Worcester Heatslave oil boiler - lockout after draining and refilling system. Can't figure out why.

[bigbob764]

Hi all

I have a Greenstar Heatslave II oil boiler circa 2015.

The AAV and PRV both needed replacing which I have just done myself. I thought I did everything by the book, but now the boiler is stuck in lockout and won't even try to fire the burner.

Here's what I did exactly:

1. Closed CH flow and return valves
2. Let system cool completely
3. Opened main drain point and drained water in boiler until pressure read 0
4. Took off expansion vessel to empty it, then reattached and recharged air side to 1 bar
5. Removed and replaced AAV
6. Removed and replaced PRV
7. Opened main flow air valve
8. Opened filling loop until air valve passed water, then closed air valve
9. Closed filling loop once pressure reached 1 bar
10. Bled heat exchanger air screws
11. Bled nearest radiator (no air in it really)

So now the system is filled up and at pressure again, but when I try to switch it on I get the 955 lockout error.

The water pump starts to run briefly, but about 30 seconds later I get the error.

The burner doesn't fire. I can see its LED lights up red and flashes orange a few times, but that's all. Pressing the burner reset button does nothing.

I did not touch any oil or burner related things - only the water side.

I thought I had done everything right and took great care to do everything so I'm very upset that it's not working.

Any advice would be appreciated.

Thanks

Bob

 

[robinbanks]

The water pump starts to run briefly, but about 30 seconds later I get the error.

I know nothing of this system, but this is my first wondering just from the “sequence of events”; is the pump definitely pumping something, or is it airlocked and that’s being detected?

 

[bigbob764]

P.S. I also bled the pump screw until it bled water.

P.P.S I read that the lockout error is usually related to air in the oil line. I find this unlikely in my case because I didn't touch the burner or oil line at all. However, I was going to try bleeding the oil line anyway but can't figure out where the bleed point is on the pump.

This is what the burner looks like. According to the manual, I think the bleed point is the large silver hex bolt at the middle left:

However the manual shows it with a large protruding extension "(1)" which mine doesn't have:

Is there even any chance it could be oil related since I didn't touch the oil?

 

[bigbob764]

I know nothing of this system, but this is my first wondering just from the “sequence of events”; is the pump definitely pumping something, or is it airlocked and that’s being detected?

If it is airlocked, how would I remove the air? I thought I had bled all the air points including the pump head itself. Maybe I need to do it for longer?

 

[robinbanks]

Have you revisited every bleed point and checked that they still emit water rather than air? (Again, I know nothing of the process or operation you’ve performed and I would happily accept someone coming along and telling me I’m barking up the wrong tree, I’m just seizing on the last thing you’ve seen successfully happen, before the system shuts down)

 

[Johntheo5]

If it is airlocked, how would I remove the air? I thought I had bled all the air points including the pump head itself. Maybe I need to do it for longer?

It's the blank plug,1, immediately below the adjusting screw, with the boiler off put something underneath the plug and slacken it right back until oil dribbles out, then retighten it, do not do this if the oil tank is below the level of the boiler.
You could also use the vacuum connection plug 2, I've allways used blanking plug 2 on a neighbours Riello G5X burner.

Was there any prefix in front of the alarm 955. Like 9F or 8F??

 

[dilalio]

Is the pump running?
Can you get it to turn easily using a screwdriver in the bleed port?

 

[oilhead]

If you have attempted more than 5 resets, the control will lock out and the M.I's suggest a call to worcester , or an engineer.
Have you by any chance turned off the oil supply and failed to turn it back on again?
When you first restarted, did the burner motor run?

 

[bigbob764]

So after double-checking everything and bleeding all radiators without any success, I started to think it might actually be a problem with the burner.

I bled the pump; plenty of oil and no air in the line.

I noticed the burner's reset button LED was flashing red then orange. According to the service manual, this indicates a fault with the fan motor. I used a multimeter to measure the resistance over the motor wires and it seemed normal (~32 ohms).

Then I noticed what should have been obvious from the start... a massive string of capacitor fluid coming out of the capacitor cover.

Yeah... that'll be the problem:

I've ordered a new capacitor which will hopefully sort things out.

P.S. here's a diagram for anyone who has similar issues in the future:

 

[dilalio]

So after double-checking everything and bleeding all radiators without any success, I started to think it might actually be a problem with the burner.

I bled the pump; plenty of oil and no air in the line.

I noticed the burner's reset button LED was flashing red then orange. According to the service manual, this indicates a fault with the fan motor. I used a multimeter to measure the resistance over the motor wires and it seemed normal (~32 ohms).

Then I noticed what should have been obvious from the start... a massive string of capacitor fluid coming out of the capacitor cover.

Yeah... that'll be the problem:

View attachment 409759

I've ordered a new capacitor which will hopefully sort things out.

P.S. here's a diagram for anyone who has similar issues in the future:

View attachment 409761

Many pump failures are due to caps going.

 

[oilhead]

Glad you found it. It's a shame you did not notice that the burner did not start at the first switch on. I never like coincidences but this obviously was one and after your work it is a distraction to fault finding.
At least you have found out how to bleed the oil line

 

[bigbob764]

Shock update: I replaced the capacitor and the fault still persists. The burner is still flashing red / orange which indicates a fan motor fault.

I'm not sure if I should try another capacitor or just bite the bullet and buy a replacement motor. I thought the motors were fairly reliable so find it difficult to accept the motor should have died completely.

 

[Johntheo5]

Shock update: I replaced the capacitor and the fault still persists. The burner is still flashing red / orange which indicates a fan motor fault.

I'm not sure if I should try another capacitor or just bite the bullet and buy a replacement motor. I thought the motors were fairly reliable so find it difficult to accept the motor should have died completely.

Can you access the fan impeller, if so, use a screwdriver to see if it will rotate without much effort. (Ensure boiler switched off)