Oil Furnace issue

General Lee · Nov 18, 2012

I have what I believe is called a 2 line system on my oil furnace. The oil supply line and the return line. I've been having some issues with the furnace "choking" on start up. I've had 2 companies come out and one couldn't get it fixed. The other found air was entering the system from somewhere. Other than the air getting in somewhere under the ground where the tank is (chose not to do any digging) there was no other source of leak found.

The tech said it could be also a vacuum issue due to the long oil line runs. He disconnected the return line and low and behold no air was showing up upon doing a bleed check. So now the furnace is set up as a single line system and so far I have not heard any choking of the system. The tech said there is no down fall of having the return line disconnected other than you have to manually prime/bleed the system after maintenance, oil filter change etc. The return line just helps prime the system faster and automatically so to speak.

He also did some diagnostics to rule out an oil pump issue and it appears the oil pump is fine. I guess my question is, anyone have experience with this stuff and agree that its a non issue having the return line disconnected?

Chooglin · Nov 18, 2012

General Lee said:
I have what I believe is called a 2 line system on my oil furnace. The oil supply line and the return line. I've been having some issues with the furnace "choking" on start up. I've had 2 companies come out and one couldn't get it fixed. The other found air was entering the system from somewhere. Other than the air getting in somewhere under the ground where the tank is (chose not to do any digging) there was no other source of leak found.

The tech said it could be also a vacuum issue due to the long oil line runs. He disconnected the return line and low and behold no air was showing up upon doing a bleed check. So now the furnace is set up as a single line system and so far I have not heard any choking of the system. The tech said there is no down fall of having the return line disconnected other than you have to manually prime/bleed the system after maintenance, oil filter change etc. The return line just helps prime the system faster and automatically so to speak.

He also did some diagnostics to rule out an oil pump issue and it appears the oil pump is fine. I guess my question is, anyone have experience with this stuff and agree that its a non issue having the return line disconnected?

I cant really answer your question,but I can tell you that my oil furnace has a single line.
Although it does need to be primed after service,its not that big a deal.(once a year)

Dana Warner · Nov 18, 2012

If you install a tiger loop the single system will work perfect even on long lines. My furnace is 12 feet off the shop floor and runs a 50' single line. It self bleeds and has been great.

nybirdman · Nov 18, 2012

Single lines are fine,only have to bleed when serviceing.Very common hook-up.

etcallhome · Nov 18, 2012

Our church furnace has a single line, everything had worked fine till we changed our buried tand from 250 gal to 500 buried tank. Fri we found out why once or twice a year we would have to prime the furnace.
One of the flaried fittings had a crack about 1/2 way around cap (and of course couldn't see the crack till Fri after digging the line up and trying to tighten the fitting.. Cut off the flair put on new cap furnace worked fine last evening and today. Oh we have two furnaces the other one also has a single line has worked fine since day of installation at least 15 yrs ago. Your should be fine with single line

dave1949 · Nov 19, 2012

I have found that how well oil furnaces work, or not, is directly related to the skill of the maintenance service they get. :laughing: It also helps if your oil supplier keeps their tanks and trucks clean of goop build-up. I don't have an oil furnace anymore, but mine was a single-line and getting it re-primed was the least of it's challenges.