Thread: 2 oil lines to burner

Can't say I have seen this before. One oil line from bottom of the tank and another from the top of the tank. Both connect to the burner. What's this setup do?

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That is a recirculating system which insures no air gaps in the supply line. Older design and no longer used as a new install but no inherant problem. Recommend upgrades at time of boiler or tank replacment.

Originally Posted by wayne soper

That is a recirculating system which insures no air gaps in the supply line. Older design and no longer used as a new install but no inherant problem. Recommend upgrades at time of boiler or tank replacment.

Technically there is no reason to recommend anything. This is one of two ways (that I know of) to get oil that is located lower than the oil pump on the burner.

It's been 20 years since I worked on oil furnaces. Where did that time go?

Two pipe systems are usually seen with buried tanks or situations where it cannot feed by gravity. The bypass plug is removed from the pump on the oil burner so, as previously stated, it can recirculate. The problem is, you have more chances for air leaks. To combat air, install a Tigerloop or better yet, TL Ultra, which has a secondary 10 micron filter built in. Burners firing at rates less than 1 GPH should have two filters anyway. The TL is a callback buster.

You can put the Firomatic valve either at the burner or tank. In the case of buried tanks, you see it here on the pump intake or prior to a TL.

While most burners get by with 3/8th inch ID copper tubing, twin lines should be 1/2".

Most copper lines are buried under mortar, which is a bad practice. It can react with the copper but it also hides leaks. The best lines are the new copper with a Polyurethane coating with markings similar to CSST. It comes red and notes fuel oil. The plastic protects and insulates it as well.

Many gravity tanks have Webster oil safety valves. Won't flow oil unless the pump pulls at least 3" of vacuum. There must not be more than 36" of vertical drop from the tank or the oil can syphon through the valve.

HTH,
Bob

Thanks for the info!

Originally Posted by wayne soper

That is a recirculating system which insures no air gaps in the supply line. Older design and no longer used as a new install but no inherant problem. Recommend upgrades at time of boiler or tank replacment.

2 pipe systems are still used when a burner is located higher than the tank or, when the lines come from a duplex fitting in the top of the tank. As for increasing the size to 1/2 ", unless the manufacturer deems this necessary 3/8" is fine. 2 pipe systems actually can extend pump life when set up correctly. Pump pressure to the nozzle should be measured and adjusted to proper mfg settings.