Can someone explain what the difference between Nett and Gross efficiency is? (The other option is Condensing, which I know.) Which is the one (if either) which should match SEDBUK rating? This is a Kane 250 analyser, BTW.
Also, what sort of figures should I be looking for for a non- condensing boiler (Potterton Profile 50e in this case)? Boiler installation/servicing instructions are silent on this matter.
AIUI: Efficiency relative to the net and gross calorific values of the fuel. Gross calorific value includes all the heat of combustion, both sensible and latent (including specifically the latent heat in the water vapour from combustion). Net calorific value excludes this latent heat, and is about 10% less than the gross CV.
??? Why is that different to gross?
Presumably gross. Gross is the British way. The declared calorific value on your gas bill is gross CV. Net calorific values have customarily been used in some other European countries, as well as by IMM to enable him to quote condensing boiler efficiencies of over 100%.
Pass - other than somewhere in the range 60-80% at a guess. Don't they quote i/p and o/p power power figures anywhere - or o/p power and input gas rate?
Leave the gadget on Gross for all types (because the boiler rating plate and SEDBUK use this scale) [1]
I think you will typically get 80-something% efficiency from a typical fan assisted non-condensing boiler when it first fires but it will drop to the upper 70's when warmed up.
Anyway those are the results I get with my Kane 400.
[1] I think some continentals and you-know-who might use the Nett.The message from Andy Wade contains these words:
According to a table I have the lower CV for North Sea Gas is 34500 while the higher is 38500, Kerosene 43300/46200 and Diesel 42700/45400.
Hi,
I use a Kane 400.
I don't use the efficiency function. SEDBUK efficiency is just a mean of leveling the playing field, so that the consumer knows that th figures quoted by manufacturers are based on the same method. Hence th wording (S)easonally adjusted (E)fficiency of (D)omestic (B)oilers i the (UK). You can't arrive at their percentages with your analyse because you aren't there every day of the year and coming up with a average at the end of the year.
The two main things to check are Co/Co2 ratio which British Ga engineers are taught should be less than .004 but if the boiler i serviced and seems to be working right .008 is acceptable. The othe indicator is Co level. less than 50 ppm is the aim.
I mainly bought mine for the Co/Co2 testing and also as an acurat manometer for setting up the gas/air ratio on Boulter Buderus boilers
-- Paul Barker
Thanks. I worded my original question badly, and it was actually these figures I was after. The SEDBUK part of the question was just which of the 3 efficiency settings should match it.
CO was 19ppm. I forgot to read the CO/CO2 ratio and it doesn't seem to be one of the saved values, although CO2 was 5.9%, so I suppose CO/CO2 ratio comes out at .00032 if you can just do it by simply division, which sounds OK by your figures.
In any case, I should check again when it's properly warmed up; it was raining at the time;-)
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