Question about Aprilaire 700 Humidifier

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Aprilaire Model 700 - not achieving 40% humidity

I live in a Townhome - 1600 sq.ft built 13 yrs ago. 3 yrs ago I purchased the Model 700 with the automatic control and external temperature sensor. I live near Washington D.C where average temperatures in Jan and Feb is around 30-35 F. Very rarely it drops to 10 F - once or twice a year. I have alway been suspicous of the efficiency of the humidifier. I recently got an authorized dealer to make the control manual and change the water panel. They found the solenoid faulty and replaced it under warranty. I now get 1 quart of water from the drain in 2 and half minutes and this appears to meet the specification. I was hopeful that by keeping the control at 45% I would get 40% at the least but I never see readings better than 33% - with my Brookstone monitor and also matching the "click" on the Aprilaire humidistat. I have checked with the authorized contractor and they now say that this is the best I can get. I somehow am not convinced and was hoping to hear from other Model 700 owners if they have this problem and how they deal with it. I plan to also work with the Aprilaire regional manager but would like some more facts when I meet with him.

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  • dennissoans Jan 26, 2009

    After some research I now realize that my furnace is running under 50% of the time when external temperature is 31 F (dewpoint 10 F and RH 38%). Inside temperature is 70 F and RH 29%. I believe the Model 700 is rated for 35% RH at 70% run time. It appears on cold days - around 12-15 F it gives me around 33%. This appears to be as designed. The reason my furnace is running only 50% is probably due to the fact that I have closed the basement vents and 2 rooms on the upper level.

  • Anonymous Jan 28, 2009

    I too live near D.C in Loudoun Co. and just moved into a new home. The builder installed a Aprilaire Model 700 and I am not getting anything past 33%. I have a hot water line connected to the humidifier. I have called the installers and I don't think they know what the problem is. I am a musician and have lots of instruments in my home and need the R.H. to be at least 40-45%. I have tried running the fan but it has not worked. Please inform me if you find a solution.

  • dennissoans Jan 28, 2009

    Yes, I have tried running the fan but it makes no difference at all. I have hot water supply to the humidifier. The capacity specification for the Model 700 is 4000 sq. ft so I believe I am well within that limit. The real reason is that the furnace is not running above 70% as this area had mild temperatures and other factors (closing vents to reduce demand) which I have listed. I am now leaning towards the Honeywell Steam Humidifier which supplies moisture on demand and is not dependant on the furnace. I am reasearching the pros and cons of that system. The claim is that it uses less water also and can be installed remotely - does not have to be installed on the supply duct.

  • Anonymous Feb 23, 2009

    I have the same problem, I can't get it above 32% humidity. I believe the fan on the Aprilaire probably can't overcome the pressure inside my duct work and the moist air is blowing out of the humidifier. Check to see if your unit is drawing outside air by holding tissue paper up to the vents on the outside of the humidifier. If the tissue paper moves away from the humidifier then have your service people hook the control to the burner, at least you'll get some moisture into the house before the heater blower motor comes on. When it comes time to replace, I'll use the bypass model.



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If it is set up right, you should be able to run your fan 100% of the time and the humidifier will come on when there is a need for humidity. you can experiment with leaving the fan on and see if this helps. it will run your electric bill up a little and also you will have a lot of waste water. that is a drawback to the bypass type humidifiers. also a factor is if the water supply is hooked up to the hot or cold side. it will humidify better on the hot side, but you tend to get more deposits that plug the solenoid over time and you will be running your water heater quite a bit. 1600 sqft may be pushing the limit of this humidifier.

Posted on Jan 27, 2009


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Technical Support
Research Products Corporation

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