Tiger Loop

Servicewiz_3

What is the reason for a Tiger Loop?

leonz

To eliminate air in the fuel line.

Jamie Hall

Particularly on top feed tanks. It can be remarkably difficult to get all the flares to seal properly.

EdTheHeaterMan

You never need a tiger loop.  You can use them for convenience though.  Fuel line purist herein will tell you that you need to have perfect flare joints so air will never be a problem on your fuel lines.   

I included a tiger loop on every oil burner install just to make my life easier.  You get all the benefits of a single pipe fuel line from the tank to the burner.  You get the benefits of a two pipe system at the burner.  Best of both worlds.

If you feel like reading a good story, here is one about a customer with no heat and the oil company that delivered their fuel oil called me one unusually cold evening at about 9:PM.  The tank was located outdoors above ground and therefore the fuel oil was quite cold.  Cold enough to affect the viscosity of the fuel flowing through the fuel lines.  There were two pipes from the tank to the pump so the oil was moving through the fuel lines at an accelerated rate. (as fast as the pump gear set could move it which was about 17 GPH).  

The fuel oil company owner was there for about 3 hours that day trying to get the oil burner to operate to no avail.  That is when I got the call.  When I arrived I took a look at the chimney , the oil tank location, and the fuel line route before I went inside the home.  (that was a habit I acquired from 15+ years of doing service calls on heating equipment.) The fuel lines were buried just below the surface of the top soil in the flower bed next to the home.  I could see the fuel lines near the surface of the flower bed in a few locations as they went about 18 feet until the copper turned to penetrate the basement wall near the oil burner location.  

When I got to the basement there was the homeowner and the fuel dealer with several cans of oil from trying to prime the burner.  (You don't need to prime a fuel pump that has a return line to the tank) They were able to press the reset button and the burner started right up with no problem.  As the pump was running you could hear the noise of the pump straining as the pump was drawing a higher and higher vacuum.  Another thing I noticed was the copper tubing was collecting frost on the exterior of the tubing.  It actually reminded me of a refrigeration system low on refrigerant when the evaporator coil eventually freezes up.  

Without even putting a vacuum gauge on the fuel line inlet, I could see that the fuel oil was too cold, the viscosity was getting like molasses, and the pump could not move 17 GPH of that thick fluid thru the ⅜” copper pipe.   I suggested a tiger loop for $V00.00 and the customer was not going for it. “We never needed a tiger loop before, Why do I need one now?”  

My reply was: “When was the last time your half buried fuel lines were in -3°F?” I then proceeded to do the necessary diagnostic proof by installing my vacuum gauge on the inlet line of the pump.  The vacuum started out low as the burner operated with no problem, Then the pump noise started to indicate the high vacuum and the vacuum gauge climbed to 7”Hg.  The flame was still burning.  As time went on the noise of the pump became louder and the vacuum climbed until it reached 16”Hg and the flame quit.  I then took out the specifications for that fuel pump and it indicated the maximum operating vacuum was 8”Hg.  Now with proof in black and white that the pump can’t pump molasses, I recommended the tiger loop again (now for $V58.00, and the homeowner agreed.  After the Tigerloop was installed the burner came on and the fuel pump did not have a problem priming itself as a two pipe system would.  The fuel moving thru the one ⅜” tube was now at a snail's pace of 0.75 GPH.  The firing rate of the oil burner.   The copper line was no longer frost coated as the slow movement thru the basement allowed time for a little warming of the fuel.  The Tigert loop then removed the air from the fuel line as may have accumulated.  (The second return fuel line was added two years ago because the burner kept losing prime.) So the answer to my query above, about “the last time your half buried fuel lines were in -3°F?” Wound have been “NEVER” and he could have saved $85.00.

So you never really need a tiger loop… it's just a nice thing to have to get you out of a jam once in a while. 

RyanMitchell

A Tiger Loop isn’t strictly necessary, but it’s a handy trick to keep air out and help stubborn fuel lines prime, especially in cold conditions.

clammy

One minor note tiger loops are all most universal in europe on oil burners for a few reason being those europeans ar a bit brighter . Ends any issue of return line leaks ,prevents constant filtering of fuel your not burning and prevents circulation of fuel that is not being burned form picking up temperature and forming condensate in above ground fuel tanks . Not to mention that it reduces any chance of vacuum being pulled which can greatly effect any flame retention oil burner .Burners operating at high pump pressure are effected when the burner starts to pull vacuum. Personally over the years ever oil burner i ve installed that had a 2 pipe system was converted to a single pipe and a tiger loop was installed plain and simple especially any in ground and or above ground outdoor tank. Its a win for all involved . A 2 pipe oil system w a inground tanks is a issue waiting to occur$ and one thing you will not see in the father land for sure . also forget about the vacuum gauge they come w they usually leak and suck air .

peace and good luck ,