Evaporative cooler integrated into forced air furnace ducting

[Radkon]

I guess this should have been posted in the AOP forum originally...not General Discussion, my apologies. Maybe it's not even appropriate for the site.

I currently have a window mounted evaporative cooler in my living room. The house is a two storey, 3 bedroom home with a full unfinished basement. The cooling capability of this was quite good this summer and the AC I had originally considered installing I have now deemed unjustifiable (I moved in at the end of May and I live in dry high desert of Colorado’s eastern plain). I am considering an alternative installation for this unit to correct or mitigate the following shortcomings of the current window mount:

1. Noise (mainly squirrel cage/motor vibration, but air flow as well)
2. Improved distribution of cooling air thru house
3. Full reclamation of the window for views and lighting.
4. Reducing the thermal leak of the unit during winter months.
5. Controlling the unit thru my existing or new whole house thermostat.

To do this, I’m considering the following:

1. De-mount the unit from the house and set it up on a concrete pad much like AC compressor units are installed. This would eliminate vibration into the house from the unit.
2. Run a re-movable air duct from the output side of the cooler to a port cut into the side of the house at the basement ceiling level. This duct length would be almost straight and about 2 ft long & would be installed for easy removal in winter so the house side duct could be effectively capped off with an insulated cap, as well as an un-insulated cap for the cooler to keep winter debris out.
3. Construction of a duct from this port to the return plenum of my whole house forced air heating system.
4. Interfacing my thermostat to the blower motor of the cooler as well as just the blower portion of the whole house heater.

This system allows control of the cooling from the thermostat, provides dual fan locomotion of the cooled air to all of the floor and wall registers in the house for better air distribution. I realize I still need to leave windows open to allow outflow. I probably want to close off the return plenum connection to the rest of the house as well, either in the return plenum itself or at the satellite return intakes.

What are the concerns/risks of doing this? Why can I find no mention of an install like this anywhere I’ve looked on the internet or in commercial literature? Am I exposing the furnace heat exchanger to corrosion, even thought the humidity wouldn’t be condensing on the exchanger? Are there code issues with shutoffs on return plenums?

Any insights or warnings about an installation like this would be appreciated. Thanks for reading.

[motoguy128]

High humidity in metal ductwork sounds like a bad idea all around as well as possible mold issues.... which is an issue anyway with evaporative cooler. They are called swamp coolers for a reason.

Personally, I'd rather open windows and just use fans and save up for a proper central AC to add to the furnace. You can probably install a fairly small unit for as little capacity as you likely need in your climate.

[Littlebull38]

Hey Radkon, Please reply if you did what you wrote, Like to know how well it cools. I got with 2 engineers, 3 HVAC techs and I have been a cooler guy for 30 years.
Both engineers and the 2 oldest HVAC techs say it will work great, one HVAC tech said it will not cool.
All this at hand, I decided to go ahead full stream with a 7500CFM Breezair with a Inverter driven 3 phase motor. On a concrete pad, hooked up to my basement window. I will reply again another day and let you know if the whole thing was a failure.Or Victory.

[CraziFuzzy]

High humidity in metal ductwork sounds like a bad idea all around as well as possible mold issues.... which is an issue anyway with evaporative cooler. They are called swamp coolers for a reason.

Personally, I'd rather open windows and just use fans and save up for a proper central AC to add to the furnace. You can probably install a fairly small unit for as little capacity as you likely need in your climate.

Why the hate for evaps? In the right climate, they are far more efficient than an A/C. And swamp coolers put out about 90-95% RH air into the duct. Guess what the humidity in the duct is from after your A-Coil when dehumidifying? about 90-95%.

If it's hot and dry, opening the windows and drawing in the hot and dry air is NOT going to do any good.

[bmathews]

As far as moisture issues in the ductwork and in the furnace. The other problem I see is that if it is not a ducted swamp cooler and you are adding ducts to it. It may not have enough pressure to force the air down the duct system and distribute it into the room properly.

[CraziFuzzy]

Capacity would be my only concern, because, as mentioned, ducts provide a lot of drag that the unducted blower wouldn't have to deal with. A/C systems usually provide the same amount of cooling with smaller ducts, so the typical home would not be able to be cooled with a swamp cooler connected to the same ducts. If you've got large enough ducting in your furnace to handle the cfm of the swamp cooler effectively, it might work, otherwise, it may require adding another supply duct from the blower to, say, a main location in the home to handle the excess. (this would provide you the intended benefit of distributing the cooling to the rooms, while still providing the full cooling capacity of the cooler to the home envelope).

Considering this home appears to only have a furnace, and no AC, it's hard to even guess at what cfm the duct is designed for.

[DirkRoper]

I've seen this done two ways: supply side and return side.

Supply side installations typically duct the evap cooler into the supply plenum. They often "work" OK because 1) some air makes it out the supply, 2) some forces its way back through the furnace and exits from the return air grille, 3) owners have low expectations.

Return side installations typically are ducted into the return duct and have a manual "damper" of some sort that blocks air from the furnace and forces it out the return grille.

In both cases the path of the air through the house is controlled by which windows are opened for pressure relief.

I've never seen either version done well enough to keep from losing massive amounts of efficiency during heating because of poor work on the evap cooler ducting connections. I've seen situations where cold air was being drawn through a poorly sealed evap cooler into the return ducting, which brings in cold outside air that has to be made up for by forcing conditioned air out of the house - a double whammy.

I've also seen very badly damaged ducts from the evap cooler water. While the normal air from the cooler may (or may not) be OK in metal ducts, oversized blower motors (which some put in to get more cooling from their units), or problems with the water distribution system often allow more than expected amounts of water into the ducting.
You are probably moving 3000 - 4000 cubic feet per minute of air with your evap cooler. Your ducting system probably isn't going to properly move any more that about half of that if it's typical.

I wouldn't try it, and I wouldn't hook it up for a customer. If you want to try it, I would recommend:
* Run it through the return, keep it out of your furnace, and forget the double blower approach.
* Enlarge the size of the duct, and probably the grille, so that you can move enough air when in cooling mode.
* Watch your ducts religiously for signs of leaks or water damage. Inspect the "stub" of duct that you're blocking at the outside wall while the heat is on to see if it's leaking somewhere you don't really want to put heat.
* Learn to distribute your air better by opening and closing the right windows the right amount.
* Evap coolers are noisy. To some extent you have to get used to it. I've seen people choose a less noticable location and cut a hole through the wall to bring the air in there rather than using a window.
* If it's a true window unit (as opposed to a side discharge standard unit), it probably plugs into an outlet on the inside of the house and has its controls on the grille of the unit. You'll have to figure out how to make that work for you.
* Most swamp coolers us high voltage thermostats. There are some (Master Cool) that have low voltage controls, or you could install a relay system, but it's going to be extra work and parts to make your existing t-stat control a swamper.

When it's all said and done, I still say "don't."

[Littlebull38]

Thanks for the reply, My coolers are not noisy, very quiet, Tradewinds and Breezair.

Also I do not plan any connection to the heating system as my heating system sucks.

I am just going to blow the cold air in through my basement, food storage area, and open the windows on the top floor,

I am removing my 6500 CFM Tradewinds, and installing my 7500 CFM Breezair.
We just want it off the roof, damn thing leaks.

[DirkRoper]

Sorry for the confusion, I was replying to Radkon.

As for your setup, I suspect that it will work well as long as your basement is well sealed and doesn't smell funny, and you have a large enough stairwell or other open area for that much air to move through your home to the exhaust points.

[CraziFuzzy]

The only complication you might find is that injecting the humid air into the already coldest part of the home would make you more susceptible to condensation on any cold surfaces in the basement.

[Rivadavia]

I live in Denver and have a 1500 sf ranch house with a full unfinished basement. I replace the original furnace about 6 years ago. I have new energy efficient double hung windows and the attic has good insulation. About three years ago I had an attic fan installed to keep the attic cooler in the summer. For 15 years in this house I have not needed air conditioning. But this summer we have already had almost a week straight of 100 degree weather, and future summers will probably be the same.

So I have decided to get an Evaporative Cooler installed. (Excell is offering rebates this year.) They are known to be less expensive to install and operate, more environmentally friendly, and work well in a drier climate. However, I have read about the regular maintenance they require so I don't want it to be on my roof.

Like Radcon above, I am wondering if it would work to blow the cooler air into the main floor of my house via the heat ducts, and out the top openings of my double hung windows. I don't want to use a main floor window for the cooler, or cut an opening in the side of my house.

So I am wondering if the Ev Cooler has to be installed outside, or could it be mounted in my basement next to a very small basement window that faces to the front of the property. That location would be near water pipes and close to the duct system. Because that window faces front, I think the city will not allow the cooler to be installed outside at that window, even if I hide it with bushes. I don't want to blow the cooled air into my basement because it it already cool enough down there.

Also, Excell approves many brands of "swamp" coolers. Coolerado, PMI, Seeley, Speakman, Symphony, etc. So I am not sure which brand would be very reliable and lower in maintenance. I tend to purchase larger ticket items in the mid price range.

Thanks very much for your professional advice.

[catmanacman]

Growing up in Arizona all we had was evaporative coolers when it was 110 outside it would cool the house down to about 80