Upgrade to condensing boiler - do I need to clean the gas oil tank?

Gas oil & kerosene behave very differently under cold conditions. For instance, gas oil, at 0°C, begins to cloud due to the parafin content within it. When temperatures of -10°C occur, it begins to solidify and block the oil filter. This is known as its gel point. This is where I have come across the separation from kerosene. Where the fuels have been mixed in the oil tank, the heavier parts with more viscosity solidify and block the filter. By opening the filter, you will see that it can contain more gas oil than kerosene, therefore separation. Just because you have mixed the fuels does not change the chemical make up of their components.

The second main difference between both fuels is their viscosity and it too plays a very important part of the fuel & burner. This is why gas oil is referred to as 35 second oil and kerosene as 28 second oil. A given amount of each fuel takes 35 or 28 seconds respectively to pass through a given opening. It is the reason why gas oil requires a much greater pump pressure than kerosene.

In colder temperature regions of the world, oil burners that use gas oil will have pre-heaters built into the ignition process to pre-heat the gas oil before it enters the nozzle, similar to a diesel engined vehicle. They will also take precautions such as insulating the fuel lines, etc. Just mixing with kerosene will NOT suffice.

Whilst on the other hand, kerosene can withstand temperatures of -30°C and generally does not have the same issues as gas oil. The other issue is that kerosene does not contain FAME (fatty acid methyl esther) and as of 1st January 2011, as an EU directive, there has been an increase of 40% of FAME in gas oil throughout Europe. This also introduces a whole other issue/problem and another reason why not to use gas oil in home heating oil systems.

Shane, think what you will find on this type of subject as always in Ireland is the attitude, 'ah sure that'll be alright' rather than people adopting what is the best approach, whats recommended by the manufacturer and considered industry best practice, hence why almost every oil tank installation in the country is not to regulation and the vast majority of gas installs are on 'semi-sealed systems'

Here Shane, have a loan of my brick wall to keep banging your head off (btw +1 shane)

There was an American poet/educator, Henry Longfellow, who once said "It takes less time to do a thing right than it does to explain why you did it wrong".

How right he was!

We are talking about a few parts per thousand of impurities here i.e. a few liters of diesel in a 1000 liter tank. The fuel is delivered to the tank from a truck which supplies diesel and kerosene through the same supply hose. Any delivery can result in slightly impure fuel being supplied to the storage tank. Advising anybody to have their tank and feed pipe cleaned as suggested is excessive and is adding needless cost to them.

Bstop and Shane, I really appreciate your opinions and thank you both for taking time out to offer them. Bstop I would prefer to take your approach as it the less expensive of the two but when I have to commision the boiler they will know full well that I ran gas oil through the boiler at some stage albeit a tiny amount. Shane I think it would be best to empty the tank and start fresh as you said, I am sure the both of you know your stuff but having gone from one disaster to another in the past 8 weeks I dont have the patience for another mess, Thanks for the input lads, Also thank you DGOBS and Villa.

My point is always get somebody who is certified and registered to do the job in the first instance. A competent OFTEC engineer should always do the job right. If your installer fitted a condensing boiler running on gas oil, I would very much doubt if it has been commissioned with a flue gas analysizer and set up to suit site conditions. I would also very much doubt if your boiler passport has been filled out correctly and returned to the manufacturer, therefore leaving you with no manufacturer's warranty whatsoever. If an OFTEC engineer was used, you have a definite comeback through OFTEC in Dublin.

With regard to excessive and needless costs to the customer, it takes me approx 3 to 4 minutes to attach my compressor to the oil line at the oil tank and disconnect the flexi-hose from the oil pump in the burner, place in a container and switch on the compressor. This is not an extra cost to the customer but part of the service which should be standard practice. You are going to the trouble of removing the gas oil from the bottom of the oil tank anyhow! As DGOBS says, perhaps if more best practice was applied, unhappy customers such as Salaried would be a thing of the past.

Salaried: By having your boiler commissioned, not only will you receive a manufacturer's warranty, but you will recoup the cost of having it commissioned in savings in oil, running cleaner, more efficiently and less further complications down the line. See http://www.ofteconline.com/locatecompanyIreland.asp for a registered technician.

Typical cost for commissioning boiler and certifying boiler passport when works not carried out by the engineer are €70.00 + VAT @ 13.5%.

Liffey Oil provide a fuel swapping service. They will take away your existing GasOil (diesel) and replace with the same amount of Kerosene. They charge €150forthe service. When this is done there will be a small amount of diesel left in the bottom of the tank below the level of the outlet pipe. The new kerosene will float on top of that because it is much lighter and will not get sucked into the flow to the boiler. Once you have changed the oil in your tank you then have to bleed whatever is left in the line between the tank and boiler. The boiler fitter can do this.