Oil central heating boiler problem

[Thomas]

Hi

I wonder if anyone here can throw any light onto a problem I have with a new replacement oil central heating boiler.

The boiler is a Potterton and the burner is a Riello.

After installation the technician switched on the boiler and I noticed it was smoking badly from the chimney. He then proceeded to set up the oil pressure and air adjustments using a pressure gauge and analyser.

The boiler then seemed to work just fine, no smoke from the chimney and the boiler efficiency was, according to the technician, as per the manufacturers specification.

Everything was fine for a few days then I noticed that the chimney was smoking badly and there was a smell of kerosene from the boiler after it had finished a cycle.

I checked the air adjustment and was surprised to see it set at zero. The manufacturers optimum setting was 2.4.

Out of interest I altered the air adjustment to see if I could effect the combustion characteristics of the burner but to no effect. Increasing the air to the boiler reduced the size of the flame but had no effect on the smoke coming from the chimney.

The flame at all air adjustment settings seemed to me to be very yellow and not the bright perky sort of flame I seem to remember seeing through the peep hole of the old boiler.

Obviously I will be calling back the guy who did the commissioning but wondered if anyone here could throw any light on what the problem could be.

[John]

"Thomas" wrote in message news: [e-mail]...

Fortunately Potterton oil boilers are not so far suffering the same decline of reputation that their gas models suffered in the shapre of the Puma et al (IMHO)

"optimum" subject to variances of flue draught and other site variables!

The zero setting of the air intake is worrying. Was it loose? The shutter adjustment should be fixed after adjustment or commissioning and if not it may have vibrated closed. Which model of Riello burner do you have as there are a variety of models. Early ones were easily identifiable because the grey plastic control box with red reset button sits on top of the unit. This model mutated into a balanced flue version enclosed in a cast Aluminium enclosure with spigot for air inlet hose on top. In both cases the air adjustment is via a rotating disc with apertures which cover or expose the fan inlet. This is secured via a locking screw (sometimes a nut). An alternative adjustment flap was later used either on its own or with a hydraulic ram operator linked to the oil pump so as to close the air inlet when the burner is not running. While rare it is not unknown for the oil pressure adjustment to fail and you could have a problem there but on balance I'd suggest the first thing to check is the air setting as you have done. I'd then take a look at the swirl plate in the burner blast tube. If the air supply had shut off to nearly nothing this swirl plate could easily have carboned up thus limiting the airflow when the air adjustment is opened up again. Cleaning it and putting the airflow right is fairly trivial to do but you will need a combustion analyser or a Fyrite kit and a smoke tester. Riello moved on to the RDB range of burners which are good but not as easy to work on as the earlier ones in some respects. The principles remain the same however except the air adjustment is a bit more finicky and most of the spares are not compatible with the earlier models (how amazing! or is this part of a sales drive for the spares stockists?). Other things to check:- Oil nozzle is not loose and allowing unatomised leakage into the blast tube. Any air inlet routes remain clear (no kinked intake snorkel tubes etc) If a two pipe oil system is in use the return pipe is not restricted since the pressure regulator relieves into the return pipe and blockage will result in a pressure rise.

HTH

[Thomas]

In article , John writes

The air adjustment is via an allen key on the front of the unit. I have moved the adjustment a bit and will monitor to see if it changes. The adjustment friction seems to me to be high enough to render this unlikely.

It's a Riello RDB1 with the inlet hose on the top. The boiler flue gasses vent into a conventional chimney.

Many thanks for the reply John. I will check the points that you have raised.

[John]

SNIP

It would be worth checking that the conventional chimney has a liner fitted. Older oil boilers had a much higher exit temperature than the current increased efficiency models and condensation in an unlined existing flue is almost guaranteed. Take a look at the installation and service booklet for guidance.

SNIP

I'd be very wary if the air setting was zero on an RDB1. I agree it is very unlikely that the adjustment would move accidentally. Did you get a written record of the combustion readings and smoke content of the flue gases?

[Thomas]

It has a SS liner but there is no insulation installed between the liner and chimney brickwork. I think you are absolutely right here; what I am seeing is condensation and not smoke. It is only visible during cold weather. The installation manual indicates that insulation is required so I guess I need to introduce some form of insulation between the liner and chimney. Any ideas as to what I need to do?

No unfortunately I didn't get a record from the technician who did the adjustment. As you indicated in your previous post that I should check the fuel nozzel installation I purchased a replacement from the local plumbers merchant just to be on the safe side and set the air adjustment back to the manufacturers nominal setting. The unit seems to be functioning in a satisfactory manner now. I am however, after my experience, somewhat wary about letting an 'expert' tweak my boiler. Is it possible to hire a flue gas analyser in order to do my own set up.

Many thanks

Thomas

[John]

It depends on the "cooling" of the liner within the old chimney. If the chimney is in good order and restricts the convected cooling air currents then the practicalities of the matter are that you will not suffer from top end corrosion of your boiler. If the old chimney is leaky and excessive chilling does occur condensate will appear inside the top of the boiler with corrosion of the mild steel following close behind. If this occurs you will have to find a way to fill the void around the flue with vermiculite or similar, possibly via a hole cut into the masonary :-(

I don't know of any hire service for analysers but you could enquire of a large hire company such as HSS. A "proper" OFTEC registered technician will have demonstrated his/her competence and be able to do the job right. What area did you say you lived in?