Hi,

I have a Utica SFH4150WT Furnace with a Beckett AFG oil burner & a L8124A Aquastat. It is approx 10 years old and is only used between November & April For the first 2 heating seasons (2011/12 - 2012/13) That I started monitoring the oil usage I had been averaging about 2.5 - 3.0 gallons per day based on a 100 gallons lasting between 30 - 40 days. In February 2013 I had the furnace cleaned and adjusted, since then it has been using almost double the oil per day (4.5 - 5.0). last year (2013-2014) was bitterly cold so I just assumed it was the temperature causing it to burn more oil. This year however it has been mild to normal and I am still burning the same amount of fuel.
I also have noticed a yellow soot collecting under the flue pipe suggesting unburnt fuel or high sulfur content in the fuel. could this also be from the aquastat settings? Aquastat settings are: Hi = 198 Lo = 120 Diff= 10 the furnace is turning on at 120 and shutting off at 175 this doesn't seem correct. any suggestions on settings? Could this also cause the excessive fuel consumption? Thanks, Jim

 

I'd set the aquastat at 160 low & 180 high. The differential of 10* is fine. The yellow is probably sulfur & often due to the stack temp being too low. I'd bet the flueways in the boiler are covered with it too.

 

Thanks, for the reply..

Will the furnace run more / burn more oil with that setting?
Also with the aquastat set at 198 and the furnace shutting off at 175. would changing it 180 then shut it off at 158?
Is it possible the aquastat is malfunctioning?

Thanks again,

Jim

 

You can't trust either the aquastat to be accurate. Nor can you trust the gauge on the boiler. You need to allow the burner to shut off & attach a reasonably accurate thermometer to the supply pipe as close to the boiler as possible. Depending upon the type of pipe, lazer thermometers are reasonably accurate, inexpensive, & easy to use.

 

Does your boiler also make the domestic hot water via a coil or indirect hot water tank or is there a separately fueled hot water tank? (electric gas propane?)

 

It does have the coil but we don't use it anymore. I put in a separate water heater about 6 years ago and bypassed the coil. because the pressure was terrible I do plan to replace the coil eventually.

 

Then you need to disable the low on your aquastat. There is no reason to keep the boiler hot when there's no call for heat. It should only run on the high limit setting and only when there's a call for heat. If the aquastat has drifted to much, consider replacing it with a single unit as there's no reason to have a low do to the removal of the DHW production.

That should get you where you should be in regards to oil consumption.