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View Full Version : NOT: House heat system improvement, machining included.



Evan
01-18-2012, 03:02 PM
( NOT=Not Off Topic)

Since we are having a spell of colder than usual weather I installed a small extension of warm air moving infrastructure at the request of the General Manager. Our house is well heated by a central natural gas burning 65000 btu heater located in the direct centre of the basement and vented into the centre of the upstairs living space. The house is a fairly open plan so it is easy to heat.

The exception is two bedrooms at the north end that don't receive a lot of circulation. That isn't a problem as a bedroom since it should be cooler than usual living room temperature. However, the GM has converted one of the bedrooms to a hobby room where she manufactures greeting cards with her CNC and manual equipment. Given the temperatures lately I offered to improve the air circulation.

A 24 foot length of 5 inch duct was installed hanging from the 2x12 floor joists and vented in the far end of the hall to the bedrooms. Since we don't have a forced air furnace I needed to arrange for air to be moved in that direction. The inlet is placed directly above the gas heater and wood burning stove at ceiling height. That part of the basement utility area ceiling is sheathed with aluminum flashing to help move air to the vent upstairs and to reduce possible fire hazard. The walls are all concrete, brick or mineral board.

It is very warm in that area so all that is required is to position the inlet of the pipe near the ceiling. However, it is so warm that mounting a fan motor near the inlet is not a good plan. Placing the fan at the far end would be too noisy. This posed a small problem which I solved in this way.

The finished device:

http://ixian.ca/pics9/heatblower1.jpg

A little CNC work was required to make a spider for the fan and spindle. After cutting it was dressed to an airfoil profile.

http://ixian.ca/pics9/heatblower3.jpg

The fan was made from a disk of 0.063 aluminum using strictly manual methods via hand layout, drill press, band saw, files and buffing with some assistance of a vice and wood dies to curve the blades.

http://ixian.ca/pics9/heatblower2.jpg

The unit mounted for use.

http://ixian.ca/pics9/heatblower4.jpg

The bearing on the spindle inside the pipe is PTFE as it has an operating temperature up to 500F. With a 1/4" shaft at 3450 rpm it is running at about half the recommended maximum SFM velocity. The outside bearing is a regular ball bearing.

The ex hockey puck in the mount provides sound and vibration buffering as does the foam weatherstrip tape on the fan housing. A small side benefit is the copper pipe is for hot water and the bathroom tap now enjoys instant hot water.

Black_Moons
01-18-2012, 03:27 PM
Very nice job man! Using a long shaft (or pullys + belt, anything to get the motor outta the airflow) is how iv seen other high tempature fans done when I looked into it. Just not worth trying to make a motor that will live in such high tempatures.

Willy
01-18-2012, 03:41 PM
Very nice workmanship as usual Evan!

I'm sure it does everything you hoped it would. However you could have saved yourself a lot of work by inserting the motor and fan directly into the duct itself as the temps encountered are well within the operational capabilities of the motor.
Most commercial heating duct booster fans use the same type of motor that you used.

Still, good excuse to spend some time in the shop and not outside, nice job.

Evan
01-18-2012, 03:45 PM
the temps encountered are well within the operational capabilities of the motor.

Not in this system. The air temp is around 200F at this end of the pipe.

Black_Moons
01-18-2012, 03:58 PM
Not in this system. The air temp is around 200F at this end of the pipe.

Hmmm, Id be a little worryed about that romex if the pipe gets that hot, But so long as it stays a few inchs away it should be fine.

PS: I don't think its legal to staple romex like that to the ceiling :)

sasquatch
01-18-2012, 04:01 PM
Another impressive home brewed problem solved!!

No fun trying to work in a room that is not up to temperature!!

Thanks for posting that, nice job!!

Evan
01-18-2012, 04:23 PM
Hmmm, Id be a little worryed about that romex if the pipe gets that hot, But so long as it stays a few inchs away it should be fine.

I knew somebody would comment on that. It's an illusion. If you look at how far it is from the copper you can see that it isn't even close to the duct. BTW, I didn't do that wiring. The person that did made it necessary for me to replace about half the wiring in the house because it wasn't safe. I always put the wiring through the joists.

Weston Bye
01-18-2012, 04:27 PM
The motor would have functioned OK in the duct, but the grease in the motor bearings would have hardened up a few years prematurely. Evan did the right thing.

wierdscience
01-18-2012, 07:28 PM
Nice job,you know that looks like it would make a good welding fume extractor too.