Aprilaire 700 not raising humidity in my house


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Old 12-28-04, 09:53 AM
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Aprilaire 700 not raising humidity in my house

I installed a model 700 about 2 weeks ago (about 2300 sq ft home). It is functioning properly the best I can tell. It is connected to the HUM terminals of my blower and when it comes on, the solenoid opens and water flows, I also see water coming out the drain line. The unit is on the hot side of the duct just above the furnace. The humidstat controls are on the supply side and the OD probe is mounted outside the house.

My problem is that I cannot get the humidity about 31% in the house. In fact, before I turned this thing on, it was at 30% and only moved 1%. I started with it on the 5 setting (automatic mode, not manual) and just turned it up to 7 two night ago. No change.

When furnace is blowing, if I turn the knob down to when the solonoid closes and then turn it back to when it kicks on, it clicks open around 3 or 4 setting, so the humidity is low compared to what I'm asking to to be at. I also confirmed that the Aprilaire fan is blowing when powered.

I have 2 different humidity sensors in the house that both read roughly the same number (30% or so) so I don't think those are incorrect. There is also no condensation on my windows. I just laid those meters one my heat vents while it was blowing and they registered 22% humidity and 105 degree air!! What the heck?!?!

Help is appreciated. Thanks...
 
  #2  
Old 12-30-04, 03:42 AM
Scotaku
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The humidifier is being held back by the furnace and thermostat control. You've set the temperature in the house to something comfortable to which the furnace is responding and raising the temp to just that level... but the humidifier is only able to work when the fan is blowing. Once the temp has been reached, the system shuts down and effectively keeps your humidifier from finishing its job.

Don't worry. I figured this out after a little thinking and wondering myself.

Since the humidifier needs the air to be moving, move the air. If the furnace is triggering the automatic fan to cut off after a temp has been reached, why not separate the two? I cranked open my humidistat control to 10 (full on, Noah and the Great Flood setting) and changed the thermostat's fan control from Auto to On. If the furnace needed to burn to heat the house, fine. I let it go like that for the weekend after Thanksgiving... it took two days to raise the humidity in the house (my hygrometer is in my computer room on the second floor) but it worked exactly as I thought it would. It's a nice 35% now and the thermostat fan is back to Auto. To set the humidistat, I paid it a visit while the fan was back on Auto and, while running, turned it down to just above the point where the humidifier shut off. It's been steady ever since.

For the record, I'm using a Desert Spring humidifier. Running the fan the way I've just described should work for any type of system though. Don't let the furnace cut off the fan until you've got the humidity up to a level you want.
 
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Old 12-30-04, 08:09 PM
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To add to what Scotaku posted, the HUM terminal of the furnace may only allow the humidifier to run when the burner is on. You may need to move to another power source (like a terminal for an air cleaner) to get the humidifier to run with only the fan on. Then switch the fan to the on setting and let it run for a while. With a little luck you'll find that the humidity goes up and stays up like Scotaku's did. It's also possible that the humidifier is not big enough for the house. Many factors besides square footage have to be taken into consideration.

Doug M
 
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Old 01-25-05, 09:46 AM
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Installed a flow through Honeywell 360A a few weeks ago on the supply side of my basement furnace. Mechanical humidistat on the return side. Cold water supply. I took Scotaku's advice and ran the blower/humidifier for 48 hrs straight to try and raise the relative humidity in my home. Verified water flow and fan operation on the 360A. However my relative humidity has only gone up maybe 1-2% (22->24% or so read from the mechanical humidistat.) I'm heating approx 2500sq ft - basement and main floor open floor plan. I have a secondary furnace 2nd floor w/ no humidifier that heats bedrooms only. Am I asking too much for the 360A (specs say up to 4200 sq ft home but I guess that is running continuously?) Outside temps have been about 20-30 degrees F for the past week. Any advice appreciated.
 

Last edited by djwcaw; 01-28-05 at 03:41 AM.
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Old 01-28-05, 03:39 AM
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Scotaku: Did you have your Desert Spring hooked up to a hot water source? Outside temps yesterday in my area dropped from 30F to 15F and my humidity level shot down 25% to 20%. Last night was a very dry, uncomfortable one. I cannot seem to get my level past 25% (see previous post.) I'm thinking I need to hook up to a hot water source so I can get the high evaporation I need and run the blower for 24-48 hrs or so. Though I'd rather not use the more expensive hot water for daily auto operation.
 
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Old 01-28-05, 07:29 AM
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Just a note: Using hot water instead of cold is generally not any more costly, assuming the same fuel is used to heat both the house and the water. The heat from the hot water is transferred to the furnace air stream where it adds it's heat to the house and decreases the amount of heat the furnace needs to deliver to satisfy the thermostat. If you check the water flow comming from the bottom of the humidifier, you'll find that it's quite cool (in fact, mine's quite cold).

Doug M.
 
 

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