DIY - How To Install a Whole House Humidifier

Copyright Randy Melton 2007

Section 1 - Background

Our new house didn't have humidifier as a standard feature. The builder charged $700 to install what he called a wick humidifier. I decided I could get a better one for less money. This page details my research, the installation and the results.

When I started this process I had the following humidity "tools":

Digital Hydrometer - which read around 20%
A one gallon steam humidifier in our childs bedroom (filled each night so 1 gallon/day)

Section 2 - Review the available humidifiers

Type	Cost	Mfg	Notes
Steam	$700-$1500	autoflow s2000	??
Pad/Wick	$150	aprilaire 700	??
Drum/Wick	??	??	??
Biscuit	??	??	??
Centrifugal Atomizing	??	Trion 707U Walton Labs WF-225 Walton Labs WF-225	??
Drum/Disks	$200	desert springs ds3200	??

bypass - This refers to the fact that it is connected to both the intake (return) and exhaust (hot air plenum). This in exxect uses the furnace fan to move air across an evaporative surface. atomizers do not need this, and some evaporative units have built in fans that move the across the evaporative surface (ie the Aprilaire 700).

Section 2.1 - An Estimate of the Energy Consumption of a Steam Humidifier
Assumptions:

An autoflow s2000 consumes 1.4kW when energized (from product spec) (I assume there is a feedback setting the onn/off duty cycle of the heating element. Depending on heat loss from the chamber and evaporation rate. I was trying to guess this)
It evaporates a maximum of 18 gallons/day (from product spec)
Assuming you need to raise 18 gallons from 105°F to 212°F (supply is from hot water tank)
A U.S. gallon of water weighs 8.3 pounds (from wikipedia)
A guess at the heat loss to the vent (ie heat lost that doesn't contribute to evaporation) say 50%
The Calculations:

107°F * 18gal * 8.3lbs/gal = 15985.8 BTU (1KWh/3410BTU = 4.7KWh)
Assuming the 50% efficiency factor thats around 10KWh/day
4.7KWh * 7-cents/KWh = 33 cents/day or $10/month (see gasVsElectric)
10KWh * 7-cents/KWh that's 70 cents/day or $21/month (see gasVsElectric)
Working back that says the duty cycle is something like 15-30% ((5KWh or 10KWh)/(24*1.4))
Note that using room temp water (assume it drops to room temp between humidity calls) gives:
(212°F-65°F) * 18gal * 8.3lbs/gal = 21961.8 BTU (1KWh/3410BTU = 6.4KWh)

In reality the house will achieve a balance between humidity loss and humidity added. I doubt that is 18 gallons a day. So the initial ramp up will draw between 33 and 70 cents a day. After that the energy required to maintain depends on humidity loss. (I'm not ready to attempt those calculations)
It should also be stated that a bypass humidifier is not free. The act of evaporating water will cool the air (see heat of vaporization or evaporative cooling) I'm not going to calculate this but I'll assume it is much less than 33 cents/day especially since I'm using gas heat. (note to self: I need to double check this assumption. I found the Latent Heat of Evaporation of water to be 970.4 Btu/lb which is higher than I remembered. Wikipedia says it is 5 times the energy required to heat from 0°C to 100°C.) Since both steam and evaporative units have to supply the energy for this heat of vaporization I'll stick with my assumption that evaporative units use less energy.

Section 3 - Installing the ds3200

I selected the ds3200 based on the fact that is seems to be a reasonably priced bypass unit. (I like the steam units but couldn't justify the extra up-front purchase price.) I found that the local Lowes store carried the ds3200 for $198 (less than they advertise on the web site.) This combined with a 10% coupon was the final push. If this unit doesn't work out I'll replace it and document that here. (I found a review by Gray Watson to be useful.)

Section 3.1 - Unpacking The ds3200

Here you can see all the parts included in the box. It includes everything you need for an install assuming you have access to a water line eith from an existing unit, or are willing to use the saddle valve to pierce a nearby copper water line.

I had to purchase the fittings to tee into a pex water line and reduce it down to the 1/8-inch supply line. I also purchased a garden hose connector, a ball valve and some 1/2-inch pex to add a drain valve. The ds3200 includes a cap for the drain, but I wanted an easier way to drain it.

My furnace has a humidifer and elecrtostatic power supply output on the main board. These are 110v screws that are energized during heat calls (The cleaner is energized whenever the fan is running.) I bought a metal electical box and wall plate to attach to the side of the furnace. I wired this to the furnace "hum" terminal so I would have a convenient place to plug the wall transformer that powers the motor in the ds3200.

Section 3.2 - The Install Process

Drill	Pilot holes in ducts
Metal Snips
Pex Crimp Tool
Pex Cutter
Crescent Wrenches	Used for the brass reducers
Screwdrivers

metal juntion box	I wired the HUM/COM output from my furnace to this box
electrical outlet	(same)
pex to brass fitting	I don't like the sadle valves especially with pex
brass 1/8-inch reducers
brass cutoff
1-foot 3/4-inch PEX	This is my water line. I added a tee and a ball valve to feed the basement.
PEX crimp rings
1/2-inch PVC ball valve (used for drain)
1/2-inch pex line (used for drain)
1/2-inch Barb x 1/2-inch MPT male adapter (drain, valve to pex) UPC-084169687807
3/4-inch FH x 1/2-inch FIP Hose Adapter (drain, garden fitting o DS3200 to ball valve) UPC-048643071926

3/1/2010 Update - 3 years in service

3/1/2010 - Here is an update on the service maintenece and reliabillity of the humidifier after 3 years of service. Up until this point it has been relativey maintence free. I flush it about twice a season (which is not neraly enough.) Each time I have noticed calcium buildup seeping aout from around the lip between the lower and upper housing. It is easy enough to remove the upper hoiusing and clean the unit. This involves removing the drum (which lifts out) and cleaning it as well as cleaning the interior of the unit. The basi is pretty clogged with calcium. I use a solution of CLR and water in a spray bottle conbined with a small putty knife. I considered the automatic flush but didn't like the idea of it cycling without me being present. (The drain pipe I installed just goes to a floor drain in the basement. With the angle of the drain pipe I'm uncomfortable taht wtaer might puddle past the drain.) I'll probably start manualy flushing it every month at this point.

Last year the motor make noticable niose but I ignored it. This year I was wondering why it was so quiet. I investigated and found that the drum had stopped spinning. So today I took it apart for a more thourough cleaning. I removed the motor mounting plate to get easy access to the motor. I noticed that the mounting bracket had very noticable wear and was near the point of failure. (see photo) I assume this is caused by friction where the drum shaft rides in the plastic slot. constant clockwise presure/rotation has worn almost completely through the plastic guide. (Desert Springs advertises the replacement part on thier website, but they seem to no longer stock the 2007 motor. The have a new "gearless" motor that comes with a new side bracket. From the looks I assume this means the drum will be more difficult to remove/clean so I'm not taking that option yet.

Given the prospect of buying a new motor and bracket I decided to try to clean/repair the existing one. (I am reasonably comfortable working on parts like these, but I do not recommend this for the average homeowner.) There are 4 pressed metal tabs that hold the motor together. It was simple to pry these open and get at the insides of the motor. There was a lot of for lack of a better word "gunk" and some calcified deposits on some of the nylon gears. (I'm not sure what the gunk was, it seemed to be part calcium, part rust, and the rest just junk.) There are four nylon gears not counting the output drive gear and the rotor. It looks like the back of the motor unit contains the windings of a synchronous motor and the rotor is a permanent magnet which is easliy removed. I cleaned all the gears nd rotor and reassembled the motor applying a small ammount of lithium grease. It runs smoothly now. I am attempting to reinforce the bracket with some plastic epoxy (brand name "Plastic Welder"). I'm not sure of the relative hardness so I don't know how well this will work. The drum shaft has some rust or pitting so that it will be abrasive. After teh epoxy cures I'll test it. I expect to have to fix this again with a year. If I can't devise a better drum guide I'll try the new "gearless" option from desert springs.

All things considered this has been a reasonable unit. It will require annual maintence.

References

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