Measuring heating oil flow for furnace, what would you use?

Strouty · Feb 3, 2016

I am interested in knowing what I actually use for heating oil based on my thermostat settings. I know there has to be a sweet spot, but trying to gauge it through a 275 gallon tank is not exactly scientific. Anyone know what I should use?

I am not even sure how many GPM it flows at full blast, I was thinking some sort of low flow meter, but the ones that come up are like $400. Any ideas would be great.

Furnace is forced hot air system running fuel oil.

nh_yota · Feb 3, 2016

The burner is going to use the same amount of oil/min whenever it's running, so use an hour meter on the thermostat instead.

Movover · Feb 3, 2016

Hour Meter on the burner, you can look at the nozzle for GPH and get a pretty close idea from there.

Strouty · Feb 3, 2016

I guess that makes sense that it would be uniform. Most hour meters have tenths of an hour, so that will be much more accurate than the look at the tank gauge technique that I have been using. Now I just have to figure out how to hook up an hour meter on the burner now.

nh_yota · Feb 3, 2016

Easy - most furnace/boiler controls and thermostats run on 24v, so find an hour meter that can take up to 24 input and tap it off the switched side of the thermostat.

nh_yota · Feb 3, 2016

Actually let me make a correction - it depends on what type of heating system you have. If you have forced air or steam, you can wire up an hour meter like I previously mentioned. If you have forced hot water with zone valves, you made need to tap the hour meter off the aquastat since the burner does not always run when the thermostat is calling for heat.

Bondo · Feb 3, 2016

Ayuh,... Or a 120v meter run off the power wire for the burner, from the burner control box,...

Gallons per hour/ minute is stamped on the side of the nozzle,...

Strouty · Feb 3, 2016

Seems like it would be more accurate on the burner rather than the thermostat. I know the thermostat tells the burner to start, but I though the burner could switch off and on depending on the need for the blower? I really don't know that much about my furnace, as you can probably tell. I do know how to bleed it and how to reset things, but I have never been much deeper than plumbing it up and installing the thermostat.

Strouty · Feb 3, 2016

It is forced hot air using fuel oil. From what I understand so far, I will need to know what size nozzle I have and the GPH rating of the pump in order to get the actually flow. Is this correct?

nh_yota · Feb 3, 2016

It depends. With most furnaces I've seen, the thermostat controls the burner and the blower is controlled by a thermostatic switch in the furnace.

Either my way or Bondo's way would yield more or less the same results but it depends on the particular setup.

Strouty · Feb 3, 2016

I will have to look things over, the thermostat is definitely lower voltage and I know the burner is running on a 120 volt circuit. I will snap a couple of pictures and post them.

nh_yota · Feb 3, 2016

If you really want to get scientific about it, you can run two hour meters - one that counts the call for heat and another that counts burner run time.

nh_yota · Feb 3, 2016

Some of the more sophisticated thermostats can also track run time (at least the call for heat). I've thought about wiring in a 24v hour meter on my boiler to monitor run time, but mine also heats domestic hot water so I would need to wire it specifically to the thermostat so it ignores run time for the hot water.

Yamaguy · Feb 3, 2016

My Nest thermostat will keep track of when my natural gas forced air furnace runs. Now I'm not sure if it looks at the total cycle, or just when the burner is lit.

Strouty · Feb 3, 2016

I looked at the thermostat settings and it keeps track of run time, but only in weeks. They use it as a guideline to replace the filter.

The furnace is going right now so I am not going to mess with it. The tag on the unit says .75 GPH

Strouty · Feb 3, 2016

I have a nest at my house and the thermostat does not go low enough at my shop. I would like to be able to use one that is controllable as I have a 30 minute commute and I could turn it up before I arrive. Currently I have all the adjustment times set to the lowest temp that I use (45 degrees) so if I leave with it set higher it reverts back to the lower setting. I had one year that it got set higher and left that way for two weeks, burnt an entire tank of heating oil.

ctfjr · Feb 5, 2016

A 115 volt hour meter wired in parallel with the burner motor will give you the run time hours.

The name plate is the max the unit is rated for. You would have to open the burner & slide out the drawer assembly to see & read what stamped on the nozzle. ie if the nozzle is stamped .75 80 H its a .75 gal per hour, 80 degree, hollow spray. BUT that rating is at 100psi oil pump pressure. To be accurate you would have to measure the actual pump running pressure (there should be a tap on the pump for a gauge or you can use the bleeder port).
Your system may be designed for 140psi (very common in modern oil burners). If it is 140psi the actual oil consumption will be ~1.21 times the stamped nozzle rating.

Measuring heating oil flow for furnace, what would you use?

Strouty

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