Furnace fan air speed-I need a way to slow it down

[barnartist]

Now that I am installing radiant in the remainder of my house, and since it is going very slowly with all of the challenges in this house, my plan is to connect each circuit and use it. The problem is that as I turn of the air vents to each room that no longer needs hot air, I am adding allot of pressure to my furnace fan. When I start this latest run of radiant, my furnace will be about 65-70% blocked off.

I need a way to turn down the speed of my furnace fan, at some point this whole house unit will only need to heat one room. I still plan to use the water to air heat exchanger for this, so im thinking all I need to figure out is the fan speed problem, if this is possible.

Please keep in mind that this same furnace will be needed again for summer cooling, so the fan will have to be returned to normal state every season.

 

[Dune]

This may generate some controversy, but it is true, nonetheless.

The BEST way to reduce the output of a blower is to reduce the inlet opening. This makes no extra burden upon the motor(unlike a rheostat or any other form of motor speed controller).

If you make or install a movable flap you will be able to continually adjust the flow downward as your radiant install continues.

 

[dogwood]

BarnArtist, locate the wiring schematic on your furnace. I found one glued to the back of my furnace door, one in the manual, and maybe one on-line too. I needed to go the opposite direction and increase fan speed. On my furnace the schematic showed there were three speed settings. By moving a single connector you could switch your fan from high to medium to low speed. In the summer you could return the connector to its original position. On my Lennox Pulse the cool air setting was high speed, the medium setting was for heat. Never did figure what speed the fan-only setting was set at. Some furnaces have more settings. I'm not a professional but this seemed easy enough to figure. Hope this helps.

I'm hoping on mine the high speed is enough to blow sufficient air through the w/a heat exchanger I purchased from Nationwide Coils, designed just like Pybyr's who I have been meaning to thank for his w/a hx design and lead on Nationwide Coils. My hope in the future is to go radiant you are doing, by adding radiant panels with TRVs a room at a time. Let us know how your retrofit goes. You're several steps ahead of me. Are you using in-floor radiant or radiant panels? How is the radiant working for you so far, relative to the forced hot air. Do you recommend going this route judging by your experience thus far? Good luck.

Mike

 

[Dune]

(broken link removed to http://www.iforgeiron.com/forum/f85/fan-speed-controller-14362/)

This thread covers many options of slowing down fans. On page three and four you will see inlet restriction discussed. Note that overspeed does not apply in your situatiuon because you have already created downstream resistance.

See if you can figure out which poster is me.

 

[barnartist]

Thanks Dune, I'll have to try that and see how it seems to effect the fan. I can hear the pressure as I block off the outlets, never thought to try the inlet.

I'll have to look for the schematic layout Dogwood, I think it might be better if I could use less power for the fan-this is one of the many reasons I am trying to get away from forced air. I have radiant in half of my house, and we love it. Love it. It is in floor radiant. I'll put it like this, I have a night mare of a floor to get this stuff installed-had to tear out drywall, and then this old modular house has some freaky strange floor joist layout. Lots of added blocks and double joists, we think to make room for the 4 axel trailer and its tires. It will be well worth it when finished.

 

[dogwood]

What type and model furnace do you have Barn Artist? On mine if you look on the furnace's fan motor housing the different connectors are all right in front of you, stacked four or five five slots high encased in white plastic if I recall. You just move the color coded heating wire connector up one or down one of five slots and the fan will either blow at more or less speed accordingly, at least on mine. You just have to figure which one is the highest speed slot and which are the lower speed slots. Just that simple and cost free.

When I get my installation done I will be moving the connector for blowing heated air up one slot to where the cooling circuit's wire connector is now, to use that higher speed. I'll flip them back in the summer. I hope the higher speed will blow enough air through both the cooling coil and the new W/A hx going in above the furnace, so I won't have to change out the whole unit to one in that puts out more cfms of air. I couldn't find a larger capacity blower motor to fit into the limited space in the Lennox. If you ever get to Virginia we can swap furnaces and solve both our problems.

Mike

 

[barnartist]

I have a Trane XL90.

I opened up the panel, I don't see any kind of board like that, but will try and find another panel to open.

 

[dogwood]

Try this long link for what may be a wiring schematic for your XL90. Look at Table A on the bottom of page 12:

http://docs.google.com/viewer?a=v&q...LHuFwr&sig=AHIEtbQqBOP9v6WKGw7yU6s6zVDpVZhHwA

 

[laynes69]

If its the same furnace, that diagram will work. I would put red on low heat and yellow on high heat if your only going to heat one room. That should be plenty for a single room. The Black wire could then be put on cool and that way you wouldn't have to change anything come summer. I did the same thing with our old wood furnace and was able to set the blower speeds according to the wiring diagram. Our diagram was behind the cover plate for the board which in our case was located in the area of the blower at the base of the furnace.

 

[barnartist]

Sweet Dogwood. Now I just need to find that wiring area. Maybe when I see the wires I will better understand. The power must go out to the wires.

 

[Fred61]

Reducing the inlet size will not damage the fan. It will run at a higher RPM because there will be less load on the vanes which could reduce power consumption, if it was a measurable amount??