"Ed Sirett" wrote in message
news
On Wed, 03 Nov 2004 18:07:27 +0000, Wainscotting wrote:
"Ed Sirett" wrote in message
news
On Mon, 18 Oct 2004 17:06:43 +0100, Wainscotting wrote:
"Ed Sirett" wrote in message
news
1) From completely cold with the instant switch off does the boiler
fire
when you run a tap? If no then the problem is with the DHW flow
sensor
(diaphragm) or more likely with the micro switch this sensor
triggers
or
its operating mechanism.
Just tried this and no, with the instant hot water switch in the
"off"
position and hot tap running, the boiler will not fire up and there
is
no
evidence of the pump running. If I switch to instant hot water whilst
the
tap is running the boiler will fire up no problem.
OK. The problem is definitely with the DHW flow sensor.
This is a differential pressure type with a rubber diaphragm.
1) This could have split.
2) The pin it pushes could be stuck
3) the microswitch it moves could be duff.
4) the wires to the switch are broken.
When you put the instant (hot standby) switch on the boiler fires
because
it is trying to preheat the innards, as you draw HW the preheating is
thwarted and the boiler delivers HW after a fashion.
Update - The cold water section diaphragm seems to work ok. When drawing
water the pin lifts straight away and the microswitch contact is made.
Are
you referring to the actual flow switch? The one that has two
microswitches?
There is a metal lever that rises and falls depending on whether you are
using hot water. When the lever is in the down position it makes the
right
hand microswitch and the boiler comes on for water. When water is turned
off
the lever reverses it's action and moves away from one switch and makes
the
other. It seems to take about 2-3 mins to move from radiators position
to
hot water. Can the flow switch be refurbished or does it have to be
replaced
as a unit?
I'm less familiar with Sines than other Vaillant combis. I'm fairly sure
that the switches should go back and forth between the modes in a second
or two. I know that 242s have a three position diverter valve unit which
has CH-neutral-DHW positions. However they are indrectly servo operated
by pump pressure.
You'll have to ask at a heating spares shops if they have a 'service kit'
for
the unit. A new unit which sounds like its a DHW flow + diveter valve
unit is likely to be pushing £100.
Incidently I notice that the cheaper the boiler the more expensive the
spare. This part is £140 for an Alpha, and £110 for a Pott. Lynx.
A possible cause of failure is spindles getting sticky on the O-ring
glands, or a load of gunk in the primary circuit part preventing free
movement of the valve.
--
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 once again Ed. I might try removing it and ceaning it as best I can
before I think about buying another.