On Sun, 23 Sep 2007 03:24:06 -0700, Daljit wrote:


What flow rate are you getting for the DHW?
Pump problems (OK I accept they are more likely now we have eliminated the
common stuff)
temperature sensors.
PCB problems.

Flow rate is approx 7 l/min when DHW control turned to max. I haven't
noticed the flow in the

OK with that flow rate the boiler should modulate and give a steady stream
of HW at a steady temperature.


Is there anyway i can check pump is working optimally?

We have the surprising behaviour of the CH cutting out as well as the DHW.

Here are some of the possibilities in no particular order:
1) There is inadequate flow in the primary circuit; so the temperature
rise in the primary heat exchanger is too great and the boiler cuts out.

To diagnose you need to work out what is getting hot and what is not.
In CH mode make sure at least one or two TRVs are full on.
Correct operation: The flow pipe is a little warm and continues to warm up
steadily over 5 -10 minutes to untouchable. If the pipe is cold and then
very hot there is poor primary flow. Either pump is bad or the heat
exchanger is blocked or some other fault with the same effect.

2) The Sensor is over enthusiastic,T so the PCB thinks the boiler is
over heating and shuts the burner down.
raden/geoff can say better than me - but 10k Ohm cold and 1k Ohm hot
would be in the range.

3) The modulator is working right mechanically but is being told to do
the wrong thing?
The ignition rate looks plausible. The gas pressures during operation are
crucial here. Full for DHW until steady state has arrived in which case
for 7l/min something in the mid range should be OK.



PCB - I'm not that good with electrics, so would be lost if the
problem's here.

Alas, the game nowadays requires electrical, mechanical and IT skills.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html