Aprilaire - 720A

My "professional" HVAC person just installed a 720a on the return plenum-only place it would fit-but plumbed it to the cold water instead of the hot. Its only been a day but minimal change in relative humidity. Should I have him replumb it to the hot water and how big a difference will it likely make?

Thanks for reply. Not tested for all environments, I have learned the evaporative rate gallons per hour is about half on the return side compared to the supply side, so even if it is replumbed to hot water, likely will not be adequate for my home, or certainly not water efficient. I will have them look again, there may be a way to make room to move it to the supply side and plumb it to hot water.

I'm in the same boat. I bought a 720A. I'm thinking option #2 but I have an electric water heater. I'm also concerned about getting all the electrical correct. Not sure if I feel comfortable doing it myself. It seems complicated with all the different HVAC systems and not easy straight forward instructions. Why are you going manual vice automatic? I also don't understand the recommendation to go bypass. Doesn't the humidifier need to be installed on the supply side with a plenum from the return in a bypass setup?

If you're on a budget, aprilaire's AA720A model humidifier offers the best price/performance. Only down side is you need lots of room to install it on the supply plenum as it's a big boi. Water panel replacement is like $38 and done once a year. Alternatively, steam humidification will absolutely blow anything out of the water. It's just much, much better and completely water efficent. It's like $800 (plus tax/shipping) my cost for an AA800 series steam humidifer. Maintenance consists of a replacement canister once a year, like $100. However, it's pretty much maintenance-free otherwise. I'm a fan of ecobee's offerings for thermostats. However, you'd need to pull a new thermostat wire to accommodate the new humidifer. Something like an 18/10. Alternatively, both honeywell and Trane/AmStd make thermostats that have equipment interface modules. The thermostat uses 3 wires to "talk" to the module and the module controls everything from that. This eliminates the need to pull a new thermostat wire, however will have added cost to perform the job.

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.

Aprilaire 720A fan powered is easier to install and a far superior product. One ductwork hole, one electrical run, one water feed, one drain. It's better to purchase a smart thermostat and run a new 18/8 thermostat wire. However, it's easier to wire in the aprilaire automatic humidistat. Bypass 600m works great on single stage units. However, it sucks on virtually anything else, and someday, you will want to upgrade your system to a better comfort product. Might as well spend the extra hundred bucks and go fan powered.

You want the Aprilaire 720A model humidifier. 60% less waste water, internal fan means no drop in performance, and it's got a 5 year warranty slapped on the front, with a VERY easy to change HydroCore panel which replaces the pad, cradle, and feed tube all in one go. It's cost effective, and will be significantly better than the ancient 600 series.

720 series is better. Let's just leave it at that.

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??

Get the 720a. The 600 and 700 are good units but old designs. They are great and I recommend, install, and sell them all the time. I didn’t know April air came up with a new unit and I looked it up from seeing this post. The 720a looks like it solves A LOT of problems those two older models have. The old units use a ton of water, run a lot, and sometimes leak. The 600 is good if you don’t have a 120v plug nearby. The 700 is good for tight spaces, but you need a plug. If you really want a super high end humidifier you should get the steam model. You can make your 4600 sq ft house the Amazon rain forest with those. But they are expensive, have expensive maintenance, and are sometimes over kill.

A 600 can be 1300. 700 will be the same but in Maryland it has to have its own gfi plug so it ends up being 2300. The 720a should be the same. But honestly, anyone with a pair of tin snips and the ability to read the install manual should be able to do this on their own.

We just installed a 720A in a 5,000 sf house. In two weeks we went from 20% to 40%. It’s wonderful plus no more bloody noses! We have nearly same set up as you with furnace in attic and basement (humidifier is in basement). We are in Colorado so lack of humidity is a major problem. We didn’t do the 800 as we were warned of much higher electrical usage and we were required to run new electrical lines to the basement (panel is in the garage).

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.

What type of furnace do you have (gas/heat pump, single/dual/modulating stage)? And how much does it run in the winter? Ecobee should report runtime. If it's less than 30 minutes per hour on cold days, then I would advise going with a fan powered humidifier piped to hot water. More than 30 minutes per hour on cold days you should be okay with bypass.

It's not the coldest part of the winter yet, but that runtime is still bit low. I would advise you install the humidifier piped to hot water and with the digital control (Model 600 not 600M) for blower activation for enhanced humidity output. Someone else mentioned the 720A as another option, they are both comparable in output, quote both if desired.

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.

If you have good air sealing, AprilAire 720a is a good humidifier. I just installed one at my Mom's last week.

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.

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