This is another article on one of my favorite subjects and the key to figuring out any combustion problem, draft.
It’s amazing that after writing dozens of articles and two books on the subject of draft and combustion it’s the subject that still not only captures my attention but also keeps me going back to the greatest and most ignored statement ever written on oil burner service: <i>“Faulty draft conditions cause more flame and combustion problems than any other single factor.” </i>
Although many give me credit for that statement, it was first printed in a manual on the installation of low-pressure Williams Oil-O-Matic oil burners published in the 1930s. It’s an 80 year old statement that has never been more up to date than it is today.
This article is also about some snail mail and e-mail, a few phone calls I received and a few postings on my website discussion board. People get upset with me because I call out right from wrong. Sorry, but that’s what it is and I’m not smart enough to make this stuff up in my own head. So here goes.
The question was asked “Does the Massachusetts Code, 527CMR4.00, specify the location of a draft control?” Specifically, no, it does not, but in reality it does.
That’s not a trick question or a twisted answer, it’s a good question and touches on virtually everything we do every day. (People say there’s no such thing as a stupid question; well, there’s about nine in the oil heat service business, but who’s counting and that’s not one of them.) In reality you’ll find that the Code, Regulation or Standard (NFPA31) in use doesn’t specify where everything is supposed to go, you are supposed to know that or have read the instructions.
The positioning of many items such as valves, controls, and automatic devices is determined by only one thing, where does the manufacturer (OEM) want it installed and how does he want it installed. Although many in this business like to quote past practice, also known as “We always did it that way,” or what seems to make sense to them, improper installation and the misuse of many components is the leading cause of everything from oil leaks to smoke damage claims.
It’s important to note that although you may think your way is better than every Code and an OEM’s wishes, there is a statement that will trip you up in court every time. It states that “The equipment, appurtenances, controls and devices must be installed following the manufacturer’s instructions.” Regretfully, many of these devices are not.
I keep seeing these mistakes when I do expert witness work and field consultations. They can and do become very costly for all involved. You can bet doing it wrong will eventually catch up to all of us, so for your own sake or that of your employer, follow the instructions.
Without a doubt, I see two items that keep getting put in the wrong place, the oil safety valve (osv) and the draft regulator. There is no doubt that these are both essential and valued devices and that when used properly can greatly enhance not only the quality and safety of a job, but also help protect the image of oil heat. I’ve written a few articles on both and yet I keep seeing them put in wrong in my travels. So, here’s the “real deal” on the positioning of the regulator following one of the newest drawings out there and my thanks to Field Controls for its use.
The draft regulator or control has a lot of names; a draft door, barometric regulator, a damper, a flapper, a butterfly and a host of others or variations that include my favorite, the Draft-O-Stat®. Let’s take a look at the legal definition of a draft regulator right out of the Code books.
“A draft regulator is a device built into a fuel‑burning appliance or made a part of a chimney connector or vent connector, which functions to reduce excessive draft through an appliance to a desired value by admitting ambient air into the appliance chimney, chimney connector, vent or vent connector.”
A few things of note, a chimney or vent connector is a flue pipe or what most of us still call one of the dirtiest terms in this business, a smoke pipe. Ambient air is surrounding air or in most cases room air. Keep in mind that a regulator will only reduce draft output from a venting device, it will never make it, and that as I say on my website is a FACT!
I don’t expect every inspector or tradesperson who works around oil burners to read a Code book, but in my seminars I strongly suggest to all that you at least read the definitions section. Reading the definitions section not only clears up a lot of technical issues but also prevents a lot of misunderstandings with inspectors.
Using Figure 1 note the proper locations for the regulator or even more importantly, where it’s not supposed to be.
It should never be in a plumbers tee or in the run of a tee. That puts the regulator into a bullheaded tee and those opposing flows are wrong. If you tried to do this with steam, and in many cases water or air, it just wouldn’t work, so why do we expect it to work with draft? Remember, draft is just another word for air.
The problem with putting it into a tee like that has to do with air flow. Although the draft regulator in a plumbers tee will work with atmospheric gasburners it creates a problem for powerburners: oil or gas. The problem is not the draft regulator, it’s the fan within the burner. The fan is pushing the air to reach the outside. We all know that will work because of our experiences with direct venting where the burner fan does all the work. With a high static (air-box) burner, draft regulators may not be needed and draft inducers and all kinds of other fans are completely useless if the job is installed correctly to the manufacturer’s requirements.
Imagine you are a molecule of air. You’re hanging out with more air in a combustion area because you are a very social animal. Air loves to be with more air, isn’t crazy about steam, doesn’t like water and in a group you can compress so small you will raise hell with anybody who tries to get rid of you. (If you’ve ever tried to purge a large hot water system or had a steam main pitched wrong, you’ve been there, seen it and heard it.)
So, the burner comes on and starts to push you towards the exit (chimney), but you really want to hang with the new air coming in so you hesitate. Now ignition takes place and not only do you have more air still coming in trying to push you out, but it’s also getting very warm and you’re expanding like crazy. So, you start to leave. (By the way, this is the best reason for every burner having a pre-purge period; it allows the air to begin to move and acquire direction before the ignition sequence takes place.)
Everybody starts to head for the exit door, the chimney or venting device (through a six inch pipe) and you reach this elbow and now you really have to struggle because you like to go in straight lines and there’s this turn. (If you use 45 degree elbows you’ll find you have better draft because they have less than half the resistance of 90 degree elbows.)
You make it through the elbow and wham, an intersection! Here’s this tee, one way goes back to the room and the other goes to the exit, but it’s dark and you can’t tell which way is out. Unlike a valve or fitting there are no arrows on the outside to tell you which way to go. It’s at this point that we face the old “path of least resistance” problem. Do you go out to the room or do you go out the door? Which door? (Remember the regulator is a door.) On top of that it requires no effort for you to travel in a straight line (unless it’s over 18 inches long), but to make it through this tee is like traveling through another 38 feet of pipe.
Man, are you getting tired. But, most of the molecules are headed for the chimney so you go with them because you’re a social guy, right? Although everybody is working hard to get out, it’s tough and then whoof, the fan shuts off, oh-oh!
Now it’s which way to go again. The regulator and the room are only 4 inches away, the top of the chimney is 35 feet, and so what do you do? Hey, if you sneak out the regulator who’s gonna know? Well, my little molecule, everyone will, because you smell! See, you’re not a smell-free molecule of air anymore. Oh no, you’ve become a molecule of flue gas and you smell just like the combustion process you just passed through whether it was oil, bioheat, kerosene or LPG, you stink, bad! But in addition because you’re carrying that fuel residue with you, you also make lots of tracks and so you stain the regulator opening, and fall to the floor as soot. Bad little molecule!
Although I‘ve hopefully made you chuckle or even at least smile, keep in mind that this is serious stuff, and doing it wrong can never be justified by just saying, “Well, it hasn’t caused me any problems.” Trust me, it all catches up to us, so be careful and do the job right every time. By the way, if you read the directions you will find that not only do all the people who make draft regulators not want you using the plumbers tee (except with atmospheric gas), but neither do the appliance manufacturers.
By the way, we have more to say about draft regulators in our new book Venting (Conventional Gas & Oil Systems). See ya.
*George Lanthier is the owner of Firedragon Enterprises, a teaching, publishing and consulting firm. He is an industry trainer and the author of over 25 books on oilheating and HVAC subjects.
He can be reached at 608 Moose Hill Road, Leicester, MA 01524. His phone is 508-421-3490, fax at 508-421-3477 and his web-site and chat room can be found at www.FiredragonEnt.com