is ductless heating better and more efficient than oil heat?

te

we just moved into this old house with an old oil furnace.  technicians from oil companies have taken a look at it and says that the machine is still very efficient despite its age which is about 60 years now.  i am fine with the heating it produces but the system is huge and right in the middle of my basement that i have thought of replacing it with new smaller one.  problem is of course is the expense.  i read something about ductless heating and now i am wondering if this is the right route to go.  is ductless heating more efficient heat-wise and money-wise?  what maintenance goes with ductless heating and how does it work?  with oil, in addition to buying oil, we spend money on yearly maintenance and duct cleaning.  there is also the tank contract and all that expense with maintaining the oil heat.  is it a wiser decision to switch to ductless heating?

Brad White

Ductless

To get our terms straight, when you say "ductless", I think of the so-called "Ductless Split Systems", made by Daiken, Mitsubishi, Sanyo and others.



Aside from their small tubing, flexibility and sometimes multiple zones on a single outdoor condensing unit, they are, in principle, the same as any AC system/Heat Pump.



So the answer is, "it depends"!  It primarily depends on where you live and what your lowest outdoor temperature is. See, these are, in the residential lines, air-source heat pumps. They in effect cool the outside air and the rejected heat goes to your living space. (Walk by a conventional AC unit in summer. That warm air? Same thing but in reverse, into your house, in winter, in simple terms).



Air source heat pumps in general work "ok" down to the mid to high 30's outside and the ductless variety can go somewhat lower. An old industry standard rating point is 47 degrees. But you see, the capacity drops off as it gets colder outside. If your house is well-sealed and insulated, it has a lower "need heat" point, but also a lower "Balance Point".



The balance point is the temperature at which the heat pump still produces enough heat to meet your heat loss at that temperature. Put another way, it is the temperature where your home heat loss and the heat pump heating capacity intersect.



Below that temperature, you will need supplemental heat, either electric, gas or oil hot water.



Is it more efficient than oil heat? Probably. Depends on your electric rate.



If oil costs you $2.75 a gallon (140,000 BTU content) and you burn it at 80% efficiency, you are paying $2.75 for 112,000 usable BTUs.



If your purported heat pump as a COP of 3.0, it will put out the equivalent of 10,240 BTU's per kWH. It will take 10.9375 kWH to equal that 112,000 net usable BTU quantity.



If your electric rate is $0.18, that will cost you $1.97 for the same amount of heat. Your electric rate would have to be over 25 cents per, to break even with oil.



But COP's of 3.0 are not constant and performance will drop with the outside temperature.



Personally, I advise clients who want AC to get heat pumps to take the edge off during the many hours between 40 and 55, where they just begin to need heat. No one has regretted that, but it is not the only heat they have either.

Jack

Absolutely!

The way to make oil more efficient is to burn less of it. In checking the BIN numbers (total heating hrs/ location in 5F increments) for Portland, ME you have a total of 5603 total heating hrs per yr. There are 90 hrs at less than 10 F, 307 from 10-20, 655 from 20-30. Below 30f you have a total of about 33% of the heating season. Check www.miniheat.com for the bin numbers for your area.

Next lets look at unit outputs. I represent Fujitsu in New England so l'll use their outputs. Selecting a 12RLS heat pump at 5F outside and 70 inside the unit will produce 11,700 btu while drawing 1.31 kw or 4472btu.At 23F the numbers are 12,700 out at 1.36 kw or 4643 btu. As temps increase, output performance goes with it. This is a stunning increase in performance since the introduction of the 410A inverter units.

Frequently people have oil. They own the system. Keep it, but use it only when the HP can't keep up. The shoulder seasons can be handled entirely by the hp, depending upon the choice of unit(s) and location. When it gets really cold, fire up the oil. The customer is completely in charge here. They determine their balance point.

My advice to my dealers is to sell the equipment based upon heating output. That is where the return on investment comes. Then we can give you the cooling and dehu.

I just pulled the central furnace, a/c and all ductwork out of my home and put in a 24 dual with 2/12 evaps, one 12RLS and two Rinnai EX22C's (whom I also represent). All "net to the space" equipment. Great performance! Pretty cool.