Pulsacoil 2000 problem - Clueless

Hi Mike and Fellow Boilermen,

My Pulsalcoil 200 boiler/heater has come to a grinding halt, and I haven't been able to recover it over 2 weeks now. So I really appreciate some help on this. I am an owner of this model and have over the last 10 years dealt with the various problems this boiler throws up. Though I am not a trained technician I have a fair understanding of things electrical and electronic. So I have clinically eliminated the obvious ones. (water top up in the top shelf container, thermistors)

Issues that have progressively changed over the last few weeks now, (please bear with my explanation):

1. The problem started 3 weeks ago.It started with inconsistent heating. The lower heater did not fire up for many a night (inconsistently) until it finally stopped working completely.
2. The boost/upper heater during this period would work. However as time went by the boost/upper heater too became inconsistent. It would start heating the element, I could hear the clear water boiling and it would switch off in few minutes. Never really fully heating the thermal store. After a few days the boost/upper store has stopped working as well.
3. The PCB is showing the following LED pattern through all this  **..**..**..
4. I called a technician (who turns out misled me and left) suggested changing the PCB. Though I was not convinced, I ordered it from Gledhill and replaced, to no avail. The LED pattern is the same and issue remains.
5. I also replaced the thermal sensor cable GT 153 on reading some forums. After I did this the upper heater kicked worked for a day and gave up totally.
6. The technician also said that there could be an issue with the pump. I have tried to vent the pump a few times. There is voltage into the pump, I can hear it kick in, both during off-peak and more so during boost. However I have a suspicion it may not be pumping well enough. When I insert a small screwdriver and try to rotate the pump, it does not always feel smooth. It takes a few continuous rotations to get it moving smoothly and even then I can sense a jerky rotation, as though it is stuck a little.
7. Couple of days ago the unit started tripping at the beginning of the off-peak. I tested it again during daytime, this time by turning the thermostat quartz timer off-peak dial, to force the off-peak time. Every time I do this, the unit trips . On one such occasion it blew the timer unit itself. I have just replaced that with a new timer now.

After all these changes (PCB swap, GT 153 sensor swap, Quartz timer swapped, new thermistors) the current status is:

1. Boost/upper heater does not work. I can see the element is heating up, the PHE warms up a little on the upper half. I can sense a little pump sound, but not heating. No hot water.
2. As soon as I force the timer to off-peak, the unit trips, with a loud bang and sparks in the lower thermistor/element region. So lower heater too is not working.
3. PCB LED shows **..**..**.. (manual seems to suggest this is working fine)
4. There is a constant buzzing sound in the PCB which is at its highest intensity when the pump regulator know is at its highest and drops quite low when I switch the pump regulator know to lowest point. This sound has always been a constant feature however since I have known, I can't quite link it to the onset of all these problems.

I am at my wits end. Yes I can call in another technician, I have also ordered a replacement pump. But its got to a point where it doesn't seem to make any logical sense anymore. Any urgent help here will really be appreciated. My family has lost all their patience with my DIY streak as you can understand :-).

Thank you
Deepak

Well first of all.
The PC 2000 is covered lots on here.
If your unit is not hot.
Then you will get nothing.
Checked the E7 timer? For burn out etc.
You need to change the bottom heater and stat.
Have you checked them out?
Same applies with the top heater too.
Common is leaking rod stat pockets / wet rod stat.
You really have nearly changed everything.
Mike

mike wrote:Well first of all.
The PC 2000 is covered lots on here.
If your unit is not hot.
Then you will get nothing.
Checked the E7 timer? For burn out etc.
You need to change the bottom heater and stat.
Have you checked them out?
Same applies with the top heater too.
Common is leaking rod stat pockets / wet rod stat.
You really have nearly changed everything.
Mike

Mike, how can I thank you enough. I replaced the bottom heater and that fixed the issue. The pump it turns out is working fine. Fed some inhibitor before filling up the tank and that maybe the reason the heater is silent. No sounds during heating and piping hot water again. Thank you again.