Payback time for condensing boiler

JohnBoy

Hi,

Not the right place to put this, buttt, i figured probably the best place all the same.

How would one go about calculating the payback on a more efficient oil boiler.

Our current boiler seems to be rated at 85.7% efficiency, and the best boilers of similar size on the sei site seem to offer 95% efficiency.

is it simply a case that the new boiler would use 9.3% less oil per annum?

sinnerboy

at first glance it is simple

add up all your oil bills for a year

13.5 went up in smoke with you current boiler

Change it and only 5% will

So you can predict an annual cost saving . No one has a crystal ball , but a reasonable guestimate would be to assume oil prices will rise at 10% annually from here on untill --- i don't know

however

this assumes that rads sizes are correct and that the system is balanced and optimised so that the new boiler can run at it's ( MAX ) 95 %

you will need to pay for new boiler . possibly new rads .

But even supposing existing rads are ok and the system is balanced well ..... your 86% boiler aint bad . Keep it serviced .

If you want to invest , have your house air pressure tested ( €600-800 )

This will point out where you need to seal air leaks . This is usually not expensive - tapes , silicone , expanding foam . For less than grand you could really save energy .

JohnBoy

Cheers for the reply.

yeah i figured it would be something like that.

I've replaced most of the rads in the house at this stage, got a few more waiting to be changed. we had the most ramshackle heating system imaginable. with some stupid thing i dont fully understand which caused the boiler to run an awful lot of the time.

basically either the fill or return was connected too close to the boiler. cant remember exactly but i got a plumber to look at everything and i'm following his reccomendations and that one change cut the running time in less than half, still more efficiencies, and one stupid loop to be found though.

I wouldnt see the payback on the boiler before we leave this place again, but i'm tempted to get an air test done, but the house is 60-100 years old so i'm not sure how much i'll be able to do about it.

Doctor_L

I would recommend that you seek the opinion of a few plumbers about condensing boilers. One plumber I spoke to, reckons that you get between 20 and 30 % savings with a condenser boiler.


This at first glance doesn't make sense unless the ordinary boilers I highly inefficient.

Plumbers will however have an idea if they are worth the money or not

AckwelFoley

Did somone say oil boiler?!

Grrrrr

*spits*

ednwireland

as far as i understand having looked into this condensing boilers only operate at that efficiency if the return temps are low enough (ie with underfloor heating) standard rads dont so this and hence you lose all that efficiency from the condensor.
also the uk efficiency rating (sedbuk) caps non condensor boilers at 85.7 efficiency even if they are more efficient. i replaced my oil boiler a couple of years ago a (to a grants multipass) and didnt go down the condensor route because i think i would gain anything.

i have halved my oil consumption with insulation and replacing a very old inefficient boiler in the last couple of years.


Difference between GROSS/NETT and SEASONAL EFFICIENCY
There are two different systems of determining a rated boiler efficiency, Gross and nett which used in Ireland and most of Europe excluding the UK and seasonal efficiencies which is used in the UK. On our brochures we claim 95% nett. which is correct, however the same boiler sold in the UK would be 85.7 seasonal efficient. This is where the difference is. Below is a further explanation of efficiencies.

Gross or nett efficiencies
Gross or nett efficiencies refer to an efficiency calculated using either the gross or nett calorific values of the fuel. Gross Calorific Value is the maximum heat in the fuel, including the latent heat, released during the combustion process. Nett Calorific Value is the gross calorific value, less the latent heat produced. The latent heat converts the water produced during the combustion process into steam. This heat is normally lost with the combustion gasses through the flue system. An efficiency calculated ignoring the latent heat, i.e. using the nett CV will always be greater than one where the latent heat is included, ie. using the gross CV. Therefore, the so called ‘nett efficiency’ will be higher than the ‘gross efficiency’. All boiler tests in Europe use the ‘nett efficiency’ method for calculating appliance operating efficiency!

Seasonal Efficiency
The UK use a different system of determining the boiler performance which is based on the seasonal efficiency of the boiler, this is called SEDBUK
SEDBUK is the average annual efficiency achieved in typical domestic conditions, making reasonable assumptions about pattern of usage, climate, control, and other influences. It is calculated from the results of standard laboratory tests together with other important factors such as boiler type, ignition arrangement, internal store size, fuel used, and knowledge of the UK climate and typical domestic usage patterns.

Note; When calculating the seasonal efficiency of a standard oil boiler the part and full load are used in the calculation, however they are capped at 91% and 92 % respectively, so no standard boiler can achieve a seasonal efficiency above 85.7% hence the large difference in the two figures.

sinnerboy

Great post there Sir !

May I ask - to what extent did you sort out your insulation

AckwelFoley

Well, this is very true, the asdvantage with uderfloor is that it is more efficent than rads, so no matter what you are burning.. let it be oil or pellets, because you are working on low temp efficency, you will burn less fuel.

But to get the full advantage of the condencing boiler, yes.. good insulation and underfloor heating.

ednwireland

sinnerboy wrote: »

Great post there Sir !

May I ask - to what extent did you sort out your insulation

guess what havent looked at this for 2 months
the insulation wa basic loft insulation (18") the only problem was getting high efficiency solid insulation in slabs to push down a 4" gap where our upstairs rooms go into the loft (old house)
also i had wooden uninsulated doors from munster joinery which were atrocious so i put polystyrene board in the recess and then covered that with tongue and groove (ceiling boards left over from something else) that made a huge difference to heat loss and condensation on the door)

sorry to anyone for dragging up an old post

theoneeyedman

sorry for digging up an old thread but was wondering......

boiler packed up today and need to replace it. old one is a utility boiler a grant euroflame ane we run 12 rads off of it (3bed-semi with attic converted)-it is a 'traditional' radiator set-up and i wouldn't be interested in replacing rads at this time. Is it worth spending extra on the condensor type burner or just replacing like-for-like......above posts suggest condensor not too effecient with traditional rads or am i reading it wrong?

DoneDL

you seldom have to upgrade the rads as they are generally oversized anyway.