Which is better to use? Heater and burner says either. Installed in 1991 and I thought they said #2, but that may have been my memory from the unit they replaced. I just called and phone answerer said use whatever the manual says.
If it can use either, then use whichever one is cheaper.
That’s generally the reason that some heaters are designed to work on multiple fuels – so you can use whichever one is cheaper at the time. For big heaters, you’ll even see ones designed to use completely different types of fuel: either fuel oil or natural gas or LP gas, etc.
in my experience only #2 is available. Perhaps #1 is available in colder places where #2 would gel.
In any case #2 has more energy content so use it unless #1 is a lot cheaper or cold weather (like sub-20F) is an issue.
Are you quite certain #2 has more energy content? My references say that in general average figures, the two are almost identical, with #2 having just slightly less energy (mabe 99.5% of the energy of #1). I mean, FO2 is a heavier distillate of FO1 after all.
Well I wouldn’t say “quite certain”, I’m not the type to argue with the SDSAB, and I have no direct cites. My comment was based on what is considered “common knowlege” over on the diesel car boards. Winter fuel, which is generally a blend of #2 and #1, is well known to give a significant decrease in MPG vs. straight #2 due to it’s decreased energy content.
A quick google on the subject turns up several anecdotal comments about #2 having higher BTU content, but nothing that would pass for a cite around here. 
Yes, FO2 (which I assume is essentially identical to diesel #2) is a heavier distillate, and heavier distillates have HIGHER energy densities, no?
TYPICAL HEATING VALUES OF FUEL OILS
No.1 - 137,000 Btu/gal and 19,670-19,860 Btu/lb
No.2 - 141,000 Btu/gal and 19,170-19,750 Btu/lb
taken from here.. The same table can be seen on Page 115 of 291 on this EPA publication
A good rule of thumb is that petroleum products have pretty much the same energy content by weight, not by volume.
Another good rule of thumb is that wood has pretty much the same energy content by weight, not by volume.
I would be interested in volume energy, right?
You tell me. Are you buying by volume or by weight? In any case it is a simple conversion. The bottom line is that you are insterested in energy obtained per dollar spent. That is the bottom line.
of course, and I buy in gallons. But is my heater’s btu output related to gallon or lb of oil’s btu?
Ah. You see, I was thinking terms of “Btu/lbm”, and as andl_fl posted, and what my CE and B&W book say, as well as my fuel database, FO1 generally has a higher energy content per mass. But you are correct in that it has a higher Btu content per volume.
While a residential customer buys in gallons, some utility customers buy in terms of mass. In the US I think they do volume as well, but lately I’ve been working in Europe and for some odd reason several Eastern European countries seem to like to work in “tonnes” of oil, not m3 or l.
So I guess we’re both right.
Hm. I did a little bit of flipping through some of my oil systems design literature for residential and business structures, and I would guess they calibrated it in terms of the typical heat output produced by the volume flow of oil, as opposed to the mass flow (which people like me seem to be stuck on…).
Whether you are measuring the fuel by volume or by weight is irrelevant. The question is how many BTU’s per dollar are you getting. The more the better. Then, unless we have specific information to the contrary, it is safe to assume the efficiency of the furnace is about the same in both cases. In other words, if the fuel has more BTUs per unit of volume or weight then you will be using proportionally fewer units. So the question is getting the most BTUs for your dollar.
Liquid petroleum products have more constant BTU content but gaseous products vary more in their composition and in their BTU content so gas is sold by the BTU (actually by the Therm), not by weight or volume.
Yes, the more BTU per $ the better. If #1 and #2 cost same per gal and #2 has more BTU per gal, BUT heater output is based upon mass, and #1 has more BTU based on weight, then…
Also, #1 being thinner, might burn faster.
What is used to thin #1 oil? Something flamable?
I came here for a simple answer, I should have known better (he smiles)
I dont think anybody said the heater rating is based on mass, I believe the opposite was stated. So… assuming the same price per gal, #2 would provide more BTUs. However, the difference is only a few percent, so pretty much any price differential would be the deciding factor.
I dont think the thinner/burns faster factor needs to be considered, because even if it does burn faster, you will likely still get a very similar heat transfer efficiency into your house, and therefore it doesn’t matter.
Also, nothing is used to “thin” #1 oil. It’s simply comprised of “lighter” fractions of petroleum. In short, crude oil is made up of hydrocarbon chains of varying lengths. The lightest (shortest) chains are so light that they are gaseous at standard temp and pressure; that’s “natural gas” as well as propane, butane, etc. The heaviest/longest chains form thick solids, waxes and tars, such as asphalt, paraffin, grease and, well, tar. In between we have all manner of petroleum products including (from lightest to heaviest) various thinners and solvents, gasoline, jet fuel/kerosene/#1 diesel(which are all very similar products), #2 diesel, lubricating oils, and very heavy fuel oils as used by powerplants, ships, etc. And then there’s many inbetween products that most people have never heard of.
So in other words #1 is simply hydrocarbon chains that are slightly shorter/lighter, on average, than those that make up #2.
btw- When I had gas heat in my house, IIRC it was sold by volume (cubic feet).
I think you are getting lost and bogged down in details which are irrelevant. A gas furnace is burning gas with different heat content all the time so the gas company just adjusts the price according to heat content: you pay for the heat content, not volume. Then for every 100 BTU’s you put into the furnace, you get X% of them into the heating system and the rest go up the flue. It does not matter whether those 100 BTUs came from more or less volume of gas, you get about the same transfer - efficiency rate.
Unless you have information showing the contrary I would say it is safe to assume the same thing for your furnace. I don’t care if one fuel burns faster or slower or this or that. In principle the furnace will transfer X% of the heat to the house and the rest to the flue. (I guess you could start getting picky but you do not have the information to even start.)
My last post was not addressing economics per se but heat output, in response to the question by paul’smars. What I am saying is that it’s likely that the furnace is not a constant Btu device but a constant volume-flow device. I was saying that his manufacturer’s spec Btu output is likely calibrated to a certain assumption of volumetric heating value, as well as whatever the full-power volume flow is. Of course the viscosity could impact this as well. Overall, I’m not certain that it’s not nitpicking at this point beyond the level of actual accuracy. 