no gas as rural area, looking for best alternative for boiler

kerrydan

Hi we are thinking about purchasing a home with no gas supply, they currently have a very old oil boiler. Is it more economical to go with another oil boiler or go for an alternative? If so what type of boiler and what are the running costs and price of installation?
thank you

macman

Oil is the cheapest non-mains gas alternative.
Just because the boiler is old doesn't mean that you need to replace it, if it's running OK.
No one can tell you the install cost without knowing the spec and CH system.

G_M

You could think outside the box.

If you are planning on staying long term, and are in any case going to invest in heating, plus have upfront capital, why not investigate heat pumps (air or ground source), solar, wind etc?

Initially more expensive but longer term?

But if you are just comparing LPG, oil and electric, stick with oil.

reeac

kerrydan wrote: »

Hi we are thinking about purchasing a home with no gas supply, they currently have a very old oil boiler. Is it more economical to go with another oil boiler or go for an alternative? If so what type of boiler and what are the running costs and price of installation?
thank you

I would agree that oil is a better bet than electricity or LPG. Do you know the actual age of the boiler? There's lots of PR nowadays about the low efficiency of old boilers compared with new ones but our 16 year old boiler [non-condensing] still shows 85% efficiency when tested at the time of annual servicing. With a fuel bill of around £1100 p.a. we could save maybe £110 p.a. with a new boiler but the change would cost ca. £3000 and I believe that servicing would cost more than our current £55-60.

matelodave

I would see how you get on with the existing boiler before spending lots of money on replacing it. You won't get much change out of £2k or more and if you save £200 a year it will take you 8-10 years to recoup the cost. There might be a case if you could get onto mains gas but you've got more flexibility with suppliers with oil than you have with LPG.
If you were looking at a whole heating system refurb then there are all the other low energy possibilities but see how you go before pulling it all out.
Spend some money on improving the insulation in the loft, walls and draught proofing as that's where you get the biggest return on investment

Cardew

reeac wrote: »

There's lots of PR nowadays about the low efficiency of old boilers compared with new ones but our 16 year old boiler [non-condensing] still shows 85% efficiency when tested at the time of annual servicing.

How did they test?


What do you think that 85% efficiency means?

J_B

In my experience about 4 years ago, an LPG boiler was around half the price of an oil boiler

gamston

I live in the sticks, no gas, so we have stayed on oil, with a multi-fuel stove with back boiler connected to the central heating
price of oil feels expensive to me, but I go back to days when I could get it for 9p a lt
is your oil boiler in the house, that could give you radiated heat from the boiler, ours is in boiler room so no heat gain for inside the house
if I was starting again I would look at ground or air sourced heating, I would also look at having an aga multi-fuel if you can get wood/coal free or good price

reeac

Cardew wrote: »

How did they test?


What do you think that 85% efficiency means?

They test by analysing the exhaust gases e.g. for O2, CO2 and CO content. These figures give a measure of the completeness of combustion of the fuel. There are two efficiency figures - gross and nett.... as an example, a printout that I have shows gross 85% and nett 91.8% but I don't know what's included in each. When I chose the boiler [over a condensing one] in 1996/7 its efficiency was quoted as 85% cf. 92% for a condensing one and didn't think that the extra gain was worth the extra capital cost.
As to what 85% efficiency means - as I said above I'm not sure but it probably means that 15% of the heat produced is lost up the chimney. The analysis certainly includes exhaust gas and ambient temperature. I asked the service man about these two efficiency figures once but couldn't get a clear answer from him!

bobmedley

This is an overview of what Flue Gas Analysers calculate when they provide a boiler efficiency % - not overly detailed, but it sets out the basics;

The objective of a boiler is to burn the hydrogen contained in the fuel with oxygen from the atmosphere to produce heat.
Combustion efficiency analysers exploit the fact that by knowing the fuel (and its chemical composition) and measuring the flue gas temperature and either the oxygen or carbon dioxide level the efficiency of the boiler can be calculated.
On some boilers the settings can then be adjusted to maximise the efficiency.
In a perfect world the maximum efficiency would be achieved with 0% oxygen in the flue and the lowest flue gas temperature. In the real world allowance must be made for variations and uncertainties and so 0% oxygen is not practical. The settings on a boiler must allow for differences in fuel composition, atmospheric pressure, wind direction, boiler demands etc.
If the oxygen level is set too low and something changes the combustion process can become ‘fuel rich’ as there is insufficient oxygen for all the fuel to burn. This can cause high levels of CO to be generated and in the extreme enough fuel to enter the boilers flue and ignite (explode) outside the combustion chamber.
Typically for a natural gas boiler oxygen readings may be in the range 3% to 5%, for an oil boiler 5% to 8% and for a coal fired boiler 8% to 10%.

Combustion Efficiency v Boiler Efficiency
A combustion or Flue Gas Analyzer is used to measure the efficiency of the combustion process within a boiler. This is not the same as the boiler efficiency as it does not take account of, for example, the heat losses from the case of the boiler. So generally the efficiency stated on the rating plate of the boiler will always be lower than the measured efficiency of combustion.

Net Combustion Efficiency v Gross Combustion efficiency
Net combustion efficiency calculations assume that the energy contained in the water vapour which is formed as a product of combustion is recovered and is not exhausted from the flue or stack.
Gross combustion efficiency calculations assume that the energy contained in the water vapour is not recovered.
Typically the difference between the value of Net combustion efficiency and the value of Gross combustion efficiency for a natural gas fuelled boilers is around 8% with the net value being higher than the gross value.
Most boiler manufacturers now quote their boiler efficiencies based on the Net combustion efficiency.

My non-condensing oil boiler's gross efficiency when serviced always tends to be around the same as the manufacturer's stated efficiency i.e. 85%, so for better or worse I always use that when working out the oil cost per kw (or kw/h or whatever LOL).

Interestingly the last paragraph suggests that a gas condensing boiler that isn't in condensing mode is 8% less efficient.

Cardew

bobmedley wrote: »

My non-condensing oil boiler's gross efficiency when serviced always tends to be around the same as the manufacturer's stated efficiency i.e. 85%, so for better or worse I always use that when working out the oil cost per kw (or kw/h or whatever LOL).

Thanks for that info.


My understanding is that the Combustion Efficiency as shown by the Flue Gas Analysers(i.e. 85% in your case and that of reeac) is not the same as the manufacturer's stated efficiency and that quoted by SEDBUK.


In fact the quote below from your post seems to me to confirm that stance:


Combustion Efficiency v Boiler Efficiency
A combustion or Flue Gas Analyzer is used to measure the efficiency of the combustion process within a boiler. This is not the same as the boiler efficiency as it does not take account of, for example, the heat losses from the case of the boiler. So generally the efficiency stated on the rating plate of the boiler will always be lower than the measured efficiency of combustion.



This is an extract from SEDBUK:

Boiler Efficiency
The efficiency of a boiler can be measured or calculated in a number of ways for different purposes. For simple guidance it is sufficient to look at the SAP 2009 annual efficiency, which is an estimate of efficiency when installed under typical conditions in Britain, taking into account climate, housing conditions, occupancy patterns, and controls.


The various measures of efficiencies in the database are described below.
SAP 2009 annual efficiency
This is the best available estimate of annual average efficiency when installed in typical domestic conditions in the UK, and it is used in SAP 2009 (the government's methodology for calculating the energy performance of dwellings). For boilers which have been tested for full-load efficiency and part-load efficiency and the results accepted for the database, the SAP 2009 annual efficiency will be SEDBUK(2009). For older boilers, where test data is not available, the SAP 2009 annual efficiency is a default value based on type, age, and fuel, as found in Table 4b of SAP 2009.


I have a 25 year old gas boiler(Ideal Mexico CF125) that is shown of the SEDBUK tables as having an efficiency of 65%. From the installation and servicing handbook it gives the maximum input as 46.1kW(157,300Btu/h) and the maximum output as 36.64kW(125,000Btu/h) which is 79.4%.


Like all boilers of that age it has a pilot light that consumes a large amount of gas, which is one of the factors that drags down efficiency in a 'typical' installation.


IIRC when I did have the boiler serviced by BG, the Combustion Efficiency as shown by the Flue Gas Analyser was always 85% on the report I received.


Apart from the pilot light size, there is absolutely no adjustment on the boiler. That also applies to a similar age Combi I have in an Annex.


The full servicing schedule consists of cleaning and visual inspection. So I can only conclude that there is no way to 'tune up' the boilers to maintain efficiency.


So IMO - and I stress 'in my opinion only' there is little point in using the 85% combustion efficiency obtained by flue analysis as the basis for comparison with the quoted efficiencies of new boilers.


P.S. The quote' button hasn't been working for me over the last couple of weeks. Anyone else?