Air in lines

wmechanic01

I have a miller cmf 80 , the problem is when it first fires it starts fine then it sounds like air is in the system ( no flame for about 1 sec ) then it's fine for the rest of the cycle , I have a Roth tank about 55 foot away from the burner outside with a two pipe system , I do not believe it's a nozz issue because if u put a new one in it still does it , the burner is new only a few months old . The vac gauge on the garber says around 10-11 . It not a delayed ignition problem it seems to b air . All lines are new ,can I run a air check valve on the suction line and would this help I know suntec states not to do this but where do I go , a tiger loop maybe? Here's all the info on my system. Roth tank 2 pipe system with about 55 foot run off top feed tank and about 3ft lift to burner , becket burner , garber filter , miller cmf 80 , also this is not a gelling issue because it does the same thing when it's 50 degrees out , all fittings are tight , no junk in the lines. Any opinions would be helpfull!

STEVEusaPA

You really don't want to put a check valve on the supply line. I would follow the manufacturers instructions about checking the line with a vacuum gauge, and checking the pump with vacuum gauge (on the pump, and running vacuum) and pressure gauge (to check operating pressure and cut-off).
For starters, you could try to disconnect the supply. Make up a short copper supply and stick it in a 5 gal. container of clean heating oil. Run the burner and see if you have the same issue.
You could have a restriction, which would be the high vacuum. A high vacuum starts to separate the liquid and it will look like there is air in the system.
If you have no oil initially at the nozzle, that would indicate a vacuum leak that's allowing the fuel to return back to the tank. It could be a fitting or it could be the filter or packing nut in a shut off valve.
Fixing that leak and a power bleed may fix the problem.
A tiger loop will probably not 'fix' the problem, but will mask it and allow everything to appear to be working fine. If you attach a tiger loop, you could watch it for diagnostic purposes and see if air is indeed getting pulled into the fuel line.
I just don't like 2 pipe, if I can do it with a single pipe. If that exceeds manufacturers specs, then consider a 1 pipe, 2 stage pump. If that still exceeds specs, then a tiger loop.
Another band aid, but recommended on a properly working system, would be to add a delay oil valve.

EBEBRATT-Ed

You have a suction leak. Find it and fix it end of story. A 10" vacuum is getting close to the maximum that I would want.

In my opinion stay with two pipe (others will differ) forget the band aid tiger loop. You don't need a device to remove air when your lines are tight you will have no air. Check the oil filter it is the most likely spot.

One other important item to check. Your return line should go to the bottom of the tank. If it does and your lines are tight you shouldn't need a check valve. I am not against a check valve but it will raise your vacuum.

If your return line terminates at the top of the tank that could be your problem. When the burner shuts off air can migrate back into the pump through the return line. If it is submerged to the tank bottom this can't happen

wmechanic01

I had a tech come out and he installed a check valve on the return line I do not believe it is submerged in the tank , the valve did nothing at all but I did notice if I Shortly ran it as a one pipe setup it did not do this so I am thinking there is something up with that return line also , wouldn't that check valve do the same thing as a submerged return line ?

Jamie Hall

wmechanic01 said:

...wouldn't that check valve do the same thing as a submerged return line ?

If it were perfectly tight, it might. But that's asking an awful lot of a check valve, unless it's a very high price mil grade spring type.

EBEBRATT-Ed

A check valve just sitting there... it could easily allow air to work it's way back. The check valve will work better if it's "wet". If it's in a horizontal pipe at the top of the tank....no good. If it is at the burner or anywhere in the return line so the check is "in oil" all the time it will work better.

to picture the oil lines without a check valve Picture a bucket of water. Take a short hose (like a washing machine) hose. cap the bottom end and fill it with water. Submerge both ends into the bucket without loosing water, take the cap off and with the loop above the bucket top, the hose will stay completely full. water can't leak out unless air can get in. put a pin hole in the hose above the bucket and the water flows back to the bucket.

Just like putting a straw in a glass of water putting your finger over the top and taking the straw out of the glass..... the straw stays full

That's how you want your oil lines 100% tight and submerged in oil. If your oil lines are like that it will work 100%.

Anything else is just a maybe

STEVEusaPA

Check valve is against code, and against manufacturers specs, voiding any warranty.

EBEBRATT-Ed

@STEVEusaPA I see Suntec installation manual does not recommend check valves. I see nothing that prohibits them or voids warranty. Where are you finding this??


Thanks,
Ed

STEVEusaPA

You're right it doesn't-directly. However it states in the warranty about being '...properly installed, maintained and operated under normal use...", "All installations should be made in accordance with local and national codes". And NFPA 31 doesn't allow check valves.
I think we both agree that finding/fixing the vacuum leak fixes the problem.

wmechanic01

I'm going to start with having the return line in the tank the same length as the suction line in the tank would this be a good place to start? Or can I even have a tiger loop in a crawl space that is lower than the burner level or would that just continue to create problems? I have had techs come out and I have yet to get a good one and honestly I can't afford one right now to come here and simply waste my time changing a nozzle. Another question is it ok for this furnace to operate like this when it starts it starts fine and about 5 to 10 seconds in it gets about 3 quick air pockets that cut the flame out about a second each time then runs fine for the rest of the cycle , there like little puffs I guess u could say. No soot or anything just annoying. Also the puffs are not big or creating a Big Bang or anything I'd say like a tap of your boot on the floor.thanks for all your insight as always!

EBEBRATT-Ed

What you have is a CLASSIC air leak. 1. I would extend the return line to the bottom of the tank.

2. Have them check the oil filter tighten everything , take the joints apart, check the flares, re dope the pipe joints. Whatever they have to do to find and fix the leak that what they need to do.
3.Call the service manager and have a discussion with him tell him you wan't his best tech and you want it fixed in one trip or YOUR OIL BUSINESS GOES ELSEWHERE.

HVACNUT

Dumb question. Does it always cycle like that? The Miller down flow has the door with switch. I've gone to many calls for no heat, reset and runs for a while, then cuts out or hesitates and starts again and a lot of times its the door switch not fully closing the circuit. The door switch will interrupt power to the burner but not the blower motor.
Try cycling with the door open. Hold the switch in manually and have someone raise the thermostat. Does it still happen?
You can bend the latch to engage better.
Is this a mobile home? I don't recommend a tiger loop, or anything else in the crawl space. No room for a filter unless in the burner compartment. You should be burning Kerosene with that application. I've got hundreds of clients with the Miller. All 1 pipe whether top or bottom fed.
Re do the flares.

wmechanic01

Yes it's a downflow and the switch works fine I believe I've tried what u said about trying it with the door open . The burner dosent loose power it sounds like air , it dosent do it exactly the same time always and not always a lot but when it's running a lot it will do it more.

HVACNUT

I would redo the flares.

wmechanic01

The miller cmf 80 with outdoor tank and such a long suction line would b fine on just a one pipe? Should I just do that and can I do this myself by just removing the bypass plug out of the pump? Any adjustments need to be made or anything? It's ok to run it like that not going to cause a leak or anything anywhere ?

HVACNUT

Yeah, remove the bypass plug ( 5/32 allen wrench) and get a 1/4" black plug for the port. Prime and start. Keep in mind, if you have a suction leak, it still needs to be repaired.
As far as adjusments, your not changing oil pressure or air settings so you should be fine but all work done on an oil burner should be completed with a smoke test and combustion analysis.

wmechanic01

Thanks hvacnut, I'm going to have the return line about a inch shorter than the suctioned line done. If this does not solve and all flares check out and filter , then it will b changed to a one pipe. I noticed garber says to use some vasoline around the filter at the top , does anyone actually use this practice because I have not and that may simply b the problem possibly, but who knows!

HVACNUT

Sometimes guys over tighten the filters and Hercules has to get it off with a pipe wrench. I carry a zoom spout electric motor oil to apply to the gasket.

wmechanic01

No Hercules'n it on here lol learned that lesson along time ago !

Marz

11" of vacuum is too much for 1 stage IMO. Could be a suction leak.

wmechanic01

It's running @ about 5-7 vac on a 2 pipe now , have my tech coming to extend return line tomorrow. Hope it
Works will let u all know thanx

Steamhead

EBEBRATT-Ed said:

You have a suction leak. Find it and fix it end of story. A 10" vacuum is getting close to the maximum that I would want.

In my opinion stay with two pipe (others will differ) forget the band aid tiger loop. You don't need a device to remove air when your lines are tight you will have no air. Check the oil filter it is the most likely spot.

I don't agree that a TigerLoop is a band-aid or that it's not preferable to a two-line system.

There are two problems with two-line:

1- the return line runs under pressure, so if it leaks you'll have a mess at least and a Superfund site at worst;

2- since more oil flows thru a filter on a two-line system, the filter will clog more frequently, possibly causing no-heat calls.

For these reasons, we change two-line systems to TigerLoops wherever possible. The TigerLoop will allow the full suction capability of the pump to be applied to a single line without causing excessive vacuum at the pump. See the following thread for an example:

http://forum.heatinghelp.com/discussion/148292/megasteaming-by-the-river

I do agree that this is a classic case of air being drawn into the line. A bad flare is one thing that will cause this. And you won't necessarily see an oil leak, since air can pass thru a very small opening that oil cannot.

So find the right pro who can fix this. Where are you located?

wmechanic01

I'm in Ma any suggestions? Had the company who did the tank run the return line same length as the suction , same outcome as before I'm getting tired of it and need this resolved . It's not causing no heat the furnace still runs but I'm not stupid and know the system should be air tight ! Let me know if you have any recommendation?
Thanks to all of your advice ! Better than the stupid techs around here I swear there idiots

EBEBRATT-Ed

@wmechanic01 said" Here's all the info on my system. Roth tank 2 pipe system with about 55 foot run off top feed tank and about 3ft lift"

@Steamhead said"There are two problems with two-line:

1- the return line runs under pressure, so if it leaks you'll have a mess at least and a Superfund site at worst;

2- since more oil flows thru a filter on a two-line system, the filter will clog more frequently, possibly causing no-heat calls."

This is something I will always respectfully disagree with.

When I started we were taught by Sundstrand (now Suntec) & Webster and where I went to school (Burkhart's book) that if you have lift (oil level below the pump) two pipe, gravity flow to the burner..one pipe.

Low lift, single stage pump that comes on the burner is ok, over 5" of vacuum two stage pump,(two sets of gears)

Everyone always talks about return line leakage, what about gravity feed to the burner?? Just as hazardous.
I admit Tiger loops and osv valve were non existant when I started so I guess I am just stubborn (no, I know I am)

My theory with two pipe is it keeps the tank and lines cleaner because it has more flow.

Show me a job with a .50,.65 or .75 nozzle, that's the job that will plug up, not just the nozzle because it is small but the oil line and the filter will plug. Not enough flow, too much settiling time.

@wmechanic01 Your problem as I posted previously is an air leak. If the line was TIGHT it would run weather it was one pipe, two pipe, with or without a tiger loop, a check valve or anything else.

The old books used to say "there is no substitute for a tight suction line".

That's something that will never change.

You need a technician that will dig in and find and fix the leak.

Guess there's not many of them left.

The easy way out, usually doesn't work

Steamhead

EBEBRATT-Ed said:

Show me a job with a .50,.65 or .75 nozzle, that's the job that will plug up, not just the nozzle because it is small but the oil line and the filter will plug. Not enough flow, too much settiling time.

My house. 0.50x70B at 225 PSI in an NX, because I could. Gravity feed, about 50 feet of 3/8" soft copper with a General 1A-25 and it hasn't plugged yet.

We might have better fuel quality though.............

EBEBRATT-Ed

@Steamhead , probably not a 40 or 50 year old tank though, that would be the test. I always liked the 1A-25, seldom leaked, filtered good even with the wool element, now they have the micro...whatever they call it. If you had sludge the General would plug and the oil line , pump strainer and nozzle would usually be ok. Most of the filters up here in MA. here in the old days were the "Fulflow" with the cotton yarn. On those jobs the stuff went straight through, plugged line, nozzle strainer etc

Steamhead

Actually, it is that old, which is why I hope to replace it.

wmechanic01

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Patchogue Phil_2

> @wmechanic01 said:
> .

Anything new?

newagedawn

what kind of pump is it? suntec they are rated for about 8 to 10 inches of vacuum, i like to run one pipe on roth's ( less headaches) could be that trap you created by going up three ft, could be creating just that moment of drag when it starts

wmechanic01

@newagedawn & @Patchogue Phil
Ya it's a suntec av2a7116 and the company kept scratching there heads and decided to put a check valve before that last 3 foot lift and it fixed the issue my concern is the valve makes a slight rattling noise I guess u can say not anything big but you can hear it a couple of feet away. The system has been running great for about a few weeks now. All the guys on this forum swear against the check valve so I'm gonna wait it out till the summer and have a good comp come out and address it I would leave it like that but I feel like that's a bandaid we will see!

newagedawn

im not a fan of the check valve either, but if it works it works, to bad there wasnt a way to get rid of the 3 ft in lift, then that pump should have plenty of vacuum to pull the oil through

Patchogue Phil_2

Well then, maybe a brand new fuel line with flare fittings is in order. New pump or at least diaphragm/gaskets.