't broken. He
also noticed that the size of it was only a 1 inch rather than a 2
inch 'diaphram'. He said this would be the reason that we nearly
always have to turn on the tap full before the boiler kicks in.

So 100quid later he had replaced nothing, but it appeared to work,
until ...... this morning when the same thing happened, but by the
time I left for work, it was all back to normal.

My questions a

Could this be caused by a combination of occasional low mains pressure
and this smaller 'diaphram' that causes the boiler to never kick in?

Is this a known issue with older Vaillants?

How can I rectify it?

Is the 'diaphram' answer from our bolier man fact or fiction?


The model is fairly helpful in these matters!
VCW models I am quite familiar with. Theres a good chance it is one of
them. (Enammeled metal casing, two hinged doors, lots of 4mm diamter pipes
inside? Try looking from underneath for a model name?).

There is a diaphragm valve which _initiates_ the process of water heating.
This valve moves a micro switch and operates another valve. The actuator
pin can become stiff and fail to reliably move the switch and/or the valve
in responce to the water flow.
Unfortunately it requires a significant amount of disassembly to get at
the pin to help it move.

AFAIK boilers are not made with a selection of diaphragm sizes if the
diaphragm is only 1" then that the right size!
On VCW the diaphragm is about 2.5" diameter however the valve it moves
(which could be mistaken for another diaphragm valve) looks like it might
hold a 1" diaphragm. In fact it doesn't, it reverses the action of the
pump pressure via 4 x 4mm pipes upon other components.

The boiler should light up for water heating at a modest flow rate.

HTH


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

Thanks for the all the replies.

I have searched for the boiler model underneath but can't find it.

However, I am pretty sure that it is a VCW242 or 282?? The only
reason is because the boiler engineer accidentally left the manual and
your description of VWC models fits ours exactly.

I am also pretty sure that the 'diaphram' is the one that you are all
describing.

Therefore, any ideas why twice in 10 days the hot water stopped, only
for it to come back again later on in the day. When it failed, the
pressure / flow rate through the ho****er tap was a lot less than
usual.

Many thanks

In article ,
Dave Clark wrote:
Thanks for the all the replies.

I have searched for the boiler model underneath but can't find it.

However, I am pretty sure that it is a VCW242 or 282?? The only
reason is because the boiler engineer accidentally left the manual and
your description of VWC models fits ours exactly.

I am also pretty sure that the 'diaphram' is the one that you are all
describing.

Therefore, any ideas why twice in 10 days the hot water stopped, only
for it to come back again later on in the day. When it failed, the
pressure / flow rate through the ho****er tap was a lot less than
usual.

Sounds like the diverter valve sticking -- you should
be able to see it moving through one of the inspection
holes if it is working properly.

Now, if anyone can give me ideas on why my later Vaillant
combi still makes horrible clonks whenever the diverter
valve operates i'd be very grateful :-)

G.

On Fri, 05 Mar 2004 04:32:38 -0800, Dave Clark wrote:

Thanks for the all the replies.

I have searched for the boiler model underneath but can't find it.

However, I am pretty sure that it is a VCW242 or 282?? The only
reason is because the boiler engineer accidentally left the manual and
your description of VWC models fits ours exactly.

I am also pretty sure that the 'diaphram' is the one that you are all
describing.

Therefore, any ideas why twice in 10 days the hot water stopped, only
for it to come back again later on in the day. When it failed, the
pressure / flow rate through the ho****er tap was a lot less than
usual.

Many thanks

As a wild guess I'd say that the diverter valve is sticking and/or has a
split diaphragm and possibly you have times when the water supply is low.
Which means that at those times the there is a chance the boielr won't
fire.

AFAIK there is no active control of the flow rate by the boiler. The DHW
temperature knob (always stuck immovable IME) is simply a flow restrictor:
the less flow the grater the temperature rise.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html

AFAIK there is no active control of the flow rate by the boiler. The DHW
temperature knob (always stuck immovable IME) is simply a flow restrictor:
the less flow the grater the temperature rise.



--
Ed Sirett - Property maintainer and registered gas fitter.


Funnily enough the DHW temperature knob on my now junked VCW242
was stuck immovable!

BTW my installation of a Vaillant Turbomax 828 to replace it went OK,
thanks to all those on this board who helped with my queries. The worst bit
was getting the pipes through the cavity wall ( moved the new boiler to an
outside loo location ).

Worst screw up was finding out the hard way that a single drop of
water left in a system when fitting solder joints will screw up any chance
of getting a sound joint.

Second worst screw up was not realising that mild flux and end-flow
fittings do not work well together. I thought that brightening the copper
end of the pipe with wire wool would obviate any problems, but it turned
out ( obvious really ) that you needed to brighten the inside of the copper
fitting as well! I eventually used a much more active flux ( Everflux ) and
abraded any copper surface which was going to have solder flowing
over it.

Andy