19% Humidity !! WHY???

[ettevroc28]

Help please! I could use some informed opinions or advice!

I just spent $xxx for a Carrier LFP Humidifier, and the last two weeks have seen my indoor humidity decrease all the way to 19% as measured both by turning the knob to listen for when it clicks, and using a Radio Shack test meter.

The company who installed it sent someone out who took the lid off and showed me everything was soaked. That and the pump is actively dumping water down my drain every few minutes are the two things he said he could check to prove that it's working right. He tried to tell me it's that dry outside and that it would be much worse than 20% without it. I have a forum at work for safety and environment type questions, so I asked on there and about 10 different people who also live in this (N. Virginia) area said 19% is way too low, and that their home is in the 40-50% range no matter what the temp/rel humidity outside is. So what do I do to make the company come and fix this thing? How do I prove to them that it is not doing it's job?

Many thanks!!!
Mike

[Edited by BC1 on 03-11-2005 at 03:14 PM]

[jacob perkins]

Originally posted by ettevroc28
Help please! That and the pump is actively dumping water down my drain every few minutes are the two things he said he could check to prove that it's working right.
Many thanks!!!
Mike

[Edited by BC1 on 03-11-2005 at 03:14 PM]

So,it is dumping down the drain,or it isnt?
Is it warranteed?

[dhvac]

how cold was it out what was humidity outside?

[midhvac]

[QUOTE]Originally posted by ettevroc28
I asked on there and about 10 different people who also live in this (N. Virginia) area said 19% is way too low, and that their home is in the 40-50% range no matter what the temp/rel humidity outside is.


You don't want the RH in your home "to be in the 40-50% range no matter what the temp/rel humidity outside is". That's a perfect recipe for mold. To prevent moisture from forming inside the walls or on the windows when outside temps are lower, the humidity level inside must also be lower.

The cause of low RH inside the home is the difference in temperature between inside and outside the structure. This happens because the higher the temperature the more moisture it's capable of holding.

Keep in mind that although your home is your castle, a large amount of air is constantly being interchanged between it and the outdoors.

When the air outside is at 35% RH at 20 degrees, the amount of moisture contained in that air is only enough to make the indoor air achieve 4% RH at 70 degrees.

The looser your house is, the more air interchange takes place with the outside. So the humidified air that is being added by the humidifier is rapidly being replaced by outside air containing much less moisture. So the same humidifier would be able to maintain a much higher RH in a tighter home.

You must also keep in mind that the humidifier only operates when the furnace does, so anything that raises the temp in the house will make the indoor RH lower because it will increase the number of degrees between inside and outside air. I.e., if you have another heat source you're using or there is a great deal of solar radiation through lots of windows and skylights the house will warm up without the furnace coming on.

You'll have the same problem if the furnace is oversized for the house. The furnace won't stay on long enough for the humidifier to add enough moisture.

Also, the colder the water going to the humidifier or the cooler the air going through it, the less water will be turned to humidity.


[Edited by midhvac on 03-11-2005 at 08:00 PM]

[teddy bear]

Most humidity meters are unable to measure %RH below 30% accurately. For a check, at 70^F, a glass of ice sweats at +28%rh. In a cold climate, this is max for humidity or windows sweat.

[nicholasa]

TB You back ?,
Just for comparison:
I have 4 humidity/temp sensors around the house.Foam house, interior temp 70 deg, night time ext temp 20-25deg.

Interior humidity 40%, no condensate.
I let the humidity climb to 44% and had slight condensate on the bottom corners of 1/2 the windows 1 morning (anderson series 400 wood tilt sash)
After that I am keeping the inddor humidity below 40.

My mechanical ventilation is not up and running yet, but this has giving Me a chance to "play/experment" with a foam house using the exhaust ventilation and cracking windows.


Using the multi speed jennair air for exhaust and cracking windows for intake. I found that it takes alot of CFM to Bring indoor humidity down, but then not much to maintin it. With a family of 5, intermittent does not work well, once the ventilllantion stops, the indoor humidity goes up, then it take high CFM to bring it down. This is with spot ventilation in baths being used at bath/shower time.

I think many underestimate how tight a "foamed" house is, or how leaky a FG batt house is.

Starting some row home Rehabs in Federal Hill Baltimore (11'-6"W x 30'-00" deep) these places are going for 400K-600K finnished, Complete gut jobs. I have abandoned FG insulation for good, but as the builder, have better understand the Ventilation issiues.
While I hire Lic HVAC contractors, I find they dont understand/care much about anything past "setting the unit, and getting the check", so I end up doing most of the design work
(dont get me started about Arch-i-techs, "Yes mam, very nice floor plan and perspective drawing, but Would You mind producing a set of structural drawings")

Nick

[RoBoTeq]

Unless you keep your house above 80º, you don't have 19% humidity in Northern Virginia, something is wrong with your hygrometers.

[teddy bear]

Originally posted by nicholasa
TB You back ?,
Just for comparison:
I have 4 humidity/temp sensors around the house.Foam house, interior temp 70 deg, night time ext temp 20-25deg.

Interior humidity 40%, no condensate.
I let the humidity climb to 44% and had slight condensate on the bottom corners of 1/2 the windows 1 morning (anderson series 400 wood tilt sash)
After that I am keeping the inddor humidity below 40.

Using the multi speed jennair air for exhaust and cracking windows for intake. I found that it takes alot of CFM to Bring indoor humidity down, but then not much to maintin it. With a family of 5, intermittent does not work well, once the ventilllantion stops, the indoor humidity goes up, then it take high CFM to bring it down. This is with spot ventilation in baths being used at bath/shower time.

I think many underestimate how tight a "foamed" house is, or how leaky a FG batt house is.

When changing %RH in a home, you are changing the moisture content of the air and materials. This requires extra moisture removal. If the interior materials weight 10,000 lbs, changing %RH, you may require removing or adding 3-4 lbs for the air in the home and 100-400 lbs of moisture from the materials.
Regarding the moisture level before condensation, depends on indoor air temp, insulation of window, outside temperature, and wind velocity. Your home sound good for air tightness. Keep us posted.

[drk]

40 - 50% is not to high! Im in VA also I'm at 55% today at 71 inside 47 out rain. Get your HVAC company to take it out and give your money back. Go and by a table top humidifier works better, less cost, less maint.

[nicholasa]

Drk,
What type of insulation do You have ?, is it a tight home ?

I am in maryland - outside 45 deg/ 80%RH.
I am now running an ERV and inside temp of 71 deg.

Looking at the Psychrometric chart (if I am using it correctley) 45 deg/80% RH air warmed to 70 deg should be about 33% RH.

So either your home is tight, You are producing alot of water vapor in the home or I messed up on the chart.

With My ERV running 24/7 for 1 day now My indoor RH is 41% @ 70 deg. a little higher than I wanted, but not to bad for rainy 45 deg outside. I would be concerned if it was Jan (20deg OAT) and My ERV kept the inside at 40% RH.
another 2 months and I will need the Whole house Dehumidifier to work with the ERV or inside RH will climb above 50%, or I may just cut the ERV off and use fresh air intake with the Ultra-Aire for spring/summer/early fall months. I plan on monitoring the temps/RH through the year, So I see what works, and what does not.

Nick

Nick

[drk]

House about average as far as tightness goes. Bat in walls 3.5 in Atic 5 inch blown fiberglass 6 inch blown paper