High CO

STEAM DOCTOR

History: hot water boiler being used to heat bath house. 500 mbtu. Has history of spill switch tripping. There is a duct that is supposedly connected to outside to bring in air. Owner hires someone to add fan to duct in order to increase air. Next day CO alarms start ringing. Spill switch does not trip. Owner hires different plumber who tests flue and finds 1100 ppm. Plumber cleans flue passage ways in between boiler sections. Flue CO goes down to mid 200s. Flue temp is 115. No CO in room. This morning I am there and CO alarm goes off. Ran home and get personal tester and there are 90 ppm in room. Shut boiler down. I am in middle of combustion training. Ideally we should get someone fully qualified to look over system BUT we are in hurricane sandy area and no one is around(in general there are not many qualified and reliable gas combustion people in this area). What is the next step. I can get my hands on combustion testers but I would need some guidance from the folks on the wall. Why would bring in more fresh air result in higher CO levels? Is it possible that the fan is pressurizing the flue and preventing the flue gases from entering the flue? is there too much cold air coming in which is lowering flue temps?

JStar

CO

Where are you located?



My guess is a flue or draft problem.

STEAM DOCTOR

queens

This place is low on funds so they will hesitate if they have to spend big money( I know that doesn't make sense but its the reality). Why would the CO problem start after they put in the fan?

JStar

CO

CO can be caused by too much, or too little air. Ideal combustion is a big diva. It is very particular.

Steve Whitbeck

CO

Any chance this a Slant Fin boiler? Biggest I have seen was 300,000 BTU.

They have a lot of flame impingment on the heat exchanger. This causes high CO readings in the vent pipe.

If the fan is pushing fresh air into the boiler room then somehow vent gasses are getting into the room.

Any chance the air intake is down wind of the chimney?

Steve Whitbeck

CO

Any chance this a Slant Fin boiler? Biggest I have seen was 300,000 BTU.

They have a lot of flame impingment on the heat exchanger. This causes high CO readings in the vent pipe.

If the fan is pushing fresh air into the boiler room then somehow vent gasses are getting into the room.

Any chance the air intake is down wind of the chimney?

Steve Whitbeck

CO

Any chance this a Slant Fin boiler? Biggest I have seen was 300,000 BTU.

They have a lot of flame impingment on the heat exchanger. This causes high CO readings in the vent pipe.

If the fan is pushing fresh air into the boiler room then somehow vent gasses are getting into the room.

Any chance the air intake is down wind of the chimney?

STEAM DOCTOR

WM 500000 atmospheric hot water boiler

I dont know much more then that. I hope to go tomorrow or next day to do some detective work. Is there a way positively determine if there is too much air coming in?

KCA_2

It may be a matter

of cleaning the boilers heat exchanger...  Often when I see high CO ppm numbers it's because of a dirty exchanger..



  :-)  Ken

STEAM DOCTOR

cleaned

The heat exchangers were throuly cleaned at with point flue co went from 1100 to 250. Boiler was runnning for few days before co alarm went off

JStar

CO

The biggest statement here is that somebody added the fan, and the CO went up. Turn the fan off, or get a refund.

ColoradoDave

Cleaning may not be clean enough

Early this summer, I was on a call to a 4 year old Buderus GC boiler (cast iron).

I was brought in to clean the boiler.  The original installer cleaned it 2 years ago (again ONLY a 4 year old boiler) and got soot all over the place.  So we were brought in to clean it this year.  I pulled a ton of soot out of the boiler and had extremely high CO readings in the flue.

Ended up having to pull the boiler out to the back yard and power wash the heat exchanger.

That being said.... reinspect the heat exchanger.  If it's sooted up or built up condescent again... you may need to inspect the flue and combustion air setups again.  Perhaps an induction fan would be appropriate instead of a combustion air fan.

STEAM DOCTOR

vent cap

Went today to check out. Turns out that besides for the fan they always changed the vent cap. I had them disconnect the fan before I came. I did a basic smoke test. The smoke did a U turn when it came close to the vent. When I held the smoke next to the sheet metal part of the draft hood the smoke slowly moved upwards until it hit the metal then it lazily dissipated. When moved back towards the vent itself the smoke made its U turn again.I held a paper towel in the vent hole and it noticeably blew away from the hole. I took off the vent cap and the same thing happened. I was not able to put the previous vent cap on because it was bent out of shape. Is it possible that bifferant vent caps would result in backdraft? In the meanwhile the new vent cap is on and the boiler is off untill the "pro" comes back to fix his mess.

JStar

Vent

I'm having a hard time visualizing what you just described. Can you make a diagram?

STEAM DOCTOR

diagram

Sorry but diagrams on computers are beyond the scope of my technical expertise. I would have to wait until my kids get home from school. Try this. Make some smoke(match, light some cardboard whatever). The smoke will rise. Put your hand in the smoke. The smoke will spread across your hand. Now make smoke again and this time blow on the smoke. The smoke will obviously be blown away from your mouth. This what is happening in my situation. When I put the smoke in the hole where the combustion gas is supposed to exit the smoke is visibly blown away. The smoke actually makes a U turn away from the hole. When I hold the smoke against my hand the smoke will move up into my hand.

Patchogue Phil_2

down draft from flue?

So you are experiencing a downdraft at the flue when you should be getting an updraft,  right?



Is it very windy there?

STEAM DOCTOR

Exactly

There is some wind but not more then any of the other buildings in the area. The vent cap was changed but not sure why that would make difference.

Patchogue Phil_2

Something is sucking or blowing air

Either the configuration of the roof and flue (w/o the cap) is causing wind driven air DOWN the flue,  or something from inside is sucking air FROM the boiler room and that flue is the least resistance.



What else is capable of pulling air down the flue?   Exhaust fans from connected rooms/buildings?    Water heater with power vent?



Look around.  If you open a door to outside or a window,  does the down draft go away at the flue?

STEAM DOCTOR

update

I finally had time to go take another look. Did the smoke test again and there was a very obvious back draft. I shut off all the ventilation fans and HVAC units and there still is the same back draft. I went up to the roof and put a flame near top of chimney and the flame was clearly being sucked into the chimney. There was almost no wind outside. When I did the smoke test in the boiler room away from the flue the smoke acted normally. Something is obviously causing suction down the flue but I cant figure out what it was. Any ideas would be greatly appreciated.

ChrisJ

vents

I really don't have any experience with this being a homeowner and not a pro.  But the two things that came to mind is a radon vent system or some of these semi rip off dehumidifier systems like the wave system and humidex system.  The wave and humidex are just a large fan that constantly pulls air from the basement.

STEAM DOCTOR

shut

Every single appliance with a fan was shut. I even shut the circulator thinking that maybe that was creating suction

ChrisJ

chimney

Can you kill the main just to be 100% sure?



Also going by memory I recall the chimney should be something like 2 feet above the highest part of the roof. Is that the case?

RJ_4

flue size

check your flue size per boiler specs,  also as Phil said look for negative press in and around boiler rm.  look for bathrm or kitchen exhaust fans. they may be on intermittenly.

STEAM DOCTOR

co

I think that I had everything shut. I will go back when I have achance and kill the main just to sure. Lets say for arguments sake that one of the exaust fans or hvac units or whatever is creating negative draft in the building. How long should it take for the draft to stabilize after everything has been shut?

STEAM DOCTOR

flue size

I am getting backdraft even with the boiler shut. Incorrect flue size shouldnt create back draft with boiler shut down

STEAM DOCTOR

uei eagle 2x

Just got my first combustion analyzer. Still learning my way around the machine. For now I am able to do basic combustion analysis of flue gases et. Can the uei eagle be used to measure room positive or negative pressure?

RJ_4

neg press

Do you have a sealed boiler rm ?  check at the boiler rm door do you feel air being pulled from rm, if so get door to seal, also check this fan that was installed for fresh air, make sure fan rotation is right, make sure this fan and fresh air inlets were sized per code.   There is a company called Selkirk that can provide flue and combustion air tables. after shutting all external air moving equip.should only be a minute or so.

SWEI

Eagle 2X

Has a differential manometer which will easily read room pressure.  Put one probe outside the room and one inside and read the difference.

STEAM DOCTOR

thanks

Havnt had chance to go back yet. Does it make sense to test the draft directly in the flue? The boiler has been off for a few weeks.What numbers should I be getting? Also does it make sense to test the pressure differential of the flue from the roof? If yes what sort of numbers should I get? Thanks