1.5 pipe oil system

LRCCBJ

I am interested in discussing what I characterize as a 1.5 pipe system. The burner has a return line, similar to two pipe, however the line doesn't return to the tank. It terminates in a Tee back to the supply line about six feet from the burner.

Why would anyone setup a system in this way? Any air that would enter the system could not easily be eliminated via the return line as it would simply be dumped right back into the supply.

Can such a system be bled in the conventional manner via the bleed port, despite the fact that the return line is functional?

Thanks in advance.

STEVEusaPA

It's sometimes called a cheater loop. Also used on commercial burners with 2 solenoid/two stage oil burners.
Got any pictures?
There might be a reason, maybe to allow the pump to take advantage of it's TGSC (total gearset suction capability) to help with a lift job pulling high vacuum.
Also, poor man's "warm up the oil".
But I also don't see how it eliminates any air.

EdTheHeaterMan

Depending on the distance from the tank, it may only be a 1.25 pipe system. LOL

And I have seen this before. If there is air in the ½ loop, it will foam and entrain in the liquid oil. Over time there may be enough air forced with the foamy oil that gets to the nozzle to reduce the total amount of air in the near pump piping. Not the best idea but as @STEVEusaPA mentioned, it can help on some commercial special systems that require 2 pipe operation that the internal fuel pump bypass can not accommodate. So you fool the pump with the ½ loop

Big Ed_4

Before the tiger loop we use to try that system , back then we also had a two minute safety

Solid_Fuel_Man

Mmmmmm, the 2 minute safety. Those were the days

LRCCBJ

Thanks for the confirmation.

This is a residential setup with an oil fired furnace and an oil fired HWH, BOTH of which are three feet below the bottom of the tanks. There is a single line from the tanks (about 30') that has three Tees...............one on the supply for both units...............two on the supply for both units (from the pump returns).

I could take some photos but it is nearly impossible to properly see the routing..............a pathetic collection of snakes on the floor................around the units.

The only possibility I see is that the installer did not want to run a return back to the tanks. It is a complete bottom feed setup from both of the 275's. As an aside, I was thoroughly impressed with the cleanliness of the leaking tank (35 years of age). Doesn't appear to have any sludge in the bottom as best observed with the measuring tape. We will see when the last 20 gallons is removed.

I have to break into the system to change one of the tanks and will likely introduce a bit of air into the system because of the bottom feeds (minimal since the work is 3 feet above the burners).

Can I bleed them using the pump bleeders or must the return be properly closed to accomplish that? I would assume that the pump would rather feed right out of the bleeder than send the fuel through the return...........?

Or, since minimal air will enter the system, will the burners eventually clear the air themselves without the need to bleed? i suppose it depends on the amount of air introduced....................

STEVEusaPA

You can bleed them using the pump bleeder. DO NOT, I repeat, DO NOT close off any return. You'll instantly destroy the pump(s). The bypass plug in each fuel unit must be removed to convert it back to a single pipe (no return).
After initial purging/bleeding air is introduced by vacuum leaks. You can have a vacuum leak without seeing an oil leak.
If you're breaking into system, and based on your description (with no benefit of pictures) I'd repipe everything, clean up the piping.
Out of the bottom of both tanks, shut offs (should be firomatics by code), teed into a General filter and spin on w/vacuum gauge combo. Then Tee off the outlet, and an Oil safety valve and jacketed oil line to each burner. Remove bypass plug in each fuel unit, convert back to single pipe, and put a firomatic at each burner input. Power vacuum bleed, never have another problem.

LRCCBJ

Thanks for the info.

I will pipe it as suggested, however, due to the bottom feed, I plan to use a Racor 120AS to easily monitor and potentially drain any water that develops. The Generals are a PITA in that regard as the entire can needs to be dropped to perform a water check even if the filter is still good.

STEVEusaPA

Always wondered why that wasn’t a standard idea for oil heat but I don’t think it’s allowed by code.
I’d have to confirm with the authority on this for a reason why…or why not.

LRCCBJ

I have the new system installed with the manifold and the Racor 120AS. The two units that are below the level of the fuel work fine. I left them at 1.5 pipe.

My issue is the two additional units (one pipe individual feeds) that are just slightly higher than the fuel tank level. However, I did raise their lines to the ceiling. The first one is about 80 feet from the tank and it must lift approx. four feet to the ceiling. The line is 1/2"

Of course it would not bleed itself in the conventional manner.

I did see your setup for a "power vacuum bleed" using the auto radiator overflow tank. Quite clever!

I do have one question:

The recommendation is to close the firomatic at the burner until the pump starts to whine (high vacuum). However another part of the instruction seems to indicate that closing the valve AT THE TANK might be preferred to develop the vacuum all the way back to the tank prior to opening the valve. In my situation, I have the benefit of closing the manifold valve for this burner only. If the manifold valve is utilized in lieu of the firomatic at the furnace, can the valve at the tank be opened about 45 seconds before the bleeder is opened? It will take 45 seconds to return to the furnace and open the bleeder (80 feet with 4' headroom).



Thanks for your assistance.