On Dec 16, 2010, at 8:02 PM, Jim Shorney wrote: > On Thu, 16 Dec 2010 12:32:48 -0500, mike bryce wrote: > >> should it blow in >> >> or suck out? > > This would seem to be a question of spot cooling vs. system cooling.
I'll chime in with my $0.02 here... The "suck it out" versus "blow it in" debate (aka negative pressure versus positive pressure ventilation) has been raging for years in the fire service. When I went through firefighter training 25 years ago, the current wisdom was leaning in favor of positive pressure, but this has shifted a couple of times. These days both are in favor, but use varies depending on the space you need to ventilate. Generally, positive pressure is going to create a column of pressurized air with most of the effort going in one direction and is best for a limited space with few entrances and exits, whereas negative pressure will draw air from any place air can come from, and what you get is better although lower pressure evacuation of many spaces. I prefer negative pressure for my Twins and TR-4 as it can help draw warmer air from many places in the rig, not just the finals, although the finals are where most of the benefit will be found. It also limits the incoming dust being concentrated heavily in one location, which aids in periodic cleaning. Tom -- Tom Swisher, WA8PYR "A wise and frugal government, which shall leave men free to regulate their own pursuits of industry and improvement, and shall not take from the mouth of labor the bread it has earned - this is the sum of good government." - Thomas Jefferson
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