Aprilaire - 720M

Thank you! I purchased a 720M. I found a wiring diagram on setting it up with a smart thermostat so I didn't need the more expensive 720A.

Tbh, I'd return and get an Aprilaire AA720M, install it above the cased coil on the supply. Call it a day. Bypass humidifers are not recommended on two stage and modulating furnaces. Given you got a Dave lennox signature series/elite series I know it's got a constant cfm motor, and I know your just going to waste lots of water. AA720M uses an internal fan and mounts like the bypass. 24vac to the Lennox board to be used by icomfort. While it has a 120v outlet plug for the fan. Internal circulator and powered by hot water means best price/performance you can get.

A bypass humidifer relies on the furnace fan blowing heat over the evaporator pad to humidify the air. The less air and heat you have, the less effective the humidifer is. The Lennox SLP99V is a modulating furnace, so it runs at very low speeds for most of its life. This means you wouldn't get enough hot air to get full use out of a bypass humidifer. The AA720A has an internal fan and it's installed on the supply side, so it eliminates the issues with pairing a bypass to a constant cfm furnace.

600 is a bypass air humidifier. 720 is fan powered. 800 is steam. 720 is 60% more water efficent over 600 model, has an easy to change hydrocore, and is better performing. While having no performance drop on 2 stage and variable speed furnaces. I'd go 720

Ive never heard of a single stage A/C that can't be paired to a two stage or modulating furnace before. Blower speed for the furnace heating will be variable, however for A/C cooling it will be a single constant airflow speed. To be honest with your current configuration the 600 will do just fine. However if you are considering a two stage model, which I will highly recommend, it should be paired to a 720 series.

What a silly contractor. Very silly. Lennox doesnt make anything that locks you into a single stage furnace. You dont go two stage or modulating to save gas. You do it to reduce noise, get better temperature distribution, more even heat across the home, with a gentler temperature curve. Plus it significantly reduces start/stop wear and tear, so its as reliable or more reliable compared to single stage. My company may install a couple hundred furnaces a year. 90% of those furnaces are two stage models. 7% modulating, and maybe 3% single stage. A two stage model really is not much more than a single stage, and boasts significantly better comfort features. I've never had a customer in my entire career regret upgrading.

If you don't have an existing humidifier, you want an Aprilaire 720A series, its fan powered and requires no bypass duct. It's got better humidification properties than a bypass and is fully compatible with psc, constant torque, and constant cfm motors across single stage, two stage, and modulating furnaces. Aka it will work with ANY furnace/air handler, regardless of make and model. plus, it's 60% more water efficient over the 600 series.

Ask the different tech for a quote on a 720A??

EXACTLY what I did. I just finished my install a day ago. In rearching my setup, I realized I could get and insstall a 720M (and NOT the 720A) and just hook the bugger up to my NEST thermostat. I however had the fun extra task of rewiring my thermostat wire; my furnace (2-stage, with A/C) uses 6 wires, and that's EXACTLY what the stupid hvac guy installed when the furnace was replaced a year ago. Had I been home when he did it, I would have asked for more wire. So, I ripped out the 18/6 thermostat wire and replaed it with 18/8. With the extra wire now available I hooked that to my "\*" terminal on the NEST and I was good to go. Works like a charm, and frankly,wiring in a smart thermostat to that humidifier was way EASIER than using Aprilaire's humidistat and transformer combo.

Weve installed a bunch of 720's since we swapped to them about two months ago. I think it's a better design than the 700, less waste, better blower design. How they hold up remains to be seen. I don't hate the hydro core idea, a lot of 700's should have been getting a new pad holder frequently that weren't and this will take some issues out of the equation. Hydrocore cost is 34.99 and it's way easier for a homeowner to change than on a 700. A generic pad from Lowe's for a 700 was still 12.99, cost difference is not that high.

The 720 is a brand new humidifier with unproven failure points. Same with the 620. Plus the water panel assembly is going to be a more expensive change. And my understanding is the 720 is louder than the old 700. I would stand by the 600. Aprilaie made the 620 and 720 save water but are you going to clean out the little orifice every time it plugs? The only way you know it's plugged is a loss of humidity. Then you have to go in with their little needle to hopefully clean it out?!? The OP lives outside Chicago where the mineral content in the water is definitely going to cause that to happen. Get a 600A if you don't use the Ecobee thermostat, a 600M if you do.

Yes. The difference between the M and A is the humidistat so you're getting started to the cheaper option because you're going to throw out the manual humidistat. The Ecobee is going to be your humidifier control. The humidifier will run without heat at times (I assume the Ecobee can do that). There is a slight drop in output for the model 600 (all evaporative humidifiers) when there isn't hot air so it's recommended to plumb to hot water.

720 piped to hot water will probably keep up, otherwise get a steam humidifier if you're really worried about it.

EDIT: 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.

I just installed the Aprilaire 720 last weekend, easy as pie!

See if you can open the duct to the upstairs bedroom. Ductless would be a potential solution, but personally I prefer ducted. You may need to add some ductwork to accommodate a ducted heat pump. If the unit is properly sized, it should dehumidify in the summer ok (although in the shoulder season, running a dedicated dehumidifier may be necessary). A central humidifier during the winter is recommended. The heat pump shouldn't take as much humidity out of the air as the oil furnace does, but will likely still need help. I used the Aprilaire 720 and it raises the humidity enough to be comfortable. But you may need a steam based humidifier like the Aprilaire 800 if the 720 isn't enough. Steam is more expensive to install and run, so I hesitate to recommend it.

I have whole home water softener and then R/O in the kitchen. I use that water in my nursery humidifier. I also have a furnace-based Aprilaire humidifier for the main level furnace so I run three different humidifiers. Furnace, nursery and master bed. I live in Colorado and it’s really dry there. I still keep it at about 35-40% humidity in the winter.

Depends on what brands your getting quoted aprilaire is the king here and most others I've seen tend to junk out after a few years that's a fair price for the work being done