Inefficient Oil Fuel Usage Closed Boiler System

gorodn

I posted a question a few weeks ago and have a question regarding our updated situation:

• 1100 sqft apartment in 1st floor of duplex
  
• Closed system boiler used only for heat, not hot water
  
• 6 radiators active (upstairs has rads but are presumably off as they use central air/heat)
  
• Received new 275 gallon vertical oil tank Model # 204201G Pic of Model: https://imgur.com/dDqDd0y
  
• Oil tank was filled to 250 gallons, floating fuel gauge read full in early October.
  
• Floating fuel gauge now reads slightly under 3/4 full level
  
• Pressure gauge reader is broken so I cannot provide that info
  

Boiler was turned on (and left on) 30 days ago. Thermostat was set to 69-70 when home and 65 when away. Avg outdoor temp was in the high 40s and mid 50s when heat was running. We run the heat 2-3 times a day for under 30-45 min each time when its cold. For 15 of those 30 days. we did not run the heat due to it being 70-80 degrees outside and I clicked the thermostat from heat to off.

Floating fuel gauge is reading at slightly under 3/4 fuel. Assuming its a 275 gallon tank with a 266 capacity filled to 250 gallons, that still seems like a lot of oil is being used to heat a small apartment a few times a day for ~15 days over the last 30 days in Virginia fall.

Does this seem accurate? I feel like we are burning far more oil than we should for this time of year considering the thermostat setting and outdoor temperatures.

How can I figure out exactly how many gallons I've used so far? I know I can dip a stick and convert inches of depth to gallons but I don't have a chart for this particular tank.

Any insight would be greatly appreciated.

Jamie Hall

Tank fuel gauges are notoriously inaccurate -- even worse than your car. Further, filled to full isn't all that accurate either, although the gauges on the fill trucks are (they have to be!). So... the only really reliable way to track oil use is to either have a meter on the line to the burner, or really know what the burner is firing at (affected by nozzle and pressure) and a run time meter for the burner. Or... take the average over a long period of time from tank fill information.

gorodn

Thanks for the response. The oil company suggested I stick a measuring stick in the tank and convert the inches to gallons. Would that not be an accurate way to measure usage?

Also, I notice just now that the boiler is on and making noise, but our heat is not on and the rads are cold. Will boilers come on and make noise periodically when not being actively used? If not, I think my upstairs neighbors may be using it to heat their apartment through their old rads instead of using their central heat.

EBEBRATT-Ed

Since it is oil the oil burner motor is 120 volt. The most accurate way is to buy a 120 volt "hour meter" and have it wired in parallel with the burner motor. Then you can multiply the # of hours run x the nozzle size in the burner to get the gallons of fuel burned. The oil pressure at the nozzle must also be known.

Post some pictures so we can see what is going on

Sticking the tank is less accurate but will give you a reasonably accurate reading.

STEVEusaPA

You're talking about 60 gallons for 6 weeks, not bad considering your boiler is probably massively oversized if it's only doing one floor.

If your boiler is running with no call for heat than a few possibilities:
-You have an aquastat that's maintaining temperature.
-Your 2nd floor neighbors are using the heat too.
-There's something wrong with your system.

Simple troubleshooting could figure that out, and if the upstairs is using it, and they don't have their own zone, you'll have to do some piping. That's pretty typical for an old system. They weren't zoned. The size and design of the piping was such to evenly heat the entire home.
If it is zoned separately, either by circ or zone valve, it is pretty easy to disconnect them.

I wouldn't open up the tank and stick measure it. The main reason is you may not seal the plug properly, and could risk a fuel spill, especially if the driver can not hear the fill whistle.

If you 'have to know', do what Ed suggested. Otherwise, if you're not on automatic delivery, just call for fuel when the gauge reads 1/4. That would be about 160-180 gallon delivery.

gorodn

@EBEBRATT-Ed Here are a bunch of photos of the system and labels: https://imgur.com/a/AhrzEBF

@STEVEusaPA The system was turned on October 19th. The heat was used for half of the days from then until now, 11/19. That would be about 4 weeks total with 2 weeks of usage time 1-3 times per day for less than an hour each time.

One thing to add, whether its relevant or not, is that I notice the temperature gauge reading the boiler sits at 140 degrees F every time I check it.

The biggest concern if figuring out if upstairs is using the system and if not, why so much oil is being used for such a short amount of time. It just seems to be so expensive to run the heat using this particular system.

I don't know when the system was last serviced other than one time last year a part broke (according to previous tenant).

I would be interested in seeing how to disconnect upstairs from accessing the heat. They have a Goodman AC/heat unit that they should be using for their heat.

Steamhead

When was the last time the boiler and burner were serviced? What did they actually do when they serviced them?

gorodn

I don't know the answer to that question. This is my first year renting here. I know that last year it broke and was repaired and that's it. The landlords are not interested in providing me with more information or fixing this potential issue for us.

STEVEusaPA

I guess I'll say it again...
"If your boiler is running with no call for heat than a few possibilities:
-You have an aquastat that's maintaining temperature.
-Your 2nd floor neighbors are using the heat too.
-There's something wrong with your system."

gorodn

Thank you. I'll keep an eye out and see when its running, especially when it gets colder out and upstairs is more likely to use the heat often.

It seems there are too many variables that could cause the system to burn too much oil. I was hoping to have something to say to the landlords or perhaps even the city should the heat not work or work very ineffectively once winter hits. I can't see the pros to having an oil system in this type of home when it costs nearly twice as much to heat as other options.

Scott M_2

Are you sure the boiler isn’t heating the hot water because the picture you posted shows a tankless coil and if that’s the case there is a auqastat maintaining a minimum temperature like Steve said.

Scott M_2

Looking at your pictures again it looks like they piped your water heater into the tankless coil as a pre heater.so there must be an auqastat maintaining temperature.YOu can have someone turn it all the way down or rewire it as a cold start boiler.And as a FYI if it was gas or propane you would still have the same problem it’s the system not the fuel.

gorodn

@Scott M_2 They installed an electric hot water heater that is hooked up to the upstair's neighbor's electric panel box. I turned off that valve and that stopped our hot water, so we get hot water through that.

Are you saying that the boiler is heating that water or that its somehow connected to the electric hot water heater? The hot water heater provides to upstairs and downstairs as far as I know. I did not think the boiler provided anything to do with hot water; even the oil company has us listed as it only providing heat to downstairs.

Leon82

Yes, follow the copper pipes coming from the plate on the front of the boiler. They go to the left, back up then to the right twards the water heater. Do they connect to it?

With a tankless coil the boiler will keep at the temperature otherwise you would have to heat all the water inside before you got hot water at the faucet.

Cold start boiler will cool to room temp and only fire when heat is called from the thermostat.

gorodn

Interesting. I'll take a look. I really don't think it was using anything from the boiler, though. We moved in and the oil tank was broken and only had a few gallons remaining and was only replaced with a new tank in late September. The gauge did not move at all until I started using the heat.

Leon82

On second look maybe it it doesn't. The picture isn't clear when you zoom in.

gorodn

I bought a measuring stick and stuck the tank. It was kind of hard to see where exactly the line was but it was between 28-30 inches. Following this chart for my 275 gallon vertical tank, I should have between 180-194 gallons remaining.

This is the chart I used, as provided by the oil company that delivered the last fuel: https://irp-cdn.multiscreensite.com/cc1989a2/files/uploaded/tankChart.pdf

This means we've used anywhere from 56-70 gallons of oil out of the 250 gallons we started with since turning on the boiler October 19th. For 1100 sqft apt, outdoor temps ranging from 45-60 degrees and keeping the indoor set mostly between 65-69, does this sound about right? Cost would be $182-$227 for 5 weeks, 2 of those weeks we didn't run the heat.

SuperTech

Open up the aquastat and take a picture of the inside of it. It sure sounds like you have a boiler maintaining temperature for hot water use.

You need to turn the low limit off.

gorodn

I had to google what an aquastat looks like so I hope I took the right pic. It's a Honeywell brand. I also included a pic of the gauge to show that it tends to keep itself heated to 140 degrees (though the gauge could be off seeing as the pressure side is broken). I can provide more pics or even a short video if needed, just let me know.

https://imgur.com/a/0icBybA

Will lowering that affect the power/efficiency of the radiator portion of the heating?

SuperTech

It will not affect the efficiency or performance of the heating in any way. That low limit set to 140 degrees is without a doubt the cause of your problem. Turning it off will greatly reduce your oil consumption.
The boiler only needs to have a low limit if you are using the tankless coil for domestic hot water. The boiler would need to maintain that temperature continuously or else it would take forever to get hot enough water for a shower. It's pretty much the most inefficient way to make domestic hot water, but since you have it valved off and are using the electric water heater you can shut off the low limit and make the boiler cold start and enjoy the savings.
Any further questions feel free to ask. I have seen this same problem twice this fall.

gorodn

That's great news! My follow-up questions would be:

How do I turn that off safely?

How does this affect heating the house? Won't the boiler have to heat up that water to then flow throughout the house into the radiators? Will it take longer to heat the house and burn inefficiently? I notice now that it takes a good half hour or so before the rads get uncomfortable to touch. Until then, they are hot but I can rest my hand on them for as long as I'd like without it hurting.

STEVEusaPA

You should replace the aquastat, if you no longer need it to maintain temperature, with a modern one where you can take advantage of low water cut-off (to protect your boiler), circulator hold off (to prevent condensation), thermal purge & economy setttings.
Just turning the dial down to it's lowest setting, the boiler will still maintain about 100°.
Radiators don't need to be (shouldn't be) too hot to the touch, most of the winter.
Ideally your boiler water temperature should be controlled by a reset boiler control. However considering how oversized the boiler is, it wouldn't help you much and would probably contribute to even more short cycling.
If you turn down your thermostat at night, getting the temperature back up in the house is a slow process, maybe 1° per hour.

BennyV

I've found oil tank gauges to consistently read slightly low, and I can predict within 10 gallons what a delivery is going to be. I'm usually a bit high, since the gauge reads low in the first place. Those are on newer tanks though, older ones, who knows. YMMV.

That's the challenge with oil. If you have reset controls, you cycle more. If you don't, you run hotter than you need to. You're usually way oversized, domestic coils are horribly inefficient. It sounds like you're a renter, so there's not much you can do about that inefficient beast of a heating system, except to change the low limit on the aquastat, which will stop it from firing just to maintain boiler temp, and it will run slightly longer cycles to get back up to temperature.

Also make sure that only one side of the tankless coil is shut off, otherwise you have a pressure vessel with nowhere for the pressure to go.

gorodn

Another quick update:

I stuck the tank 11 days ago and measured 28-30 inches of oil. I stuck it again today with a more accurate stick and measured 23 inches. From 28 to 23 inches is 35 gallons, or $113.75 using 3.18 gallons per day. We've been keeping the house at 64 during the day and night, with it being set to 68 1-2 times a night between 6pm-9pm. It's been in the 40s and high 30s outside with some days in the 50s.

Seems like a super inefficient system to use 3+ gallons per day to maintain that low temperature. I even bought plastic film insulation and covered all of the windows since they were single pane. It's unfortunate to literally see my money being burned away.

Thank you all for helping me, I do really appreciate it.

Jamie Hall

My dear person -- since I can use that much fuel to simply bring the main place I care for (see my signature) up from 65 to 68 each morning... never mind the usage during the day to maintain that...

What I would suggest you do, though, is to do a thorough heat loss evaluation of your structure -- Slant/Fin's app. is easy enough to use, and very good -- and compare that to your fuel usage. Your fuel usage, assuming a roughly 80% efficient combustion (which is very good, though not great) is equivalent to 14,000 BTUh for comparison.

Gordy

If your 3.18 gallons a day is even accurate this translates on average to.

448380 btus a day
18683 btus an hour
17 btus a square foot.
That is boiler input not output.


We know nothing about the structure to make an assessment.
However those are mild temps.