Oil Fired Boiler: Black Smoke from Flue

muggin5

Hi,

I wonder if anyone could offer any advice or help. We have only been living with oil heating for just over a year since moving into a new home. When we got our first delivery of oil back in December we noticed that there was black smoke coming from the flue when the boiler was working. It did pass after a couple of days and we had always assumed that it was the fact that dropping in 1000l of oil into the tank had disturbed sediment or water and this was causing the smoke etc...

Anyway, we had another delivery yesterday and it is doing the same thing - it actually seems worse but maybe because I am noticing it more in the daylight.

It just so happened that we were getting our boiler serviced yesterday morning too and the person doing our service had never seen anything like it before and said that our boiler all seems to be running fine and looked in good shape (its actually less than 3 years old).

The amount of oil in the tank had run quite low, but not disastrously low.

Two weeks ago, we had an oil tank company come and visually inspect the tank and they did a dip test. They did say that there was a couple of inches of water in the bottom and quoted us to remove that and flush it but they didn't really come across as making it sound very necessary or urgent...

One difference from our last delivery and this one is that we can smell the smoke in the house near the boiler this time and we couldn't last time.

Anyway, has anyone else had any similar experience? 

Thanks in advance.

lohr500

I am no expert, but I suspect it could be one of three things.

1) Filling the tank has disturbed the water layer in the bottom again, causing some water to be fed through the oil feed line to the boiler.
2) The fuel/air mixture setting is incorrect causing the boiler to run rich. This could be caused by several things including a worn out injection nozzle, the air inlet adjustment has slipped or a incorrectly aligned/partially blocked swirl plate. 
3) Contaminated or incorrect grade of fuel.

Do you have details of what was done at the service? Were the filters replaced and any water traps drained?
If the service was carried out correctly then 2) should have been eliminated. 3) is unlikely but I guess not impossible.

Given it did the same thing last time you filled the tank and then stopped doing it after a couple of days, I would suspect that it is related to disturbing any water/sediment at the bottom of the tank. 2 inches of water is a lot and would take some time to settle back after being sloshed around by the filling process. I'm not sure how high up the oil outlet is on your tank, but looking at the drawing for our tank, the bottom of the outlet hole is only 79mm above the base of the tank. 

I would take steps to get the water drained out as soon as possible. (See what they quote you to do this, but I have done it myself in the past with a syphon tube into a 25 litre clear drum. Any small amounts of kerosene that get drawn through towards the end can be carefully separated once they have settled in the last drum full).
Once drained, you could invest in a "replaceable tank sponge" to absorb any more sludge and water. Do a google search. They are around £20 or so.

Please let us know if it stops again in a day or so, like last time.

 

muggin5

Thanks. I suspect its the water and sediment too. I might try to syphon some water out myself - there are a couple of youtube videos giving some tips on this.

The quote from the tank company was £275 +VAT to drain, flush and return oil but they wanted me to empty the tank even more that it was and I didn't really get a great feel from the company as a whole.

I am going to ask another tank cleaning company out of interest.

lohr500

If you are comfortable syphoning out the water, have a go yourself and then get one of the sludge/water sponges I mentioned. Look for a "jiggler" Syphon on eBay or Amazon and extend the pipe with a bit of old hose pipe. Just make sure it has an air tight seal on the joint. Fill the pipe 1st with water or kerosene before you put the jiggler end in the tank and keep your thumb over the other end of the pipe then it will be easier to get it start syphoning.

dunstonh

When was the boiler last serviced?

Oil boilers have certain bits that should be replaced annually.   They also build up sludge.  So you would expect the oil tank sludge filter to be cleaned out.

edit: missed the bit about serviced "yesterday".  However, did the service include cleaning the filters?   A previous service engineer on ours never cleaned/replaced the filters and it was only found out a failure that was fixed by a better engineer.

QrizB

dunstonh said:

When was the boiler last serviced?

Friday morning, according to the OP:

muggin5 said:

It just so happened that we were getting our boiler serviced yesterday morning too and the person doing our service had never seen anything like it before and said that our boiler all seems to be running fine and looked in good shape (its actually less than 3 years old).

OP I disagree with your service engineer. A three-year-old boiler that is "running fine" should not produce black smoke.

muggin5

Thanks. The engineer suggested that there wasn't anything wrong with the boiler to cause the smoke and that it is likely to be the fuel. I am not so sure either but we did experience this in December and it did stop after a few days.

The engineer is coming back in the next few days when it has hopefully settled down?

muggin5

I have tried to syphon today and I have a clear tub with around 15 litres of murky, yellowish liquid.

I would take steps to get the water drained out as soon as possible. (See what they quote you to do this, but I have done it myself in the past with a syphon tube into a 25 litre clear drum. Any small amounts of kerosene that get drawn through towards the end can be carefully separated once they have settled in the last drum full).
Once drained, you could invest in a "replaceable tank sponge" to absorb any more sludge and water. Do a google search. They are around £20 or so.

Please let us know if it stops again in a day or so, like last time.

I am not sure whether there is much water in this or not to be honest. It is immediately obvious? If there is 2 inch of water, then I suspect that there would be a good 75-100 litres of water in there?

QrizB

Clean kerosene is clear and looks rather like white wine (although you'd never confuse the two in any other way).

I agree with others that it sounds like a contamination problem.

Have you got a clean, empty jamjar and lid? You could put some of the syphoned fuel into it, close the lid and see what settles out over time.

muggin5

Here is a photo of my murky water/oil.
I think I can see a thin line of separation when I look close.
But for all I know, its all kerosene!

muggin5

Okay, so I had some other jobs to do...
I took the cover off the filter on the tank to see what the filter looked like and I guess it should be a bit different to what I found...

EMPTY!

Can you buy replacement filters?