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High efficiency alternative to personnel fans

asked 2015-08-17 15:43:53 -0500

Jim Dirkes's avatar

updated 2015-11-09 14:12:42 -0500

Warning: This is not actually a modeling question, but I'm guessing some of you have addressed it as part of your modeling efforts

Also called "man fans" in some of the manufacturing spaces I've visited over the years. They are propeller fans, approximately 18-30 inches in diameter, and the people on whom they blow air will kill you if you even think of removing them (or file a union grievance).

Generally there are a lot of them and they may have up to 1/2 HP motors. We would like to propose a more efficient alternative (so we're not lynched). If you have any suggestions, please let me know. Thanks!

p.s., I have not quite absorbed the protocol for this site. If the questions is not appropriate, I apologize and ask that you send a private message to

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@Jim Dirkes did you mean personal fans rather than personnel fans?

Jamie Bull's avatar Jamie Bull  ( 2015-08-18 09:01:41 -0500 )edit

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answered 2015-08-17 16:20:12 -0500

NickC's avatar

updated 2015-08-18 10:13:20 -0500

Hello Jim; full disclosure, I only have personal experience with these little fans but wanted to give my thoughts on your questions from a general perspective :)

Personal comfort, from a cooling standpoint, is more sensitive to air speed than air temperature. It's conduction versus natural convection versus forced convection. It's likely that the small fans are a more efficient way to provide comfort as compared to reducing the thermostat setpoint temperature.

From a device standpoint, large fans, which spin more slowly to move a given volume of air, are more efficient than the small personal fans. From a usage standpoint, small fans can be more efficient than large fans because they are used at the point of need and will likely be turned ON only as required. Replacing many little fans with a few big ones may or may not be better...could be a small advantage electrically and likely to aggravate people who are used to controlling their own comfort.

Just some thoughts; perhaps a mix of small fans and large space fans is the most efficient way to keep everyone cool without inflaming folks. Maybe hooking the fans to power strips that turn off automatically at night is a way to save some kWs over time. Cooling all the air in a manufacturing space down further is unlikely, in my opinion, to be cheaper than moving the air.

Best, Nick

*edit - I ran across an article related to the current conversation; it's short and nicely discusses the relationships between comfort/temperature/humidity; wish I could locate a similar review paper that takes into account air velocity as well! PDF link

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Absolutely agree on this and can add another anecdote. I've recently moved to a hot area of Spain and it was uncomfortably hot in my home office. Most people here handle this with air-con but I bought a small (25 W) fan which I use generally for a couple of hours in the afternoon on days when the temperature is over 35 °C. As @NickC says, it's the air movement not the air temperature that leads to comfort.

Jamie Bull's avatar Jamie Bull  ( 2015-08-18 01:37:35 -0500 )edit

Got it and 100% agreed with all you said. I don't intend to look at larger fans (HVLS type) because I'm pretty sure production floor mutiny would result. Thus, it's all about the smaller point-of-use types. Rumor has it that ECMs are becoming more common for all sorts of small motor applications and that they're inherently more efficient than the small single pole traditional motors... I'm hoping some manufacturer has already thought of that.

Jim Dirkes's avatar Jim Dirkes  ( 2015-08-18 04:38:39 -0500 )edit

Bigass Fans has a wide range of ceiling fans, many with ECM motors. Bigass Fans. Some come with built in occupancy sensors. I am look at the Haiku SenseME fan for home.

Chris Jones's avatar Chris Jones  ( 2015-08-18 07:27:20 -0500 )edit

Clarifying: I'm not thinking of a ceiling fan. The logistics of mounting one in a 30 foot tall space appear too costly. It will be a pedestal type or something that can attach to machinery. p.s., the Haiku is very sexy and I'm tempted to get one for its appearance and "bragging rights", but $1000 for a ceiling fan may take a century or so to payback :)

Jim Dirkes's avatar Jim Dirkes  ( 2015-08-18 07:47:24 -0500 )edit

On the other end of the spectrum are used computer fans. I get them at the used electronics store for about $5 each. A couple of the 5" fans mounted strategically work great, very quiet. You have to build a little enclosure with a switch box for the wiring mounted on one side.

Chris Jones's avatar Chris Jones  ( 2015-08-18 08:33:20 -0500 )edit

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Asked: 2015-08-17 15:43:53 -0500

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Last updated: Aug 18 '15