Does Blower Size Matter?

[firewatcher]

I have an Osburn 220 Wood insert with a 120 CFM blower. However, I have noticed that many other manufacturers have 300CFM blowers that are 3 speed. Does a larger blower mean more effeciency? Can I upgrade my Osburn? Is it worth it? How much louder is a 300CFM vs a 120 CFM?

 

[Mike Wilson]

[insert requisite "size doesn't matter" joke here]

 

[Corey]

A large blower does not necessarily mean more efficiency in a strict sense of BTU out per pound of fuel burned. It may help the "apparent" efficiency, though. If your heating demands a large quantity of warm air versus a smaller quantity of hot air. The extra airflow would probably be useful when trying to distribute heat through a relatively "closed" design with a bunch of different rooms as opposed to one big room.

As far as blower noise, that will be highly dependent on the design of the blower. A large blower or fan turning slowly would move 300 CFM so quietly you may not even know it is on. A smaller fan may scream to move 100 CFM.

Corey

 

[jjbaer]

A large blower does not necessarily mean more efficiency in a strict sense of BTU out per pound of fuel burned. It may help the "apparent" efficiency, though. If your heating demands a large quantity of warm air versus a smaller quantity of hot air. The extra airflow would probably be useful when trying to distribute heat through a relatively "closed" design with a bunch of different rooms as opposed to one big room.

As far as blower noise, that will be highly dependent on the design of the blower. A large blower or fan turning slowly would move 300 CFM so quietly you may not even know it is on. A smaller fan may scream to move 100 CFM.

Corey

HI,

A comment on "noisy fans" that I put in a thread I started yeasteday: My older Buck Stove insert has a 2-position toggle switch: one position is auto mode where the fan is controlled at one of 3-speeds by a set of three different thermostats and the other toggle position is a manual "high fan speed" that can be activated when the insert is hot or cold.

Yesterday, my low-speed fan setting failed to come on and, since the manual high speed still works, most likely it's because the low temp thermostat is dead or the low-speed tap on the motor windings is loose...anyway, that left me only with mid and high speeds and the high is too noisy and waiting for the mid fan speed to activate, loses heat that can be had at lower insert temps.

So, I solved the problem by replacing the toggle switch with a light switch dimmer, thus giving me control from "off" to almost maximum, with infinite control in-between.......In doing this, I've abandoned the thermostat completely (left it in but capped the wire with electrical tape) and connected the hot leads through the dimmer. There is a slight decrease in fan output because dimmers typically reduce power about 5-10% to save light bulbs.....but it works great!! I set it to the optimum point where it puts out good heat and is very-very quiet!

I've also ordered (get them today) new "Neoceram" windows for my double doors. This total investment of about $70 saves me from "wanting" to buy a new $2500 insert. Next job is to put a fresh coat of paint on it and I'll never want to get rid of it :coolsmile:

 

[Corey]

Using a common light switch dimmer may not be the best solution for motor speed control. A dimmer is basically meant for a purely resistive load (lightbulb) and hooking it to an inductive load (motor) may cause problems from slight overheating to total meltdown of the motor and/or the dimmer. Some motors are more tollerant than others.

There is a fairly good description of why here:

(broken link removed)

It talks about X-10 home automation dimmers, but the standard "off the shelf" twist dimmers work the same way.


In short, if you can get away with it on your setup, ok, but if either the motor or controller starts to get hot, smoke, or outright burn up, it may be time to look for a different motor speed control solution.

Corey

 

[jjbaer]

Using a common light switch dimmer may not be the best solution for motor speed control. A dimmer is basically meant for a purely resistive load (lightbulb) and hooking it to an inductive load (motor) may cause problems from slight overheating to total meltdown of the motor and/or the dimmer. Some motors are more tollerant than others.

There is a fairly good description of why here:

(broken link removed)

It talks about X-10 home automation dimmers, but the standard "off the shelf" twist dimmers work the same way.


In short, if you can get away with it on your setup, ok, but if either the motor or controller starts to get hot, smoke, or outright burn up, it may be time to look for a different motor speed control solution.

Corey

Corey,

I knew this going in but it's hard to find a fan controller this small (you're right that a fan controller and not a dimmer is the way to do it) .....will go to Lowes tonight to look for a small one.

thanks

 

[wg_bent]

The MFGs size blowers to stove capacity. If you try to move too much air you may cool the firebox too much and reduce the efficiency of the stove. That blower seems to move air pretty well, and I think you'd be unhappy with more. Also, there's not much space to add a bigger fan, so it would just have to run faster which means more noise. I don't find the fan too offensive, but much more and I would.