Problem on \"CO again\" post

Unknown

that "CO Again" post has gotten so big my problem got lost. Check it out near the bottom of the post. Let us see what you come up with. The job is shut off right now so hurry up it is getting cold.

scrook_2

to the top...

Tim asks:

Utica Boiler with a built in diverter, input is correct, it is vented into a 10" x 12" chimney which is adequate size and is about 30' high exiting the roof line with proper clearances no abuting structures. Two water heaters into same chimney no problem with water heaters (very low CO at 15 PPM On each). The vent comes directly off the top of the boiler into a 90 degree elbow and on a straight line into the chimney about 12" above the clean out. The horizontal run is about 3 feet to the chimney.

The flame is nice and blue, the boiler was taken apart and cleaned (it really was not dirty) no soot.

The boiler is in a basement 50' x 60' with no partitions and plenty of air. There are actually two chimneys in this complex. There is another identical Utica Boiler in the other chimney with a water heater and it has CO at 24 PPM and is running fine.

It is making over 2,000 ppm CO, I pulled the probe out so as to not contaminate my sensor. The gas company and one plumbing contractor looked at this boiler and said it needed cleaned. They both left it running. The pilot by the way keeps going out and the thermocouple is okay as is the gas valve.

Let us have some fun here and see what you all think should be done.

I would ask Jim Davis to hold off for a while and see what the guys come up with.

Do not be afraid to ask questions and I will give you more data based on your questions.

Jim Davis

Will sit and watch

You didn't happen to get a O2 & temperature reading on both boilers?

Unknown

Yes I did

but lets hold and see if anyone asks for any info.

pperkins

what model utica?

AGB OR MGB?I reinsulated several of the agb boilers and replaced lots of there burners.If i get high co reads,i check gas press,clean pilot and burners.Also if there's lots of that white powder, ill brush out sections.One time there was a mouse making a nest inside of a mgb burner,sooted up boiler...CRAZY WHAT YOU FIND SOMETIMES!!

GEO_3

Take a close look at the flue liner. Make sure your not looking at the outside of it. I've run into a couple of installs. one was in 7yrs the other 10 the flue liner was never punched out . The flue gases were leaching up through every nook and cranny in the chimney. Fortunatly no oue was hurt.

Bruce_6

my questions


I assume you did a combustion analyis......

tell us the results....undiluted CO, flue temp, CO2, excess air, etc.

with the room being 50 x 60, and assume 8' tall, you get 24000 cubic feet. seems large enough, but we don't know anything about the equipmet......what are the BTU ratings of ALL the appliances?

also one question, I was always told that you should at least have 12 inches before going horizontal with your flue. does it have a barometric damper, and where is it located?

Aidan

Draught suction?

Did you measure the suction draught/pressure at the boiler flue? Could it be a natural draught boiler sharing a flue with a pressurized/fanned flue water heater(s)? How do the CO figures look with 0/one/other one/2 water heaters firing?The flue suction must change when the water heaters are firing.

Otherwise I'd suspect a blocked flue.
And/Or inadequate make-up air with 0/1/2 water heaters firing (this post keeps changing because I'm still thinking about it; my answer is under development ;-) ). Or an extract fan somewhere, creating a negative pressure in the boiler room (still thinking).

P.S. You might be interested to look at
http://www.geocities.com/thegasplace/

This is about getting certified to get membership of the UK CORGI (Council for Registered Gas Installers). It's illegal to work on a gas appliance unless you're competent & competent is defined as being CORGI registered. Every gas appliance gets combustion tested when it's serviced or installed.

The pass mark for the ACS (Apporved Certification Scheme, first step to CORGI registration) exams is 100%. It's all about safety so there's no aspect in which you can be less than 100%.

Dale

If draft is ok

Is one of the orifices in slightly crooked? A bit off and not enough primary is pulled in.

peter desens

Factory help

Tim,

I'd like to discuss this with you if you could call me at my office, 1-800-325-5479, ext. 4128.

There are a numvber of possibilities, many of them discused in this thread, but to expedite more quickly, I think a phone call is prudent.

Peter Desens
Technical Service MAnager

peter desens

Factory help

Tim,

I'd like to discuss this with you if you could call me at my office, 1-800-325-5479, ext. 4128.

There are a number of possibilities, many of them discussed in this thread, but to expedite more quickly, I think a phone call is prudent.

Peter Desens
Technical Service MAnager

Unknown

Hey guys I am back,

sorry I could not post answers to your questions last night but it has been hectic aound here with emegencies.

Here goes:

Utica AGB-100
Serial 1078

Peter Desens from Utica tells me this boiler is about 20 years old.

Gas pressure is 3.4" W.C. and is set to exactly 100,000 BTU's

It has been cleaned and we cleaned it again today. I had a chance to see it for the first time this afternoon and get all the readings they have taken.

Origianl readings:

CO2 10.9 %

O2 2%

Draft -.02

Excess Air 12%

Stack Temp 750 Degrees net

CO over 2,000 ppm

Today we removed the existing flue pipe and installed a 3 foot rise directly off the boiler and into a new opening in the chimney. We cleaned the boiler again and checked for any possible inmpingement areas. Pulled all the burners and cleaned them.

New readings:

CO2 10.5%

O2 2.6%

Stack Temp 550 degrees net

Excess air 16%

482 PPM air free CO

Draft -.025

We still have to get the CO down below 100 for my satisfaction.

Any suggestions feel free to jump in Jim Davis with any help. I sort of have an idea what you are going to say. Just curious to see if we are on the same page.

Steamhead

Excess air looks low

and how is the draft in the chimney itself? It looks like when the draft increased slightly, the CO went down (but it still exceeds the standard for boilers). Do the readings change when the water heaters are running?

This is starting to look like a chimney problem to me.

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Bruce_6

shouldn't

shouldn't the excess air be around 21%

maybe installing a chimney liner will do the trick?

Unknown

This is a clay tile liner

and you are right the excess air is low.

I am going back tomorrow for some further work on this to try to get CO down to an acceptable level.

pperkins

burners

Bring a set of burners with you.......ill bet thats the problem................some of these guys are getting too deep....its only a gas boiler not a rocket ship......:}

[Deleted User]

i'm still curious what happens

to the readings if you block off the draft diverter and force the unit to pull air thru the fire box..thats a test i do with an analyzer going to see if a barometric damper would work better than the draft diverter.

rudy_2

Like Gerry says, try temporarily blocking off the draft hood and see what happens, I used to carry around a heavy duty sheet of aluminum foil just for that purpose. It's amazing how many times I've seen the O2 reading come right up to the 7 - 9% range and the CO drops to almost nothing.

Then get in touch with Field Controls and ask for a copy of the AGA Report - FT-C-07-93. They did double acting baro retrofits on 50 pieces of equipment that the draft hood was failing on - fixed all 50.

Pretty strong argument for this working.

My understanding from Field is that this could have been 'approved' as a retrofit if Field could have come up with a couple million bucks to pay for the approval..... which they couldn't....

Years ago Jim sent me a copy of sections of the Gas Engineering Handbook that is eched in my mind, said "The draft hood represents a compromize of the many design criteria".

The section on barometric regulators said 'Barometrics provide excellent, constant, static pressure regulation"

Certainly you have to check out the basics, but if everything else checks out, it is certainly simple enough to be worth taking a look at.....

Here's a pic of one of the many we did here in town (including the city hall building).

Unknown

Gerry, I am going

to do that tomorrow. I have had the local gas company looking over my shoulder on this and giving me an arguement about anything I want to do. They have red tagged this and want the boiler replaced.

Unknown

Based on my limited

experience I think the burners are fine. I have taken them out and gone over each one individually. The flame pattern on each burner is fine.

Unknown

I hear you Rudy and Gerry

When I mentioned this to the gas company who is involved with the red tagging of this job they flipped out on me. I have referred them to that Field report (I have a copy). They will not allow any modification to any vent or draft hood with out manufacturers written approval and it has to be done by a factory rep. I have not gone that route yet as I am waiting for some chimney repairs to be done before I move on. I will be alone at the job tomorrow (no gas company looking over my shoulder) and I have a few things I want to try. By the way I am involved with this job at the landlords request.

The draft hood is a compromise of design criteria because it does not need adjustment and most of the time gets you into the ball park. It has always amazed me that oil boilers and furnaces have to be field tuned and adjusted, hence a baromteric control, but not gas.

We had freedom on many industrial and commercial jobs to use baromterics and certainly on conversion burners.

This would have been a great job to hold a class with Jim. I posted this job to get some input and discussion on this issue with a real world situation.

Unknown

What do you think about

a draft inducer or power venter on this boiler????? Lets hear the pros and cons.

Unknown

Mr Smith,

there is plenty of air for combustion.

This boiler is 100,000 BTU's and is flued into a chimney with two water heaters 35,000 BTU and 40,000 BTU both operating fine. On the floor above is a 50,000 btu ceiling heater into the same chimney working fine.

In a seperate chimney in another area is a 75,000 BTU boiler and a 40,000 BTU water heater.

You are right about the vertical rise in fact I had it corrected today to a 3 foot rise and then into the chimney. Anything over 3 feet is actually considered "self venting".

Unknown

Dale

I pulled all the orifices today and cleaned them all out they are aligned fine and the burners are burning fine.

Unknown

George we had

a chance to check the flue liner today when we replaced the flue pipe and it is fine.

Unknown

Aid UK I wish we had

such a certification here in USA but we do not. I guess I have some kind of certification as I have been working on gas for over 40 years and I do have the required liscensing for my state.

The things you mentioned have all been done with limited success. There is some slight change (for the better)when all of the equipment is running. The draft increases slightly and the CO goes down a little then right back up.

Mark Eatherton1

In my experience with power venters...

they're WAY over kill. Of course very few of the people installing them even take to time to read the instructions and adjust them to field conditons, hence MEGA over kill.

I concur with Rudy. I'd try partially blocking the relief vent of the diverter to exert more draft through the fire box and see what happens. Based on the O2 reading, the fire is obviously doing a good job. Maybe too good. You could be on the bleeding edge of the combustion curve. Maybe a little less fire??? Are the burner primarys properly adjusted, or even adjustable?

ME

Glenn Harrison_2

Tim,

I was just looking at my Jim Davis Combustion sheets for a natural draft boiler, and I would say you need to go back and take a combusiton test for several minutes on this boiler. To confirm a venting problem watch for a continuous rise in CO and continuous drop in O2. Otherwise, going by flue temp, your O.K. but close to to high, draft in chimney is OK. I'll also bet that blocking off that hood and getting more draft in the boiler will clear this up. I'll be very interested in hearing the final answer, as I remember having a couple of Utica boilers a few years ago that we wound up underfiring to clean up the CO. This was of course before I got my Testo and attended Rudy's and Jim's classes.

rudy_2

You

> they're WAY over kill. Of course very few of the

> people installing them even take to time to read

> the instructions and adjust them to field

> conditons, hence MEGA over kill.

>

> I concur

> with Rudy. I'd try partially blocking the relief

> vent of the diverter to exert more draft through

> the fire box and see what happens. Based on the

> O2 reading, the fire is obviously doing a good

> job. Maybe too good. You could be on the bleeding

> edge of the combustion curve. Maybe a little less

> fire??? Are the burner primarys properly

> adjusted, or even adjustable?

>

> ME

>

> ME

>

> ME

rudy_2

The beauty of barometrics

The beauty of baro's is that they are soooo simple, and we all have learned (over and over again) "Simple is best".

Geeze, one moving part and it's not even digital!!

Unknown

You are right Glenn

I have observed that and confirmed it twice with retesting. I am fighting against local rules and regs on this one. There is some work going to be done on the chimney as soon as we can get some warmer temps here and rig some scaffolding on the roof. The chimney needs to be extended a little higher to eliminate restrictions as to being too close to roof line.

In the meantime I have to get CO down so we can leave the heat on for these people.

Underfiring was suggested by someone else but I am not a fan of doing that, I feel like that is giving up. I have had these before I will get it below 25 PPM before I am done.

Glenn Harrison_2

You're right,Tim

> I have observed that and confirmed it twice with

> retesting. I am fighting against local rules and

> regs on this one. There is some work going to be

> done on the chimney as soon as we can get some

> warmer temps here and rig some scaffolding on the

> roof. The chimney needs to be extended a little

> higher to eliminate restrictions as to being too

> close to roof line.

>

> In the meantime I have to

> get CO down so we can leave the heat on for these

> people.

>

> Underfiring was suggested by someone

> else but I am not a fan of doing that, I feel

> like that is giving up. I have had these before I

> will get it below 25 PPM before I am done.

Glenn Harrison_2

You're right,Tim

Now that I know better, lowering the gas pressure/derating is like giving up, but back them it was all I new to do to make these units safe. But if you have to lower it to get the heat on, so be it, especially since I heard the midwest cold snap is coming your way. Good luck with your battle.

Steve Ebels

Timmie

The O2 looks low and the CO2 looks high for a gas fired atmospheric. I think the key is in your draft and you're barking up the right tree with the draft hood/barometric idea. I had one that acted the same way a couple years ago. The only thing I could figure was that at a normal draft reading (.02 wc") there was less restriction through the hood than there was through the boiler sections. Consequently, the majority of the air going up the chimney was being provided through the hood at the expense of draft through the boiler. I found this out by playing with the Magnahelic over top of the fire, where it registered a positive pressure consistently. (yes, positive pressure on an atmospheric burner) I think the airflow through the hood actually cut off the airflow through the boiler as it was a stronger current. As it was just me, myself and I in the basement we decided to close off the draft hood and install a barometric. CO dropped, flue temp dropped, efficiency came up a point and a half.

Warning to DIY'ers reading this post. DO NOT JUST ARBITRARILY DO THIS TO YOUR APPLIANCE. You must have the proper equipment to determine if what you did was correct or if it caused more problems.

Aidan

OK then

I give up. I'll watch for the solution with interest (I'm not a CORGI registered technician).

The UK gas site was mentioned for comparison with your own certification. It's strange that we have no licensed plumbers and you don't seem to require licensed gas technicians. Any fool can set up shop as a plumber here, and they often do. I can't recall anyone dying as a result of a defective drain installation. There's similar certification requirements for oil & solid fuel technicians.

Jim Davis

Didn't need my help-but

The first thing that was eliminated from the initial post as being a problem was combustion air. Combustion air affects all appliances in an area not just one. After getting a draft reading it confirms that air is available because you can suck air from a room that doesn't have any.
Venting problems are selective!
Normal draft for all drafthood appliances is -.02"W.C. therefore -.025"W.C. exceeds this design criteria and that is where the problem begins. In the ASHRAE it states that a drafthood will work safe when 40%-50% dilution air is drawn in. By measuring the temperature above and below the drafthood one can see if too much is being brought in, which I am sure is the case here. Glenn was the first to mention that you must watch the combustion readings-Oxygen & CO to see if they keep changing. The only two conditions that can cause this are combustion air or venting on this type of equipment. Combustion air was eliminated by the draft reading and the other equipment.
DRAFT INDUCERS ARE DANGEROUS ABOVE DRAFTHOODS 100% of the time, DON'T DO IT!!!!
Only one manufacturer ever wrote me a letter allowing barometrics on any of their boilers. Because manufacturers are not liable, nor do they want to be, will rarely make any recommendations. If AGA, who originally certified this boiler has put out a report that says barometrics correct all venting problems and CO problems I don't see why Gas Companies want to argue AGA expertise. In the 80's manufacturer's said they would void the warranty on their boilers if you installed a flue damper or spark ignition or a Thermiser or Energy Saver. The GAMA Venting Tables specifically state that the installer must use good judgement in making modifications to venting to address all field conditions and it is their responsibility and no one else's!!

jim sokolovic

Draft hood performance...

The ANSI Z21.13 Boiler Standard, to which this boiler should have been tested to (when developed), states that the CO must not exceed 400 ppm air-free when downdraft pressures of zero to .05" are imposed at the outlet. You measure -.25" there, so your chimney draft is more than adequate. If your input is correct, and the heat exchanger and burners are in good condition, there must be something wrong with the draft hood design or it's condition, it seems to me.

tim smith_2

burners????????

I have ran into many older furnaces and boilers where the slots/holes have just slightly opened up and this has cause the combustion to go to heck. Basically you can't even tell they are larger but upon real close inspection you can see the variation between some at the end and some in the middle. We sometimes could adjust out the problem but sometimes no way to get below a 100 and could not approve it to stay on. Just a little input, ha ha.

Jim Davis

Normally orifaces get smaller over time from oxidation and pitting unless someone uses a drill bit to clean them. It takes only .00018 sq.in. of area change on a burner oriface to change it 1000 BTU at 3.5"W.C. How does one know if some burners got bigger versus some getting smaller, without measuring temperature and Oxygen along with CO?

jim sokolovic

Draft reading effect...

The -.025" reading is slightly more than what is considered normal - but I don't see it as the cause of the readings we are being presented with - wouldn't that just cause extra dilution air to be brought in the diverter, and the effect would be to lower the CO2 and also possibly the CO readings from "normal"? This one is interesting, though - the high CO2 and CO readings combined with the high stack temperature are quite baffling, given the boiler has been checked to be clean and the input is correct!

Jim Davis

Draft

Years ago I was training and testing in Montana and this hotel had to Raypack Water Heaters vented in the same flue. One had -.01"W.C. draft and the other -.015". This was at 4000' above sea level. The one with -.01" vented fine and had 30 ppm of CO. The one with -.015 was barely venting at all and exceeded 4000ppm of CO. Blocking the hood with cardboard brought the CO levels below 50ppm.
Higher dilution air blocks or displaces flue gases preventing them from entering the flue. How any draft will affect an appliance cannot be determined until it is installed and checked in its environment. Field Controls has tried to create this condition at their factory for years and can't do it even though they have seen it in the field with me dozens of times.