Need more CFM

Need more CFM

PostBy: wenchris On: Mon Nov 05, 2012 11:16 am

First off my heart goes out to those still without power, heat ,food, shelter from Hurricane Sandy. We are on Long Island and were lucky compared to my neighbors (no trees on our house)....had generator ready and plenty of gas so 5 days without cable was nothing compared to what I have seen...Just recently moved my Harman Mag combustion and distribution fan to the basement...hear that Silence :) . Hoping to up the output of the distribution fan I replaced the original 130 cfm with a new 270 cfm fan. Now I know that I wouldn't be getting the full 270 cfm because the passages were not increased but it seems that I'm getting the same as the smaller fan :? ....any ideas on increasing the cfm out of this stove? Thanx Jimmy..... Stay warm...
wenchris
 
Stove/Furnace Make: Harman
Stove/Furnace Model: Magnum stoker with water coil

Re: Need more CFM

PostBy: KLook On: Mon Nov 05, 2012 11:21 am

You are probably only getting the "heat" the stove puts out. More air flow doesn't mean more heat. The increased airflow decreases the temp of the airflow. Slower/hotter or Faster/cooler. Is this what you mean or do you mean that the velocity of the air did not change?

Kevin
KLook
 
Stoker Coal Boiler: Harman VF 3000
Coal Size/Type: rice, bagged, Blaschak
Stove/Furnace Make: Harman (Back In Maine)
Stove/Furnace Model: VF 3000

Re: Need more CFM

PostBy: EarthWindandFire On: Mon Nov 05, 2012 12:21 pm

Most any question about hvac has been answered here before, try searching but I'm sure this has been discussed. Below I will post approximations for general use.

http://www.doityourself.com/forum/gas-oil-home-heating-furnaces/70814-duct-sizing-cfm-ratings.html

4" Duct 40 cfm.
5" duct 60 cfm.
6" duct 100 cfm.
7" duct 150 cfm.
8" duct 200 cfm.
9" duct 300 cfm.
10" duct 400 cfm.
12" duct 600 cfm.
14" duct 900 cfm.
16" duct 1,400 cfm.
18" duct 1,800 cfm.
20" duct 2,300 cfm.
EarthWindandFire
 
Hot Air Coal Stoker Furnace: Leisure Line Lil' Heater.
Other Heating: Oil Furnace and Kerosene Heaters.

Visit Lehigh Anthracite

Re: Need more CFM

PostBy: wenchris On: Mon Nov 05, 2012 4:06 pm

Yeah, I was looking for more velocity. I have a 8 inch duct coming off the stove that goes into my kitchen, about 10 ft. The front of the stove plenum is partially blocked to allow heat to the living rm. I thought by getting a fan with a larger cfm that I would get more velocity (pressure, flow, etc....) But,by looking at the chart apparently not. Not looking for much just a little more flow...velocity.......Thanx Jimmy
wenchris
 
Stove/Furnace Make: Harman
Stove/Furnace Model: Magnum stoker with water coil

Re: Need more CFM

PostBy: coalnewbie On: Mon Nov 05, 2012 4:21 pm

I am not an expert here but I guess you can push more through with a bigger fan. However, I worry about noise and so my anthraKing 110,000 BTU fan puts out about 1000cfm and to keep noise to a minimum I was aiming at 2 to 4 mph but the HVAC boys use LFM , so I used this table and decided I needed a 14" round duct.

http://www.calculatoredge.com/optical%2 ... 20flow.htm

So part of the complex calculations were my brilliance and not just because Dave at LL said "use a 14" duct" and I dumbly followed his advice and it worked. You see I'm a liberal now and much smarter. It's very quiet and I love it.

HAHAHAHAHAHAHAHAHA - I slay myself
coalnewbie
 
Hot Air Coal Stoker Stove: LL AnthraKing 180K, Pocono110K,KStokr 90K, DVC
Hand Fed Coal Stove: Hitzer 50-93,
Baseburners & Antiques: Invader 2 Wings Best, Glenwood #8 + Herald 116x
Coal Size/Type: Rice, Chestnut
Other Heating: Heating Oil CH, Toyotomi OM 22

Re: Need more CFM

PostBy: LsFarm On: Mon Nov 05, 2012 8:10 pm

The most important thing to do to increase the heat output from your stove is to create a cold air return duct from upstairs to the inlet of the distribution fan, this will creat the all-important circulation loop.

If your distribution fan is drawing in cold air from the basement floor, this is the coldest air in the house. Feeding this cold air to the stove only reduces the temperature of the heated [output] air.

So, a duct from upstairs to the inlet of the distribution fan will greatly increase the heat output of the stove..

Try it, it works..

Check out WNY's cold air return ductwork he made up for his Hyfire stove.. it made a huge difference in the temperature of his living space.

Greg L
LsFarm
 
Stoker Coal Boiler: Axeman Anderson 260
Hand Fed Coal Boiler: Self-built 'Big Bertha' SS Boiler
Baseburners & Antiques: Keystone 11, Art Garland

Re: Need more CFM

PostBy: Flyer5 On: Mon Nov 05, 2012 8:15 pm

coalnewbie wrote:I am not an expert here but I guess you can push more through with a bigger fan. However, I worry about noise and so my anthraKing 110,000 BTU fan puts out about 1000cfm and to keep noise to a minimum I was aiming at 2 to 4 mph but the HVAC boys use LFM , so I used this table and decided I needed a 14" round duct.

http://www.calculatoredge.com/optical%2 ... 20flow.htm

So part of the complex calculations were my brilliance and not just because Dave at LL said "use a 14" duct" and I dumbly followed his advice and it worked. You see I'm a liberal now and much smarter. It's very quiet and I love it.

HAHAHAHAHAHAHAHAHA - I slay myself



Every now and then my Kentucky windage calculation pays off. LOL There are a lot of wood chucks that wish they could dis-agree. :D
Flyer5
 
Stoker Coal Boiler: Leisure Line WL110
Hot Air Coal Stoker Stove: Leisure Line Pioneer

Re: Need more CFM

PostBy: wenchris On: Tue Nov 06, 2012 10:55 am

Hey Greg, the distribution fan pulls air from the other side of the house about a 5 foot run( Ranch,floor plan is like a tight "U") with stove and return at the top of the "U". The circular air flow is good. I have a 6 inch insulated ridged duct that comes off the top of the stove that runs to my kitchen thru a insulated attic which is at the bottom of the "U". Combustion air now comes from the exterior. I brought the larger fan hoping to get more air volume (flow) to the kitchen. I would have gotten a duct booster fan but the temperature of this duct when the stove is cranking can get quite high. One would think that a larger cfm fan would push more air thru a smaller duct with more pressure therefore more volume.... :? But by looking at the charts that Earthwindandfire, coalnewbie and Flyer5 sent maybe I on the wrong track....and confused.....things could be worse.....Jimmy
wenchris
 
Stove/Furnace Make: Harman
Stove/Furnace Model: Magnum stoker with water coil

Visit Lehigh Anthracite