to two or not to two (pipe) riello F5

archibald tuttle

2.5 years trouble free riello in pensotti. burner is about the level of the bottom of the oil tank, coarse and fine filter at tank , overhead 3/8 oil line, flare connections.

suddenly started airing up with 3/4 tank of oil. changed filters, cleaned screen, can run it from a can no problem for hours at a time. (got a flare tee with a shutoff and flare cap at the boiler end that I use for testing and to quickly oil up the burner so it's not running dry and then I choke the valve coming out of the can and open the one from the tanks.. thats my bleeding technique so it doesn't have to run dry long. so the tee is there to run it out of a can in emergencies, out of oil, filter problem, etc.

oil flowing fine through filters, flares are all tight but if I leave it running on the tanks, the next day its DOA again. (dead on air :-)

i know the thing to do is get a T20 and check vacuum and pressure, but these things drive me crazy. isn't there some kind of low pressure fuel pump could mount at the tank and run with a relay keyed to the boiler cutout so the fuel pump would start with the boiler but stop if it did?

i guess it is one more headache but when these things don't want to run, one headache seems like a lot fewer . . . .

other contemplation is running return line that feeds down to the bottom of the tank so once primed it should help to keep up if there is a tiny bit of air getting in somewhere. or a tiger loop, but honestly the tiger loop would cost more than 25' of return.

and both of those are substitutes for figuring out why the thing ran like a top for 2.5 years and now won't run 2.5 days.

here comes the cavalcade of what i'm missin' . standing far enough back from the screen so i don't hit by tomatos of other flyin' objects.

Big Ed_4

Dirty filter or oil lines would increase resistance and pull in more air though a leak . Are there any oil line fittings higher than 3/4 oil level ?

Jamie Hall

No flying objects... and only the obvious: Somewhere along that line between the level of the oil in the tank (and including the piping inside the tank) and the burner you have a very small leak. Probably a very small leak, since it takes a couple of days for the system to lose prime (I presume it does take a couple of days? It runs fine if you shut it off and then try to restart say 15 minutes later?).

Problem. It won't show up as a visible leak. Worse, it may well not leak under pressure -- it's quite common for a leak to leak under a vacuum, but not under pressure, or vice versa. Worse yet, it could be anywhere along the line. The flares and filter gaskets are the obvious villains, of course -- but check every inch of the fuel line for cracks as well. They do happen in flexible copper...

HVACNUT

archibald tuttle said: isn't there some kind of low pressure fuel pump could mount at the tank and run with a relay keyed to the boiler cutout so the fuel pump would start with the boiler but stop if it did? 

It's called a lift pump and Day tank with a vacuum breaker. 

EBEBRATT-Ed

People will through darts at me all day but I would 2 pipe it.

The way I look at the Tiger loop band Aid is it is a deaerator. If the lines are tight there is nothing to deaerate.

Everyone bad mouths two pipe the horrific "what if the return line leaks"

If you two pipe it and the return line goes to the bottom of the tank you have a sealed system..

Maybe the pump seal is letting air in. It will suck out of the can but under higher vacuum it sucks air.

I have on occasion put a refrigeration sight glass on the suction line to look for air.

yellowdog

Why is the oil line overhead? I have found with a Riello, any overhead line needs to be 2 piped or have a tigerloop at the burner. It prevents nuisance callbacks.

archibald tuttle

@EBEBRATT-Ed hmmm. hadn't thought about the pump seal admitting air. if that's the case, it won't show up on the site glass because it is not coming from the line but at the pump itself, right? i like that idea.

@HVACNUT so is there a commercialized version of this lift pump w vacuum breaker in this type of install or do folks build them up themselves? use a 120V pump with a relay and or if it is small enough draw, a 120V feed from the burner motor junction under the safety relay or . . . ? albeit if "day tank" means there is some small reservoir it pumps over to maybe it runs on a fill signal from the small reservoir and that's what needs the vaccuum breaker so the reservoir can empty?

@Big Ed_4 changed all the filters, cleaned the screen. Riello rep told me to check that the screen cover doesn't have the cork end gasket vs. the o-ring which is apparently a common problem when air is being introduced. i didn't do the screen clean and don't remember but I'm going to check when i'm there tomorrow. no joints above the oil level in the tank even above 1/4 tank nevermind 3/4

@Jamie Hall which makes me wonder if it is possible that the tubing could be the source. it was new copper at the install 2 and half years ago. seems unlikely that the tubing got compromised all of a sudden after that relatively short period of service. albeit if i rule out all these peripheral problem, line inspection or change out seems in order.

@yellowdog i think overhead oil lines these days are the kind of fuel oil equivalent of a hartford loop, so the line doesn't run on the floor subject to damage or under the floor where it might leak undetected. never really thought of this change as that much of a problem until we started to get these boilers that optimize for pressure over lift. as i said to the riello rep yesterday, this kind of system would be more resilient with a small lift pump keyed to boiler opp. I feel the same way about my duramax diesel where they decided to use the two grand injection pump as the lift pump as well. WHY would you do that. Electric automotive lift pumps are a dime a dozen. Why not pump the fuel to the injection pump so at least it doesn't end up running dry, maybe it would cough if it got water or clogged filter so signal to check the fuel system but it would get something.

while i respect the combustion advantages of the higher pressure, i'm still of the opinion that the best most resilient systems i've seen are the ones that use a low pressure oil pump to deliver the oil and air to atomize. not only seen this in waste oil burners, but also in onboard hydronic heater for a high end motor home that drew fuel from the diesel tank. clever little boiler. wish i saw more of this tech.

Big Ed_4

Your micro screen is dirty .... my thoughts....

archibald tuttle

@Big Ed_4 cleaned the screen but i'm going to take a kit with a new one back. residential application rep told me the cork gasket for the screen cover has been a source of problems and suggests an o-ring instead, although i'm not clear if there is a boss for this o-ring in either the cover or the receiving face on the burner. or maybe it just takes advantage of the formed shape of the cover?

I was not there when the screen got cleaned so I didn't observe the way in which the cover sealed or could seal . . . going there tonight. film at 11.

Jamie Hall

You really can't effectively clean a microscreen type filter -- install a new one. And for good measure -- always install a new gasket or o-ring, as the case may be.

HVACNUT

Does the oil line come off the bottom of the tank, go through the filters, then turns vertical up to the ceiling, then turns and runs horizontal along the ceiling (How long? How many hills and valley's?), then vertical down to the burner. 
Or, same thing but the oil line comes out the top of the tank? If it's top fed, how many inches is there from the bottom of the pick-up line to the bottom of the tank?

IDK what kind of MacGyver test setup you made, but it seems like a lot of extra fittings to leak. 
With the right tool you can check pressure and vacuum right at the fuel pump... AT THE SAME TIME. What a country!

archibald tuttle

@HVACNUT the westwood T20 i got it since this seems to be the wave of the future. i meant emperically testing if it will run without the pipe length and filters engaged, not to connect instruments. my tee is a flare tee to run out of can. and that is always how I primed these overhead lines, get it running out of a can then throttle the can and open the overhead line gradually over 3 or 4 minutes until i'm just running on the tank. And I leave that setup to run out of can in case of running out of oil so I don't pour 10 gallons in tank and have it essentially disappear and have to be sucked up and across that reach (30 feet, 1/2" OD) off the bottom of an almost empty tank.

You're not wrong that it is something else that can leak air, but never had that issue, at least not before. i've never dealt with these burners before either. I guess anything could start to leak if the vacuum goes up with clogged filter but we changed those. i guess the best information for diagnosis would have been to test vacuum before and after change.

got a new strainer in the truck and headed there tonight. and will test it wth the T20.

thanks,

brian

Big Ed_4

Pull micro cartridge out to see if it was the issue ...

Jon_blaney

You have an air leak at one or more of the valve/filters like a firematic. Opening and closing wares on the gasket/seals resulting in minor air leaks under suction. The suction increases as the tank level decreases, the head increases. A Tigerloop is probably the best long term solution.

archibald tuttle

@Jon_blaney I don't disagree with the premise, kind of a suspicion of mine although it cropped up steady state that could be as a matter of stasis and material degredation vs. lots of operation of moving parts, e.g. valves. do you prefer tiger loop to two pipe or, depending on difficulty/length to run pipe? I thought about a tiger loop but decided that was halfway to two pipe and, given the access and relatively short length of run, actually cheaper to two pipe.

one other mystery for all. i got there and put the T20 on the existing setup wanting to get a baseline without changing the screen to see if i could get any evidence of what was going on. it's running out of a 5 gallon can sitting 5 feet from the burner and no vacuum shows whatsoever unless i throttle the valve to the can tee almost closed. then the vacuum starts to climb. now maybe that is because the run is so short there is very little pipe friction and in a one pipe set up it just lays off the input thus meaning less pull in the supply line.

it's running like a top. 155 psi steady as a rock until i throttle the supply to almost nothing and ride it just into vacuum of maybe 1" hg, then the pressure flutters down to 150 and back up to 155. if i shut the valve all the way the vacuum spikes up toward 10 but i didn't wait to see how high I could make it cause i don't like to run the pump dry. but it sure seems like the pump seal must be OK.

EBEBRATT-Ed

Seems like the pump should deliver oil to the nozzle with more than 1" of vacuum.

archibald tuttle

yes, two pipes is better than one (and winston tastes good like a cigarette should). but I worked late so the verdict didn't come in til after midnight so its on the noon news this morning instead of the 11 oclock last night.

@EBEBRATT-Ed absolutely. it was delivering oil with no vacuum out of the can so it was still doing fine at 1inch hg as I throttled the valve, but it not being a flow regulating valve, I really couldnt get it to balance at higher vacuum without essentially closing or being so close to closing the valve that I starved it off.

i don't know if that no vacuum was because of the lack of pipe friction or because @HVACNUT was right about what i thought was a clean screen still being a problem (I'm not sure what that looks like at microscopic level, if it could have film or i don't know what). much as I would have liked to change only one thing at a time to really identify why i was having such grief, it was late when i got there last night and i had finally obtained all the bits for the two pipe conversion (all of which came with to begin with but the two metric bent nipples they give you, one is bent less and maybe that is because it is supposed to sit next to the other but they definitely don't have the geometry right so the original kit, if i had two piped, would have had to carve up the housing. as it is gotta notch a little) so I put on the second pipe and changed the screen at the same time.

and, as hint from tim tagman at riello, I put a couple good squirts of light machine lube oil into the vacuum port before attaching the T20 meters, another thing I could have tried independently before two piping it. Anyway, the friggin thing primed the overhead line in less than 10 seconds and off to the friggin races. 3" vacuum 165 psi. Didn't screw with it too much on adjustment last night. just checked CO - was like 18 and the overfire and breech draft were both too high. so throttle the adjustable damper to get back to -.02 breech and throttle the air a little bit to get down to .07 overfire and the CO went up to 23. stack was 373 i think and efficiency 85%

I have seen some folks mess with the turbulator setting. i don't if that moves the air baffle forward and back or what it does. but it seems if you really know these burners, getting educated on turbulating is part of fine tuning. I gotta go find the pensotti manual to see what they wanted for pressure. I think the 165 is a little high from my recollection but that was 2 and a half years ago. If I was smart I would have wrote this **** on the boiler in sharpie along with little stuff like nozzle spec and screen kit part #, but i not smart.

the only unexpected anamoly I encountered was the supply house gave me a P193-126G strainer kit. the fit seemed right, gaskets were right, but the strainer is domed and the one that came out is flat. and the strainer cap hits the domed strainer maybe an 1/8" before it makes up to the flange. now maybe that is to hold the thing nicely in place because the screen really barely catches on the pump boss it is intended to sit on. and maybe only a little bit of the screen surface is occluded by having the cap right against it. as i said, the thing primed and ran like never before. but just thought i'd check with folks who seen more of this wild game in the field.

brian

Grallert

"People will through darts at me all day but I would 2 pipe it." I'll quote EBEBRATT-Ed here. There is an issue and it needs to be resolved but in the mean time I'd install a TigerLoop. Riello pumps like them and with or without fuel line issues.

Jon_blaney

A two pipe system will not decrease the suction on the supply line. That is where the problem is. The supply hydraulics change as the tank level drops. How about running a new supply line with no joints and move the filters close to the burner after the line drops down from the overhead. Have a vacuum gauge on the filter. Do you really need two filters? Every joint is a potential source of air leaks.

archibald tuttle

@Jon_blaney if you mean that every joint makes me less careful in my work, that's the price of legal marijuana . . . oops wrong joint.

I'm a believer in your general line of thought as abstract matter but then it always comes up, what is needed in an oil line, or what connections are worth the risk and where, e.g., the vacuum gauge is a tee whether in the filter housing or independently . So my historic approach has been coarse filter, fine filter with gauge tapping, firomatic and emergency tee with valves. I try to use the most efficient fittings so i'm not stacking bushings and adapters and all the joints are below oil level–which doesn't eliminate the wiles of vacuum, but i feel like the degree of vacuum is attenuated over distance and volume of flow so while there is necessarily a pull on the oil at the tank it is less than the pull at the pump (although on occasion that can be the problem). am i thinking that wrong fluid engineers?

i still wonder since i was reading no vacuum in my short line setup to the emergency can then that means i couldn't be pulling air anywhere cause i got no vacuum. of course i have to have some vacuum in order to get the oil into even a short 5 foot line at the burner level but it must be such a negligible vacuum that it doesn't show up on the meter.

I always put the filters at the tank so i didn't get junk in the line, but i don't necessarily dislike the idea of moving the fine filter to the boiler with a vacuum gauge although that wouldn't reveal loss of vacuum in the oil line? Maybe someone should make a filter housing with an electronic sensor cast into it. now i suppose that could leak around the casting. there is no winning. and despite all the connections and double filters at the tanks, this install ran with no trouble for two and a half seasons. and I get no indication of significant air introduction with that same setup just adding the second pipe. now i changed the screen at the same time, hard for me to believe the screen was the problem looking at it. maybe there is some micro fine air being entrained that builds up over a day to shut the thing off without it being able to escape back to the tank in the return line.

I also have never seen an overhead line bleed that well, maybe even with a beckett or carlin but I wonder if that is because I dosed the pump with light oil at the suggestion of the riello residential specialist.

i agree i still don't really know what the problem was because i changed several things at once to overcome it and one thing i could have done was eliminate all joints except a single filter and firomatic valve and see if it got better before i made any additional prophylatic or belts and suspenders changes, but guy was getting antsy running out of a can and i just finished it.

in the end, i still go back to the theory, if vacuum is that nettlesome of a problem with the fanciest high pressure burners why do they have the injection pump also function as the lift pump? lets have lift pump kits (and as i've said, vs. the high pressure smaller nozzle approach, i really like those systems that use lift pump and compressed air atomization so the nozzle doesn't have to be so damn small. i would be willing to have a few more moving parts to service, e.g. lift pump and small compressor and air line, for a system that can operate with much less concern for fine particles clogging the nozzle. then i don't need to stack up 2 or 3 filters in a row because the bottom muck in the tank is, you know, mucky.)

i've been running oil burners piped identical to this setup with little problem with vacuum leaks for my almost 50 years at this (well alright, my first ones had one filter and not a permanent emergency tee and what's worse, all the early ones had compression fittings rather than flare–but i've changed to my standard install over that time).

now i understand technology is not going to sit still while I spend 50 years perfecting how to deal with the old school stuff, and new technology brings new challenges and i shouldn't be resistant to change simply because it is change if we're getting a lot of benefit from the change, but what are we actually getting? and if change might be good, if there could be better designs, why do they all rest on tinkering with the status quo platfrom. why not try broader change, e.g. the waste oil model (which is also employed in small onboard diesel fueled boilers for RVs I have serviced) with lift pump and compressed air. I doubt there is any reason why that kind of system can't be optimized for efficiency and emissions the same way that a high pressure small nozzle is used with these riellos to get better atomization.

While we're all seeking efficiency, it shouldn't come at the expense of thousands of man hours to keep the things running because that is not efficient. I'm surely interested to hear that folks who run a lot of these are finding whatever 5% efficiency gains?? In a world where there are simple low cost low maintenance solutions like electric resistance heat that can me made at least monetarily and systematically efficient not by expensive replacent with a heat pump, but add a few bricks and a blower and take the heat at time of day when there is excess electricity and save it for time of day when there is shortage, how far down the rabbit hole do we go improving the existing tech. if i'm willing to rethink tech on the modest scale necessary to kick this riello in the ****, i'd like to think that manufacturers are pushing the tech way beyond what we've got.

a big problem is that, with the war on fossil fuel, making a significant change in direction and the attendent large investment in a departure from the status quo and then looking to get a significant installed base is risky as a matter of reward–even if you have built a better mousetrap. It's kind of like the end game of the betamax VHS thing vs. the inrun version of competition. just not apparently worth it to break new ground on fossil fuel combustion in the face of the massively subsidized forced march to heat pumps, so people that make great fossil fuel tech are at a dead end, and I feel that's sometimes where we get left as the last link in the chain of fossil fuel techs.

I saw this with a friend who was desiging fluidized bed coal fired power plants to burn the dirtest coal cleaner than other plants burned the cleanest coal. then somebody decided CO2 was dirty and all that effort to deal with sulfur and particulates, etc. was down the drain.

well, back to my yurt and coal stove to think about this.