Do I need a transformer if my furnace has HUM port

Hello, yes the transformer will get a 120 volts from the Furnaces control board, there should be a terminal labeled HUM on the control board. You need to bring 2 wires one from HUM and one from a nuetral tap on the board to the line side of the transformer, this way every time the blower motor on the Furnace turns on the humidifier will aswell.

Hello, in order to turn your humidifier on with the furnace the 120 volts coming from your humidifer you must hook it up to a step down transformer, then the transformer will provide 24 volts to you humidistat and solenoid valve. So you need a wire from the HUM on your control board to transformer primary side and a wire from neutral on the board to primary side of transformer. Then you need low voltage wire from secondary side of transformer to humidistat from humidistat to humidifier.

Okay, I looked up the installation manual online to see exactly what you are working with.
Yes the R anc C need to be hooked to the transformer supplied with the unit. The primary 120v side needs to be hooked into the power coming into the furnace. this can easily be done were the L and N get hooked into your furnace or circuit board on the furnace. This will provide the contiuous power to the unit. Preferably you will hook this after the door switch of the furnace so that you will kill the power toit if you take the blower door off.
The ODT terminals are for the outdoor sensor if you want to hook that up it will vary the humidiy in your home according to the outdoor temperature then.
Now the W/G and Cf terminals. If you have 24v coming from the HUM terminals of your furnace you DO NOT need a second transformer. You must check your furnace manual or check the voltage to them with the furnace blower energized. The HUM terminals will only have power to them when the blower should be running.
If the HUM terminals are 120v then you need to get another transformer and hook up the primary side to the HUM terminals so it is powered only when the the blower is running. Hook the secondary side to the W/G and Cf terminals.
So bottom line is that you need to figure out what voltage your furnace is giving to the HUM terminals and then go from there. Some times the EAC terminals or the ACC terminals will be 24v on the furnace board. Either of them could be used also, as they are only energized when the blower is running also.

Heatman101

some one has the humidifier hooked up to the R and W on the furnace.
1. it should be hooked up to its own transformer or to a proper low voltage terminal on the circuit board(beware there are high voltage HUM terminals) markd HUM and the other wire to C or the common.
2. You could hook the wire to W or white and C Common but I would rather see a seperate transformer since there is a possiblity this could cause solenoid chattering

it is best to use a seperate transformer for the hummidifier, but in some cases you can use the low voltage t-stat wire that runs your furnace, you will need to have one wire run to common, and the other to the heating side of your low voltage, normally its the red wire hooked to the w circuit of your terminal board, if you do decide to go with an extra transformer, make sure you you have it wired to bring on the humidifier only when the unit calls for heat, hope that helps

control board has eac terminal . will provide 110v to hum transformer anytime fan running.

also can pick up current sensing relay to sense blower power up and will then power the Hum. transformer.

See if you have a screw marked EAC This to power an Electronic Air Cleaner unlike the HUM it also gets 120VAC only when the fan comes on. Not sure what make of furnace you have but if your heat is working OK don'tn change the control board the can be very expensive. there are other ways to wire humidifiers without using the HUN screw

Sounds like you may have put 120v through a 24v solenoid and humidistat.
Is the HUM terminal on the furnace 120v or 24v?
If it is a 120v terminal you will need a 120x24v transformer and a new solenoid and maybe a new humidistat.

Make shure the 24 volts is hooked up to power that is only powered up when the blower is running. Some furnaces have a HUM terrminal on control (make shure the HUM is 24 volts some are 120 volts then you must use the transformer supplied with the AP 600). You can use a RP # 50 relay that senses current only when the furnace motor is running on the heating speed. Hope this helps

I WOULD CHECK TO SEE IF YOU HAVE ENOUGH V/A OUT-PUT ON TRANSFORMER. I DONT KNOW IF YOURS CAME WITH ITS OWN TRANSFORMER. IF IT DIDNT YOU SHOULD HAVE A MINIMUM OF A 40 V/A RATING STAMPED OR PRINTED ON THE EXISTING TRANSFORMER. IF THE TRANSFORMER IS EXTREAMLY HOT ... YOU MAY NEED A 75 V/A TRANSFORMER WITH THE SAME VOLTAGES. INCREASING THE V/A CANNOT DAMMAGE ANYTHING IT JUST GIVES YOU MORE POWER WHEN EXCESIVE CONTROLS AND WIRING ARE ADDED TO A HVAC LOW-VOLAGE (24v) CIRCUIT. IF YOU LIKE YOU CAN CALL ME AT 727-363-7071. I AM A RETIRED HVAC&R CONTRACTOR WITH 45 YEARS EXPERIENCE. I HATE THE NEW SENSORS THEY HAVE TO ACTIVATE THESE NEW HUMIDIFIERS. I USE TO WIRE THE HUMIDIFIER TRANSFORMER (SUPPLIED WITH HUMIDIFIER) TO THE LINE (110V) SIDE TO THE LOW SPEED ON YOUR BLOWER MOTOR. THAT WAY THE ONLY THING THAT INTERUPTS THE CICUIT IS THE HUMIDISTAT. YOU NEVER WANT THE HUMIDIFIER TO RUN IF YOUR SYSTEM IS NOT "CALLING FOR HEAT". NEVER TRY TO ENERGIZE THE WATER SOLENOID THROUGH YOUR HEAT WIRE(USUALLY SMALL THE WHITE WIRE) FROM THE THERMOSTAT. THIS WILL RESULT IN BURNING YOUR HEAT ANTICIPATOR OUT ON THE T-STAT.