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Draft Inducers and Controls


Feature Story


by George Lanthier


Figure 1

I’d like to preview something new with you and talk about one of my favorite subjects again ‘ draft. When I first started writing for magazines about 20 years ago, my first editor joked to me to, ‘pick something easy to start off with, like draft.” That was one of the greatest understatments of my life and led to what has become virtually one of my passions the search to produce the perfect flame and vent it. That search has given me material for dozens of articles and a couple of books on the subject. Our latest book, will be on draft, oilburners, combustion and just how complicated it all is. Although the book is titled Advanced Residential Oilburners, it won’t be an oilheat book. By that I mean I’m not going to try to cover the whole subject of oilheat with snippets, but rather take just the operation of an oilburner completely apart and diagnose how and why an oilburner works and more importantly why sometimes it doesn’t.

The draft inducer is one area of combustion venting that gets a lot of bad press and, in a lot of cases, deservedly so. Although every code in the country tells you that you must prove air with an inducer, how many actually have an air proving switch on them? Whose fault is that? Well, as it turns out it is going to be yours if anything goes wrong. I’ve tried to convince the OEMs to sell inducers only with air proving switches, but their answer is ‘one won’t do it, if the other won’t.” See, it’s a competitive marketing thing and I understand that.

Another explanation is that it may be a replacement unit, but for the record, would you put in a new oilburner and reuse the primary control from the old burner? You might, I wouldn’t. Now both of these may be valid reasons for an OEM not to supply it, but that doesn’t exempt the installer or service technician of record and that could end up being you.


Figure 2

So, let’s take a look inside my new book and move on to draft inducers, Figure 1. I am not a big fan of draft inducers ‘ excuse the pun ‘ since it is not a positive displacement device like the fan found in an oilburner or powerventer. The inducer is merely a paddle wheel in the pipe and as such just creates a mechanical breeze in the flueway. We use the term flueway because depending on the size of the appliance and the venting application it could be a part of the unit, the fluepipe or the chimney. They are made in several configurations and can be located just about anywhere.

By definition, a draft inducer is a device that is to be used ‘when down drafts, negative building pressures, undersized flues or long horizontal vent pipes are present.’ 1


If the burner fan, housing and air handling parts are designed to move air and lots of it, you might just need the right burner and not an inducer. So, the real job is to pick the right burner. The best part is that you have never had a better selection from all of the burner companies to accomplish this than right now.

Okay, let’s get on to what I really don’t like about draft inducers. From my perspective the real problems I see with draft inducers are in order:

Bad installations.
Bad installers.
Poor service.
Lack of education on use and service.
Too many parts.
Bad installations

Poor service. In my new book, you’ll find that this looks a lot like my checklist for powerventers: that’s because it is and guess what ‘ the problems are exactly the same.

The typical draft inducer gets put into an existing installation simply because someone did not put the right burner in or ignored all of the basic rules of draft. That’s the reasoning behind numbers one and six on the list. The fluepipe is too long, 90 degree elbows, joints not sealed, etc, etc, etc. You really need to read the manual that comes with these new units you’re putting in. Many OEMs now limit the amount of fluepipe that can be connected, and 10 to 15 feet, I’m finding, is average.


Figure 3



As with most powerventers the draft inducer never gets enough or any maintenance at all until something goes wrong. We take too much for granted. When inducers and powerventers do get serviced, it’s because the motor is noisy or just not working. Well, when is the last time you cleaned a fan on one of these things when you did the tune-up or used the proper lube oil to lubricate the motor?

Finally, too many people break codes and ignore the right way and put in the majority of these things without proving switches, Figure 2. Come to think of it, that’s why I hate these so much. Most of the one installations I’ve seen have been put in by people with a lack of training on them, but is that the inducer’s fault? Just imagine what would happen if everybody not only put in proving switches, but also put in draft inducer control systems, Figure 3. Think we would all have fewer problems with combustion and soot claims? Oh sure.

In closing ‘ and it’s just my opinion ‘ there is just not enough training on inducers and that puts them in the same league with powerventers ‘ misunderstood. When did anybody ever teach you anything about inducers? If they taught you right, why do most inducers that require an air-proving switch don’t have one? Again, my favorite pet peeve with most of this industry: a general lack of quality training and education for service technicians.

As with powerventers, the issue of parts also goes with the territory and you do require some basic service parts, an air proving switch, and a fan and a motor to properly service the inducer in the field. So, the bottom line is if you’re going to use an inducer, then use a proving switch or find another way to vent your job. By the way, one more thing, when is the last time you really oiled the motor on that last inducer you griped about?

1 Taken from Powerventer/Draft Inducer Application Guide, Tjernlund Products.

George Lanthier is the owner of Firedragon Enterprises, a teaching, publishing and consulting firm. He can be reached at 132 Lowell Street, Arlington, MA, 02474-2756. His phone is 781-646-2584, fax at 781-641-7099 and his e-mail is FiredragonEnt@comcast.net

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