Draft diverters revisited ...

Unknown

some more on draft hoods.

Glen

It's been one of those Sundays where one can kick back - catch up on some reading - ponder a little. My reading was here on the Wall and a few other sites.
To say the least I am mildly concerned when some info is not correctly presented - and this is an assumption on my part by trying to read between the lines in a recent post regarding draft diveters. Is replacing a draft diverter with a barometric device a recognized practise in the US? This sent me scurrying to my gas code. Now gas is gas - and it burns the same and must be vented the same regardless of geographic location - unless you are a mile high and altitude demands recognition.
Let me quote from the Canadian Gas code - CSA B149.1-M95; "The draft hood either supplied with, or forming part of an appliance shall be installed without alteration." item two; "A draft regulator shall not be used as a substitute for a draft hood". In my mind this is straight forward stuff - and our local gas inspector would have my gas ticket pulled in a New York moment if I tried such a stunt. So please - am I missing the gist of the discussion - or are gas appliances being modified for the immediate benefit of homeowner or contractor without legal authority to do so??? I support the notion that barometric dampers are not the same as draft diverters - but there might be the odd instance where the appliance manufacturer has no preference as to which might be used (unlikely). What does the NFPA say about this? And where is the local gas inspector (authority having jurisdiction) on this issue? Lots of questions - and I had to ask.

Unknown

Very interesting

I do not think things are any different in USA.

Mark Hunt

Is it possible

that there are times when that code is just plain wrong?

Codes are important so please do not take what I say here as a blanket discarding of them, but I can tell you that codes can not cover every variable.

And codes can change.

Here in NY it is "code" that a chimney liner be installed in exterior chimneys when equipment is changed. So now a heating contractor installs the liner as per code and walks away. Everyone signs off on it. That code is designed to "prevent" drafting problems that may occur due to the higher efficiency of new equipment. But what happens when the unit does not draft due to depressurization of the combustion appliance zone?

No amount of adjusting a gas valve or gas pressure or air mixture will ever over come the negative pressure! But hey!! There's a chimney liner!!
Neither a draft diverter or a barometric will overcome the pressure imbalance either.

So what do the codes say about that? Cut a big hole into the side of the house! Well let's think about that. Why does the "make up air" want to come into the CAZ? It is because there is lower pressure there than there is outside. The CAZ will still be depressurized otherwise the air would just stay where it is.

And how does one decide how big an opening should be? It's in the code book. OK. Well how do the code officials know the amount of leakage already present in a CAZ? Does anyone ever check?

Again, I am not saying that ALL codes are wrong, I am just saying that they aren't ALWAYS right.

And just so you know, section 7.12.4 of the National Fuel Gas code book says the following:

"Additional Devices.

Gas utilization equipment (except incinerators) requiring controlled chimney draft shall be permitted to be equipped with a listed double-acting barometric draft regulator installed and adjusted in accordance with the manufacturers instructions."

Mark H

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Rudy

The problem I see is that codes are prescriptive as opposed to performance based – meaning that it should probably work that way, but, under ‘actual operating conditions’ there is a chance equipment may not perform as it was designed, engineered, listed and approved.
If you look at the Gas Engineering Handbook it states that “The draft hood designed for a typical gas appliance primarily represents a compromise of the many design criteria.”
It goes on to say that a barometric regulator “… provides excellent, constant, static pressure regulation.”
If you look at the AGA report (FTC-07-93) that Tim mentioned you will find pretty compelling evidence. They went out to 50 installations where draft hoods were failing. They put on barometric controls, which corrected every single one of them. I think you can still get a copy of the report from Field Controls.
I don’t run around changing every draft hood to a barometric, just the situations where, in my professional opinion, a safety hazard is present and sealing off or removing the draft hood and installing a double acting barometric will eliminate the hazard. I’ve done this many times in my service area (including a high school and the city hall building). The way I see it, I’m between a rock and a hard spot. Do I leave it operating (dangerously) as it was listed and approved or do I modify it to ensure safe and efficient operation?

Jackchips

It appears

that what is being said here is just what Tim mentioned in his previous posting. As long as the situation requires a barometric damper, the installer is thoroughly trained and the AHJ signed off everything is ok.

Is that what most people do when they make these changes?

Unknown

Mark would you

be so kind as to explain to many who may not understand what " not drafting due to depressurization of the CAZ (combustion air zone)means.

By the way just to bring it up to date the code section you referreed to is now 10.12.4 in the 2002 code. There is an asterick * which in the code means further instructions in Appendix "A". In appendix "A" A.10.12.4 states that you have to install a blocked vent switch. The blocked vent switch then has to be wired into the gas valve circuit. In order to install blocked vent switches they have to be tested under ANSI standard. There have to be temperature tests run and approved.

A question, in cases where we have depressurization or as us old timers call it "negative pressure" been a problem for years by the way. Every Dunkin Donuts in the north east for years had a problem. Having run a restaurant service business for 9 years I ran into it all the time. We did two things.

1. Introduced make up air (different by the way than air for combustion) this was to equalize the pressure in the building and equipment area. One kitchen I worked on had 80 pieces of gas equipment.

2. We also equipped the heating or water heating equipment with power venters which had to be interlocked with the fuel system to prevent operation in the event of power venter failure.

Would these still be acceptable procedures based on what you have learned in your training?

Just one more thing that caught my attention. When a chimney liner is installed I would assume now days it is a metal liner. I am also assuming that the only equipment going into that chimney is Category I equipment. All Category II, III and IV equipment has to be vented in accordance with manufacturers instructions. Most of those do not allow venting into any masonry chimneys lined or unlined. There are some exceptions but very strict guidelines to be followed in order to ensure safe operation.

It was never practice to adjust any equipment to overcome lack of air or negative pressure. The problem is not the equipment the problem is the building and the exhaust system or other causes adjusting the equipment could actually make the conditions worse.

I always take note that during these discussions on CO,air for combustion, venting all the equipment reps are sort of quiet. I think that is because there instructions in their manuals are pretty clear on what should be done to install the equipment correctly. It is the improper installation and lack of training on the part of many installers that becomes the problem.

Some times we just do not read the instructions.

Unknown

This is the procedure

I follow.

1. Discuss alternatives with homeowner explaining that there is nothing wrong with the equipment but the entire system air, vent etc is problem. Explain what you are going to do. Be careful not to give any guarantee that this will solve all their problems but is a step you are recommending as a possibility. Remember you can always put the draft hood back.

2. Call the manufacturer and get their input. If possible find out if this has been a problem for them in the past. They may have a solution for you. Do not be suprised if they refuse to go along with your solution. At one time the gas company I worked for required a written letter from the equipment manufacturer giving permission to alter their design. It was not unusual for their rep to come out on the job while this was being done.

3. It is then a good idea to get the gas company, plumbing and heating inspector, and any other authorities in your area involved.

4. The service tech who is going to do this is a fully qualified gas service and combustion technician with at least 10 years experience in these type of change outs.

5. Upon conclusion of installation full combustion and pressurization testing be done to ensure proper operation.

6. Complete documentation and a signature from the customer giving their approval of what you have done. In a sense you are entering into an agreement with them.

7. We also used to take before and after photos and these would be included in the file with the equipment.

Let me last of all say that it was a rare occurence when this had to be done. There are many service techniques that can be done and other alternatives to solve these problems.

The problem we have today is everyone wants a quick solution. Get in and get out move on to the next job. Sometimes you have to pull up a chair and think about what is happening. I like to picture myself as the boiler or furnace find out what is making them so unhappy. May sound silly but it works.

The first old timer I went out on a job with always carried a folding little chair. When we got on a tough job he would tell me to go get his chair from the truck. He would sit down, chew on his unlit cigar (he never did light the things) and say to me "we have to figure out what this boiler/furnace is thinking about". "Kid" he would say "if you sit here long enough it will talk to you"!!! I used to think he was crazy, strange thing was they always gave him the jobs no one else could fix. He would also take old controls and equipment that were being thrown away and take them all apart. He would say that was how he found out why it finally failed. I still do that kind of stuff today.

Fellas and ladies it takes a long time to learn this stuff. Do not jump on the first thing that comes to mind and get others involved.

When I train people (enhance their existing skills) on CO and air for combustion it starts with Fundamentals of gas, circuitry (what does that have to do with combustion?) come find out, Hydronic or warm air controls, electric igniton and advanced electric ignition, powerpile systems. Then and only then do we go over gas conversion burners, why? because when you can learn how to safely convert old coal and oil systems then you will begin (note I said begin) to understand combustion and related subjects. Emphasis always is CODE-SAFETY-COMFORT-EFFICIENCY-TIME-COST. All those must be considered.

Do not get fooled by exciting dog and pony shows that teach radical ideas that in a court of law you may have trouble justifying. PYOB I always say PROTECT YOUR OWN BUTT.

Glen

Let me wade in further ---

It seems that I have touched a raw nerve. So then - let me voice my perspective clearly from the onset. My gas code is a minimum set of rules to safely install a gas appliance. It is not wrong - what we find in the field is wrong and it's our duty to fix it. Whether it's the CAZ, venting, make up air, vent air, gas pressures, combustion, and any other thing that may be fouled up. About now you should be phoning your gas inspector for advice - this guy is your friend - he will save you money anguish and tears. Your customer might not agree - your insurance agent will thank you. Phone the gas inspector often.
Gas is my business & I have learned that I have not learned everthing yet - and have accustomed myself to accepting that I may never learn it all - it's been a painful acceptance. In every set of gas technicians tool box should be the following: combustion analyser with draft and printout, Magnehelix gauges (or digital), carbon monoxide meter ( your choice as long as it's accurate) and a good set of thermometers (delta T is important to forced air as well), a gas code and the cell number of your local authority having jurisdiction. Learn to use each well. This is your starting point - if I have lost you by now, contact your liability insurance agent as you will become initimate friends. There is no room for cavalier modifications in this business. I have been following the posts here on the Wall now for about 4 years - and have the utmost respect for all of you - you have taught me much and I appreciate it. Every one of you deserves to go home each night safe, happy and law suit free. I like what the above post states - protect your butts, cover your ****. Shut down that appliance when you know it's behaving badly, phone the inspector, equipment rep and sales folk. Yell help loudly. The gas code is a minimum set of rules. Learn the rules.
A barometric damper is not a replacement for a draft diverter - and until you have a letter signed by the Chief Gas Inspector in your area, a letter signed by the equipment manufacturer stating subsitution is ok, and a letter from the UL or AGA - and a letter from your insurance agent (who won't know the difference between atmospheric and fan assisted) stay out of this line of work unitl you do. The gas code is not wrong - but can be wrongly interpeted.
Still safe in the Canadian Rockies.
cheers

Mark Hunt

Worst case depressurization

Nearly every installation manual for gas fired equipment recommends this test.

When you install a new appliance you should close all of the windows in the home to similate winter conditions(not hard to do that today I can tell you!!).
Then turn on any and all exhaust fans, clothes dryer, and run the blower on the furnace or air handling equipment.

Test for draft to see if things are going up and out, or down and in.

We use digital manometers and record our findings.

I find more situations where flue gases are entering the home because of this. Contractors just don't do this simple test.

I am curious as to why I or anyone else would bother installing anything but sealed combustion equipment?

And for the record, I have used double acting barometrics in only two instances.

I would prefer to use a power vent or if the equipment is nearing the end of it's life span, replace it all with sealed combustion units.

Adding power venters can cause greater depressurization in the "Combustion Appliance Zone" and fixing one problem could cause another.

TEST,TEST,TEST!!!

Mark H

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gas man

CO, make-up air -combustion air , new construction .old constr

I respond to gas leaks.Co calls - and no heat calls etc. What concerns me is new construction , and even more so ,do it yourselfers. Anytime I enter a furnace or boiler room and close a "door" behind me > I stop and look for venting, carefully looking for signs of heat marks on draft hoods and the front of equipment. No basement, should be altered in any way without a permit pulled so that the local gas inspector doesn't pay a visit . All to often the inspection has been completed before the -home is even close to being occupied ! He see's an unfinished product ! the big box should be held liable , selling any piece of equipment that a license is required to do the installation,should at least be showed the building permit and the license of the plumber ,electrician, or gas man doing the job !!!! home owners , scare me , just as much ,finishing off the basement ,placing 2x4 's on flue piping (front to back splits ) ,one guy decided to brick the wall off, nice job until I shoewd up and told him the flue was rotted out and had to be replaced ! And the lack of anyone doing a damn thing about it is what pisses me off even more, I've even pulled a simple door sweep off a metal door going to the bulkhead ,and reverse a chimney from dumping all the flue gasses into the house ! We need to educate people, the importance of CO detectors , anywork done in the home should be inspected by the proper authoritys, when in doubt call your town or city etc. I work for the local gas company , I tag everthing I come across . Hoping the inspectors will follow up , I try and explain why contractors r needed and permits , may cost you a few dollars ,but what's that compared to the cost of burying a loved one ! And know with deregulation and the company being told to get out of service , well I don't want to use this as a sounding board , but there'll be 1 less person who does care about everyhome I enter - and leaving it safer than I found IT !!1 There's nothing wrong with draft hoods , although they all should have spill switches on them ! And every home I enter ,before leaving , I recommend CO detectors> I best stop now , and frank from philly , hope all is well for you and yours , miss you on the wall