Rotten Flue Pipe Direct Vent Oil fired Burner

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Old 07-30-12, 02:55 PM
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Rotten Flue Pipe Direct Vent Oil fired Burner

As Always Love your guys help. I Flue pipe on my oil fired burner after about 6 years of owning the house rotted apart.. below is a picture of it in my driveway..

It has a direct vent and has a tankless hot water heater.. So in the summer it runs for very short periods of time.

I put a new flue pipe on it about a month ago and today I noticed it has a small crack in it again and starting to rot out with only about a month with the new flue pipe on it.

I was thinking it could be

1. Increase the post purge draft on the sideshot. I turned it down from like 2 minutes to 1 minute.
2. No drippage from the outside.. it's pretty well hidden from the rain
3. The Boiler's heat exhangers I think are rotting out. I can tell when I opened up the burner door and there was a tiny drip of water in the chamber. It goes away when hot/expanded. So thinking some of the water going in the chamber when it cools is starting to rot out my flue pipe.

Draft is set at neg .03 wc... air adjustment and pump pressure ok.
Lay it on me.. is it time to replace the furnace. I replaced the Beckett oil burner with a Carlin EZ-1 about a year ago... I think it's boiler time now...

Thank you


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Old 07-30-12, 03:08 PM
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correction the vent was setup for 1 minute post purge and I moved it on November 2011 to 30 seconds (Checked my boiler log). I read that not enough post purge can cause water in the flue so I just bumped it back up to 1 minute purge today.
 
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Old 07-30-12, 03:58 PM
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No pro rick but I think it may be caused by condensation.

Is there a boiler bypass in the piping? Perhaps you can take a picture of the near boiler piping and post that here.

Here is some reading from comfort-calc.net.

Bypass_Piping_Explaination
 
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Old 07-30-12, 04:59 PM
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Thanks for the reading. I checked and there is no bypass piping. Was a good article thanks for posting. I just replaced the Flue pipe again (lower section only) and put the post purge on 1 minute. I also will try to keep the boiler 'hot'. With the tankless hot water heater and the summer, the boiler does go down to 70 when not used so this looks like bad news for condensation when the boilermate water tank calls for heat.

Will keep playing with it, but also will look at how to plumb in a bypass fitting.

Thank you
 
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Old 07-30-12, 05:22 PM
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What type of heat emmitters do you have? Rads, baseboard, etc.

Whats the make and model boiler and how many BTU's.

The condensation is from cold return temps to the boiler and the fact that it may take your boiler a long time to heat up.

The pros will be on shortly to offer further advice.
 
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Old 07-30-12, 05:45 PM
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That flue pipe corroded like that in one month? Best to call in a real pro to check it out. In the meantime, I would shut it all down. Dangerous.
 
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Old 07-30-12, 08:05 PM
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The picture was from a flue pipe that was over 6 years old. The direct vent/sideshot is interlocked with the burner so it tripped on safety when the draft got too low and the first initial crack developed. I ended up ripping it open just to see what was the damage and this was the photo I took in my driveway.

4-6 weeks ago I changed out the flue pipe and the 90 degree bend. Today when I was poking around the boiler I noticed a tiny crack in the brand new shiny flue pipe so I just replaced it again. The interlock/safety did not trip, I still had plenty of draft over the fire to keep the diiaphragm on the safety switch pulled in.

Have baseboard and one cast iron radiator in the Kitchen.

First Flue lasted 6 years, this one only 4-6 weeks. The aquastat is set so the boiler cools off to room temp during the summer when no hot water is being made.

Thanks for the help. I put back the post purge on the sideshot/power vent back to 1 minute and will try to keep the boiler hot and take more hot showers and see what happens.

Thank you all for your knowledge.
 
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Old 07-30-12, 08:10 PM
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Boiler is a Vailant 75 W 40 PP
140K BTU
 
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Old 07-30-12, 08:20 PM
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Have baseboard and one cast iron radiator in the Kitchen.
Cast iron base board or copper?

If your flue looks like that what do you think the boilers cast iron sections look like?

 
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Old 07-30-12, 08:24 PM
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Copper Pipe baseboard in all the rooms except 1 cast iron in the kitchen.

This is the new flue that I caught today...and replaced again..

 
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Old 07-30-12, 08:33 PM
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That reminds me... I just replaced a zone valve about 3 months ago. The Motor and endswitch was ok the valve was impossible to turn. So thinking about this more, I think the entire boiler is shot
 
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Old 07-31-12, 04:47 PM
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Rick, you have a 'boilermate' water heater? Technically, that's not a 'tankless' but an 'indirect' water heater. There's a big diff... the boilermate is in fact a 'tank', so it's not tankless.

In general, an indirect water heater will not cause condensation issues in the boiler... unless the cycles are so short that the flue passages don't have time to dry out. The return water from the boilermate to the boiler is going to be above the problem temp almost always. (because the water the coil is immersed in is still pretty warm when the boilermate calls for heat)

Understand that this 'condensation' we are talking about isn't the same thing as the dew on the grass... that the 'dew point' of the flue gases is MUCH higher than that. (say 115-120 for an oil fired system). This condensation occurs when the hot flue gases contact surfaces that are cooler than that. So, as soon as the surfaces get over 115, the condensation stops and any condensate that has accumulated is dried.

That flue pipe you used... what gauge is it? Is it NOT metal ductwork commonly used for A/C systems and forced hot air? If you bought that at HD or Lowes, chances are that is exactly what it is. When you replace it again, use actual FLUE PIPE that you should be able to purchase at a real plumbing and heating supply... or even a local wood stove store.

The 'drip' that you saw inside the boiler could possibly be condensate from the humid summer air that is drawn through the boiler when it's off. If your home is also air conditioned, that means that the water in the baseboards will be cool too... possibly below the dewpoint of the AIR flowing through. As this water in the baseboards is cooled, it will (or can) flow back to the boiler, cooling the cast iron enough to cause the humidity to condense inside of it. Not saying that's what it IS, but what it COULD BE.

My personal opinion... Vaillant's SUCK. I've had nothing but trouble with mine for YEARS... it's a really crappy design. I would certainly not blame you for getting rid of it... take a look at the Burnham MPO boilers.

How often does your boiler get cleaned? I mean REALLY cleaned? are those plates on the top removed and the vertical flue passages brushed out? Does yours still have the combustion chamber inside and intact?

P.S. I thought your screen name looked familiar and I checked your back posts, so I know now that you DO know about those stupid plates on top and have cleaned out the flue passes... but still wonder if yours still has the combustion chamber intact?
 
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Old 07-31-12, 04:57 PM
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By the way, a stuck failed zone valve is not an indicator that the boiler is shot... but I not sure that's the way you meant that...
 
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Old 08-01-12, 06:42 AM
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NJ trooper thank you so much for your info. I appreciate the help. I know it sounds dumb, but I really enjoy learning about the beast that lives in my basement.

Here is when I unzip my fly and all the 'pros' bash DIY guys. NJ trooper you are right on. I sent the photo to my Uncle and he e-mailed me back 'stop buying crap at Home Depot' and go to Universal supply and get real flue pipe.

So I wanted to know more, I got the micrometer and measured the thickness of the walls of the pipe. It converted very close to 30 gauge, so I will round and say it is 30 gauge.

I found there is building codes that define thickness for an oil fired vent to be 26 gauge. And for wood stove is 24 gauge. I went to a local plumbing supply and got flue pipe. Kept the story to myself because the place was loaded with DIY bashers.. and understood you can kill yourself with a boiler, but life is short and the government is going to hell so at least this keeps me off the streets. I measured the thickness and converted it and got roughly 26 gauge. It also has a lot less 'soda can' feeling to it, meaning it does not flex to easily.

The new pipe is all swapped out. So thank you for all your info.

I will look at Burnham MPO. I was not sure about the Vaillant, Every October I take those little clips off and brush out the passageways. As for the combustion chamber, My uncle put in a new 'target wall' looked like a piece of fiberglass? The combustion chamber also looks 'rusty' but not sure how to grade a good combustion chamber VS a bad one. I can take a few photos. It still has some fins. I put a bunch of do dads on it like new air vent, new expansion tank, put all new side shot power vent parts, tiger loop, got rid of the beckett and put a Carlin EZ1 that seemd to run a bit cleaner new tank and one of those spin and grin oil filters along with a gauge so I can see when the filter starts to 'pull' telling me it's getting dirty. I heard from a few folks that the 'Bunny Boiler' AKA Vaillant was not the favorite one out there. What do you think about the weil mclain? seems to be pretty common around here in NJ....

Thanks again for the help for taking the time to teach me more about boilers. I'm having fun.
 
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Old 08-01-12, 03:29 PM
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Is the boiler downfired? If it is you should measure the temp at breech and confirm it hasn't been downfired too far.

If it is in fact condensation due to low return temps you could also look at a suitably sized thermostatic or actuated mixing valve to ensure proper return temps. This would ensure the boiler reaches proper return temps before ever sending heat out to the zones/indirect, the delay wouldn't be noticeable on the user end.
 
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Old 08-02-12, 03:26 PM
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Thanks for adding that Spider! When I was replying to Rick I had intended to mention that myself. I'm pretty sure Uncle must have measured it though...

In line with this ...

Rick, are the 'baffles' still installed inside the boiler flue passages? (those riveted together plates that hang inside before you put the plates back on...)

How have you been sealing the plates after cleaning?
 
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Old 08-18-12, 06:19 AM
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Some more shots.. NJ trooper kept talking about those metal clip things so I decided to clean it out...

I also put a new 26 Gauge flue pipe, set the draft to -.02 and put the air setting on .6 (I still have to borrow the combustion analizer I know I know) It runs a hell of a lot better now with it cleaned out. But thanks guys for all your help!



 
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Old 08-18-12, 06:28 AM
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Shot from the exhaust side.. There was so many nooks and crannies to clean out and some parts I had to put my hand in and sweep out with a little brush..


 
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Old 08-18-12, 07:41 AM
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Those Vaillants I think are the hardest boiler to clean properly. I don't know WTH they were thinking when they designed that.

That shot of the flue pass looks nearly plugged at the start! There really shouldn't be that much black soot buildup in there.

I guess your model is slightly different than mine, those vertical flue passes are a very different shape. Maybe it's newer / older ? Mine is about 28 y.o. In mine, the vertical passes don't have the fins on the inside and instead have these assemblies of 'baffle plates' that actually hang on the inside of the passages. I guess they serve the same purpose of the cast in 'fins' that yours has.

Ahhhh, but me not to worry... soon, very soon, that old beast will be history here. There's a brand new MPO on the way as we speak.
 
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Old 08-18-12, 06:35 PM
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If you guys think a Val is hard to clean, try a pin boiler, such as a W/M, some Burnhams, Slant Fin, etc. sometime. I'd rather clean a Val any day & believe me, I've cleaned my share of boilers.

Rick, I don't like the looks of all that rust around the domestic coil gasket.
 
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Old 08-18-12, 09:26 PM
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There's a brand new MPO on the way as we speak.
I don't believe it. Take pics and document in a post......!!!!


 
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Old 08-19-12, 10:17 AM
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I don't believe it. Take pics and document in a post......!!!!
Not to hijack... but neither do I ! But yeah, I finally pulled the trigger, after how many years?

I will start a new thread, promise.

Ain't gonna be nuthing fancy as far as install goes, just a cut and switch. Nothing to be gained here by any fancy setup.

Back to our regularly scheduled programming:

Grady, thanks for pointing that gasket issue... it does look pretty nasty, don't it?
 
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Old 09-11-12, 03:20 PM
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Hello gang,

I got my hands on a Fieldpiece SOX2 combustion analizer on Ebay for $175. After the cleaning and fuel pump filter (little screen on pump) the Inline oil filter (Spin on looks like a car oil filter) New nozzle, set electrodes.. the numbers came to
Draft -.02
0xygen ~2.5%
excess air ~10%
Net Stack temp 380F

I don't have one of those slide ruler caclculators but I think by looking at a chart I have it's about 80%.

Did I miss anything?

And yes the 'Domestic Coil Gasket' Is their water or exhaust gas behind this gasket? I'm thinking if I take it off It will never seal again and was going to put high temp epoxy where the face meets the boiler.

But this could be an accident ready to happen, so I started looking at other boilers. What is the MPO? My uncle is raving about the 'System 2000', but I noticed the top of my flue is cold to the touch so I think most of the heat is radiated into the basement (good thing).

Thanks Everyone and sorry for the response.. been crazy work
 
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Old 09-11-12, 05:42 PM
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There is water behind the domestic oil gasket.You might be able to find a replacement gasket online or at a plumbing supply house.

Was that draft reading taken "over the fire" or at the smoke pipe? .02 is good for over fire draft; usually you want it a little higher than that at the smoke pipe (.03 -.06).

I'll let the pros comment on the other numbers.
 
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Old 09-11-12, 06:11 PM
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That 2.5% oxygen is definitely suspect. Either the analyzer is out of calibration, the O2 sensor shot or you are running with too little air. Even in commercial/industrial sized boilers we rarely run below 3% oxygen. In a domestic boiler I would not run less than 5% oxygen.
 
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