With the recent massive increases in heating oil prices, I've been wondering if there would be anything to gain from replacing my existing Grant Multi Pass oil-fired boiler - now around eight years old - with a newer model.
I'm not having any problems with the boiler (other than a few baffles that needed replacing a couple of years back) - and it is regularly serviced. But I do seem to be getting through a huge amount of oil, which at almost three times the price it was a couple of years ago, is no laughing matter.
I have replaced a couple of rads with larger units, but this has been offset by an extensive program of pipe lagging since I moved into the house and also the fitting of thermostatic valves on every rad.
It could well be that filling my tank at a cost of almost £900 means I'm just noticing the running costs more than I did previously, but if there are any significant fuel savings that could be made by replacing the boiler, it wouldn't take that long to recoup the expense.
Are there any particular models of boiler known for being more econonic to run? Has anyone had experience in this area?
The service guy should be giving you report sheets with combustion analysis figures. If you can quote these to give an idea of efficiency now it will be possible to make an assessment.
No, I've not been given any reports - and as I didn't have the boiler installed, it wouldn't be possible to compare the figures when it was new (if that's what's required).
I did speak to a service engineer last year and he said the boiler was running well (after he'd changed a few baffles) - but I was more interested in knowing whether newer models offered any significant improvement in running costs.
Go to oil boilers then refined search. Pick your boiler and see what the efficiency is. It probably have drop a few percent. Then look at the efficiency of the condensing boilers.
From what I can gather, my current boiler is rated at a 'C', offering around 85% efficiency - whereas current models are rated at 'A' which equates to an efficiency of around 95%.
Would this 10% increase in efficiency offer me a straight 10% saving in running costs - or is it (as I suspect), more complex than that? And where does size (output) of the boiler enter the equation?
Probably more as your boiler nay be less than 100% efficient.
You size the output to what the building demands. Your boiler may be oversized, which is common. When oversized it may cycle, which is inefficient. So if oversized you may be more inefficient than what you think. Best to install an extra layer of insulation in the loft, then size up the boiler to what the building needs. Then get a modulating condensing oil boiler. This will modulate the burner down to what the buildings heat demands are once the house is up to temperature. If the cylinder is a standard one, get a quick recovery coil cylinder too. This will take all the boiler's heat and promote condensing efficiency.
Heat lost from the boiler (and any conventional flue pipe) may still be useful to you if it helps to keep your house warm! I doubt that the boiler efficiency tables take this into account, and to that extent I don't trust them.
Remember that condensing boilers produce condensate which needs to be disposed of.
They are a guide and they say anything arounf 3% is basically the same. You can engineer a system to take full advantage of a condensing boiler, promoting great efficiency, which it also does not take into account.
The makers defined efficiency when new might be relevant but in view of your remarks about the service guy replacing baffles but not giving you any combustion analysis or report figures I'd not be sure the boiler is operating anywhere near that efficiency now. Efficient use of fuels does depend on checking the combustion at periodic service. How can you or he have any confidence in the effectiveness of the combustion otherwise? I strongly suggest you insist on him carrying out combustion analysis tests when servicing and on seeing his combustion readings from these tests. If he is doing the job properly he WILL be carrying the correct test equipment. Most commonly a chemical (Fyrite or Briggon) test set as these are more tolerant of oil flue gases than oxygen cells in electronic analysers.
For what its worth a surface coating of soot on the inside of a combustion chamber is an excellent insulation barrier to heat transfer into the water, A displaced or missing baffle allows the heat to escape the boiler before absorption into the water, too rich a fuel/air mixture produces soot (smoke) and poor combustion efficiency, too weak a mixture burns all the fuel but the excess air sweeps heat straight through the boiler and out of the flue so again poor efficiency. The efficiency curve has quite a sharp peak.
It will give you a cost saving BUT you need to do a proper costing exercise before spending lots of cash on replacing your boiler, especially if you intend to fund it with borrowing. Bear in mind that the present price of heating oil is not likely to stay at its present level. The price of crude fell lately and this will slowly filter through to the end user. Heating fuel prices do vary widely between different suppliers over the year from winter to summer. Normal practice is to have a tank big enough to hold a years supply and buy when its cheap.
The output rating of the boiler "should" have been designed to match closely the needs of your installation, but oil boilers of domestic sizes are generally not built to modulate. They switch on/off under the control of the boiler thermostat. When the unit is fully loaded in deep winter its performance will be at maximum efficiency. As the season warms up the duty cycle of the boiler will become more off than on and the true efficiency will be much lower, eventually in summer the only load will be hot water. Under these circumstances switching on from cold will show a steady demand to heat the cylinder but once it is heated only small burst of replenishment heat (subject to the cylinder thermostat) will be required. Under these conditions you will obviously not get the same efficiency as during winter with full load demand.
The Grant multipass is a decent boiler so unless there is a deterioration problem I would not expect the sums to justify replacement purely on the gain in efficiency for a reasonable payback. however do make the effort and work it out properly for yourself.
Using a quick recovery coil cylinder that take all the boilers output and two cyclidner stats, boiler cycling is eliminated, and efficiency is "very" high heating DHW.
Many thanks for this detailed reply - you raise some inteteresting points.
Unfortunately, any cost/efficiency analysis I could carry out would inevitably be compromised by the rather er... 'unusual' house in which I live - a thatched former dairy, listed (to prevent the replacement of the ill-fitting steel window frames), laid out in a long L-shaped row of rooms, with wind (I kid you not) gusting through the loft areas because is isn't the practice in this area to put felt (or any other kind of membrane) between the roof timbers and the thatch.
Needless to say, insulation has been a number one priority, but as long as the planners/listed building officers here in Dorset continue to value authenticity more highly than saving the planet (or my wallet), I'm stuck with what I've got. And I won't even mention the construction of the walls...
But ultimately, I think you've answered my questions. It probably wouldn't be worth changing a functioning boiler for a more efficienct model - but that I really need to keep on top of servicing and make sure the engineer caries out combustion tests.
Other than that, I suppose it's down to waiting for Bush to vacate the Whitehouse and hoping that peace might break out in the Middle East. Shiiishh...
All through the thatch willow stakes (at least I think they're willow) are used to fasten the reed together. Unfortunately these poke through the bottom of the thatch (often by several inches), making it impossible to fasten any kind of sheet material under the rafters.
I did consider cutting them all off (apart from anything else, they're a bugger if they stick in your head) - but if any repairs are done to the thatch (or new thatch is added), more stakes will have to be used and this would be difficult if the roof has been sheeted. Apparently, this is one of the reasons why felt isn't used.
That said, I have insulated and floor boarded the lofts to try and keep the air above the ceilings as static as possible.
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