just moved, furnace is sucking oil

bauer

Hi,



We just purchased an old farmhouse with an oil burner that has a summer/winter hookup. our furance seems to be installed within the last 10 years, and has been sucking down the oil without providing much heat it seems. i know oil isn't the best, but we have had the thermostat set at 58 and have been using our wood stove a lot --- it's a big old farmhouse, but nevertheless it still seems to be going fast.



so here's i my question - i just got a chance to go check out the boiler. I have worked on gas fired standard boiler systems before, but the summer/winter set up is new to me. it seems that the radiators aren't getting very hot --- and there is a temperature/pressure gauge on the boiler itself (well mclain) and it never moves from 120 degrees. even when the system calls for heat and the circulator runs, i can put my hand on the pipes near the boiler --- i know in my old gas fired standard ones i would never be able to do that.



the honeywell aqua stat is set to 200 degrees ----- any idea what's up here? is the water really only at 120? I haven't a chance to hit my radiators with the infrared thermo yet to see exactly what they are heating to.

bauer

now i'm lost

ok now i'm really lost...



i was just down there - thermostat upstairs set at 58, temperature at 58 not calling for heat. boiler temp was 120. Came upstairs to post my first question, heard the boiler cycle on. checked the thermostat, still set at 58, temp still at 58. went back down to the boiler, now the boiler temp is up to 200.

Ironman

Pics

Can you post some pics of the near boiler piping and controls, pump, expansion tank, fill valve, gauge?



When you say "summer/winter hookup", do you mean the boiler has a tankless coil for DHW?.

bauer

will keep an eye

thanks for the response... i can snap some tomorrow. now that i saw the temp spike i'm going to keep a closer eye on it and see what's up, and pick up my thermometer to check the rad's themselves. i just can't believe how inefficient it has been.



and no, it has an indirect DHW tank next to it with a zone valve connecting to the boiler

bauer

update with pictures

ok here is an update with pics



got home tonight, thermostat was at 58 degrees. bumped it up to 60 and heater kicked on. water temp on boiler was at 120, boiler fired up. it has been burning & circulating for about 20-25 minutes now, and the temperature has barely crept to about 130 on the boiler. Using my infrared thermo, i checked radiators -- they are barely at 100 degrees. Outgoing pipes form boiler are at about 115-120, return pipes about 95.



after 20 minutes, could the temp of the water really have only crept up that little? I would say i have about 11-12 radiators in the house that the boiler is feeding.

bauer

45 minutes...

45 minutes into heating.... hottest rad is at about 125-130.



as i type and think about this i guess it is just taking this long to get the water up to temp? i'm not used to a house with so many radiators, our other places had about 1/2.



if that is the case and it really does take an hour or more to get radiators up to temperature when they get down to 120 --- then the question is what is more fuel efficient.... can I change the lower limit that the boiler allows the water to cool down to?



am i just short-cylcing? the thermostat just got up to 60 degrees and the heater shut off -- with the hottest the water got to being about 130-140... I feel like I am wasting the effect of getting those big cast iron radiators up to 180 degrees because they never get there.



sorry for all the ?'s --- but i need to cut down on this oil!

Ironman

Converted gravity flow system?

Do you have large iron pipes feeding the rads? If so, then you have a converted gravity flow system. The large pipes were once necessary because circs. were not available and the system relied on gravity to ciculate the water as it was heated. If your house pre-dates the 1940's, this is what you would have.



The high mass of the rads + the large volume of water act as a buffer which requires much more time to heat up than a low mass system such as copper baseboard with copper piping. It also gives off heat for a longer time after the burner shuts down (the flywheel effect). This effect naturally gives the system a kind of built in "reset" which means the water and rads will get hotter as the outdoor temp drops.



Usually, about the only inexpensive thing you can do to save energy is to insulate the piping in all unconditioned spaces (basement, crawl space, etc.). This could save 15 - 30%. Then also tighten up the envelope of the house and add insulation where needed. Insulation is much cheaper than oil and only has to be paid for once.



If your rad valves are functional, close down any that are in areas not needing heat. You may also consider putting TRV's on them to give individual thermostatic control.



The reason your boiler temp gets higher than the pipes/rads is becuase it has a bypass on it. This is necessary to keep the boiler return temp @ 130* or above to prevent flue gas condensation which would rot the the flue, chimney and boiler. This is a necessity and must remain. It doesn't cause the boiler to substantially use any more fuel.



Again, your best option: insulate, insulate, insulate.



One other thing: your thermostat needs to be setup for a cycle rate of 1 per hour. And don't use setback; it won't save anything and only makes it longer for the system to catch up.

bauer

thanks

thanks Bob, this makes sense



the supply pipes are fairly large... I just have a few quick questions then



1 - is the bypass you are referring to the pipe that t's off right above the circulator pump and goes to the left and down? if so, this has a ball valve on it that is closed, with a note that says "leave as is". due to this, my concern is exactly what you said - i measured the return water at 95 degrees -- certainly an issue for condensation, no?



2 - what do you mean by a cycle rate of 1 per hour? as i said i feel like i am not getting that flywheel effect, because the heater is never on long enough to heat up the water much past 120. i think i have a problem with a thermostat too close to a radiator --- if i leave the therm set at 60, and it drops to 59, the heat kicks on, but quickly brings the therm back up to 60...so again, the water never gets appreciably hot



thanks again

Ironman

Cycle Rate, Bypass

The cycle rate is how many times the thermostat will allow the burner to turn on per hour. If it's a digital stat, it has a means of setting this. If it's a mercury stat, it's done by setting the heat anticipator higher. If your have a heat source near the stat, then that needs to be addressed by either turning the rad off or down or moving the stat.



The bypass should be partially to fully open so that the boiler gets to 130* in 5 min. or less. It might take a little trial and error to get it set, but you definitely don't want return water that is less than that going into the boiler for more than 5 min.