the way out because you’ re getting bigger from the heat and you’ ve put on a lot of weight by mixing with the fuel oil.
Finally, all you have to do is leave the unit and find the exit as outlet draft. You’ re going to have to, in a boiler, move through a maze of pins and plates and all kinds of things that are trying to slow you down. But you can’ t be stopped now because that fan is big enough to move you, and you fly through this clean heat exchanger. By the way, if it’ s not clean you start to back-up from where you came from( back pressure). As combustion air you’ ve become a very big part of the job since you must now move the bulk you’ ve acquired due to the fuel, remove the gasses left over from the combustion process and leave the building, literally!
Now, while all of this is going on as inlet draft, you’ re also supposed to be helping out in controlling the flow of all these gasses moving through the system and have enough left over for proper ventilation of the area the boiler, furnace or water heater is in. That ventilation requirement is not only required by Code, but it also goes a long way to prevent all of your controls and wiring from acting crazy or even melting. Are you starting to see just how important proper draft is? Are you sitting there thinking,“ holy moly, there is a lot more to draft than I thought there was”. Are you still thinking that there’ s nothing to draft and it’ s very simple? I don’ t think so!
The number one, first, primo, problem out there is not enough inlet draft. It happens in new homes, old homes, commercial and industrial applications, and it’ s getting worse. It runs rampant on jobs with mechanical draft. Whether you are using a powerventer, a draft booster, a chimney turbine or anything else, you can’ t get it out, if you can’ t put it in, remember the see-saw? Before you add a mechanical device to get rid of air, first make sure there is air to get rid of.
At this point I am just going to say a few words about powerventers. These things without a doubt are an essential part of this industry’ s ability to stay competitive in the market and in new homes. In my opinion we need them, but like everything else they have limitations, and must be sized and installed correctly. My experience is that 80 % are installed wrong, and the other 20 % just won’ t work on the job no matter what you do. If you’ re not going to read the directions, you will not understand how they work or what they can do and trust me if used properly that’ s a lot! The biggest problem I see with powerventers goes right back to the front of this article, inlet draft. Everybody seems to agree with the following statement, but doesn’ t do it,“ every powerventer installation should have outside air’.
Figure 3
Let’ s get back to inlet draft. Back in the early 1970’ s Beckett brought out an‘ Outside Air Intake Kit’, Figure 3. As a burner OEM they knew the importance of inlet draft or combustion air. In fact, they even hit you over the head and emphasize their point by bringing the ability to vent right into their latest burner, Figure 4. Carlin also has an air intake cover, Figure 5, and rather than dealing with kits and adapters Riello has a dedicated burner model, the BF, Figure 6. In addition, you can get after-market boots from Field Controls.
More about those fans, keeping this
Figure 4
Figure 5
simple rule in mind,“ fans don’ t suck, they blow”. Most fans that you work with need the air brought to them. Then they will blow the air as far as they can, that’ s called fan drop. When they can’ t throw them any further, a chimney( thermal draft), or fan( mechanical draft) has to take over. Think of every fan that you work with as lazy. If you bring the air to them that’ s okay, but they are not going to do it by
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