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This is a horizontal flow air handler installed in the attic. Notice the drain pan under the air handling unit to catch condensation if the primary pan were to overflow. This is the secondary condensation pan which is installed under the air handler to save a ceiling.
Also slightly visible is a float switch which offers triple protection against flooding in an attic if the primary drain were to plug up. The primary and secondary drains coming from the air handler also drain into condensation pumps. These pumps have floats inside them and a reservoir.
Attic Installation Horizontal Flow Air Handler | HVAC Airflow
When the reservoir reaches a certain height the float switch rises and turns on the motor and the pump which pumps the condensation out of the attic and usually outside but these drains can also terminate in a sanitary drain. If the condensation drain is piped directly to the sanitary drain it is important that properly pipe methods including traps be used to prevent sewer gases from back feeding into the condensation drains and eventually into the air handler and air stream which provides air to the structure.
Conclusion
Horizontal flow air handlers can be configured in left to right or right to left configurations upon installation. This makes it helpful to retrofit a new AHU to existing ductwork as necessary. It is simply a matter for the installer to flip the evaporator coil so that the condensation pan is under the coil to catch the condensation.
Attic Installation Horizontal Flow Air Handler | HVAC Airflow
Hi I’m trying to get help for my 3 year old Mitsubishi mini split with Horizontal Flow Air Handlers. I have a 5 zone system which I dearly love but lately I’ve had trouble with the condensation drain clogging. When I went in the attic I noticed that they are not all draining from the same location. Some drain from the top and some from the bottom. And there are no vents or P traps. I’m going to contact the installer but I would like to better informed. Any help would be greatly appreciated. Jerry
There is not much space in my attic and my unit drain pipe keeps filling up with water to the cleanout. The AC guy came and blew air to clear it but a week later the secondary pan started to fill up. I’ve used a wet vac outside the house to drain all the water from the drain line but after running the AC for a few awhile it starts to fill back up. Basically coming out the unit is a short pvc with a T shaped attachment to it and the top is uncapped. The bottom part has a 90 degree angle attachment where a longer pvc pipe runs underneath the unit to the other side and then takes a left turn into the wall. Looking under the unit I can see that the pipe isn’t really sloping downward. There is no P trap that I can see and not much that I can reach by hand to make any changes to the piping. I don’t know what to do at this point and any advice would be much appreciated. I can even provide pics of the set up if that helps. I’ve already spent over $500 on the AC guys. Do I need to set up a P trap? Do I need to simply cap the opening on the T attachment?
A picture is worth a thousand words and I can’t seem to make the picture in my mind of what you are describing. Drains can be finicky if not done right. Yes, the unit needs to be higher than the drain and the drain needs to slope. It also needs a p-trap in line preferably close to the unit. P-trap is by code BTW.
$500 seems kind of steep for some PVC repair and if someone charged me that I would expect them to get it right the first time with a warranty or guarantee it will work. If not, I would be making a phone call to them telling them it’s not working. If they don’t stand behind their work or workmanship then I would never use their service again and ask for a refund. I know that part is like pulling teeth but I wouldn’t spend $500.00 for nothing.
Our home has hot water heat and therefore the A/C air handler is in our attic. We had the system replaced, both units. The previous system had a gravity drain from pan and continuous drip to outside. This new Hi-efficiency attic unit has to have a “U” shaped trap on the drain. it has never dripped continuously, but when the system shuts down it then releases water to outside after approximately a minute and a half.
We have also suffered from the overflow switch failing twice to prevent ceiling leaks. Each time called installer, Once told, the system was running too long and not able to discharge, therefore water went to overflow continuously, the float must have stuck. 2nd time there was a mechanical part not working to activate the overflow. We have no secondary drains for the overflow, so when that happens, which is very humid continuous running days lt does, someone has to go into attic with pump and hose to pump the water out of the overflow pan in order for A/C to work. Because the overflow switch is working and won’t let A/C run. This year when A/C turned on, there wasn’t ANY water coming out when it shut down on the first cycle.
(I am overly apprehensive of ceiling leaks, just saying) Shut system off for an hour, then decided to turn on again and let run till shut down. Outside temp 88, humidity 68%, inside temp 78, humidity 65%. The system was set to 74 temps. It shut off at 74, inside humidity went to 59% and no water discharged AGAIN! So I called for service. Arrived approx 3 hrs after shut down. He went up into the attic, the drain wasn’t clogged said no water in either pan. Poured water into the drain and it came out ok. Started system up, now outside temp is approx 93 humidity 80%.
After running approx 15 min, there was a small continuous drip, (have never had that) and when the system was shut down there was the usual “release” of a larger quantity of water. The service person mentioned that he thought the “U” trap was probably sucking air back and not working properly because it had no water in it to work. He suggested that it would always need to have water poured into the system drain to “trap” water in the “U” for it to work on initial start-up. We have never heard this before.
Each time we have a problem, they always send someone different, and we always have a different reason for the problem. This system has only NOT had a service call 1 time since we had it installed. (now 6 yrs old) Can you see anything from this post that may help us decipher what the heck we need to do to run this A/C correctly? Thanks, sorry for the length, but I wanted you to have an informed picture.
It’s a pressure problem (at least sounds like one). Call someone who knows what they are doing. And you don’t want a running trap, you want a P-Trap (by code).
I had a two and a half ton unit put in my attic and it sounds like a diesel truck running all time.My other unit was 6 years old and you could not hear it run.M y house is 7 years old and the coil went out in it.My electric bill went from $140.00 to $278.00 .this unit is half the size of the older one.It looks like a closet unit for a small mobile home.my house is 3 bedroom 2 baths 1200 square feet. The unit is not fastened down and bounces around. Wakes you up when it comes on. Something has to be done.
Installation is everything and most of the time the lowest bidder is not always the best bid to select from when you get estimates for replacing a unit including any type of HVAC equipment. There are many options for you to choose from including putting rubber pads under the unit to absorb vibration. The unit can be hung from the rafters in the attic using all thread and U-channel with rubber pads on the U-channel to absorb more vibration.
Also, special rubber duct made to prevent vibration and noise can be hooked up to the unit and ductwork to prevent noise. Many options to fix this problem. Also, size calculations should have been done to make sure the ductwork is sized properly for 2 1/2 tons. Both the return and the supply need to properly sized to the air handler the airflow. Ductwork that is too small will cause more noise because of increased pressure and velocity.
Lots of things can be done to alleviate many noises made by an air handler and this is why I say low bidder is not always the best. I’ve seen it many times over again where those guys just want a quick buck and they do shoddy work not caring about workmanship or quality much less the technical details necessary to get it right.
My attic installed HVAC has overflowed the drain pans and leaked water outside of them through the ceiling. The technician who came today blew out the lines and then said that I need new drain pans as one or both may be cracked and he can’t tell which one. Should I get a second opinion, as this will be costly. Thank you.
Absolutely, I always recommend second opinions especially if you are unsure. If you can get a flash light and go take a look for yourself. Sometimes this will serve as your second opinion but you can always call a professional HVAC contractor to give you a second opinion and if possible tag a long with them and see for your self so you are absolutely certain.