700
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Reddit Reviews
4kVHSI switched from three standalone humidifiers to an AprilAire 700 and it works so well that I haven’t had to run the standalone units anymore. It works really well and way less maintenance once you get it installed.
AprilAire 700 if you’re able to install one in your HVAC. Works way better than the standalone units.
FinishOk8266Steam is mainly about control and consistency. It actively generates vapor, so output isn’t tied to furnace runtime and it maintains target RH far more reliably in cold weather. Drip/bypass units like the Aprilaire 700 are cheaper to buy and run, but their effectiveness drops in cold conditions, they only work when the furnace is on, and evaporation leaves minerals behind—causing scale, frequent pad changes, and fine mineral dust entering the airstream, with the issue becoming worse as water hardness increases. Over long periods, inhaling fine particulates is associated with chronic airway irritation, can worsen asthma or other respiratory conditions, and may contribute to long-term lung function decline. Steam still needs maintenance, but it keeps minerals contained in the canister. Cost-wise, bypass units are roughly $20–$40 per season, while steam is closer to $100–$200. In many cold, dry climates, bypass units struggle to get past ~30% RH, while steam remains reliable.
Jazzlike_Paint_3893Definitely go with the Aprilaire 700 series for that setup - they're solid and handle that square footage well. Since your heat pump runs most of the time you'll want one that doesn't need crazy high temps to work properly and Aprilaire nails that
jgiacobbeWe have an aprilaire 700m humidifier built into our hvac and the best it has been able to do is hold at 37% RH. It does help though.
ldskyflyI have one and like it. I have a basic aprilaire bypass unit. If I had the space though I would have gone with the aprilaire 700. And if you have the circuit available and easy to wire, a steam unit is the most ideal.
r3hpotThank you for the advice. Is there a recommended evaporative humidifier? I already have aprilaire 700 in the hvac, but that only gets us to 40-45%. Hoping for 50-60% for the young kiddos. Could I replace the aprilaire with something “bigger”? Or wider to have supplemental humidifiers (like I have…but evaporative so I can use tap water). Trying a Canopy in our primary bedroom now, but it appears to lack the ability to get us to our desired humidity levels. It seems to hold around 45%.
Randy_at_a2htsWhy steam vs the more typical, cheaper, and cheaper to run, drip flow through humidifier mounted in the central air system, like an AprilAire 700?
TechnicalLeeEDIT: I missed it was a variable speed, so a bypass won't work very well. As much as it sucks, cutting into the side of the new coil to install a 700 or 720 is probably the best option other than steam. ~~Sounds like a good plan. Use rigid duct, an elbow, and a take-off for more bypass airflow (don't use flex duct).~~ Pipe to hot water. Get the one with the digital control and wire it for blower activation. I also strongly recommend you install the outdoor temp sensor so it can automatically adjust humidity with outside temp to avoid over humidification.
700 and 720 both pull their air from the plenum and put it back in the duct. The vents on the cover of the 700 are for the motor cooling, and the motor is mostly walled off with a plate from the humidifier airflow. There's a little air leakage through the vents, but most of the airflow is going in and out of the duct only.
That is a good question, the answer is yes. 720 is 1.75 GPH vs. 700 at 3 GPH. So you will get more heat gain from the hot water with a 700. The 720 fan pushes a little more CFM than 700 though, which helps it get a couple more GPD. Another hack you can do with a 700 (but not a 720) is replace the yellow flow orifice with the blue one to double the water flow rate to 6 GPH. That gets you more hot water if the yellow orifice wasn't enough (but that's getting to be a lot of hot water usage if it runs all day). You can also increase the thermostat on your water heater (max of 140ºF) and insulate the water line to the humidifier if it's more than a few feet from the water heater to maximize the heat. FYI the hot water thing doesn't work with tankless heaters because the flow rate is too low. Hopefully you have a standard tank water heater.
That is larger house, so you'll need an AprilAire 600 or 700 series humidifier. The type you get also depends on how much space you have on your furnace supply and return ducts. A fan-powered on the supply duct has a bit more output than a bypass humidifier. I would not get the Model 500, that is too small. The 500 is meant for apartments, condos, and small houses. The 600 is the larger size of basically the same thing. The 700 adds a fan for additional airflow.
You didn't specify your square footage. If I assume an average-size modern house, I'd figure it needs about 6 gallons per day of actual output. You will not be able to maintain 45% all winter without window condensation problems; 35% is a more typical setting. If this is a variable-speed heat pump (e.g. Carrier Infinity), you will need either a fan-powered humidifier mounted to the supply duct above the A/C coil or a steam humidifier. AprilAire models for those would be 700, 720, or 800. FYI, do not install a fan-powered humidifier on the return duct. A bypass humidifier is a cheaper option, but only if you have a single-stage heat pump (always runs at one high speed on or off). I would recommend installing the digital humidistat that comes with the AprilAire models according to the wiring diagram in the manual. Your thermostat probably doesn't have the capability to control more than one accessory. Also, install the outdoor temperature sensor so the humidifier can adjust automatically to prevent window condensation. The AprilAire automatic control does a good job and is "set it and forget it" all winter.
