bleeding oil furnace line


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Old 06-28-13, 11:52 AM
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bleeding oil furnace line

I'm wanting to change out the fuel filter for the oil furnace. If possible I'd like to avoid, or at least reduce, the likelihood of having to bleed air out of the system afterward. So it's a two line system, and at the pump there is the inlet line and also the bypass/return line, as shown here:



In the above picture you can also see a bleed valve there to which I suppose I could connect a piece of clear vinyl tubing and bleed air if necessary.

The filter housing is this type, which has a shut-off valve near it on the line there:



The method I have in mind is to simply shut off the furnace so there won't be a call for oil, then close the valve next to the filter, then change the filter. Then open the valve again and turn the furnace back on. Chances are there's gonna be air in the line after that I suppose? What's the sensible method here, how this would normally be done to expel the air that's probably going to be in the line after the filter change-out? Am I probably going to have to bleed it at the furnace at all?
 
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Old 06-28-13, 02:07 PM
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Two-pipe systems are inherently self bleeding. In the kit with the new filter there will be two fiber washers, one large to fit the through-bolt on the canister and the small one is for the bleed screw on the canister head next to the outlet pipe. If your oil tank is located above the filter (i.e. gravity feed to the filter) you can then remove the filter canister bleed screw and slowly open the fuel valve to fill the canister. Turn off the fuel and replace the bleed screw on the canister, using the new fiber washer and then turn the fuel valve on. Any trapped air should be returned to the tank.

If you do not have a gravity feed to the filter then just turn on the oil and let the burner light. It might take a time or two to work out the air and return it to the tank. Watch to see if the flame tries to ignite during these tries and when it does, and stays lit you are done.
 
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Old 06-28-13, 02:24 PM
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Furd, I do not have gravity feed to the filter.
So I guess I'll just turn off the furnace, close the valve in the line next to the filter, replace the filter (and use the new replacement washer that comes in the kit for the through-bolt of the canister), open the in-line valve again, turn the furnace back on, and watch to see if the flame tries and then does ignite, and be done. Should be that easy, no worries about needing to bleed because it's inherently self bleeding as you mentioned. Anything I'm misunderstanding or overlooking? If not, I shall proceed. Thanks.
 
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Old 06-28-13, 04:01 PM
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I had a two line set up with a buried tank for about 20 years, typically changed the filter once a year, and never had a problem doing it just as suggested.
 
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Old 06-28-13, 04:12 PM
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Okay then I'm going for it. Thanks for replies.
 
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Old 07-06-13, 10:23 AM
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I changed out the fuel filter, and now have air in the line. One thing I didn't do when I changed it, and which maybe contributed, was that I didn't fill the filter container back up with oil before replacing it, just left it empty. So anyway, I've been bleeding the line at the furnace but of course after a brief amount of time after pressing the reset it shuts off because the sensor isn't seeing a flame. To prevent this shutoff while I bleed I seem to recall I can simply put a jumper between the two flame sensor terminals on the primary ignition? Is that correct? Thanks.
 
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Old 07-06-13, 02:59 PM
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Stop trying to bleed at the burner as all you will accomplish is allowing more air into the system. Yes, you CAN short the cad cell wires together AFTER the burner ignition trial starts but it should only take two or three trials before you get oil to the nozzle. If you have an exceptionally long fuel line from the tank to the burner it may take four or five trials.

If you try to short the cad cell connections BEFORE the ignition trial you will cause the control to go into lockout.

Note, if your oil level is very low you may have a problem in "picking up suction". If you didn't get the filter canister airtight then you will be sucking air at the filter.
 
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Old 07-06-13, 03:26 PM
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The filter canister is on airtight. Oil level is not low. After inspecting things, I'm now noticing some oozing/dripping of brown goo looking stuff from where the shaft of the electric motor at an oil pump enters into it. Here's a picture of the electric motor I'm talking about and another picture showing a close-up of the goo which oozes out of the back of the pump (fuel unit or whatever it's referred as). So I'm figuring maybe a seal or something inside there blew, and may be causing the air issue now. I shut everything down until I can have a pro look it.



 
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Old 07-06-13, 04:29 PM
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You have an auxiliary fuel unit in addition to the fuel pump on the burner? That definitely changes things. Maybe some pictures from a bit further back so I can see how everything connects would help.
 
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Old 07-06-13, 05:29 PM
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Old 07-06-13, 06:08 PM
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Barring an air leak in the suction piping there is no reason that system should not be self priming / self bleeding. It is possible it is the pump shaft seal but at this time I don't think so. You can use a squirt oil can to squirt some heavy oil on that shaft and seal when the pump is running and that would temporarily close that loophole. If the oil is immediately sucked in then you have found the air leak.

I assume that relay box adjacent to the pump motor is controlled by the burner so that the auxiliary pump only runs when the burner runs, correct? Do you have any means to run the auxiliary pump without running the burner? A clear closeup of the wiring in the relay panel may help me to help you run this pump without running the burner.
 
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Old 07-06-13, 06:29 PM
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Actually Furd I'm fairly certain the auxiliary pump runs even with the burner is not running. I'm not there now and won't be there until Monday. But I do recall rather distinctly that when I changed out the oil filter I first shut the power off to the furnace(s) (there's four) and then came into the tank room there and was surprised to see the pump was still running.
 
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Old 07-06-13, 06:37 PM
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To clarify my last post: I shut of the power to the furnaces, then came to the tank room there to change the filter, noticed that the pump was still running, so pulled the plug on the pump and didn't plug it back in until I was done changing out the filter.
 
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Old 07-06-13, 06:41 PM
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Okay, since it is "down for the weekend" let me get back to you. I need to take a break from the forum for a bit, I've been here most of the day.
 
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Old 07-06-13, 06:45 PM
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Right. Will keep posted here of any "further developments".
 
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Old 07-08-13, 11:48 AM
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Update: Pro took a look at it today and agrees that auxiliary pump definitely needs to be changed out first, then we'll go from there as may be necessary to track down any other potential air leak in the suction piping.
 
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Old 07-11-13, 04:26 PM
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Update: While pro was replacing auxiliary pump I took a close look at the filter canister and noticed some wetness on the top. Sure enough I had installed the canister cap bolt back on without the little gasket under the bolt head! So indeed, Furd, just as you suggested the filter canister was not airtight, and so turned out to be the obvious cause of the air leak. And there was the gasket, on the floor. I'm so embarrassed.
 
 

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