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Heating costs VS Temp. Control

1400 sq. ft. ranch,20 yrs. old, 7 and a half ft. celings, 6 inch walls & well insulated. Oil fired furance 85000 BTU which runs at 85% efficency. I lower the temp. at nite for 8 hrs. down to 55 degrees & back up to 68 degrees the rest of the day. When the furance turns on in the AM it will run for any where from 1 hr. to 1 and a half hr. in order to bring the house temp. back up to 68 according to how cold it gets at nite here in upstate NY. Do you think that I am kidding myself that I am saving on heating costs by lowing the temp. that low at nite causing the furnace to run that long straight in the AM ? I would think that there has to be a point in between the high & low set points that would save you the most amount of money ? The furnace does not come on at nite either set at 55. What do you think on this subject ? Thx. for any info that you might provide me, Ole Retired Jim said that :)

Re: Heating costs VS Temp. Control

That sounds like too long a recovery time of 1 1/2 hours to get the heat back up in the AM---when you say "furnace" do you mean a forced hot air system, or forced hot water???

The slow response could be caused by any one of several things---you'll have to check them out.

A 60k btu unit should be enough to heat 1400 s.f.;---do you also have an indirect hot water heater; do you also have to heat the basement/boiler room/ any other utility rooms???

Another possible option would be to install an outdoor reset device if you have a lot of "not so cold days" of temps at or above 35 degrees.

Do you have R20 insulation in the walls & R60 in the attic??---good, tight storms or double-glazed windows??

How far north are you---do you get sub-zero temps during much of the heating season???

If forced air, are the ducts producing hot air to all the rooms---have the ducts been properly sized when they were installed & are there any blockages now???

Have you had your oil dealer check out the system to see what's wrong---a simple thing like a blocked air filter on the blower return could make all the difference.

Is the furnace/boiler burner annually serviced to adjust the flame combustion (annual combustion analysis) & replace the nozzle, etc.???

If forced hot water, do you have enough convectors per room???

Do you have an outside or inside fuel storage tank??

How many gallons do you average burning during a heating season???

All of these factors are usually covered by doing a HEAT LOSS CALCULATION, which tries to determine where the heating system is falling down--- free HLCs are listed below.

The slant/fin hlc is long & asks for a lot of info, but it's very accurate---the others are rudimentary, but should be done to get a ballpark figure.

If you get a high reading on your HLC (say, 80k btu/hr to over 100k btu/hr), it means excessive heat is bleeding out of your building, otherwise the problem is probably with the heating equipment.


Re: Heating costs VS Temp. Control

I view a house like a refrigerator... once you get the whole house - the floors the ceiling, the walls, the furniture, etc. - to the temperature you want it takes very little energy to keep it there.

Re: Heating costs VS Temp. Control

Any amount of temperature set back (either done manually or through a programmable thermostat) will result in energy savings because the less the temperature difference between the indoors and the outdoors ..... the less the heat loss.
The longer the set back time, and the greater the set back temperature, the greater the resulting savings.

Energy savings resulting from set back is a curve ....... the savings from a 10 F set back is not double that of a 5 F set back but it is greater.

General rule of thumb ...... for an 8hr period ...... 1 F set back = 1% energy savings.
It's recommended a minimum set back of 6hrs for maximum savings .

The amount that you set back your furnace is best determined by your comfort level.

The greater the difference between the actual temperature and the desired temperature, the longer the furnace will run, but it will be less than if it maintained the higher temperature all night long.

However ..... water radiator heated houses are slower to catch up the set back and have to be started earlier in the morning ..... giving you less total savings.

Just a thought. :)

Re: Heating costs VS Temp. Control

Answers for Nashua Tech

Forced Hot Air Fuel Oil Furnace
Heat basement & 1400 sq. ft.
R25 & R60
Double pane anderson windows & house is tight
Furance is cleaned & checked every year & is %86 effecncy
Inside 275 gal. oil tank
Avr. usage is 500 gal of fuel oil for heating basically 6 months
Temps outside avr. 10* nitetime & 30* daytime in the winter

I realize that I do good on fuel oil usage but was really interested in the subject of lowering the temp down to 55* for 8 hrs. & then back up to 68* during the daytime hrs. with the furnace running for the lenght of time it does in the AM to bring the temps back up & am I really saving on heating costs doing this or am I kidding myself , Thx. for all your opinions guys & please keep them coming , Jim

Re: Heating costs VS Temp. Control

Thanks for the info---this sounds very much like an air flow restriction somewhere inside the vents.

Sounds like you have the right size furnace & good insulation---but if you can imagine a small electric desk fan trying to deliver all the hot air to the rooms being produced by the oil burner, it would take all day for the house to heat up.

The system should heat the house within 1/2 hour or less--usually 20 minutes if proper air passage is being maintained.

Telltale clues that there's not enough air flow is the furnace/burner cycling off frequently on high limit, waiting for the fan to push all the built-up restricted hot air thru the ducting----stand next to the furnace during a heating cycle & see if you can detect this on/off fan-ony cycling.

Also check for ANY BLOCKAGES--make sure the main filter is new, check that hot air is coming out all registers, & there are no duct leaks.

Re: Heating costs VS Temp. Control

Lets really simplize my question,Is it possible to turn down a heating thermostat too low at nite for 8 hrs. because the long recovery time bringing the house back up to ones comfort level in the morning will cancel out any fuel savings you might realize from the nite time turn down , A person said yesterday on a Radio Home Repair Show here that only turn it down for a maximum of 8 degrees at night,Where he got his info I have no ideal but there seems to be a wide range of opinions on this subject :confused: Thx For Yours, Jim

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