incorrectly sized supply line diameter

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Old 04-21-11, 07:13 AM
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incorrectly sized supply line diameter

Our Riello 40 F3 + Buderus boiler has been having recurrent but intermittent false-start problems. It can take up to ten attempts before the unit starts burning smoothly. Lots of rumbling and rattling. At its worst first thing in the morning, or after the boiler has not been firing for hours. It will start up without problems if it's been running in the previous one or two hours. The oil company techs have been here a couple of times, focusing on nozzle. Yesterday at my request they installed a 10-micron spin-on, to replace the older filter.

Although I am coming up to speed rapidly, by reading and visiting internet forums, I am really ignorant of some very basic things, and would be grateful for your help here.

Yesterday, when the tech was installing the 10-micron spin-on filter, he also installed at my request a Fire-O-Matic fusible valve. He put it inline near the filter. It was the kind that does not have a valve handle, just a hex-bolt cap. But he couldn't purge the line of air. He tried and tried for 15 minutes. He said the problem was the Fire-O-Matic's narrow orifice, and removed it. It wasn't blocked. He said the Riellos are finicky because they're so efficient. With the Fire-O-Matic removed, he was then able to purge the line, and left with the unit running smoothly.

Several weeks ago during the annual service, the tech was having some difficulty purging the line too, after changing the filter. He played around with the purge nozzle for a while, and attached a pressure-gauge, but he didn't adjust anything as far as I could tell; it just seemed to start working...eventually.

This makes me wonder if the Fire-O-Matic had nothing to do with the problem.

From my reading, it seems air in the oil or in the line might also explain the false-starts. I found my way to the TigerLoop website. Don't have one yet, just reading about it. In the installation instructions PDF, there is discussion of proper sizing of the feed line diameter:

Note that choosing too large a feed line diameter for the nozzle size
should be avoided as too much air (and gas) is formed, with the result
that there is no siphon effect and oil runs only in a thin stream along
one side in the descending parts of the pipe. In such cases, it is not the
height from the oil tank to the oil burner, which should be considered
in calculated suction head, but rather all ascending parts of the pipe
(including the suction line in the tank, see fig. 1).
No TigerLoop is installed yet. For the moment I'm concerned about just getting some basic facts on the existing configuration. How do I determine the diameter of the existing braided hose? Can you tell the hose size from the end-connectors? They're connected directly to the 3/8" NPT fitting in the filter. Or do you measure the O.D. of the braided hose? The O.D. is 1/2". Would that be a 3/8" line or a 1/4" line?

If there's green oxidation on the brass threads where the hose connects to the adapter on the Riello, does that indicate a leaky connection? When I touch the braided hose there, my fingers smell of oil, but I don't see any leakage/drippage below.

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Old 04-21-11, 06:35 PM
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Tell us a bit about your tank location, and how the fuel line runs from the tank to the burner. Is the line running overhead, across the ceiling for example? Is the tank above or below the level of the burner...

Does your burner have one single pipe coming from the oil tank?

Are ALL of the fuel line fittings FLARE FITTINGS? i.e. NO, absolutely NONE of those COMPRESSION FITTINGS are allowed! They will leak air INTO the fuel system. Since the air molecules are smaller than the fuel molecules you can have a tiny air leak IN that does not leak oil OUT. Air leaks in a fuel system can be VERY difficult to find! Also, part of the problem is that the lines run in a VACUUM, rather than pressure... so leaks will often be invisible.

Your braided lines are most likely 3/8". Those should be replaced as a maintenance item no longer than every 5 years.

I believe that codes in the US require no smaller than 3/8" copper tubing, so we're stuck with that. Unfortunately in some cases, this can, and does cause problems as described in the TL install literature. In Europe apparently they are allowed to use smaller tubing. One problem that the larger tubing avoids to an extent is the lines getting plugged with sludge. Although it could be argued that the higher flow velocity in the smaller tube would help keep the lines cleaner. Who knows? Bottom line is that we're stuck with 3/8" tubing, right or wrong.

the resultthat there is no siphon effect and oil runs only in a thin stream along one side in the descending parts of the pipe
It's somewhat akin to the 'drinking straw analogy'... finger over the end of the straw, lifted out of the drink, liquid stays in the straw. Use a much bigger straw and the liquid won't stay in the straw. Surface tension is a big factor. The flow velocity is another factor. With larger lines, the flow will be slower and won't allow the air in the lines to be moved out and expelled. It's possible for fuel lines to be half full of air at all times!

Grady is our Riello 'go to guy' and I'm sure when he hears me rattling his cage he will come in with suggestions as well.
 
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Old 04-22-11, 05:00 AM
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Thanks for the detailed reply.

EDIT: I should add that the delayed ignition problem returned that evening. It was warm, boiler off all day, no one home using water. It seems whenever the boiler sits for a long time without firing, the delayed-ignition problem returns. At its worst first thing in the morning. It fires right up if it comes on again within a one or two hour window of a previous firing. I'm new at this but that suggests something other than a clogged nozzle to me.

The total developed length of the fuel line exceeds 40'. Single line. Line exits top of tank about 4'6" from ground. Riello inlet 32" above ground. Wall: 15' length. Turn. Wall: 11' length. Turn. Wall: 4' length. Turn upwards. 4' (curved) length. Actual height :36". Transition to 2' braided hose, dropping ~7" to just below Riello inlet where it turns upwards again a final few inches (see photo).

I see only a flare where the line connects to the filter using a swivel nut valve connector .Then, there come threaded NPT connections for the hose; then some more threaded NPT connectors for the hose going to the Riello inlet, where there appears to be another NPT adapter. I don't see any compression fittings.

Our hoses are probably due for a change. I am a super sniffer--good enough to give a few of the older weary dogs job-security concerns--if I were willing to work for biscuits and pats on the head. I put my nose right up to the copper line where it connects to the swivel nut. No oil smell. Move my nose along the line till it reaches the braid. There I smell oil, at the braid not at the threaded connector. I smell oil also at the other end of the braid. No more oil smell when I reach the Riello inlet tube.





 

Last edited by tr888; 04-22-11 at 05:28 AM.
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Old 04-22-11, 03:58 PM
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What you are describing sounds to me like a classic air in the fuel problem.

I think my plan would be to install the TigerLoop (or equivalent) based on the fact that you have a 'top feed' off the tank and the ups and downs of the fuel line.

TigerLoop at Patriot Supply

This:



looks like a total hack job to me... and would be a prime suspect for an air leak.

There are braided hoses made specifically for the Riello that have the required metric threads.

This page has a few items of interest.

Flex lines at Patriot Supply
 
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Old 04-22-11, 05:52 PM
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Flex lines for Riello

Thanks, and double-thanks, for that link. I've been searching all day for these.
 
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Old 04-22-11, 06:04 PM
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bypass for TigerLoop

In addition to my thanks, I have another question, if you don't mind. I am not sure what is being referred to in the TigerLoop documentation by the "bypass plug" that lets the Riello pump operate in two-pipe-mode. Is this something to buy along with the TL and flex cables when placing the order for the TL? I'm going to have someone who knows what they're doing install it -- but would like to have all the needed parts ready to hand.
 
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Old 04-22-11, 06:44 PM
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Ya know, now that you bring up the bypass plug...

How long has this system been installed, and did it EVER run properly?

I hope that the installers did not install the bypass plug, or removed it if it was already installed. Running with a single line and the plug installed will damage the pump. I'm pretty sure that your shaft seal would have already blown out and the pump would have leaked by now, so it's a safe bet that it is NOT installed now... but stranger things have happened!

You will need the plug installed as noted in the Tiger Loop installation manual.

The plug is installed by removing the return port plug and with a METRIC ALLEN KEY install the plug in the pump. Your installer should know how to do this.

I'm pretty sure this would be your bypass plug, but I'm not really a Riello guy... so not 100% certain... hey Grady! wake up!

Patriot Supply - C7001012

I'm wondering if you will need some other fittings to convert to a 2 line for the TigerLoop setup also...

This link will take you to all the Riello items that Patriot stocks:

Patriot Supply - RIELLO Products
 
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Old 04-23-11, 04:10 AM
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Thanks very much for the master-list of Riello parts. I will send Patriot a picture of what I've got and ask them to include line-items for any required fittings.

The Riello burner has been running smoothly for over four years. The delayed ignition problems began in the third week of March following the annual service which also happened to coincide with an oil delivery of 170 gallons. It took the tech almost half an hour to purge the line after he had installed the new cartridge in the filter canister and a new strainer in the pump. The Riello was working fine up to that point.

I had the tech install a new fuel hose yesterday. He blasted come CO2 into the copper line. He also disconnected the line and inserted the copper supply line a portable oil tank. He removed the pump and examined it. He too had trouble purging the line but at one point inserted his screwdriver at one location and the pump immediately starting pulling oil. I asked him what sort of adjustment he had just made but he said that he had made no adjustment. Very tight-lipped. He left with the unit running smoothly. This morning (Saturday) the rumbling and delayed ignition is B-A-A-A-ACK.

I've attached a picture of the pump as it is now. I haven't touched a thing other than to remove the cover. I know that #2 is the purging valve, and am assuming that #5 simply holds that housing in place and has nothing to do with the pump per se. But the others?

If you click on this picture it should expand into a larger, clearer one, at 60% size, and it too can be clicked for a full-size image (sorry, the numbers turned out a little small and hard to read):

 

Last edited by tr888; 04-23-11 at 06:24 AM.
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Old 04-23-11, 07:17 AM
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An experiment

I turned the thermostat up and the Riello kicked on and the ignition started rumbling and dying, so I covered half of the air intake opening with my fingers, and it began burning smoother immediately. Removed my hand. Started rumbling immediately.

This doesn't explain why the techs have been having trouble purging the line, but it does explain the ignition troubles and I think corroborates the air-in-fuel-line theory. Is the following reasoning sound?

If there's already air in the fuel (whatever the source--jostling delivery truck, from too wide a fuel line diameter with inadequate syphon, or from the tube exiting the top of the tank, or a combination of these things, but hopefully not from a leak) then an otherwise perfectly normal air intake setting could be delivering too much oxygen to an already airy mix. A TigerLoop will make the fuel element of the ignition equation less of a variable and closer to a constant, right?

 
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Old 06-05-11, 06:40 PM
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Originally Posted by tr888 View Post
If there's already air in the fuel (whatever the source--jostling delivery truck, from too wide a fuel line diameter with inadequate syphon, or from the tube exiting the top of the tank, or a combination of these things, but hopefully not from a leak) then an otherwise perfectly normal air intake setting could be delivering too much oxygen to an already airy mix. A TigerLoop will make the fuel element of the ignition equation less of a variable and closer to a constant, right?


Hi,

You won't be getting air into the combustion chamber via the nozzle to make the burner run weak, if you have or are getting air into the fuel line somewhere it will cause incorect fuel pressure making a incomplete burn or just locking-out. By covering up part of the air intake you are simply reducing the air into the burner and making the CO2% higher (making it rich). If by doing this the burner seems to run better/smoother then that would indicate that the burner is over aired and needs to be set-up correctly. I assume that the last service guy used a pressure gauge to set-up the pump pressure, a smoke gun and then either a wet tester or electronic flue gas analyser to adjust the air/fuel mixture (FGA)? BTW - kerosene does make a certain amount of gas so creating a bubble in the flexi, you can't see it but we have clear lines on certain wall hung boilers (HRM) and you can see anything from 2 to 6 inches of bubble. As long as the fuel feeds in and the pump has some fuel at the end of the flexi all is well as the clear flexi comes up and over down to the pump of the Sterling burner. I'm not saying that you will that much of a bubble, but there will some sort of bubble somewhere.

Originally Posted by tr888 View Post
Our hoses are probably due for a change. I am a super sniffer--good enough to give a few of the older weary dogs job-security concerns--if I were willing to work for biscuits and pats on the head. I put my nose right up to the copper line where it connects to the swivel nut. No oil smell. Move my nose along the line till it reaches the braid. There I smell oil, at the braid not at the threaded connector. I smell oil also at the other end of the braid. No more oil smell when I reach the Riello inlet tube.
If you can smell oil at the hose then it sounds as if that's your problem. Braided hoses can weep/draw in air, they are [email protected] and should be replaced with a long life rubber hose. If I service a boiler with a braided hose that needs replacing, I will replace it with a long life hose, a little more money, but will last a good few years. Braided will only last a year or two max.


Please excuse me if I speak out of turn here as you may have different regulations from me in the UK



Looking at the picture for the fuel feed to the Riello pump..... it looks like a bit of a bodge. Here we have fuel flexi hoses that have a 1/4 threaded male elbow fittings that screw directly into the pump and at the other end it will be either a 1/4 or 3/8 female thread. Have you had a new flexi fitted after this picture? I ask as the picture of the complete burner shows a flexi with black/blue markings and the one in this picture is just plain silver.

Do you not have these flexi's with these connections?



Your burner picture below...


1 - Return port for the flexi if you have a 2 pipe system
2 - Vent/Pressure guage port
3 & 4 - Pressure adjustment - DO NOT TOUCH if you don't have a pressure gauge
5 - Allen bolts, 2 maybe 3 that hold the pump to the motor

Originally Posted by tr888 View Post
In addition to my thanks, I have another question, if you don't mind. I am not sure what is being referred to in the TigerLoop documentation by the "bypass plug" that lets the Riello pump operate in two-pipe-mode. Is this something to buy along with the TL and flex cables when placing the order for the TL? I'm going to have someone who knows what they're doing install it -- but would like to have all the needed parts ready to hand.
If the burner has been working OK and you have not changed any fuel pipework or tank I would not think that you would need a TL. The 'bypass plug' is only used for a 2 pipe system, your pump should not have this fitted (it goes into the pump body when you remove the 15mm bung next to the feed in), if you look on the pump cover there is an arrow in & out (in - LHS, out (return) - RHS). A bypass screw would have been included with your burner, normally it would be in a folded brown type label wired to the motor. You can buy one from your local merchants. When a deairator i.e. TL is fitted (outside of the buliding as they vent into the air, but you now can fit the latest TL's inside as they now have a connection at the top to plumb a vent pipe to the outside) you plumb the pipe from the tank to the middle fitting of the TL, then you will have two other copper pipes from the TL into the building to the boiler casing or next to the boiler in your case, one will have a flexi to the feed (in) of the pump, that other pipe will have a flexi to the return (out) of the pump. There should also be a ISO valve in the feed pipe near the boiler.

Have you got any fire protection on the burner? i.e. Fire valve.

Have you got a picture of the complete set-up that we could see? Include all the fuel feed pipes, filter(s) and burner

Regards,
Steve.
 

Last edited by Paffman; 06-05-11 at 07:56 PM.
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Old 06-06-11, 05:45 AM
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TigerLoop venting

Steve, thanks for the reply.

Some weeks have elapsed since my original posting, and in the interim a TigerLoop has been installed, along with new hoses and proper fittings, and a Firomatic valve. It was installed by a service organization well-established in the metro area. They dialed in the burner with combustion and draft analyzers. I do not know the code requirements, but they did not vent the TigerLoop. Is that a plug at the top of the dome of the model shown in the picture? Sorry for the blurriness.

P.S. I'm not using BIO fuel now but bought a Bio-ready TL in case we should ever switch over. In my area it's not readily available.

 
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Old 06-06-11, 06:12 AM
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Hi,

The TL does not normally need venting as it's job is to deairate and can bleed the air if you ever run-out. Is the Firomatic valve the brass valve under the TL in the feed line? The recommendation in the UK is to fit an external remote acting fire valve - see picture.

TEDDINGTON KBB FIRE VALVE C65 x 9.0 MTR CAP - Heating Parts Specialists

The bit on top of your TL looks like the vent that should have a pipe going to the outside of the building - if it is an internal TL (looks a little to the TL we use in the UK). But either way if a TL is fitted inside a build it should vent outside. See pictures below.

External TL - Tigerloop Original De-Aerator - De Aerators (Tigerloop) - Heating Oil Eqpt - Oilybits.com - The U.K's Premier Bio Fuel Equipment Superstore

Internal TL - Tigerloop Bio, Indoor Tigerloop - Tigerloop Bio, Internal Fitting De-Aerator - De Aerators (Tigerloop) - Heating Oil Eqpt - Oilybits.com - The U.K's Premier Bio Fuel Equipment Superstore

Still not happy with the two flexi's going to your burner pump, over here the flexi's fit directly to the pump. But you may have different regulations so don't quote me :-)

All the best,
Steve
 
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