Pressure testing oil burner system, 2 line vs 1 line system, differences?

belham · January 2018

Hello all,

Writing you from Europe. In my home, I've an oil burner (gasoil--called "mazout" here) made by Weishaupt and it is mounted into a cast iron St. Roch Couvin water boiler. Weishaupt is a renowned German oil burner maker, and essentially the unit is identical to Riello systems in the U.S. This overall unit was installed in 1998, and has been maintained every year. Some background before my question:

The 3000 litre gasoil tank is outside the house, buried about 6 feet down. At that height, it is at the same height as the oil burner sitting in the basement. The only lifting is drawing it out of the tank, maybe a 2-3 ft pipe and run 12-14 ft into the house (trenched under cemented/tiled floors) & into the Weishaupt burner. A two fuel line pipe system(3/8" copper) was installed, which leads to a Oventrop filter (attached to side of the Weishaupt boiler) that has a 100 micron filter in it. In 20 years, cleaning it every year, I've never seen debris and/or oil sludge in it.

The Wesihaupt utilizes Danfoss oil pump and Danfoss nozzles (nozzles replaced every 1 year, 2 yr max). The small fuel filter in the Danfoss oil pump is/was cleaned 3 times a year, since it is so easy. Equally, I have never seen debris there either in 20 years.

The system uses the chimney as its exhaust, as the chimney was closed off in all other parts of the house to set it up only for the oil burner machine. The chimney is regularly cleaned, and honestly, there's never really anything in it. Overall, the Weishaupt unit runs great.

I guess you are asking why I am writing/posting here then.

My problem has been for the past few years an increasing "after leak" at the nozzle. What started as a just a few drops every so often-- that previously the blower had no problem pushing back out the blower tube---has now turned into seeing a tablespoon of gasoil accumulating & leaking back down the burner tube. Unfortunately, there is no option on Weishaupt burners to adjust the burner tube down slightly towards the floor of the inside the chamber. Germans didn't make it that way because their units (cough, cough) are never supposed to leak.

Anyhow, I have ruled out overdraft (or the interior chamber getting blowback & the nozzle overheating), there is no oil seal leak on the Danfoss pump (it in fact the pump is brand new), it is not bad nozzles (all new ones leak too), all fuel lines hoses have been replaced, and everything (all connections) checked for being tight & sealed. What baffles about this nozzle "after-drip" is that the Danfoss pump fires right up, hitting its 10 bar, and the Weishaupt unit runs & purrs like a kitten throughtout its whole burn run (compared to other oil burners I have heard). Still, knowing I have a growing "after-drip" problem, I am in the process of buying a glycerin test and vacuum gauges to plug into the Danfoss pump for further testing.

This brings me to my question: is a two fuel oil line system different than a 1 line system when doing the pressure and vacuum testing? What I mean is, is on my 2 line system, should I still see the pressure test gauge (once it hits 10 bar quickly on pre-firing) should I see it fall no lower than, say, 8 bar and hold there (as I prevent the unit from fully firing)? And it should stay there, around 8 bar, until the next time the oil burner machine fires? Or does this pressure stuff only apply to 1 line systems, since in a single line system it has to hold at 8-10 bar no matter what, when off and/or on, always, versus a 2 line system that only pressurizes itself when needed (like when it is turned on) and thus never needs bleeding and/or worrying about "air" in the system?

Thank you for any help, advice and/or tips.

EBEBRATT-Ed · January 2018

as far as the operation of the oil pump it will operate the same weather hooked up 1 pipe or 2 pipe. I am a two pipe guy all the way, lift or no lift. But I am the exception. Most on this forum will come at me with knives and guns LOL.

It sounds like you have exhausted most of the likely possibility's to your problem. Is it possible to pitch the burner towards the combustion chamber by adding a couple of shims or washers??

Is ignition and light-off & shutdown smooth? Sometimes a little rough start or rough shutdown with some pulsation will cause oil to get back into the burner blast tube.

Also, you mentioned changing nozzles, it could be possible the nozzle adapter is worn or damaged causing an oil drip.

I have worked on a few Weishaupt's, not many over here and have never seen their residential burners. The commercial burners are quality products...if you can understand them LOL

belham · January 2018

Hi Ed!

Thanks for replying.

Yeah, Weishaupt makes some great stuff, and this home burner stuff is no different. Took me a year when we first got here of just fiddling with it, taking it apart, trying to understand everything, before I became a bit at ease with it. Boy, it sure is true the Germans can over-engineer the heck out of anything, haha. Oh well, it just make the stuff nearly unbreakable IF you can make yourself stay on top of it.

I tried the washer trick, getting hold off a thicker gasket, but they made the cone so concentric and rapidly going in diameter from the burner end to where the unit meets the water boiler, that it is honestly just a no-go.

I thrown around in my head the idea if drilling a 3/16" hole just an inch back from where the tube ends (the nozzle unit is actually held in place by the burner tube, sort of a sausage-in-a-sandwhich type of thing), but I am worried that the flow will still make it past there.

Also, regarding the nozzle unit itself, I thought that too, that maybe after 20 years, the brass threads where the nozzle screws into have just loosened, and thus the pressure gives out at the end of the burn and then the nozzle drips.

Oh, before I forget, the unit runs beautiful and startup and shutdown, almost like the day when it was new. When I remove nozzles every year or two, they never have a mark on them and/or any carbon buildup. I always wonder why I am replacing them, but trying to keep the "preventive" thing going like my Father had taught me when I was young (and from the upper Midwest).

Can i ask, when I finally get my hands on the glycerine-filled pressure gauge, and screw it into the Danfoss "P" 1/8" port (for pressure testing) on the front of the pump & easy to get to & access for testing, if those threads on the nozzle end unit are actually worn, won't I see a big decrease after the unit shuts off from its 10 bar (145psi) operating norm? Like I had mention, the unit fires up, runs during, and shuts down so calmly, that I am baffled that if I've got an air leak or say, bad threads, wouldn't that be showing up in the pre-burn, during the burn, and/or shutdown? Or could it be that just be the only thing one might see is over-time slowly increasing nozzle drip?

P.S. That nozzle-gun unit where the nozzle screws into, you can never find them used anywhere in Europe Ebay and/or otherwise. When I asked guys in the service industry why, they said it's because "they never fail". Lol, I rolled my eyes even further back in my head. I can get a new unit, but they want 200 euro+ shipping just for it, if it is that.

belham · January 2018

Hi again, Ed,

It's really late here, a.m. hours. Eyes are heavy and I'll check this thread first thing in the morning.

I had one other question, and excuse if this is way out there and/or not relevant:

--regarding possible nozzle "after-drip", would vacuum testing have any relevance for this type of event? For example, if I don't see, say, -0.5 on the vacuum reading of the new Danfoss oil pump on this 2 line system, what should I be considering? Both copper lines (coming & returning) coming from the outside tank were tested by taking the fuel oil hoses off and running a thin inline checker, both of which ran easily through the copper fuel lines and came out cleanly into the fuel tank (in the ground)....but if I see a bad vacuum reading, how would that relate to this nozzle "after-drip" the unit is experiencing?

Thanks again, and sorry if this is a totally crazy question.

EBEBRATT-Ed · January 2018

If the burner starts and stops normally and combustion is good it doesn't sound like a oil/vacuum pressure issue.

A couple of other thoughts. If (which I don't think is your problem) you had some air mixed with the oil delivered to the nozzle the air would be compressed to 140 psi making the air bubbles if you had any smaller. The oil is not compressible. Now the burner shuts off. The the air bubbles re expand do to the decrease in pressure and push some oil out of the nozzle causing a drip.

Also, an overheated nozzle.

If for example the combustion chamber was deteriorated or the blast tube on the burner was being overheated somehow after the burner shuts down this heat could cause oil trapped in the nozzle to expand from the heat and drip out of the nozzle

Does the Danfoss Pump (which I am not familiar with) have a built in solenoid valve to start and stop the flow of oil to the nozzle? Some pumps start and stop the flow to the nozzle with an internal pressure regulator. Some use a solenoid built into the pump. You could also add a separate solenoid

belham · January 2018

Hi Ed,

Spent all day with this Weishaupt. I'm leaning towards that brass gun assembly that we talked about earlier (which the 60S 1.00 nozzle screws into) has gone bad after near 20 yrs of operation and air is getting in with the fuel, and after shutdown, is doing exactly what you describe. I know I've never over-tightened the new nozzles I replace every year or two, as I learned long ago with brass never screw around with it and try to be too manly. Gently tight is always the best policy with brass stuff

To answer your other questions, yeah, the Danfoss fuel pumps have always had solenoids built into them (and we can replace just the solenoid if we want, instead of getting a new pump). Since I just (3 weeks ago) put a new Danfoss pump on, which is the first one after 20 yrs of use and the first new thing to ever be replaced on the burner (besides the nozzles & filters), plus I also had an extra new solenoid lying around, I figure I can't be (knock on wood) that unlucky and have 3 solenoids (including the old one, which was working fine, what failed in the old pump was bearings starting to make that sound like they were gonna go sometime soon) all go bad at the same time.

I have to admit I am still intrigued, though, by the theory of the end of the tube getting too hot, thus heating the nozzle up, and causing the after-drip. But I am not sure how to test that other than the draft tests done, the actual visual chimney inspection, an orange smoke test pellet, plus a good old fashioned piece of dry tissue in the hand and sticking beside the oil burner pipe coming into the chimney and watching it continually try to lift off an go up the chimney---of course this is done without the oil burner running. Still, I wonder, but the cast iron boiler still looks really good inside, presents no heating problems for us, and it has been taken good care of every year (I manually scrub it really clean once a year, some years there's very little to scrub off, since combustion is so good and there's not much in the way of any type of bad-bun leftover (black soot or otherwise).

I also wanted to tell you I again studied the burner tube with the gun assembly in it & how it attaches to the oil burner and into the boiler, and there's just no way to get the tube even level and/or pointing down slightly with washers and/or anything else. The reason it seems is that Weishaupt was so confident in these machines that they made the burn tube asymmetric--what I mean is, it is ~5 inches in diameter back where it screws onto the burner and meets the boiler, and up near the front where it cradles the end of the gun assembly with the nozzle inside the boiler, it is only 3 inches in diameter. Thus, any leaks from that gun assembly and/or nozzle have a ready-made steep grade to flow back down the tube and gather there, making 'after-drips' a real problem.

The fan, on each run, does blow some of this 'after-drip' back out during a run, but not all of it. Unfortunately it is to the point now that about once a week, I have to take the oil burner out, and there is about a tablespoon or more of unburnt fuel lying in the back of tube, just gathering. If I would let it go any longer, let that amount get bigger, a real mess (not to mention possibly dangerous situation) would develop. Main reason is this accumulating 'after-drip' will not travel back out the oil burner, but instead will weep down and saturate into the insulation that protects about 70% of the burner tube's length (it's 15cm, or ~7 inches long). I guess I could do like they do on Beckett's and put a bead of high temp sealant back there, but then I'd just be creating a doggone damn for the unburnt fuel, that the blower would have even more problems trying to blow out what it currently does.

Anyhow, I'll get the new brass gun assembly ordered, and when I get it and put it on, I'll come back here and let you know what happens. Hopefully I am guessing right, lol. I should not complain because this burner has run for 15 years with zero problems, still runs like new now except for this after-drip, and maintenance was made so easy by how the German's constructed it thus it probably deserves some TLC in the way of some new parts. That Danfoss oil pump I replaced was the 1st thing that went after 20 years. Their (Weishaupt's at least, and Danfoss (Danish) pumps) reputations are well deserved.

Hope to talk to ya in about 10-12 days when I get the order in from Germany! Thanks again for everything!

STEVEusaPA · January 2018

Why don't you try checking your nozzle assembly to rule out a possible leak. I have a pressure gauge that deadheads the nozzle assembly (it screws in, in place of the nozzle.
With the whole assembly out side the burner (be careful of the transformer), you see if you have a leak, and you can check pressure and cut off.
You can't check pump vacuum, and for a system vacuum leak (pull a vacuum, stop burner and see if vacuum holds) on a 2 pipe without removing the return, removing the bypass plug, and plugging the return.
But you can check for a vacuum leak, as Ed suggests, with something like an Oil Watcher, which is basically a clear tube placed inline, to see if your supply line contains air.
I also have a nozzle resurface tool which basically fixes the end of the nozzle assembly back to true (when people overtighten nozzles).
Seems like if you were experiencing this after drip you should see some burnt remnants on the nozzle.
If you can't shim the burner, maybe you can shim the boiler

EBEBRATT-Ed · January 2018

As usual @STEVEusaPA has some good ideas.

I suppose you could take an old nozzle and solder or braze the end shut put it back in the nozzle adapter and test the assembly with air. Put it in a bucket of water.

BTW have you ever tested the burner with a combustion tester?

STEVEusaPA · January 2018

I would check vacuum just to make sure there are no leaks or restrictions.
I guess the obvious question is, don't they have any oil burner techs in Europe? I was under the impression that most of the oil burner service was performed by the burner manufacturer-not oil companies or independent companies. And strict regulations on efficiency and mandates for older, less efficient equipment replacement. I could be wrong and/or this may not be all of Europe.

belham · January 2018

Hi Ed & Steve!

Glad I checked this thread this morning. Here are pics of my Danfoss oil pump on the Wieshaupt WL20-A oil burner. Since I have a 1/8" glycerine-filled vacuum gauge, and Danfoss conveniently puts a "Vacuum 1/8" Test Port" right on the front of the pump (right below the other convenient 1/8" Pressure Test Gauge port), I think I am going to try to follow Steve's advice-----hoping I understand them correctly.

So, since I have a 2 pipe system and in order to do a "vacuum test", I need to:

1) remove the Danfoss's oil pump's side vacuum gauge post plug,

2) completely remove the little screw inside

3) put the side vacuum gauge port plug back in tight

4) remove my "Return Line" (R in the diagram).

5) place a plug (which I have extras since I replaced the old pump) in the "Return Line R" port, nice and tight.

6) then screw-in tightly my glycerine-filled vacuum gauge into the "front" vacuum gauge port

7) (this might be where I am a bit confused)...then, before even continuing, I have do something about the Afriso Two Line Gasoil Filter (pic below) system that is hanging on the side of the boiler. It is where the two 3/8" copper lines come in from outside the house connecting to the in-ground 3000Liter gasoil tank. Is this a correct assumption?: I cannot run a vacuum test unless the line "coming in" to the house is hooked directly to the oil pump incoming (now one line since In removed the oil pump bypass screw & sealed the return port). Is this correct??

8) if #7 is correct, then I'll start the unit, let it fire up (with the vacuum gauge in it), let it run a minute or two, then shut it down, and watch the vacuum gauge. I presume I should see something like -0.5 on the vacuum gauge reading staying nice & steady the whole time (running and shutoff), and it should equally hold there when everything turns off. Is this correct too? (what reading would be bad on a vacuum gauge for a setup like mine?)

Here's the pics below. Thank you both much! (also, Steve, where I am at, there are both independent contractors and the companies, and once they know you are a foreigner (for whatever country you you currently live in Europe--especially once they realize your from the U.S.), they charge beyond outlandish, incredible fees for basic services. There's no competition here, the independents even get in on the act. So it's a non-starter, especially after watching one guy come out years ago, when we first moved in, to do a basic set of combustion tests and check the burner (which he said was fine and needed no adjustment), replaced the nozzle, and cleaned the filter in the oil pump but there was nothing to clean as I watched him pull it out. Total time on the service call was 40 mins and---almost flooring me----the total charge for just coming to the house and performing this basic stuff was 500 euros (about $600 dollars). Never again, never ever effing again! A new Weishaupt unit at the time only cost $1200 euros, so do the math. It's a crock of crap here with so many things like this since I own a home. I do everything, every single thing, myself now. It is in no way like the States, where competition forces some bit of fairness on prices for consumers. It's a major reason Europe is always and forever in the economic crapper)

this is my exact two line Afriso filter..incoming is with the Red on/off screw valve, return goes in the other port. These Afriso(s) are weird to me. When the oil burner fires up, you watch the gasoil in the filter drop to half its height, as a stream pours in, and it stays at that half height during the whole boiler/burner run, then when the boiler/burner shutsoff, the fluid returns back to the top fully (as if under suction/vacuum) ...I asked two different boiler technicians, and they said this is how Afriso 2 line systems with these filters run, the return line needs to dump into the filter, thus the overall filter cup cannot be full while the burner is in operation---this seems weird to me still, lol, as I always assumed a filter cup should be "full" with gasoil since it is being drawn by the oil pump. There's even Youtube videos, on Youtube.de (Germany), showing how this is normal. I always thought (on any normal 2 line filter) seeing this level drop in the cup dring "burner running" meant there was "air" getting into the system or something was going on (like a vacuum problem, where the line coming into the house or at its 90 degree right elbow drop down into the tank (which I have access to from above ground, a 2' x 2' lined square in-ground hole goes down to the top of the in-ground mazout tank, for filling and checking gasoil levels plus seeing the lines going into the house and the return line at the top of the tank), Anyhow, these two technicians said "no" when asking about what I was seeing on the Afriso. They said it is "good", normal operation. Honestly am still confused about this.....I mean, how can the return line, that goes back to the tank, also deposit returning fuel into cup while also sending it back to the tank. Doesn't make sense to me ;-/ Maybe I totally whiffed in understanding the foreign language translations (French/German) as they were talking.

Just measured the two copper lines coming into the house (hooking to the back of this Afriso) and they are 12mm (nearly 1/2") external diameter. Always thought they were only 3/8". On a 20-21 foot (just measured it too) run to the outside in-the-ground gasoil tank, that's too big, isn't it? That alone would always cause a vacuum struggle for any oil pump on any residential small oil burner like mine, I would think, right?? You know, now that I think about it, the new Danfoss oil pump I installed a few weeks ago uses 1/4" fittings (the old version of the old Danfoss pump used smaller diameter fittings and hoses). I thus had to put in new fuel oil hoses (16" in length) for coming from the Afriso to the pump (the incoming fuel line hose and the returning fuel line hose). They are 8mm interior diameter hoses, that fit the 1/4" fittings. I wonder now if this, just those 2 hoses change, is helping to the increased "after-drip" I am seeing? All because the new Danfoss oil pump is struggling with the increased diameter of the gasoil flow coming from 20-21 feet away? Before, with the old 16" hoses and the old Danfoss pump, those hoses were a smaller diameter (6mm) with the smaller fittings of the old pump. Hmmmm, both Weishaupt and Danfoss spec this new pump, with 1/4" fittings, so maybe I am thinking too hard here.
(old Danfoss pump fittings, DN8 1/4" x SR 6mm LR)

(new Danfoss pump fittings, DN8 1/4" x SR 8mm LR)

Also, if either of you are curious, here's a couple of pics (below) from google.de search that exactly reflects my Weishaupt oil burner. Great unit & german attention-to-detail engineering, it is stable/dependable, runs like a champ, both easy to work on and service.

Pressure testing oil burner system, 2 line vs 1 line system, differences?

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