Hello.

Last week I posted about problems with my 15 yrs old Netaheat
Electronic 16/22 (flame going out then continuous ignition cycles).
That problem was solved by replacing the PCB with a recon unit.
Unfortunately that seems to have brought on another problem- boiling!

After being on for about 1.5 hours in its newly fixed state, there was
a loud bubbling sound from the pipes and the sound of water pouring
out of the header tank overflow. The CORGI guy who fitted the PCB
insists that it can't be anything to do with the new (well, recon) PCB
and must be the thermostat. This seems a bit too much of a
coincidence?

The thermostat is connected to the PCB by two wires which (according
to the schematic stuck to the boiler) connect to either side of the
switch within the thermostat. I've tested the boiler with these two
wires disconnected, and also with them connected to each other. On
both occasions the boiler is happy to keep on going. Doesn't this mean
that the PCB is ignoring the input from the thermostat- or am I
missing something?

Attemped ASCII art of thermostat wiring...(the top section doesn't
seem to be used for anything as the two connection block wires do not
connect on to anything else?

| Mains Live
|
--------
| | |
Conn | o | Conn block (unused?)
block | o--|-----
(unused?) | / |
------|-o |
| |
| o--__o |
| | | |
---------
| |
|
PCB PCB (these are the wires I've been playing
with)
L1 L2

Any advice gratefully accepted...

Thanks,
Dave