Fuel Oil Piping

BradleyH

I have a fuel oil water heater and boiler. I ran them both for several years off 1 suction and 1 return line. They are Y'd in the boiler room. No problems for years. I had to replace my boiler last year and now the boiler steals fuel from the water heater. I put a check valve at the pump on the WH. Still stealing oil and causing the WH to shut down. The boiler has a 3450 and the WH has a 1725 pump. The WH heater will ignite on the first reset. You can hear it pick up the fuel but it has a 15 second control on it. This really has me stumped since it ran ok for years before I changed the boiler.
Thanks.
BradleyH

STEVEusaPA

You shouldn't need any check valves. Are you sure someone put a bypass plug in the pump if you are using it as a 2 line set up?
If I were you I'd ditch the return line and put a tiger loop on each unit. If it were me, I'd ditch the return line and find the vacuum leak.

BradleyH

I'm pretty sure I did. My fuel lines are overhead. I forgot that in my post. I worked on fuel oil for over 20 years but am retired now. I wouldn't have done my piping this way for someone else. It just gets me that it ran ok for years with the older furnace. Thanks for your answer. I will do some checking.
BradleyH

EBEBRATT-Ed

I would run a separate suction to each. You can use a common return and I would skip the tiger loop

I have had similar things happen when something gets changed. It's under a vacuum. Oil takes the path of least resistance the same as anything else weather it is vacuum or pressure

dopey27177

I think the problem is the pumps.
the 3450 pump may be stealing oil from the 1750 rpm pump when they both operate together.

Running separate lines for each unit solves the problem. Retired guys should not need to trouble shoot problems in their homes. The Kiss school works for me.

Jake

Big Ed_4

Check valves are used for direction of flow . They will only add to the problem by adding more resistance ...

pecmsg

You’ve worked fuel for 20 years, run separate lines!

Jon_blaney

I fixed the same problem on my systems with tiger loops. My problem was related to tank level. As the gravity feed pressure decreased with declining fuel level, furnace would suck the HW heater fuel from its supply. Same issue you are having.

STEVEusaPA

Jon_blaney said:

I fixed the same problem on my systems with tiger loops. My problem was related to tank level. As the gravity feed pressure decreased with declining fuel level, furnace would suck the HW heater fuel from its supply. Same issue you are having.

That's simply a vacuum leak.

ChrisJ

I'm not an oil guy by any means, in fact I only owned a setup for a few months.

That being said, if it ran for years without a problem and now has a problem it sounds like cholesterol to me. The line isn't supplying the same volume it used it, whether it's restricted in the tank, or somewhere in the middle, who knows.

Ctoilman

Separate feed lines would be best, but I'm suspecting the 1725 pump is getting weak or itself is the problem.  

EBEBRATT-Ed

There is another way. Put a relay on the water heater to lock out the boiler when the WH runs. To me the best fix is separate lines but the relay trick will work. Tiger loops are band aids