Rielo F3 intermittent tripping problem

bonhomie

Hi,
I've been working on my furnace tripping for a few months now, with the help of two top local techs from the gas company. Maybe somebody else out there can help point us in a direction we haven't looked yet?

We have a Rielo F3 burner on a carrier 75BTU(?) system. The burner will trip and need to be reset - sometimes daily, other times it will go a month or two without happening. The techs have done multiple full services now checking pressure, etc, and we've replaced:
primary control unit, CAD, solenoid, fuel pump, nozzle (currently using B instead of W. issue continued with both types), filters, draft regulator, purged the fuel lines with Co2 to remove potential sludge, re-routed return line to go into top of tank.

When it's running everything looks and performs perfectly. It usually trips overnight, but sometimes during the day.

We thought it could have been sludge, or the latest theory is water in the tanks. The lines run about 30ft from the tanks to burner, with a few twists and turns.

Lastly worth noting, the issue began last year, around the same time an inexperienced serviceman accidentally flooded the furnace by not tightening the nozzle properly. Lots of smoke, etc.. Anyway, I've been told there shouldn't be a connection, but could be worth considering.

Any ideas? We are stumped and it's getting chilly up here!
Thanks in advance

Jamie Hall

Next time it trips, if it isn't too cold, don't reset it. Get a good tech. out there and see if he or she can figure out exactly what happened to make it trip. Since there are so many possible causes, that just might help.

EBEBRATT-Ed

Give us some more information on the oil line set up. You indicated it is a two pipe system. Are you setting the temperature back at night?

If the burner has to "lift" the oil out of the oil tank this could be a classic case of the oil pump dropping it's prime do to a suction leak if the burner is off for a long time

bonhomie

@Jamie Hall ok that's a good idea. It's getting down to almost 0ºF where we are at night, but we could tough it out ;-) Thanks for your input.

bonhomie

@EBEBRATT-Ed this sounds very promising, thank you. You're spot on in that I'm setting the temp down to 60 or so at night, 67 in the day. There are two 270gallon fuel tanks. The line draws from the bottom of each, passes through a filter then travels up to the ceiling (about 6ft) and across to the burner in the next room (maybe 40ft), then back down under the furnace to the side of the burner. There is a secondary filter just before the burner too, which the tech said is not really in fashion these days. Then a return line runs that same path and dumps back into the tanks.

So the pump (which is brand new) does have to do some lifting to get the fuel to the burner.

Jamie Hall

Actually, once the system is primed, the pump doesn't have to lift. But, if it loses prime it does, and that takes awhile, even with a two line system -- and it may well be tripping off before it can prime.

Suction leaks are not all that easy to find, but the tech. should be able to at least see if that's the problem (it takes only a tiny leak, anywhere along the line, to do it).

JUGHNE

If the rookie you had with the loose nozzle install changed the filter at the pump, he may have not tighten some connection there and you suck air....sometimes.

HVACNUT

In addition to what  @EBEBRATT-Ed suggested, with the set back thermostat, longer down time, cold boiler, maybe too much draft and excess air on a cold start. 
Do you have a combustion report?

STEVEusaPA

Two top techs...LOL

EBEBRATT-Ed

@STEVEusaPA

You have to be kidding. This is about the 10th post and no one has mentioned the Tiger Loop fix yet? LOL They will say it's easier to put one on then find a leak.

Don't know if that is what the problem is butt that is a classic "dropping the prime" call, or a burner that won't light when cold

@bonhomie , try running with no set back and see what happens

EdTheHeaterMan

The return line should be submerged in the oil. If the return pipe (tube) stops at the top of the tank and does not end in the oil, then that is where the air can get into the system. By submerging the return in the oil you are creating a closed loop for the oil (picture it in your mind's eye) from the tank thru the tubing overhead then back down to the pump then back up to the ceiling then back down to the tank. None of the oil in the fuel lines is subject to atmospheric pressure. So When the @Jamie Hall says that the pump does not have to lift, he is correct because the weight of the fuel rising to the ceiling is offset by the weight of the oil coming back down to the pump (in the supply tube) and coming back done to the tank (on the return side).

If however, the return tube ends at the top of the tank (not submerged) the pump must work to build up pressure to force the oil up to the ceiling to make the trip back to the tank. There is no "weight of the oil" helping the fuel back down to the tank.

This will also increase the possibility for a tiny fitting leak to allow air into the fuel line causing it to rise up in the overhead line while the fuel in the line retreats back to the tank. No visible oil leak will be noticeable in this case. The longer the burner is off, the more air is sucked into the overhead fuel line.

I would fix this with a Tigerloop and be done with it, but you might just want to look for all the fitting air leaks from poorly flared copper and extend the return line to within 5" of the tank bottom.

Respectfully Submitted
Mr.Ed

EdTheHeaterMan

STEVEusaPA said:

Two top techs...LOL

He did say they were from the "Gas Company"
LOL
You don't need a fuel pump for that fuel.

STEVEusaPA

EBEBRATT-Ed said:

@STEVEusaPA

You have to be kidding. This is about the 10th post and no one has mentioned the Tiger Loop fix yet? LOL They will say it's easier to put one on then find a leak.

Don't know if that is what the problem is butt that is a classic "dropping the prime" call, or a burner that won't light when cold

@bonhomie , try running with no set back and see what happens

ED my comment was directed at the original post from the OP, where they mentioned 'Two top techs'...yet all they did was change every component, not once mentioning that they tested anything.

EdTheHeaterMan

Agree with your assessment of "two top techs". I wonder what the regular techs qualifications are? LOL

EBEBRATT-Ed

@EdTheHeaterMan

I agree with some of what you posted the return line should be submerged. But putting in a Tiger loop to "fix" an oil leak?

That's like putting on a band aid.

And the idea that "the oil lines are not subject to atmospheric pressure" that's just wrong. The oil tank is vented to the atmosphere and there's atmospheric pressure pushing down on the oil.

This is not a "closed loop"

Find the leak fix the leak

With 6' up and 60' to the boiler and two filters it's possible there is a vacuum in the suction line at some point especially if it has dirty filters. It sounds like the oil tanks are at the same elevation as the burner but we don't know that.

The fact that the OP has two oil tanks makes it less likely that the oil return line is submerged.

@STEVEusaPA

The 2 "top techs" have pretty much replaced the whole system

EdTheHeaterMan

@EBEBRATT-Ed
I did not see anything about an oil leak anywhere? Did I miss something? The assumption is made that the reason for the intermittent flame failure might be caused by air in the fuel line, which makes sense. it makes sense because the longer off cycle seems to be a contributing factor to the flame failure occurrence. More off cycle time allows for more air to accumulate into the fuel line, whether it is from the return being open or an improper flare connection.

The manufacturer of the fuel pump recommends the return line be submerged. The reason for this is explained in my earlier post. By doing this you are removing the fuel system from atmospheric pressure and closing the loop. Once the system is fully charged with fuel the "Closed System" is subject to the static pressure of the fuel in the tank. This pressure is greater at the bottom of the tank because the fuel weighs more than the air, exerting greater pressure on both the supply and return. Not true if the return is not extended to the bottom of the tank.

By removing the fuel system from atmospheric pressure the pump does not need to overcome the static pressure on each start-up. And if I recall correctly on the Riello control, has a 15-second pre-purge, then if the fuel pressure is interrupted after the flame is proven, the control goes into a relight sequence fairly quickly. After 3 of those, then it locks out on safety. So a significant amount of air must be present in the fuel line for this to be a problem.

I agree with repairing the leak in lieu of the Tiger loop. I just mentioned it to get the debate going again. I know how much you and Steve like them. LOL

And the problem WILL go away if a TL is installed on each burner. Tell me I'm wrong!

bonhomie

Thanks for all the great ideas - helps me immensely.

@STEVEusaPA
By two 'top techs' I mean they are the most senior at this particular company (albeit in our rural area) which I didn't want to mention by name, but is a major nationwide energy supply company. Also I'm from Australia originally and we just say 'gas' for everything energy related LOL

And in pursuit of brevity I left out that every time they have come (I think at least 7 or 8 visits now) they run their full diagnostic on the system: check the fuel pressure (always spot on), make sure filters are clean, check nozzle, electrodes, wiring, bleed the lines...I'm surely missing other tests.

@HVACNUT never run a combustion diagnostic, at least to my knowledge. It's more a "the flame looks good" diagnostic. Draft was my initial thought so I replaced the old rusty regulator. I even bought a draft meter and it all checked out. I could change the weight so the regulator stays open even when cold?

@JUGHNE don't think so. They have inspected and changed those filters many times since.

@EdTheHeaterMan
@EBEBRATT-Ed
I read about Tiger Loops and was wondering about this. Glad you guys set off the debate and not me!
One vital piece of information - when the issue first arose (ie. when it got cold enough this fall, although it also didn't run last winter when I wasn't here), the return line WAS SUBMERGED. It ran back to the bottom of the second tank. The tech changed it around the thinking being that the check valve down there may have been faulty and letting in air. The problem persisted either way.

It has also failed while running without a thermostat set back, just during the day. Also a couple of times it hasn't been able to start on reset. Took a few tries.

Oil tanks at same elevation as burner, yes. I really doubt dirty filters as every other week they're opened up and always clean.

No sign of oil leak anywhere, but of course a tiny air leak could be possible.

Last time we noticed while bleeding the lines that somtimes the fuel ran lighter than the red color it should be which could be water in under the oil, right? We drained about a gallon off until it looked good, but do you think I should try to drain out a few more gallons of fuel in case there is more water at the bottom of the tanks? The fuel leaves the tank at the very bottom, not 5" up like you recommended.

Thanks again! It's really a head-scratcher, and stressful with the weather turning.

EdTheHeaterMan

Good info.

I would look at the water in the tank possibility. Based on your setup one tank is getting the return oil. This is causing that tank level to get slightly higher. Since the tanks want to be at the same level the oil flow from that tank will move oil to the other tank thru the bottom connections. Sometimes the water (if it is in the other tank) will present. Other times it won’t. The longer off cycle allows for this gradual migration of the heavier water to the tank outlet.

Can you disconnect one tank at a time to inspect for water? Do you have any water detecting paste? If not... get some. Remove as much water as you can by draining from the bottom, then add a water displacing chemical like Hot 4in1 or SuperHeat with each delivery.

Yours truly,
Mr.Ed

P.S. If there was a Tiger loop, you could see the water thru the clear enclosure.
Just saying.

Jamie Hall

I would still (sorry to be a pest) want to check for a vacuum leak somewhere... not an oil leak, a vacuum leak. The comment that the return line, if submerged, creates a close loop is quite correct. However, whether it is or not, any portion of the supply line which is above the level of the oil in the tank will be under vacuum whether the pump is running or not. When the pump is running, no big deal -- a small vacuum leak won't matter. If it's off, however, even a small vacuum leak will cause a loss of prime.

This irrelevant in the return line -- that will be somewhat above atmospheric when the pump is running, and if the oil runs out when the pump is off, who cares?

bonhomie

@EdTheHeaterMan thanks for the explanation, that makes more sense to me now. The tanks each have a valve on them. My plan now is to turn off tanks, disconnect at filter, and drain as much water as I can (assuming there is some). Would I need to bleed the lines after this? Or can I just reconnect the filter and call it a day? I'm going to buy some paste now too and try that out.

@Jamie Hall I'm still with you there too. So possible loss of prime due to vacuum leak when burner is off for a longer period between cycles. How do you test for that?

Thanks again

EBEBRATT-Ed

@bonhomie
There probably isn't a practical way to test for a leak.

Look, I have chased a lot of suction leaks. Take all the joints apart and check and re-dope and re flare them. I hope you don't have any compression fittings. Pay careful attention to the oil filters. In addition to the bowl gasket some have gaskets under the bolts. nuts and bleeder fittings. You mention a check valve most will tell you to get rid of that. Valves can leak around valve stems too.


I suspect the color change you are seeing in the oil could be air bubbles

You need someone to look at this that's not interested in selling you parts.

Has anyone put a vacuum gauge or pressure gauge on the burner pump?

EBEBRATT-Ed

@bonhomie

Yes , a vacuum leak will show it's ugly side the longer the burner sits off. That is why as I posted above I said no night set back as your first post says" Usually trips overnight" If it's tripped every morning with set back and the problem resolves without set back that is a clue to 1 of two things. Dropping it's prime or failure to ignite when cold

EdTheHeaterMan

@EBEBRATT-Ed said

“@bonhomie
There probably isn't a practical way to test for a leak.”


To find the leak use a hand pump to add pressure to the fuel line at the burner end. Blow air into the line at about 5 PSI or less. Once the line is charged with air close the tank valve. Now that the line is charges with air, use leak detection bubbles over all the fittings. Easy to find small leaks with lower pressure and bubbles

Note. If there is any liquid near the fitting, the bubbles won’t work. Must get inside of fittings as dry as possible. Push air into the tank for at least 1 minute and have someone else close the valve mid pumping stroke


Yours truly,
Mr.Ed

Edit: if you have a nitrogen tank and set the regular at 5 PSI and get a 3/8 x 5/16 flare union you can dry out the fuel line yourself.

Jamie Hall

Well... trouble with the air test is that a vacuum leak -- particularly at a flare -- doesn't always show up with a pressure test. The force on the flare is in the opposite direction...

EBEBRATT-Ed

A few fittings at the tank and a few fittings at the burner. And 60+ feet of copper x 2 maybe 2 flare couplings. Why bother testing? Your going to have to take it apart to fix it anyhow

bonhomie

EBEBRATT-Ed said:

You need someone to look at this that's not interested in selling you parts.

Has anyone put a vacuum gauge or pressure gauge on the burner pump?

Right. Well, there aren't that many parts left to sell!
And yes, they ran the pressure gauge on the burner pump. Can't remember the exact numbers, but it performed correctly.

rick in Alaska

Riello pumps are not good for pulling any kind of vacuum (lift). I am thinking with 60 feet of line, that pump is about maxed out. Check the vacuum at the pump, and if it is over about 5", I would definitely just put a Tigerloop on it. Yeah, I am not a big fan either, but they work, and sometimes are the best alternative.
Rick

EdTheHeaterMan

rick in Alaska said:

Riello pumps are not good for pulling any kind of vacuum (lift). I am thinking with 60 feet of line, that pump is about maxed out. Check the vacuum at the pump, and if it is over about 5", I would definitely just put a Tigerloop on it. Yeah, I am not a big fan either, but they work, and sometimes are the best alternative.
Rick

OMG another Tiger recommendation. Totally fer sure
Out of character for AlaskaMan.
Said with a Valley Girl accent

Sometimes you just got to go with what works. You know, if God wanted us to use fuel deaerators, he would have made some guy in Scandinavia invent one!

Oh yea... He did.

EdTheHeaterMan

I just had another thought on the vacuum leak. The proper test on the Suntec fuel pump is to place a vacuum gauge on the suction side of the fuel system, maybe in a tee fitting. Run the pump and close off the valve(s) at the tank. Run the pump until you pull the maximum vacuum ( when the vacuum gauge stops climbing) and shut off the pump. If there is no vacuum leak he gauge will hold at the vacuum it stopped at. If the vacuum slowly drops to zero then you have a leak. I believe it is the same on Riello.

Do this first to see if there is a leak. No leak then it is probably water in fuel. If there is a vacuum leak then try the pressure test with bubbles to locate the leak. As Jamie mentioned... it may not work... but it may work and you will not waste time on fittings that are not the problem.

Yours truly,
Mr.Ed

STEVEusaPA

EdTheHeaterMan said:

I just had another thought on the vacuum leak. The proper test on the Suntec fuel pump is to place a vacuum gauge on the suction side of the fuel system, maybe in a tee fitting. Run the pump and close off the valve(s) at the tank. Run the pump until you pull the maximum vacuum ( when the vacuum gauge stops climbing) and shut off the pump. If there is no vacuum leak he gauge will hold at the vacuum it stopped at. If the vacuum slowly drops to zero then you have a leak. I believe it is the same on Riello.

Do this first to see if there is a leak. No leak then it is probably water in fuel. If there is a vacuum leak then try the pressure test with bubbles to locate the leak. As Jamie mentioned... it may not work... but it may work and you will not waste time on fittings that are not the problem.

Yours truly,
Mr.Ed

Don't you have to remove the return pipe, remove the bypass plug, plug the return port, make sure the fuel unit has oil and bled, then do the vacuum test

bonhomie

EBEBRATT-Ed said:

A few fittings at the tank and a few fittings at the burner. And 60+ feet of copper x 2 maybe 2 flare couplings. Why bother testing? Your going to have to take it apart to fix it anyhow

Right, we just re-flared the coupling and put a check valve after it leaves the filter. Should tell us something. So far so good, working great. Thanks for the input!

bonhomie

rick in Alaska said:

Riello pumps are not good for pulling any kind of vacuum (lift). I am thinking with 60 feet of line, that pump is about maxed out. Check the vacuum at the pump, and if it is over about 5", I would definitely just put a Tigerloop on it. Yeah, I am not a big fan either, but they work, and sometimes are the best alternative.
Rick

I think I need to go this route. So far nothing else has worked. Still failing everyday, sometimes multiple times per day. Sometimes takes 4 or 5 goes to start it up. I usually have to hold the sight door open and battle the flames to get it to light.

GW

I always thought and believed Riello’s don’t lift. At the risk of getting scolded at with a valley girl accent, ditch the return pipe and install a Tiger. Ensure the plug is installed. 

Too much draft will kick you in the chops too 

bonhomie

@GW I hear you. But aren't they designed to work with a two line system just fine?

GW

I’m not an oil know it all, but when I lift with Riello I use the tiger