Condensation Issues in Chimney with New Boiler

pecmsg

MikeC555 said:

So I had a chimney liner installed in my 8 x 12 tile-lined chimney about 2 weeks ago. I'm still seeing a little water seepage through the wall but not nearly as much. WHen it was being installed, I failed to notice that there was not a cap installed on the T (below where the boiler exhaust T-s in. It would seem this should be capped or there nothing to prevent exhaust from condesing in the hollow area below the T. Or if drafting properly, is this not a worry? Here is a photo looking up from clean out door (which is about 2 feet below the T.

Is that vent pipe run all the way to the top?

Is there a rain cap on the chimney?

How clean is that cleanout in the boiler room?

MikeC555

So I had a chimney liner installed about 3 weeks ago. I'm still getting a small amount of water seeping through the wall but maybe this will take some time to dry out completely. One thing I didn't notice when they were installing it is there is no cap on the bottom of the T (where the boiler exhaust Ts in). It seems to me this is normally capped if the point is to prevent condensation from forming in the cool (hollow) masonry area below the T. How would this normally be capped? I would think it should have been attached to the T-section before lowering it into chimney?

MikeC555

Yes, liner goes all the way to top of chimney (around 14') and there is a chimney cap. The clean out is clean (no obstruction) and I was able to stick my arm in there with camera to take the photo looking up the chimney. Before adding the liner, on real cold days, water was also dripping from the clean out door but not now; just seepage from the area 2' below clean out door. I'm hoping it's just taking a while to dry out. I didn't have a cap on chimney prior to adding the liner and never had a water leakage but then, the stack temperature of the old boiler was 300 deg higher than the new one. There could be debris in there holding moisture. I'll see if I can get a shot looking down from cleanout.

MikeC555

I tried to get a shot looking down but the debris level is so close to the cleanout, all I get is a close up. It looks like flue tile debris and I don't know what esle (48 years worth of shyte). I took the photo just after the burner has shut down and got a few drops of water on the camera, so I defintitly still getting some condensation. I guess I could stick the shop vac hose in there and try to remove the debris. Maybe the water could then dry out faster...

Waher

The bottom of that liner doesn't look like it's properly installed at the tee unless the darkness of the image is throwing my brain off. The underside of it should extend down to the bottom of a cleanout with second tee that's capped off to seal it except when it's being cleaned. The cleanout door should be a secondary seal.

MikeC555

Thanks Bob, It is a flex liner and does have a top support and rain cap. I was hoping I could do without insulation but may have to entertain that. The liner doesn't extend down to the clean out, so getting a cap on it would require pulling the liner back out, I think. There is a combustion analysis port a few inches below the damper and I measured -.01" after it had run for a couple minutes. A bit low for breech. I removed the upper two baffles tonight, made a small shutter adjustment and getting 265 stack T, CO 45 ppm, O2 7.9%, CO2 9.7%, excess air 56.3%, smoke 1. It's been in the 30's all day and it seems to me the system is short cycling, so that isn't helping.

MikeC555

I was suprised that I couldn't get the stack temp any higher. The nozzle is a 0.65 60 A, just as factroy set it. The baffles are removed in pairs and there are 3 sets of them. I removed the topmost set as per the manual. The only thing I changed after removing the baffles was to close up the shutter a bit (excess air was 75%). Before I did anything I had 225 stack T so the rise of 40 was correct per the manual but I agree, still too low. And, with snow/rain today, I still have condesation dripping out of the wall..

DJD775

MikeAmann said:

The pros can tell you better, but 265 stack T is too low, and you shouldn't have any smoke with 56.3% excess air. This looks underfired to me, especially with 2 baffles removed. What nozzle are you using?

@MikeAmann I've read George Lanthier's Advanced Residential Oilburners front to back several times. There's a chart in there that shows smoke can be produced at high levels of excess air. I tried to find the chart online to no avail.

@MikeC555 Have you verified the pump pressure is correct?

MikeC555

I have not verified pump pressure. The boiler is less than a year old, not that that guarantees pump couldn't be a problem. I will check it but am going to call the installer tomorrow and have them take a look. I should have, but didn't get, the original numbers right after install. I do know that my CO will go above 50 ppm if I close the shutter any further.

DJD775

Good idea to get a pro in to check it out.

MikeC555

I did have the chimney liner guy come over for a look today. It appeared that in the snow storm from 2 days ago, the chimney cap had partially come off the tile (I'm not going up there with snow on the roof). I showed him the water on the floor, which has been worse with the snow melting, and his co-worker up on the ladder said the collar had shifted as well, exposing some of the original flue opening. So I guess it's possible that some of this water could have been melt water or water from the offset chimney cap dripping down into the flue. He went up there with some silicone sealer and re-bolted it to the tile, so we'll see. I aslo asked about the uncapped T and he said they always leave them uncapped for oil burners but cap the gas burner Ts. He didn'thave a good technical explanation for this... I did talk to the installer and he thought we might need to upfire it a bit to get the stack T up. He'll come over later next week...

Bob Harper

You need a new chimney guy.

Mad Dog_2

Mark Hunt always says..."Fix it NOW!! Its cheaper than a funeral!!"  Ask Vitas Geralitus (Tennis Ace).  Why would you even hesitate?   These are Life Safety Issues...ain't worth chancing it.  Yes, the only common flues I have seen are in 250 yr old Brick Farmhouses, in Stillwater New York (Site of the pivotal Battle for Saratoga in War for Independence).  Huge, open-Hearth 🔥 fireplaces that yiu could literally roast a full size hog 🐗 in.  They even had the built in Wrought Iron swing out arms to hand the slabs of meat 🍖 and cauldrons.   Boilers and water heaters added later vented fine but you  had to get up in there once a year to eyeball it and brush it out...think Charles Dickens Chimney Sweep boys.  When you can feasibly fit it in I ALWAYS want to see  an insulated liner with a drain tee at the bottom atkeast piped out on to the floor so you could monitor it.  On problem, suspect  installations Well pipe it out to a pit or floor drain.   Mad Dog

MikeC555

Yea, I'm not too impressed with the chimney guy. I asked about the lack of a cap on the T and he said they only cap them for gas boilers, but need to leave them open for oil. He couldn't articulate a good technical reason for this. After i have the boiler installer visit to check the settings and maybe bump up the stack temp to 300 or so, I'll see how things behave. I did knock a small hole in the wall where the water was seeping out and a about a quart of water pissed out. It appeared this lower opening was bricked up at some point and covered with cement (it was not hollow). I'm going to keep any eye on it for a while and see if it drys up completely. There is still a small amount of seepage but it may take a while to fully dry out (once condesation is stopped).

hot_rod

The rain makes it drip? How long does the boiler run when it fires. Ideally a 10 minute or longer run to warm everything up.

MikeC555

I don't think I've ever seen it run for more than 5 minutes at a time. I'm really not sure if rain has anything to do with it now that the cap and collar are back as they should be. The wet spot on the wall is almost gone now, so I think the hole in the wall did help to allow it to dry out faster. Since I rasied the stack temp (baffles removed), I haven't seen any evidence of water when looking in clean out. I'm still waiting for my installer to come take a look at the settings.
One test I did that had me wondering; with no other heat on in the house, I turned on the basement zone (usually off) and set it for 65 degrees (T-stat read 61). A minute or so later, the circulator starts and maybe a minute more, the boiler fires. It ran for maybe 5 mins, probably less. The temp in the heated part showed 2 degrees rise. At bit later, the boiler fires again. After 4 firings, the room finally reached 65. I do understand the boiler is set to shut down once its water temperature reaches the set point (looks like 190) and then the circulator keeps pushing the hot water to open zone valve. Maybe this isn't unusual if you're only operating one zone. The boiler just gets back up to temperature pretty quickly. Does that mean it could be over-fired? I guess I should do the test with 3 or all 4 zones calling for heat.

MikeC555

Went up on the roof today to check on this and I did notice water droplets on the liner at the exit while it was firing, so some condesation is still happening. But still no evidence of water at the clean out so maybe not enough water to drip down.

Bob Harper

Condensation at the flue gas outlet is common with higher efficiencies. You're not seeing it below because it is getting re-vaporized as it falls down by gravity. That's considered "near condensing". What you're seeing is more common with taller stacks, especially on exterior chimneys in colder climates or with unshielded, uninsulated chimneys. Did you ever install a post-purge cycle on it? You might want to look at your thermostat & aquastat settings with the long wet times and short firing cycles. Circulator speed and delta T are another aspect to consider. Aside from that, your boiler may be oversized.