wiring 110vac booster fan on a Goodman modulating 97% furnace

[Taz1956]

Hi all!, I'm new here and will be able to help a lot of people here in the near future.
But I am coming here because I cannot really find an answer to my problem on the net.
I have a new Goodman 60,000 BTU and need to wire a 110 vac duct helper fan to my furnace utilizing a modulating blower motor.
(not the easy just tap onto the motor leads and done) install.
I have the manual, wire schematic, and tried to connect a 3-32vdc to 110vac solid state relay to the black - and red + leads to the
blower motor, but did not work..... HELP!

 

[user 4883]

As you've discovered that won't work. Two different currents and volts don't work.
Can you post the schematic and/or manual link so we can see what were dealing with?

 

[Taz1956]

I thought using a 3-32vdc to 110vac solid state relay on (some) circuit that would energize when the ECM blower runs, would be a good choice.
See attached schematic. Where I marked in red dots the black (-) and red (+) to the blower I tried connecting the solid state relay to the low voltage (In) connection and then I took a hot lead and connected it to the (out) high voltage side of the relay to turn on the two duct blowers I have installed in 2 far runs from the furnace. (I got partial hum/run on duct motors when turned on power. (not good) Thank you for helping. I usually figure most things out, but not this time. Sorry for the delay response. - Bob

 

[user 4883]

I think I found the problem.
Do you have any information for the relay you are using?

 

[user 4883]

I looked over the schematic and realized that the transformer is VAC TO VAC.
115VAC to 24VAC. So it's all AC. Your VDC to VAC relay will not work, it too has to be VAC to VAC.

 

[Taz1956]

Hi!
Oh boy! I thought it was a dc motor. I was wrong!
yes, the in voltage of the relay is dc, and out voltage ac.
I see I have to purchase an ac 3-32Vac to 110Vac relay. If I connect the same places I marked on the schematic, it should work, correct?
Meantime, I will purchase a relay now anyway before you answer.
Thank you ! - Bob

 

[user 4883]

Pure speculation on my part, I don't know if the ECM/Micro is converting AC to DC for the motor. Take a volt meter and verify the type of current controlling the motor AC vs DC.
Assuming that your using a relay and not a transformer, yes it should work.
I wanted to get info on your current relay so I could verify the correct part and the watts/amps for the relay so as to not overload the circuit board and/or current transformer.

 

[Taz1956]

Hi kok328,
I am sending a screenshot from McMaster Carr with specs that is coming tomorrow (Wed. 29):

It is a ac/dc 3-30 duel voltage type and maximum 300Vac out voltage. That is the only SSR I could find. Most are dc to ac control.
This should help.
Thanx again! ..........Bob

 

[user 4883]

Cool, that will work for both AC & DC controls.

A couple of things:

- the switching action of this relay is listed as "Momentary Contact" not "Constant Contact", so I expect it to just bump the fans on/off once when the main blower is running constant.

- it's rated at 7.5amps w/o heat sink; check the nameplate ratings in the booster fans and make sure your within specs.

- you don't necessarily have to tap the motor to energize the relay, you could come off the thermostat connections "C" & "G".

 

[user 4883]

Ever get the new SSR ?

 

[Taz1956]

Hi KoK328!
Finally got to test out the relay with a power supply I have. It does work and stays on with a test 24v power supply. That is the good news.
Now the bad. The two wires I connect to does not carry voltage to the ECM motor, so the relay does not trigger. I read you said I could put the low voltage wires on the thermostat terminals, but I don't want the helper fans move air until the heat box is warmed up when the blower starts.
Looking back at the schematic, I don't know what else wires I could use coming off the blower because I think the wires numbered 1-5 are from the computer sending signals to the blower motor. There is a hot and neutral wire to the blower, but they are constantly on.
What I think happens is the ECM motor has internal wiring changing speeds sent from the computer board. It gets 115Vac from the two wires I mentioned, and internal voltage reduction happens inside the motor. I am afraid to blow the computer up connecting the other wires. I put a meter on the red and black wires thinking these are low voltage, but no current was measured. I'm thinking these are data lines from the computer control board. Is this right? I don't know what else to connect to and would like some ideas, but I don't think Goodman would tell me because I am not a certified installer. What now can I try? Any ideas would be gratefully appropriated. Thank you for all your time, and anyone else that has an answer to simply connect 2 duct helper fans to my furnace.

 

[user 4883]

Are you sure the thermostat terminals turn on the fan before the heater box is warmed up?
may have to install a temp sensor between the thermostat terminals and the SSR; designed to "close on rise" (adjustable cut in/out would be sweet).

 

[Taz1956]

I got it!
I connected my fans to the air cleaner output terminals which are 115vac, and Vola! she chooches!