620M

I’m a fan of aprilaire. That’s what I installed in my home, and recommend to customers. You should look into the aprilaire 620. With either the standard humidistat, or electronic which can base your indoor humidity level off of outdoor air temp. Bypass humidifier’s don’t usually go too much larger. There is the fan powered one which will get another couple gallons per day. Otherwise you’re going into steam territory.

As long as your return is 10” wide a 600 or 620 should work, good thing to know about the Automatic stat is it really needs a ODT to function the way it’s designed. Still nice to control the humi with the blower though if you can’t do get an ODT to work anywhere

You asked them to quote a humidifier they are trying to sell you a Cadillac. Did someone come out to take a look? The only real reason to put in a fan powered humidifier is because the installer can't get to both the supply and return ducts. You should install an Aprilaire model 600 (or 620) if possible. Also... One quote has a new power circuit and drain pump the other doesn't. Do you need those? Saddle valves are not to code but everyone uses them anyway.

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.

Steam is absolutely overkill in your situation. It's completely unnecessary and will be a huge money pit. If the sq footage you listed is total space, and not just finished space, you would get by with the aprilaire 620. You could upgrade to the 720 and be solid, but it's probably not needed in your situation. Yes you can use it with an air handler. Don't do steam, you will regret it. Steam is excellent in the rare circumstance that it's justified.

An AprilAire 600 would be the closest thing to what you have and fairly simple to install. You might have to cut the hole slightly bigger. You could also elect for the newer 620 model. I would recommend you pipe the humidifier to hot water if it isn't already, and install the digital control that enables blower activation. That will help you get more humidity when the furnace isn't running a lot. Unfortunately, upgrading to significantly higher humidification capacity would require either a second humidifier (if you have another furnace) or going to a steam humidifier which is more expensive, and also requires a new electrical circuit. I see a lot of minerals on the duct, it appears the old unit was leaking extensively. Just a reminder that you have to change the water pad every year (sometimes more often with extremely hard water), or it can crust up with minerals and leak out. Crusted pads do not humidify effectively because the airflow is blocked. Also make sure you have the water flow turned all the way up, the extra water helps flush the minerals and prevents the pad from crusting up so fast.

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.

We put in an Aprilaire 600 series on our forced air furnace around 2010. The HVAC company that put it in (Dynamic Heating) is gone, the guy retired and moved away. The control part of the humidifier needs to measure the indoor humidity and stop dripping water when it's humid enough. Ours never worked that well, so sometimes we had condensation on the windows and other too-much-humidity problems (damp plaster smell, wood doors expanding). Now it still drips water on the filter but it's either not enough water or something is failing, because right now the house is 18% humidity, and our furnace has been running A LOT since it's 18 degrees outside. We had the new HVAC people come and look at it and they saw the water dripping on the filter and said it was working as expected. Fixing this/getting a new one is on our to-do list.

Used to use those, they sucked. If you dont fill with distilled water they get white powdery shit everywhere, and they have to be refilled often. Whole house is much easier. I change the Aprilaire filter once a year. Its only used in the winter. Never would I want to walk around filling 4-5 humidifiers when theres one that never needs to filled. Plus the Aprilaire bypass humidifier was only like $275. **EDIT** nevermind, OP is talking about something else apparently, he has no central air