Cold stack slugging...

Mark Eatherton

With Old Man Winter lurking just around the corner, I thought it would be a good idea to address the potential of Cold Stack Slugging, which I have personally observed first hand, and it is a SERIOUS threat to the occupants of the building.



Here is a link to an article I wrote about this subject.



<a href="http://contractormag.com/columns/eatherton/watching_killer_work1_727/">http://contractormag.com/columns/eatherton/watching_killer_work1_727/</a>



What are your thoughts? Should this be addressed by requiring a heat source in an occasional use mechanical room?



Whaddya think?



ME

Tim McElwain

I was waiting for Part 2

before I commented???? If I read the article correctly you eliminated the draft hood and installed a barometric but the problem remained???? Perhaps I did not read it correctly.

Mark Eatherton

You read it right Tim...

The modifications did not work. When the system tried to start cold, it would spill combustion products to the point that the CSD1 ignition module would lock out due to loss of flame during a sustained call for heat.



I will find the other articles and post them.



ME

Mark Eatherton

Part 2 of the article...

“SPECIAL ARTICLE”

“Watching a killer at work”

Part 2

 

About 2 weeks later, at 4:00 in the morning, she called me at home to let me know that the pump had started, and the boiler was not lit. I quickly drove to her home, and as I entered the stairwell leading down to the boiler room, I again could sense the aldehydes associated with partially burnt natural gas. As I walked down the long hall way to the remote mechanical room, I passed a plug in type of CO monitor. I noticed the unit reading 150 PPM of carbon monoxide. I unplugged the unit, and took it with me to the mechanical room. As I entered the room, I observed that it was just about as cold in the unheated mechanical room as it was outside, which is a normal consideration for a remote mechanical room with code required combustion air, and no internal means of heat. I also noted that my eyes and lungs were stinging. I plugged in the CO detector, and after it booted up, it shot up to 250 PPM. I quickly left the room, closed the door to the room and went upstairs to converse with the concerned homeowner. She was complaining of a headache that was borderline migraine and said she felt like she was getting the flu. She asked me if I wanted a cup of coffee, to which I obliged. She took a cup out of the cupboard, set it in front of me and poured it full of milk… I recognized this as the beginnings of carbon monoxide poisoning. Confusion, headache, aches and pains and general disorientation. I told her we needed to air the house out, and we began opening windows. I found another plug in CO detector on that floor, and after about ½ hour, it had settled back to zero PPM of CO. I then went back to the remote mechanical room in the basement and it too had cleared itself of the CO that was present before.

 

I then did something that I would not recommend anyone do. I reset the boiler, climbed into the corner and held my head directly in the stream of the incoming fresh air and observed a killer at work.

 

As the boiler fired, there was a definite major roll out occurring at the combustion chamber/burner opening. It was so bad that many of the burners ignited the gas inside their respective burners. A white vapor began spilling from every opening into the room. I kept my eye on the CO detector. It started climbing quickly. I also kept an eye on the barometric damper. It was doing exactly as it was designed to do, staying completely closed, attempting to establish a negative draft within the 30 foot tall stack filled with cold air. There was a considerable amount of spillage and white vapor coming from the lower combustion chamber/burner access opening. The CO detector continued to climb until the digital readout read 999, the maximum readout capability of the detector. Bear in mind, I had my head stuck right in the incoming fresh air stream to avoid being directly exposed to the deadly concentration of CO. Suddenly, the main burner shut down and the lockout light on the ignition controller came on indicating a lock out condition.  I had finally witnessed what the boiler was doing in real time, and it was not what I had expected. This potential killer was spilling products of combustion from the lowest part of the combustion process, an area that normally sees a significant flow of air into the combustion process. It filled the room with carbon dioxide which quickly caused an elevated condition to enhance the production of carbon monoxide. As we all know, you can not sustain a flame in the presence of carbon dioxide, and when the pilot flame signal was lost, the ignition controller immediately went into a lock out status as it was designed to do. The only problem was, the room was completely filled with the killer gas, and these gasses were leaking through the ceiling penetrations above, and into the spare bedroom that the owner of the home had been sleeping in. I took a deep breath of fresh air and ran upstairs and asked the homeowner to step outside and into my warm car to get away from the toxic fumes. After having sat outside for a half an hour, I ventured back into the home and found the CO levels to be back down below 50 PPM. I turned on some kitchen exhaust fans to expedite clearing the air and allowed the homeowner back into the house. As we sat there , contemplating what had just happened, I told her that my only guaranteed solution was to replace this boiler with a sealed combustion modulating/condensing boiler. She didn’t ask me how much it would cost to do it, she just said “Replace it…” I of course thanked her for the order and explained that it was our policy to not perform any work prior to the owner knowing the cost of the recommended changes, and that I would assemble a quote for her to ponder that day.

 

After I left the job site, and kept going over the events that I had witnessed, I kept asking myself over and over why this boiler was not required to have some means of roll out detection on the lower combustion chamber opening and the draft relief hood opening like was required on smaller residential boilers.  I asked some boiler manufacturer representatives, and got no response. I guess that’s one of those questions that nobody in the boiler manufacturing business wants to answer. The other question that really kept bugging me is why the CO detector (popular off shelf brand) was sitting at 999 PPM and had not gone into the audible alarm state. I understand that the UL approval process has a time weighted value to it, but in my mind, if the CO rises above a certain deadly point, all timing elements should be thrown out and the device should go into an alarm state immediately.

 

In the end, we replaced her atmospheric boiler with a sealed combustion modulating/condensing appliance which virtually eliminated the possibility of any carbon monoxide being released into the house.

 

In retrospect, my little adventure into the boiler room to observe the killer at work could have back fired on me, and could have harmed me beyond repair, and as I stated, I would not recommend that anyone subject themselves to this kind of dangerous situation, but in my minds eye, it was the only way I was going to be able to figure out exactly what was occurring to cause this continual lock out situation.

 

So, in closing this article, I want to ask two questions of the industry.  Why is it that these commercial grade boilers are not required to have any roll out safety switches anywhere on them like their smaller residential cousins are required to have, and secondly, why didn’t the CO alarm go into an alarm status when the CO rose to a deadly level in such a short period of time?

 

If no one can give the direct answers to these questions, maybe at least someone can give me some direction as to the methods to get these requirements changed. I stand ready to help in whatever capacity I can offer.

Steamhead

You are lucky

to still be here to share your experiences!



Obviously there was a safe place to vent that modcon. What if there hadn't been- what might be a solution? Draft inducer with proving switch, maybe?

Mark Eatherton

Yeah....

Every time we'd show up prior, the mechanical room had warmed up, and the boiler caught draft lickity split, so we eliminated all the usual suspects. It finally rolled out so hard at the combustion chamber inlet that it fried the wiring that runs across the face of the boiler and dropped the transformer.



I guess the inducer could be tied to stack temperature. But it only snows when its cold :-)



Maybe an inducer on a timer with a stack temperature override. I hate those noisy/shakey parasitic excess air movers :-)



The other option is to keep the space warm so that the hot air rising up the stack keeps things flowing in the right direction, They had another identical boiler to this one in an upstairs heated garage, and we had never experienced a lock out there. But that's kinda a waste of energy too...



ME

Steamhead

The proving switch

would prove the fan was running and creating draft before letting the burner start. We used one on a job where the chimney had an 11-foot horizontal run before turning vertical.



This job cold-slugged something like yours, then when the hotter flue gases reached the vertical stack the draft would "catch" suddenly. Try setting up an oil burner under those conditions......



We paired the inducer with an oversize barometric, placed between the inducer and the boiler. The inducer created enough draft to let the burner start properly, and when the draft increased the barometric would open enough to maintain proper draft between it and the boiler. We've serviced that boiler a couple times since then, and it appears to be running well. I'll post a link to the thread if I can find it.

Tim McElwain

I agree with

Steamhead on the inducer/barometric hookup. I would get the inducer as close to the chimney as I could also.



Years ago we used to take two 200 watt unfrosted electrical bubs and rig them up near the draft hood or in some cases we actually put them inside the chimney clean out, this would keep a little delta T in the chimney at all times.



I have also when possible with poor drafting chimneys gone to running "B Vent up the chimney and eliminate the chimney entirely as the drafting agent.

Tim McElwain

Try this for an answer

www.combustionsafety.com/pdf/​2009%20ASME%20CSD-1%20...

 

 

“So, in closing this article, I want to ask two questions of the industry.  Why is it that these commercial grade boilers are not required to have any roll out safety switches anywhere on them like their smaller residential cousins are required to have, “

 

The answer to this one is probably due to the different requirements for large boilers under ANSI Z83.3 and ASME CSD-1 (Controls and Safety Devices) as compared to Insurance Underwriter requirements for boilers and controls. The residential side of codes is much less confusing. There are avenues of proposal for submission of changes to the codes. The website referenced above discusses the latest changes to CSD-1 2009 nothing about additional safeties.

 

 

 

“and secondly, why didn’t the CO alarm go into an alarm status when the CO rose to a deadly level in such a short period of time?”

 I have had this happen in the past and I believe that the level rises so fast it actually causes the CO detector to overload and not function. I have no basis for fact on this just my observations over the years. I must say I have yet to have a low level detector fail to alarm in all the tests I have run.

Mark Eatherton

The reason for not wanting to place an inducer...

The boiler room was directly below a sleeping area. The relay CLACKING was enough to wake the dead. I guess the alternative (NOT waking up) is worse...



Its fully sealed combustion with a modcon Knight boiler now. Did I mention that her gas bill dropped significantly? She also said that the area with the new boiler cleared faster than the other atmospheric boiler does.



ME

Mark Eatherton

Got another link??

That one give a 404 error.



Thanks



ME

Tim McElwain

Try again

www.combustionsafety.com/pdf/​2009%20ASME%20CSD-1%20...



or do a Yahoo Search for

• [[u][color=#8284cc]PDF[/color][/u]] [u][size=12][color=#0000de]2009 ASME CSD-1 Changes and How They Affect You By Jason Safarz[/size][/color][/u]
• [u][size=12][color=#0000de]2009 ASME CSD-1 Changes and How They Affect You By Jason Safarz[/size][/color][/u]

Jim Davis_3

cold flue

I have encountered many cold flue senarios over the years, not just on idle boilers but even those that were heated but had drafthoods.  But there have been many furnaces also.  Steamhead is correct as far as using a draft inducer with a barometric as a fix.  However even then I have had situations that the flues downdrafted so severely when the equipment was idle that the draft inducers started spinning backwards and then ran backwards on a call for heat.  De-pressurized mechanical rooms often lead to these problems.  This meant that conventional combustion air openings could not be used and had to be replaced with some type of mechanical combustion air.  Somethimes flue dampers had to be installed above the inducers to keep them from spinning backwards.

Barometrics control draft but they do not create it.  With passive combustion air even a heated boiler with a barometric can downdraft and cause rollout.  Controlling combustion air is even more critical sometimes than controlling venting but both are really equally important.  There were no sealed Mod-Cons in the early 80's, but they sure can solve many problems today, especially on something like snowmelt installations..

Seems like the industry today still wants to shortcut equipment when it come to safeties and they are even against us adding them in the field.

Mark Eatherton

Thanks for reminding me Professor...

I forgot all about the inducer that was pre-spun backwards and ran backwards when power was applied. I thought it was impossible to do with a single phase electric motor... Amazing what you learn in the field that is not taught in the class room :-)



Thanks for contributing.



ME

Tim McElwain

I have seen a similar

thing happen with side wall vented equipment here in Rhode Island along the ocean. When venting terminates on the ocean side with many times 25 knot sustained winds the draft inducers or power venters will actually stall out and fortunately the pressure switches typically shut things down.



I didn't mention it in my other post but I have also seen inducers placed on the roof at the chimney termination that run continuously and are interlocked with boiler or furnace room equipment so if they stopped running equipment would shut down. Those also should be set up with a barometric on the equipment for draft balance.



Jim mentioned devices do not create draft they only assist the process as we still typically need height and delta T to create draft. There are however many things that affect draft.

Tim McElwain

While we are taking about this

I had a conversation over the phone with a contractor concerning a boiler sooting up in a brand new installation. The boiler room was way undersized for this application and is definitely a confined space that would only allow 48,000 BTU's worth of equipment to be installed. The boiler is over 200,000.



The contractor installed a "fan in the can" to as he put it cool the boiler room which was getting very hot and the customer complained concerning this typically in the summer time as this also has a 100 gallon indirect. This is $3,000,000 house.



Apparently this also covered the need for air in addition to cooling the boiler room (I will evaluate that when I go take a look at this job). It was controlled by the thermostat however or aquastat wired in parallel. It was not interlocked with the equipment.



Well someone shut of the switch controlling the "fan in a can" and the rest is soot city. Soot for those who don't know is Carbon Monoxide. So my instructions to the contractor was to shut everything off until the situation can be corrected. They are hesitant to do this as the customer is "very fussy" also very rich. I advised them they could have a "very dead fussy" customer.



All mechanical means of getting air into a boiler or furnace room must be interlocked with ALL of the equipment.



The other scary thing about this job is that there is an air handler for the AC in this same mechanical room.

Steamhead

Hmmmmm

I don't remember that fan prover/relay system being particularly loud- it was a Tjernlund UC-1 if memory serves. No louder than the multi-zone relay box we used on that job. The inducer itself produced a soft whirrrrrrrr, which the AFG drowned out.



But there are probably people who couldn't sleep thru it.



As for putting a sleeping area right over the boiler room- what were they smoking?



Thanks for the confirmation, Tim. Coming from you it means a lot.

Steamhead

Were there

draft prover switches on these back-spinning units? If so, why didn't they shut the burners down? Is the prover looking for a vacuum or positive pressure from the inducer fan (sorry, it's been a while..........)?

Steamhead

I can't wait for the update!

what type of boiler was it? 

Tim McElwain

It is a Buderus

atmospheric boiler.

Jim Davis_3

proving switch

Yes they had proving switches and they didn't make and the equipment didn't come on.   What I was trying to show is that one solution is not always going to solve a problem by itself.  It is better to fix everything the first time, combustion air, venting etc., rather than finding yourself right back at the job with another problem.  So many times I here the same story, let's just try this first and see if this works and then we can try that if it don't and then we can add that if those don't work.