Shorter runs should get smaller duct sizes?

Dust Collectors

It seems only reasonable that the dust collector makers would sell just their motor blower units and maybe even sell a blower motor combination that was ideal for our cyclone sizing. Most say they sell blowers separately, but only a few do, and those charge as much if not more than buying a whole dust collector. Jet, Wilke Machinery, PSI, RBI and Laguna Tools all sell motor blowers without having to buy a whole dust collector, but prices are high and the impellers are too small until you get into their larger units which come with more motor than most need. The 3 hp dust collectors with a 14” impeller provides a 1900 maximum CFM and these are the best compromise I could find. Unable to find what I wanted, I worked with a few vendors to provide the right sized blower wheels and motors to work best with my cyclone design. More detail is on my Cyclone Building page.

In addition to not offering very efficient blowers, you need to know most hobbyist blower...

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Today’s topic is Duct Siz vs. Airflow. This is Part 1 of a two or three part series on this topic.

One of the big misconceptions about airflow is how to determine how much air will flow through a certain size duct, or conversely, determining what size duct you need to deliver a certain airflow. You would not believe the range of flows I have heard as “rules of thumb”. This assumes that you have done the calculations necessary to determine how much air is needed in a room. That will be a different series of blog posts, to be sure.


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If you have made an investment in a powerful dust collector, that is a great first step toward creating a healthy shop environment. For purposes of this article I will assume that you have worked with your vendor to choose a dust collector that is capable of delivering enough air flow (ideally 1000 cubic feet per minute at 4000 feet per minute) at each tool to remove all of the fine dust that it produces (bare minimum 2HP with...

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I recently had a contractor build a wall which split one room into two. The new room is an office with two computers, and four monitors. It gets very, very hot, until the air conditioning turns on, then it gets very, very cold.

My contractor does not seem to know that much about sizing ducts.

There are two ways we can run a duct to that room.

Option A - The most direct way would be to run a four inch duct (the only size that will fit in that route) approx 20 feet with four right angles.

Option B - The other option is to run a duct (up to 12 inches) 60 feet around the basement up through the house and through the attic, about 60 feet with three right turns.

I think that Option B is the way to go, he seemed to think that a four inch duct would be fine for a small room (about 90 square feet).

Is there any way that a four inch duct would actually do anything over that distance with that many angles? Neither one of us has any ideas on how to...

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It isn't only herp keepers who need extra electricity - and sometimes natural or propane gas - to keep their pets warm. Birds, while warm-blooded, are closer to herps in that they will get sick if their environments are not kept within the species optimum temperature range. Smaller animals lose heat faster than large animals, putting even small mammals such as hamsters at risk when their room air temperatures fall below their optimum range. People themselves often have special needs when it comes to their own health. They may require more electricity than an otherwise healthy, abled person due to equipment and other needs. Some may require more gas for their central heating, water heaters, and stoves due to special health and dietary needs. Thus it is that there are many people who may find the following information useful and helpful in identifying and managing their energy costs in this time of increasing demand and cost.

Since I myself am ill, and it is...

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Ah, so what exactly is this hidden flaw? "My HVAC guy put a zoned system in my house and told me it was the cat's pajamas," you may be thinking about now. Or maybe your HVAC installer described it as the bee's knees, the eel's ankle, or the elephant's instep. Doesn't matter. However they described it, there's one piece they absolutely should NOT have installed.

First of all, let's be precise in our language and clear up exactly what we're talking about. The word zoning is used in more than one way in the context of heating and air conditioning systems in a house. First, larger houses are always zoned. That is, they have more than one thermostat so you can control the conditions separately in different parts of the house. If you have a two-story house, for example, you probably have at least two thermostats — one upstairs and one downstairs.

The other way that the term 'zoning' is used is to describe a single duct system attached to a single HVAC system that serves...

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