Johnstone Supply-Contractor Tools

In addition to Johnstone's Supply's catalog, also on their website are several online calculators, conversion charts, slide rules and other HVAC/R pro contractor tools available for use online.

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Engineering Tool Box

This website contains a variety of resources such as links for air conditioning, heating, noise & attenuation, ventilation, and insulation. Here's a direct link to a handy a psychometric chart but be sure to check out the whole website. (psychometric chart pdf)