Fireplace Blower
 

I'm not sure how much a blower fan can increase the efficiency of a natural gas fireplace, but it seems like it would help extract at least some energy that would otherwise go out the exhaust.

My house has 2 identical 12,600-18,000 BTU gas fireplaces. One has a blower and the other does not, though there is electrical already installed.

The squirrel cage blower consumes 56 watts and is moderately noisy to run. I think these are typically rated to 130 CFM. My high school electronics teacher said squirrel cage blowers aren't very efficient.

As a proof of concept, I rounded up all the spare PC cooling fans I could find and set them into the intake of the fireplace. The 4 fans (3x 160mm, 1x 120mm) consumed 6 watts, was whisper quiet, and seemed to move about half the air.

I could purchase a purpose built squirrel cage blower with rheostat and temperature switch for $60, or I could purchase 6x 120mm fans for around the same price. I'm thinking if I mounted 6x 120mm fans, I could get equivalent air movement for 18 watts.

Amazon link

https://ecomodder.com/forum/attachme...1&d=1604783276

I use energy start quiet bathroom fans.
I don't know how many watts the 4 inch quiet fans draw but they move a lot of air.

Our old 1940's brick, wood burning, fireplace has a natural circulation setup where it pulls cold air off the floor, runs it through 4 thick walled 4" pipes behind and over the burn chamber, and then dumps them out about chest high in the room. It's neat to get it rocking and actually feel the air "blowing" out those pipes even though there is no fan, just natural heat rise.

So in your case, I wonder if you actually blew those fans into the back, beside, and over the insert, with the hottest air coming out the top would take better advantage of natural heat rising.

Edit- I see that's exactly what you are doing already!

So you're halfway there. Fabricate a log manifold (no pun!) to manage the airflow. Maybe get some matching fans?

When I worked at Nextstep electronics recycling, I started out in the warehouse, dismantling. I tore apart an Olivetti PC from the 1970s that was way overbuilt (the thing had three motherboards!). It had a [six inch in metric] cooling fan with a cast aluminum body. It would replace any two of the ones you show. Prolly still around here somewhere, it turned into sort of a souvenir.

Need maybe 4 more of the big ones to fill the gap. You're losing pressure out the front sides. Better heat transfer efficiency will occur if you slow flow through the system a bit.

6 of the 120mm fans would just about fill the width, and would fully fill the height. I'd make some frame that blocks off any gaps.

I wonder why fans seem to be an afterthought to these fireplaces? It would be a simple matter to have a fully ducted and sealed system that draws air from the bottom and sends it around through the top. The fans themselves could be mounted to the grate in front so they are out of the way when accessing the gas controls, and would be easy to service if one went out. Plus those computer cooling fans are stinkin cheap.

At any rate, I've decided to buy a purpose built fan since it has a speed controller and thermostat switch built in.

Exactly describes my friend's fireplace. I've helped them pull the sheet metal insert and re-grout the firebrick, twice.

I suggested a manifold. It could be a cap across the full width with a single fan at each end. This would slow the airflow and stop reversion.

I knew the price was too good to be true at $60. The fan I received uses bushings despite being advertised as ball bearing, and arrived sans thermostat. I’m sending it back, which means I’m contemplating my own setup again. I need to find an outlet switch that can be closed via thermostat.

My grandpa gave me a home made electric smoker that has a thermostat that controls an outlet you plug the cheap hot plate into. Otherwise it's just an old BBQ. It holds temperature as well as the digital smoker I bought last year.

I use an old Airconditioning thermostat on the cool Side since that is the logic I need and the thermostat mercury switch is rated for 1/2 hp and never arcs the contacts shut. I have a newer one that has similar rated relays, plus the setback timer feature. Maybe $5 @ habitat for humanity

Similar to above, I had a programable t'stat that plugs into an outlet (or cord) and used it in cool mode to turn on a fan pointed at the wood stove when I had one.

I think it was Lux lasted quite a while in a pretty hot environment beside the stove even with an fan blowing near it.

Just my two cents:
- fans at bottom, leave the rest open.
- This setup (four inches space between stove and wall is meant as fire precaution. Any restriction of free airflow and you made a hot chamber behind all the decorative finish. It is compromise between aesthetics and functionality.
EDIT - i didn´t read its a gas stove, so never mind, it has probably some sort of fire protection...

- wire protection covers (salvaged from PSU or bought separately - something like that: https://www.amazon.com/Easycargo-Gri...FXDP14FFV3CMAY) do not restrict airflow and add ton of finish.

I fabbed something similar for my parents wood stove with four 12-cm PC fans and no thermostat, just PWM speed control module (cca $3.90, e-bay) to controll it manually. (Unfortunatelly my mother is more for aesthetics and does not like to mix "country" with "techno", as she said)

If you want to go redneck style, get temperature controlled switch from old electric kettle. Closes/opens at boiling point.

Sounds like nice project to me!

P.S: If you want no project, just 100% style, go for this: https://www.ecofan.co.uk/
or this: https://www.stirlingengine.co.uk/d.a...VULCANSTOVEFAN

(there are also cheaper e-bay versions, but afaik these are the originals)
- you could try thermocouple modules to power your CPU fans... No need to control, runs when your stove is hot enough... - get inspired by that ecofan

Well, 2 years later and I'm getting closer to actually implementing this idea. This weekend I mocked up the fans using double sided tape, wired them together, and tested operation using my switching power supply.

I had to remove the igniter from the mount because it was hitting the fan, but this setup seems to be best. I'll run screws into the grate to secure the fans.

I'll use the temperature switch from the squirrel cage blower to activate the fans, and a 12v AC adaptor I've got laying around. At 12v, 0.31 amps are drawn for just under 4 watts. These are way quieter than that noisy blower.

I will block off the sides using coroplast (maybe, unless I find something more heat resistant). It really isn't feasible to put fans on the ends.

https://ecomodder.com/forum/attachme...1&d=1667236818

https://ecomodder.com/forum/attachme...1&d=1667236818

Oh, that light in the ziplock bag is a WiFi switch so that the Chinese can control my fireplace using IoT. I've got Google starting the fireplace automatically during the morning routine. I had to become an expert on how the gas switches on and off electronically to get the right switch. Fireplaces that use a pilot light generate low voltage from that heat that is then used to open the gas valve when the switch is closed. I made the mistake of initially thinking regular house voltage was switched to activate the valve.

This reminds me, we haven't seen anything from Major Hardware's Fan Showdown in a month:

www.youtube.com/playlist?list=PLHLn2U7i45M_EXIsnqUyI-nqCCk-wfCU9

Which One is REALLY the BEST | Fan Showdown S4 Finale

I happen to have the fog machine at the ready for Halloween. Might as well use it to test airflow in the fireplace.

The new managers realized the ground is laced with natural gas pipes, so they had them tested. Apparently I have Natural Gas available as a service.

I have 2-burner range, would I need a compressor for a car or a fuel cell for electric backup?

Need my rusty BBQ? All burners still work, you just might need to light one of them by hand instead of the sparker.

Finished a project. Squirrel cage blower seemed to throw the air everywhere. It takes 33 minutes after turning the fire off for the thermal switch to turn the squirrel cage blower off.

With my quieter 4 watt total, 120mm fans, it takes just 10 minutes to cool the heat box to the point the thermal switch opens. Seems like it's 1/10th the power, 1/10th the noise, and 3x as effective. Ima patent this when I get a round tuit.

I don't get why these fireplaces come with $200 ineffective blowers that are too noisy, when they could come with $20 worth of case fans that are way better.

I did have to drill mounting holes in the grill that are not externally visible to mount the fans. Then coroplast on the outside and duct tape to seal the small strip next to the fans.
https://ecomodder.com/forum/attachme...1&d=1667805521

EDIT: The fans are so effective that it can cool the heat box down enough that the thermal switch opens while the fire is on. This is something the standard blower was never capable of doing. Once the thermal switch turned on, it ran the fan until 30+ minutes after the fire was turned off.

I might even put a speed controller on there so I can turn the noise down even more, and that would put less cycles on the thermal switch.