Oil Boiler Efficiency, Turning the Thermostat Off for Long Periods

I've been experimenting with an idea of mine - that's a dangerous thing - and I wanted to run it by those of you that care! But first, a bit about my home's configuration.

I'm heating a 1900 square foot 1855 limestone beauty... with a combination of wood and oil heat. The oil boiler (a new yorker) is a 138K BTU boiler that was installed in '97. This indicates to me that our heat loss isn't as bad as it could be. We have a wood insert in our living room with the thermostat that controls the oil heat to the upstairs/dining room/kitchen/first floor bath in the dinning room - adjacent to the living room. The temperature differential between the two rooms - as it gets colder outside - grows from 3 to about 8 degrees between living room and dining room.

Last year, we set the thermostat at 70 degrees and left it. The boiler kicked on and off pretty much all day when it got really cold (like 20's and below) Because the boiler didn't fire for more than 10 to 15 minutes - all it took to get the dining room back up to 70 degrees, the upstairs suffered. Not a big deal for most families - we have small children who play in their rooms and still take naps.

This year, I programmed the thermostat to run the boiler for 45 minutes at 2:30 in the morning, and at 2:30 in the afternoon. The house gets fairly warm during and after those times for about 3 hours or so. Then the temps begin to fall a bit till the next firing of the boiler. The radiators get pip'n hot and stay hot for a while, and then the hot water moves upstairs and continues to give off heat for another hour after the rads in the downstairs have cooled.

Question: is this an efficient means of heating???? I figured that I could at most burn 1.25 gallons an hour... so no more than3.5 gallons a day with hot water... seems logical in my deranged manner of thinking... what do YOU think?

I'm hoping to use the same or less oil as last year and yet have a warmer house. I use about 5 chords of wood, and about 450 gallons of oil. Before wood, I was burning about 1100 gallons a year (ouch!) We're in the process of selling this home and building a new construction... fit with coal as our main source of heat (very exciting!!) - but until then... this is what I'm attempting. Like I said, what do you think?

Take care all,

Pret

Just my opinion and I get in arguments with Dad about this over the air conditioning but I don't think fluctuating temperatures are conducive to any savings. If you take my air conditioner example turning it on during the day when its really hot and then letting the house heat up over night just makes the air condition run a whole more to catch back up when you turn it back on in the morning instead of having to run briefly a few times during the night.

Add to that you're providing a less than desirable living environment with the large fluctuations, if you want to save turn the thermostat down to to 65 and put a sweater on.

I insulated my furnace and then turned my aquastat down to 120-140 and my basement stays warm and the burner head isn't firing that much. If you don't have a domestic coil in the boiler then you don't need to run it at such high temps. You'll have a more constant temp and the boiler won't fire as much. Give it a try.

I would have to agree with the coalman, playing with the temperature isn't worth it.

120* is kind of low, I would think it impossible to remove entrained oxygen from the water at that temp.

Pret, A few questions for you before I get into one of my confusing post not really. How many Zones do you have on your oil boiler, if more then two which rooms are on each zone. Do you use a electric hot water heater, domestic coil in the boiler or indirect hot water heater. Your heating in the rooms are they baseboard, Cast Iron Radiator, or something else. what is the coldest outside temp you see during the winter, how hot do you keep your house.

i think what you did may be a good thing, long on times increase efficiency, and increase the lifespan of both the chimney and boiler. you should save money. the loss of efficiency due to fluctuating household temps will likely be more than compensated for by the sizable increase in efficiency you will achieve through longer boiler run times; you will probably be better off.

U235a4, I have two zones, the living room is on its own zone and is outfitted with baseboard. The rest of the house is on the other zone, controlled by the thermostat in the dining room, and is outfitted with radiators - not the small thin ones you see in a lot of early 20th century homes - the coils on these radiators are rounded rectangles about 2" by almost 3" as far as dimensions (this is the smallest I have... there are a couple that have larger coils). I have a hot water coil in the boiler, which by the way holds 60 gallons. I have no other storage for the hot water than in the boiler/system itself. The coldest temp we see is maybe 7 degrees, but we get a lot of wind - we live on a hill. The wind kills us! The house is surrounded by porches on three sides.

So far I have burned an eighth of a tank (275 gallons) in 16 days under this type of arrangement. I live in central Pennsylvania.

Coalman, the greatest delta in temperature is maybe 4 or 5 degrees from from end of boiler firing to next boiler fire 12 hours later. The house temps are fluctuating greatly overall. The upstairs, by far the coldest, is normally around 60 degrees on a cold day (20 degrees), and about 67 on a warmer day - like temps in the high 30's. This is probably due to the wood insert in the living room. The stairs are only about 12 feet from the fireplace - almost directly in front of the fireplace. So I know heat travels up and cold air travels down, you can feel it at the top of the stairs. After the boiler is nearing the end of the 45 minute cycle, the rooms upstairs are nearing 68 or 69 degrees, and stays that way for a while - at least 2 hours or so, before the temps begin to drop to around 60 - 64 depending on the temps are wind outside.

I hope I have described everything clearly... I really think that this is going to work... I just wanted to know what the experts thought of my crazy idea. I haven't seen excessive oil consumption yet... put 200 gallons in Nov 29 (589 BUCKS!) - and it's been a typical Dec here... temps in the high 30's during the day and low 30's or upper 20's at night.

Coaledsweet, I share coalman and your opinion about changing temps... I don't. It's better to leave the thing alone... it takes more energy to heat the things in your home that than the energy one saves by turning it down a couple of hours and then back up again. But the cycling on and off of the boiler last season worried me. I did leave the thermostat at 70 last year, burnt about 450 gallons, while stuffing that wood insert. The year before, I burnt about 325 gallons with the heat off, and only turning it on when absolutely necessary, again stuffing that insert. Now I'm stuffing the insert as well and think I might get away with less than three hundred gallons if my calcs hold out. 16 days, 1/8 tank - got 4 of those 1/8's left before I need to put some more in... that puts me at the end of January. One hundred and 50 gallons is the bare minimum that I can order and that would definitely keep me till the warm weather hits.

I don't know where this is going, but maybe - if my theory holds out - this could be a better way to keep the house warm IF one uses a 'secondary' radiating heat source. Please comment.

Thanks everyone!

Pret

Pret, Do the radiators in the room with the thermo stat have valve on them if so close them about half way to slow down how long it takes them to heat up which will give time for the other to warm up and will hold heat longer. As for setbacks with heating systems it does save money by doing so. explaining it would take a great deal of typing that my fingers just won't let me do, but basically Any boiler that is cycling off and on a lot and runs for short periods will get poor fuel efficiencies because it takes serveral minutes for a boiler heat the large mass being return water, pipes, rads and the boiler case itself.

I would run a separate zone for the upstairs and shut off or bypass the radiators near the wood insert. It seems to me what is happening is the wood fire is satisfying the thermostat causing a short cycle before the upstairs gets enough heat. I assume your boiler has had a recent tune-up, all clean and the correct nozzle and good smoke test and Co and everything, a mis-adjusted boiler wastes tons of oil and if your oil man works for the oil company then I can almost guarantee it's burning more oil that it needs to, they are trained by people who make profit off every gallon of oil they sell so think about it.

I had the boiler tuned up in Oct - co is at 11%, and EFF is at 86.7. I don't have the second zone on... it takes care of the living room where the stove is. This power outage has really kicked me in the jimmy. It's a stone home... and it got cold, so now I'm experiencing a tougher time keeping the temperatures up, and the heating seems to be more difficult as described earlier.

Each radiator does have a valve. I'll try turning them back. It gets warm in that room (with the thermostat) so quickly because the room has two large rads on either end of the room.

I've upped the time the boiler runs to 1.25 hours twice a day. increasing the burn time by 25% will decrease my interval free from oil purchase... not liking that!

The wind we've been having really made it hard to keep the temps up. I guess wind chill makes a difference. I assumed it would, but I didn't think it would be 'the same as' a day in the single digits. The wind chill have been in the upper single digits and the lower teens the last three days. OUCH, for central PA. Double OUCH OUCH for old homes.

Thanks fellas... I'll keep you posted.

Like e.alleg said, your thermostat is in a bad spot.

Since you are selling, I would run a temporary wire to a location further away from the stove room. Running your boiler on a timer is not the most efficient way to save oil, it sounds like you over shoot the temperature. The greater your temp differential between inside and outside, the greater your loss of heat.

Once you move your thermostat, you could derate your boiler to 1gph giving you a longer run time ( sounds like you have a 1.25 in it ) Going to anything less you need to change your burner cone and install an oil return line.

86.7 efficiency sounds high given the 11% CO2 reading, your stack temp should be around the 330F range - if its not you could use a cleaning.

The co level is at 11%, the co2 is at 6ppm. Does that sound a bit better? Is it difficult is change out the nozzle? I reported a 1.25 gallon an hour because of the boiler label.

sounds worse

I would think/hope the 11% is your CO2 - you basically want to get that high - up to the point without smoke. I have my WeilMcLain set for 12.5%, 84% efficiency. Most techs then back off a bit because if anything changes you get hard starting, less efficiency & internal soot forming. If your stack temp goes too low or you short cycle - you can have acid rain forming in your chimney - very bad for the flue. I don't know about the 6ppm (maybe smoke or CO) - my combustion test set measures CO2, stack temp, draft ("wc) and smoke ( scale of 1 to 10) - oil burners don't make much CO. ( unless its a blueray - which I got rid of) Changing out the nozzle is easy, but you need to get the correct spray pattern and GPH.

edit - I thought it was installed in 1987 - not '97 87% is high - don't know if I'd mess with it too much. It may have a 1 gph nozzle in it already. If you go lower than 1gph you need a return - because the oil travels too slowly in a single feed line. (Sedimentation occurs = clog) You can contact New Yorker - they wil help you to go down in nozzle size.

Thanks Coalbin... I'm going to contact the guy that serviced my boiler in Oct to determine the nozzle size. I'm going to try and turn back the rads in the dining room with the thermostat to see it that helps. Right now, I have it timed to fire for 1.25 hours... it was too warm in the house when I got home today... but then again, after the power-outage, I think the house needed a good dose of warm temps inside to raise the overall heat content of the home. It's a stone home... I don't fully understand the quirks yet - 6 years... of course I haven't really been all that diligent in learning either. I'm sure heat loss is linear, so I agree with the larger the delta in temps - outside and inside - the greater the heat loss.

Again, thanks for your time and expertise.

Pret

I have a delavan book on oil nozzles that shows if you increase the pump pressure from 100 psi (standard) to 145 psi, a 1.25 gph nozzle can be reduced to 1.0 gph and the fuel will be atomized better by decreasing the droplet size. Beckett burners should be able to handle 140 psi with no problems, My riello runs at 150 psi. You will need to verify your nozzle size and spray angle to reduce it to a smaller one. I will try and post the chart.
George