Update: Troubleshooting exhaust problem with boiler

vals

Hi: I have a 7-year-old Bryant hot-water boiler, which I inherited when I bought a house six months ago. We turned on this boiler for the first time six weeks ago, and it seemed to run fine except the basement was getting steamier and I noticed myself feeling ill (headachey) after trips into the basement. I had no carbon monoxide detector. Ten days ago the pilot light went out and there was a strong smell of natural gas, so we shut off the gas to the boiler and called in a technician. He cleaned the heat exchangers and replaced the valve that controls the natural gas flow, which fixed that problem, and restarted the boiler. Four days later steam was building up again and then the pilot went out. Before I relit it, I plugged in a carbon monoxide detector. The unit had been off for several hours by then, and the CO alarm didn't go off. Because it wasn't too cold that day, I didn't get around to relighting the pilot for several more hours. After I relit it, I noticed steam coming down from the top of the unit, flowing into the room, and the CO alarm went off within 15 minutes. I turned everything off and called the repair guy back. He came two days later, relit it, set the damper to be permanently open (in case the damper motor was malfunctioning), and it was running fine (we both noticed that it was leaking steam for the first two or three minutes, and then the problem spontaneously resolved). Now, three days later, the CO alarm was going off again this morning (within 15 minutes of the boiler turning on) and steam was flowing into the room. The repair guy said the next step would be to get a chimney person to examine for blockages. But if there was a blockage, wouldn't the problem be constant, not intermittent? If anyone has any ideas, I'd really appreciate them.

DZoro

Turn off the boiler. Get a new HVAC company to look at it immediately. Check chimney, and properly inspect and test the boiler. Don't wait....

newagedawn

its probably plugged, take the flue off and take top off and look, then it needs to be brushed,vacuumed and filter,strainer,nozzle, then do combustion test, some think a new boiler doesnt need to be cleaned, but IT DOES every yr weather you think it needs it or not

Lance

Did you ever look at the chimney after warm up for white vapor when running? If you see it you will have a breech in the heat exchanger.

Lance

To further explain the condition you see. When steam leaks into the burner area it affects the flame, hence the CO. It displaces some of the volume and pushes both up the flue and out the burner area into the home. the pilot goes out because there is a lack of oxygen to support the flame. Had this not happened the safety would not have shut the unit down and it could have been fatal. Some units can leak out the burner area and not extinguish a pilot. The CO detector was the best thing to do. A clogged chimney would not extinguish a pilot unless the boiler room oxygen level got low enough. You also can have a good chimney and a good boiler and still have this problem if you have a downdraft of the chimney due to negative air pressure.
You also could have a combination of issues due to damage caused by a steam leak. Boilers leaks come and go with temperature changes but the never go away. They just get worse. Soot accumulation is a definite sign of a possible interruption of the flame, or clogging of the burner slots due to corrosion and soot.

EBEBRATT-Ed

@newagedawn this is gas fired. @Lance it's not steam it's a hot water boiler.

@vals @Dennis gave you the only advise you should listen to. I very strongly recommend you do not run this unit. Contact a different repair company. Check "find a contractor" on this site.

Sorry to say your repair company is completely incompetent. This has the potential to be a very unsafe. use caution

Bob Harper

A UL listed CO alarm can get you killed. They are designed to alert only once you've met the medical definition of CO poisoning. It is not a professional calibrated CO analyzer, which is what a pro would use. Shut it down and get a pro in there.

vals

Thank you for your comments. We are not running the unit. We had a chimney person here whose theory is that extending the vent pipe further above the roofline (it's currently at the roofline) will eliminate downdrafts that happen on windy days. I'm left wondering whether that is a sufficient fix or there is a problem with the boiler itself. My next step is to find a different HVAC contractor to consult.

Jamie Hall

Extending the vent pipe will help, but not necessarily cure, the situation. A rule of thumb I remember from somewhere is that the top of the vent pipe should be at least three feet above anything within ten feet horizontally from the top...

vals

Update: Consulted a boiler technician with 40 years of experience. At first he concurred with the chimney guy that we needed to extend the vent pipe 2 to 3 feet to improve draft. Then he talked to an engineer who said that the height of our pipe is fine (it goes up 50 feet along the outside of the building and there are no buildings in the way once it reaches the roof, only the neighbor's exhaust vent a foot away). Now the theory is that it's a problem with cold flue gases in the pipe and the proposed fixes are to replace the B vent outside with triple-wall pipe (very pricey) or to install a fan to induce draft (also expensive but less than half the cost of the first proposed fix). The risk of keeping the B vent is condensation damage down the line, as I understand it; the current pipe is 7 years old and we do see one small rust spot around a screw near the top of the pipe, but otherwise no evidence of damage yet (at least on the outside of it). We have been using the boiler mostly without incident during daylight hours, but once the sun sets the downdraft tends to happen, and when it does we have to shut the boiler down for the night to avoid carbon monoxide poisoning. Do any of you have a thought about which of our options would be a better solution over the long term?

Steamhead

Doesn't explain the steam. Where are you located? Have you tried the Find a Contractor page of this site?

DZoro

could you take a big picture of the boiler with piping to the chimney. Certainly would help us

DZoro

Is the chimney inside the home or on the outside? How big is your house, and what size is the boiler? Is there any make up air in the boiler room? How large is the boiler room? Did your tech run any combustion numbers and did he leave them with you?
Something is seriously wrong, and really need more info on your system

vals

We are located in Philadelphia. We called in a very experienced and licensed contractor, though not one from this site. The steam is coming down from the front of the unit, apparently carried by the downdraft. Unfortunately when the contractor was present, the problem didn't happen. He didn't run combustion numbers. The house is 1300 sf, and the boiler is 105K BTUs. (Is that what you mean by size?) The boiler is in a basement without much ventilation. Previous owners had screwed plexiglass panels over the windows. We removed the screws on one window yesterday (others were impossible to loosen) and opened a window to let in more air for combustion. Boiler ran fine during the day yesterday and today, until about 5:30 p.m. and when it came on again (after cycling off for about an hour) it was not drafting properly. Some steam was coming down from the flue vent. I've attached photos. Let me know if you need better ones of the vent connection. The chimney pipe exits the building at the basement wall and runs up three stories on the exterior of the building to the roof.

DZoro

Is the outside chimney insulated? 3 stories is a long way without a insulated chimney. You have a draft damper on top of the boiler you could try and lock it in the open position. It is not economical, but it maybe safer and help let some of the boiler heat into the chimney and keep it warm during the off cycles. Should be a switch on it to lock it open. There looks to be a tee in the chimney pipe, is there a draft damper in there? When you have a steam situation does the steam come out of that? I could be wrong, but on that boiler I don't believe that is necessary, the draft should come from the front of the boiler. By having all the draft come from the front will increase the stack temp. Maybe someone else can chime in on this, but I believe that could be locked closed.

vals

Thanks for your comments. The outside chimney, as far as I know, is double-wall B vent; I don't believe there's any insulation beyond that. We have already tried to lock the draft damper open, and alas it made no difference for the week that we tried it. The damper motor seems to be operating normally. Steam is not coming out of the tee, and I don't think there's a damper in there (unable to check right at the moment).

unclejohn

I saw the damper as well. It also appears to be a second flue connected to the flue after the damper. Around here a 6" flue is maxed at 9' you seem close to that.

DZoro

Is that smaller pipe also connected to the same chimney? Water heater? Venter assist is probably going to be needed. That could possibly be able to go out the sidewall and not up the 3 stories of b vent. The two shouldn't be in the same b vent, at least in this situation Have to make sure it meets code in your area. Still make sure the boiler heat exchanger has been inspected, covers removed, visualized, cleaned, and combustion readings confirmed safe.

vals

The smaller pipe is for the water heater, and yes, it's connected to the same chimney. I will confirm with the technician that he did a thorough inspection and ask him to take readings. Thanks.