Heatslave 20/25 trip out question

[Incrisis]

Hi everyone

I know there are quite a few threads already about this, but I can't seem to find one that matches my experience.
I know my boiler is old, over 20 years since it was fitted, it was brand new, and over the years it has had almost everything replaced, but I still get lock outs very often, even after being serviced, and has been doing this for quite a few years now.

Description of the fault is:
It will fire up and run until everything is up to temperature, but when it needs to fire up again, it locks out.
When resetting, it goes through the start up process, clicks once when attempting to fire, then locks out.
I can, sometimes, get it to fire up after resetting 3 or 4 times, yes I know this isn't advised, but what I have found works almost every time, is to leave it a few hours before resetting. It will then reset, but repeats as above, it runs until everything is up to temp and when it needs to fire up again, it locks out.
However, sometimes it will run fine for a day or two before doing this.
Quite often there is also quite a strong smell of the kerosene when it trips.

I am wondering it is a fuel supply issue, too much, or not enough, although there isn't a way of regulating how much oil it gets as it is gravity fed from the tank to the fuel pump in the boiler.

Has anyone else experienced this?

 

[Burnerman]

The main item affected by heat alone is the solenoid coil, behaving once more after it cools down. The coil sits on the side of the oil pump.......it's notorious for giving problems, but the Diamond replacement is said to be better. Keep a coil in stock anyway!
These things often give problems after 10 mins or so.......if you are quick with a multimeter you may find that it is open circuit when it is hot.
Next, when was the boiler last serviced, including an oil pressure check and a flue gas analysis?
Here's the start up sequence that may help you understand things better:
On switching on:
The motor starts, which is connected directly to the fan and oil pump. This is called the purge cycle, where it is blowing clean air through the boiler and flue. Although the pump is spinning, it isn't pumping oil. The ignition spark is present at this time.
The spark electrodes are a couple of millimetres behind the nozzle, but the blast of air blows the spark into the oil spray.
After a few seconds (8 maybe) you'll hear a click as the control box instructs the solenoid coil to open the oil valve deep in the pump. The burner should now light.
The photocell now looks at the flame, and if it can see light it instructs the control box to keep the oil flow on. if it can't see the flame, either due to dirt or the flame darting about, maybe - the burner locks out.
The pump will supply the necessary oil on demand - the supply from the tank sounds fine.
John

 

[Hairymelon]

Is it a balanced flue model with a tightly fitting alloy box over the burner or is the burner uncovered?

 

[Burnerman]

Always worth trying with the burner box off!
John

 

[Incrisis]

Is it a balanced flue model with a tightly fitting alloy box over the burner or is the burner uncovered?

Always worth trying with the burner box off!
John

It has the fitted alloy box, but it doesn't seem to matter if the burner cover is fitted or not.

 

[Burnerman]

In which case, the fault is elsewhere.....there isn’t any flue obstruction evident here.
John

 

[Incrisis]

The main item affected by heat alone is the solenoid coil, behaving once more after it cools down. The coil sits on the side of the oil pump.......it's notorious for giving problems, but the Diamond replacement is said to be better. Keep a coil in stock anyway!
These things often give problems after 10 mins or so.......if you are quick with a multimeter you may find that it is open circuit when it is hot.
Next, when was the boiler last serviced, including an oil pressure check and a flue gas analysis?
Here's the start up sequence that may help you understand things better:
On switching on:
The motor starts, which is connected directly to the fan and oil pump. This is called the purge cycle, where it is blowing clean air through the boiler and flue. Although the pump is spinning, it isn't pumping oil. The ignition spark is present at this time.
The spark electrodes are a couple of millimetres behind the nozzle, but the blast of air blows the spark into the oil spray.
After a few seconds (8 maybe) you'll hear a click as the control box instructs the solenoid coil to open the oil valve deep in the pump. The burner should now light.
The photocell now looks at the flame, and if it can see light it instructs the control box to keep the oil flow on. if it can't see the flame, either due to dirt or the flame darting about, maybe - the burner locks out.
The pump will supply the necessary oil on demand - the supply from the tank sounds fine.
John

Sorry, I missed this reply.
I did have the solenoid replaced a few years ago, I will get a new one and see if that helps, from your explanation, it does make sense why it doesn't fire back up until it has been left alone for a few hours.
The starting sequence is doing all things as you say, but not firing after you hear the click. I have checked, and cleaned, the photocell to make sure that isn't it, that was also replaced a couple of years ago.
If I recall, almost every time it is serviced, they tell me the baffles have dropped, so maybe that isn't helping, as I guess that helps the airflow out of the boiler.

 

[Burnerman]

Dropped baffles? That’s a new one on me, but you can expect to find sulphur deposits on them, easily wire brushed away. There will be some rust, oxidisation and carbon debris on the baffles and in the bottom of the fire box.
If the burner is overfiring, due to excess fuel pressure maybe, you can see where the edges of the baffles have been burnt away .....often you can swap them around if they are all the same shape.
John

 

[Incrisis]

Thanks for all the replies, they have helped a lot.

 

[Incrisis]

Hi everyone, thanks again for all the replies.
I replaced the burner solenoid coil, but the problem still persists.
it is doing the same as always, runs ok for a day or two, locks out.
Sometimes it fires back up straight away, other times it takes multiple resets., either spread out other time, or repeatedly resetting when it allows me to.

 

[Incrisis]

It has been a few months, so I thought I would update.
After changing the coil, at first it was still tripping and having to leave it alone for a while before it would fire up again.
However, that seems to have sorted itself for the most part, I am still getting the odd occasion where that happens, but maybe once a month, rather than every other day.

 

[Johntheo5]

Have you renewed anything on the fuel supply side like the fire valve which could possibly be drawing air in over time through the valve spindle, how much higher is the bottom of the fuel tank above the oil pump?, is this monthly problem tending to happen when the fuel level level is lower?.
I read somewhere of a similar problem which was finally fixed by installing a tiger loop, but if your system is a two pipe then it should not require this.