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Measuring Oil flow to home heating boiler

I have just installed an Emonpi for my Solar PV and electricity usage and that all seems to be working fine. I was wondering whether I can install a flow meter to my oil boiler or an oil tank level meter and work out how much oil I use. Does anyone have any advice for this and what hardware I need to buy and install.

Welcome to the OEM forum, Phil.

My instinct would be to install a flow meter with a pulse output in the oil pipe line. The emonPi has a pulse input which you can use to count pulses to give the energy consumed, or by looking at the pulse rate you can deduce the power input to the boiler.

I don’t have experience of oil flow meters, so it’s a case of seeing what fits your pipe and your flow rate (i.e. you want a few pulses per second at the maximum normal flow rate if you want to see the power/energy consumption in near real time, but if you’re only interested in hourly or daily totals, then obviously fewer pulses will suffice.)

Having just done a quick search, beware: “digital” does not imply a pulse output.

For installation, all you need (if it’s a short run) is a pair of telephone-type wires from the meter to your emonPi. If it’s a long run, then a microphone-type screened cable might be necessary, to reduce the likelihood of counting interference as oil!

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Most oil boilers use a gear pump with an internal bypass. The pumps are normally constant volume therefore if it weren’t for the bypass then the running time would give you the volume.
All is not lost though. The oil jet in the burner will be designed to give a flow rate that is stamped on the jet. So all you need to do is calculate the burner on time, ie. When the oil is passing through the jet. This can be done by using the pump solenoid, which controls the oil flow.

I have used insanely expensive fuel flow meters, on which the calibration alone was £700. I don’t know a low cost alternative that would be more accurate than the method outlined above.

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I looked into this a long while and price was prohibitive …

You could try this https://www.ebay.com/p/Liquid-Fuel-Oil-Flow-Meter-With-13mm-Diesel-Gasoline-Gear-Flow-Sensor/898799123 or just the sensor https://www.aliexpress.com/item/5pcs-G1-2-OF-201-Oval-gear-flow-meter-oil-flow-sensors-Hall-flowmeter-Milk-chemicals/32460227815.html

I would guess they wouldn’t last long though in heating oil ? …

Dave.

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This is in US gallons per hour BTW (0.65 on mine)

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Thanks for all the advice here guys. I’ll have a go at some of these and let you know how I get on.

you probably could use a fuel gauge from an automotive fuel tank and just extend the float arm… a little math and get it working that way as well… based on the resistance

Yes. As mentioned before try to measure time. If you create a on/off controller then you can use those timings. (if you create your own heating controller - please use the security parts to avoid overheating) or you can use a Hall sensor to detect the on/off state of the burner - there is a part on which you can stick and measure… Then use those timings.
To get almost an exact calibration you can disconnect the ignition, open the burner, put a bucket in front of the burner and turn on the ‘burner’. Then there will be oil flow and you can measure the weight (before and after) to calibrate…!! Please do all this by caution!! (I can tell this works fine)

Thanks for that. I’m currently looking into how I can use the jet rating and timing the on/off to the boiler at present but I think that would give a good total use as well - especially as my method will need some calibration I expect.

Thanks for that. Great suggestion.

Hello @

I monitor my oil usage by use of a relay input that is connected in parallel with the burner oil pump start circuit. When the pump is [on] the oil nozzle is delivering, in my case, a constant 1.05 gph. which corresponds to about 148,000 Btu/hr. -the heating capacity for my furnace. I’ve found this to be quite accurate and when I refill the tank it’s always accurate to within a few gallons.

I used a 120V relay rated for 10 amps purchased from here. You need to use caution when connecting the relay as the voltages are high, if you’re not confident have an electrician perform the work.

I totalize the relay input signal using node-RED on a Raspberry Pi and and use MQTT to also send to the signal to emonpi/emoncms where it is also totalized.

Best wishes,

Beware - Neil is in the USA. You’ll need a relay with a 240 V coil.

Good Point, thanks for catching that.

Another point - relay contacts rated at 10 A are probably silver cadmium oxide, which won’t be good at the very low currents (in the region of milliamps) that a likely with a pulse input. You should probably looking at gold as the contact material.

you could always use a split CT instead of a relay - but with no load they tend to bounce around abit … but if you say greater then 50w is on – under 50w off- as the pot blower motor is usually around 100 watts –

I’ve been monitoring my oil boiler for ears with this simple Hobo data recorder from Onset computer.

!

They just attach magnetically to the pump/blower motor and record the on/off cycles to the second. It runs for years on a coin cell. Read out using a standard USB cable and their free software (PC). The software provides for a scaling factor so that you can plot usage in time, gallons or BTUs. Data can be organized into intervals of minutes, hours, days etc.

The nozzle flow rate is for a particular pump pressure. It’s an ok starting point but modern burners operate at various pressures, so I calibrate mine by dividing an oil fill gallons by the run hours. The calibration can be applied retroactively once calculated.

It’s not a real-time instrument, but very accurate and easy to install and use.