On Mon, 22 Dec 2003 22:42:58 +0000, Richard Faulkner wrote:



Why am I writing this?? Well, I suppose it is to say that there seems to
be no real way of diagnosing the cause of a problem with certainty, and
it may be necessary to spend money on a number of possible cures in
order of reasonableness, in order to exclude particular things.

I suppose the order in which things are tried to resolve an intermittent
problem is partly 'reasonableness' = likelihood of being the culprit.
partly the cost of the item and partly known track record.

For over heating this would normally be either a flow related problem or
a faulty sensor.

So if the temperatures of the boiler seem reasonable then
pumps, bypasses (or lack), All TRVs+ warmth are reasonable.

Given that over heat sensors are cheap they are probably changed as the
first or second item on the list.

A pump is simple to change and is still much less costly that a call out so
that would be the next up. Although an intermittent pump failure is not
common IME. (Open circuit, Earth fault, Total erosion, or duff capacitor
would be the usual suspect).

The PCB would be towards the end of the list (unless a Suprima).

For instance if someone reported delayed or no CH after DHW on a Puma then
you might aswell go and get a diverter valve actuator on your way there.


--
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