Any Way to Control Fan on a Carrier Furnace?

We have a Carrier Furnace, I believe it's called the Weathermaker or something like that. Anyone know of a way to control the fan in this thing? Last season, we tried turning the fan ON from our thermostat and just letting it run to circulate the heat from the Hyfire, but it's a 2 speed fan that, when the furnace is on, runs on low, until a certain temp is attained, then it switches to high. When we turn the fan on manually from the thermostat, it will not run on high, it only runs on low, and low is not enough to move the heat thru our ductwork. Our neighbor, a licensed electrician, took a look and he could not figure it out, neither can my husband.

if it's a 2 speed fan, there has to be multiple connections into the motor somewhere to tap the low and high speeds, you may have to follow them onto the circuit board and tap directly into them with a plenum switch or something.

It is possible to do and I did it to my Weather King Furnace. made by Rheem. What you need to do is add a few 115 coil 125VAC 8Amp contact relays to the system, a barrier strip, and a few terminal connectors.

The high side of the fan circuit board goes to relay one, plus a ground from the furnace. You need to run a 110 wire that activates your Hyfire circulation blower to relay two, both hot and common.

The contact sides of both relays need to take 110 power from the feed of the furnace circuit board and run to each relay normally open side. Then the normally closed side from both relays goes to a barrier strip where all of the screw terminals connect together. Then run a wire from the barrier strip terminal to the high fan wire.

This will allow the high speed fan to work whether the furnace calls for high speed, or the Hyfire calls for the fan to operate, or if both call at the same time. If you show this to your electrician friend, he should be able to assemble this to work.

If you don't want the Hyfire circulation blower to automatically activate the high speed furnace fan and only want a switch, this description should also allow your electrician friend to modify the wiring to allow for a manual switch. At least it will get your electrician friend on the right thought pattern.

Hi, Doug, our electrician friend said that it looked as if everything was going into a motherboard. Does what you described pertain to a computerized furnace?
(circuit board = mother board?)

We will definitely show your instructions to him to see what he says. Thanks much!

WNY wrote:if it's a 2 speed fan, there has to be multiple connections into the motor somewhere to tap the low and high speeds, you may have to follow them onto the circuit board and tap directly into them with a plenum switch or something.

Dave, thanks, we'll get this working somehow! We tried to get info from Carrier, but it's a big secret... they don't want anyone to know!

Yes, the furnace circuit board has terminals for the different fan speeds that attach to the proper color wires on the multi-speed fan motor. Some furnaces have two, three, or four speed fan motors, but only use what is needed for the duct static pressure. Usually high speed is for Air Conditioning, medium speed is for the Heat, and low speed is just the fan running for circulation. The terminal that connects to the fan is where you tap off to activate the coil in the relay. Then the fan wire can be connected to the contact side of the relay.

I used this relay I got from Graingers. http://www.grainger.com/product/STEVECO-Enclosed- ... elay-4E941 But depending on how you plan to wire it, you could use the 24 volt side to also activate the high speed furnace fan from your Coal-trol, if you have a Coal-trol and it is equiped with the 24 volt terminals.

Here is a link to the relay page from Graingers. It should help your electrician.
http://www.grainger.com/Grainger/hvacr-relays/hva ... sst=subset

Doug, THANK YOU SO MUCH! Yes, we have a Coal Trol. How do we know if it has 24 volt terminals?

Last year a lot of our heat wound up coming out of a return duct on the 2nd floor, with some weak air flow from the 1st floor ducts. The upstairs return duct is straight up from where hubby tied the stove into our ductwork in the basement, and the furnace fan on low was not enough to blow that hot air thru the system. The upstairs bedrooms were sweltering and unusable, even with the heating ducts closed from the basement, between the return duct heat and the natural rise of heat from downstairs. (It's 3 bedroom house and we don't use them, they're basically guest rooms, but still...)

Our main floor was still warm, we maintained 69-70 degrees which was what we keep the Coal Trol set at, and our basement, where the stove is located, was toasty too (about 72), even though unfinished with no insulation. (A condition that we wanted to have rectified this year, but I was out of work for 1-1/2 yrs, so no money to buy insulation). I'm sure we'd use less coal if we weren't heating the 2nd floor to 90 degrees or more (and of course if we insultated the basement)! So, we heated 2700 sq. ft., 1100 of which is uninsulated basement, and 500 of which was way overheated (90+) with no problem. We did have to fire up the 2nd burner on the Hyfire II a few times, though, to keep the 1st floor at 69.

This year he wants to connect the stove to its own run down in the basement over to another area close to the furnace where he will tie it in to our home's duct work, (probably his choice of area where the stove is currently tied into also contributed to most of the heat going straight up to that return duct) and he thought to use helper fans, but if we can get the furnace fan to cycle on and off and to utilize the higher speed that it uses if the propane heat is running , that would be perfect.

We were also wondering about switching out our 2 Hyfire fans to the 512k fans that LL has been working on. Wonder if one 512k, (with one burner lit), would be enough to move the air thru our ductwork without the furnace fan or helper fans... current fans are 265 cfm each, I believe.

Wow, you have a lot going on. I see that you need the hot air to circulate. From what I understand, is that you have the Hyfire near your return furnace duct and you want it to circulate better through the house using the high speed blower fan on the furnace.

Okay, you have a Coal-trol. The Coal-trol has a 110 outlet specially designed for operating an auxiliary fan, usually a duct booster fan, on the main box. This is a great option for you to take the 110 power from to the coil of relay number two in the first description. The fan or control this outlet operates is done through the Coal-trols thermostat. Read through your Coal-trol manual and you'll see that you can set the fan on at a setting that you determine. I use this Coal-trol outlet to activate a small booster fan in my duct to a distant room when it gets cold. I set the fan to come on at a predetermined firing rate of the Coal-trol thermostat. It has solved my heating issue with that room. This is how the Coal-trol will activate your furnace blower, using the relays.

Even if you have the 24 volt taps on your Coal-trol, I wouldn't use them for this application, because the only place they would be useful is for operating the low speed fan by way of the thermostat wires. To get the high side to work using the 24 volt side, you would need a transformer and then back to the original description with the relays.

As for using the 512k fans, I'd see how this works before I'd change them out. The 512k fan will not be strong enough to blow through your supply duct system. Your low speed furnace fan is probably 700-900k and is balanced to your system. The high side is probably 1100-1500k.

I hope this helps.

If you want to have the Coal-trol turn on your furnace fan you'll need to get the "dry contacts" added to your Coal-trol control module. We do this for a small fee and you'll end up either with a set of screw terminals on your control module box or a set of break out wires that you can use to hook up to the furnace fan control circuit.

You should not use the convection blower output of the Coal-trol to control a relay. That output is speed controlled and will feed "chopped" power to the relay and may end up damaging it and the fan. You'll get buzzing and all kinds of odd results from the relay and the fan. If you want the Coal-trol to control the furnace fan the only way we recommend is to have the dry contacts installed on the AUX output of the Coal-trol.

There is another option, you can install a temperature limit switch into the plenum of your coal stove and use the output of this switch to control the relay on your furnace. You should be able to wire it in parallel with the furnace plenum sensor/switch so that both can control the high speed blower.

pvolko,

I agree, the fan limit switch attached to the coal furnace is a great idea and that is what I'm using to control my gas furnace fan to activate when temperature rises in the coal stove. I do run that to the relays though to activate the proper speed in the gas furnace.

I use the convection blower plug output on my Coal-trol to run a small inline duct booster fan. It was my thinking that if the amperage of the fan or multiple fans combined amperage was higher, a relay set up would be needed to handle the load. I stand corrected if this is not the case. I thought that the convection fan output was a steady on or off 110 voltage and not pulsing to vary the fan speed.

Paul, please advise me if I am understanding this correctly. If I needed to run more than one inline booster fan that exceeds the Coal-trols rated 3 amps convection output, wouldn't using that output to a relay to activate a higher amperage circuit be the proper way of doing that? Or is this output vary in pulses and not recommended?

Thanks because I was thinking of doing just that this season to push some heat to a needed area. DOUG

You should not run a relay off the convection fan output. If you had need to run more fan current than the convection fan output can handle, then you would have to get the dry contacts installed and use that along with a power source and relay to control a higher load set of fans in an on/off fashion.

However, you do bring up an interesting use case. Wanting the convection fan output to act as a on/off output instead of a speed control output. This is something that could be done in the software and would expand the flexibility of the control. If that were available then you could use that output to control a 120VAC input relay to control a high load output. Will put it on the list for the next rev of the software.

I don't know if this will help you but I have a heat pump with a 3 speed fan. The way mine was set there are 3 hot wires going to the motor. Red,blue and black, for the different speeds. Now I added a hydronic fancoil and a separate thermostat for coal heat. I use the air conditioning thermo. on fan run, which makes the fan run all the time. I keep this on fan run and have an aquastat on the fancoil, when it feels the pipe is hot the fan will run. Then I have a switch on the motor to turn from air conditioning to coal heat in winter. THIS way I don't have any electric backfeeds between the 2 units, just the aquastat feeling the heat to turn on the fan.

Mine is black-high , blue-medium and red is low speed. Mine only had 1 speed so I switch to different wires manually for different speeds. Switching the low and high speed wires might work ??? Ask your electrician friend first.

Thanks Paul. You have a great product and I am so happy I purchased one when you first introduced it here on NEPA. It truly is the best way to control your coal! I'll be looking for the updated version. Thanks again, DOUG

Pocono Newbies:
We spoke today about your "Carrier Furnace 58mvb" furnace. I have downloaded the installation manual and the "Coal-trol Auxiliary" fan option should work.
For this furnace there is the capability to select the speed by setting some DIP switches on the furnace control circuit board. The Coal-trol will run the fan automatically at the set speed.