humidfier not working on Arcoaire H8mpv furnace

[WB3BSN]

I have a problem with low humidity. I have arcoaire H8MPV 2 stage 80% furnace (75,000 BTU). I also have Kenmore powered 3000 humidifier. A Honeywell TH8320U1008 thermostat (2 stage).

The humidifier comes on with the inducer fan. The humidifier drum is turning, the blower is working and it is getting water.

I have set the therm on low fire on 2cph and high on 3cph.

I have lowered the main blower speed.

Previously had a Amana 1 speed furnace it worked great. I had humidity levels of 45% or higher. I could keep the thermostat at 65deg and it was warm. No bleeding nose, no itching, no creaking floors.

Why won't the humidifier work on this newer furnace?

Thanks

[Jay11J]

Has the pad been replaced? An old/dirty had won't do much good.

Also, your older furnace was most likely was over sized, and it had a lot of heat to help w/ the evaporation of the water, where the newer ones are a bit cooler.

What is your avg run time on the furnace?

[WB3BSN]

Both furnaces were 80%. The old unit was also 75,000btu. I also live in a row house (heated neighbors on both sides). The powered humidifier is mounted above the A coil in the heated air. No external air, just heated air.
The pad is new and it rotates. The heater runs about 8 min, on low fire.

Is there anything I can do to correct this.
Thanks Jay

[Jay11J]

8 min is way too short of a run time on a two stage furnace. I'd say your furnace is oversized.

My 1st stage runs about 20 min.

[WB3BSN]

Jay11J
But the size 75000btu input on high fire and 42000btu on low fire is lower. The older Amana was 75000btu 1 stage is more. Both are 80% efficient. It would seem that this Arcoaire H8mpv is a lower output on low fire. The high fire does come on when it is very cold. Is there any setting on the thermostat?

[Jay11J]

How many sq ft is your home? When the dealer was out pricing out for your furnace, did they do a Manual-J (Load Calc) on your home? (Measure every room, windows, type of windows, and other info and enters into a computer)

When you said when it's cold 2nd stage does come on... Does it come on and run till the stats shuts off the furnace? or does go back to 1st stage and run?

[WB3BSN]

My home is 1600 sq ft plus a heated basement with a unheated garage built in. My OE furnace lennox was 100,000 BTU (1953) forced air. The man who did the sizing was hvac engineer. He did a lot of measuring and Had us put in return registers at the ceiling and floor to be changed seasonally. All of the neighbors had 2.5 ton units but we had a 2 ton unit with R30 insulation blown in.

The heater was a 75,000 Btu 80% single stage Amana. The house was warm and had humidity around 45%. The best part was the house was comfortable at 65deg.

The last heater Arcoaire h8mpv will drop back #1 stage and run.

The heater was just changed because of the need for a vari speed blower for a/c 17 seer.

The size and efficiency were the same on #2 stage.

Would closing off the supply in the room with the thermostat make a difference or changing blower speed?

Thanks for the help Jay11J

[Jay11J]

You could close off the vent in the room w/ the t-stat, and see if it can make the run run longer.

Blower could be dropped slower as long it stays mid range of the temp rise specs on the data plate on the furnace.

The drum style are a dying breed, and flow though are used more, and with those hot water can be tied into it and helps with adding humidity.

[WB3BSN]

Well it has been cold out.I have tried it for 2 days. The 1st stage runs much longer. Closing the vent in the room has made the house warmer. But the RH is still around 25%. There is something missing to answer this problem. How can a humidifier that worked so well before not work at all now?

Our water bill is high enough now, I don't like the fact that the bypass humidifiers waste so much water. And I don't even know if they would work.

BTW
Thanks Jay for being so patient with me.

[Jay11J]

Should be working.. Did they add a fresh air run into the return from outside?

When you remove the cover, you feel the hot air blowing into the humidifier, and air getting sucked back in?

[WB3BSN]

The humidifier is mounted on the duct above the A coil. There is no outside air supply. The humidifier has a squirrel cage blower and a small cooling fan for the motor of the blower. There is also a motor that rotates the drum.
The drum and blower are sealed when it is assembled. I have removed the drum, rotating motor, and reservoir. Once it is out you can feel the hot air blowing out of the holes of the plenum stiffener.
thanks
Rob

[Jay11J]

Ok, that is an older style, I have not been around those....

make sure the fan on it is working.

[WB3BSN]

Jay, I want to thank you for being so kind and trying to help to help me.

I'm a 52 year old ASE master auto tech. If I can ever help you please contact me.

Rob

[Jay11J]

No problem, Couldn't be much help at this time.

Feel free to help others on here in Automotive section of this forum.