HVAC Why AC Sytems Have Condensate Traps 

Oooh thanks for the explanation because I wanted to know if the pump can act as a trap

It happens if someone doesn’t realize the only way Water can drain on the negative side of the blower is using a vapor barrier

Only time you can get ride of trap is if it’s after the blower motor. If not the unit will hold water in pan until fan shuts down. Yet many times when hot and humid the pan will over fill before blower stops

@@thehvachacker This video is very interesting. I get clogs like anyone else, but it usually lasts about 3-4 months before I need to clean the drain again. My system does not have a p-trap. I read where you say it's not needed if it's after the blower motor. I am not 100% certain if mine is, but it does normally drain and I don't get the float shut offs until after approximately 4 months. ( I just went to the drain to see and it's blowing cold air out so I suppose it after the blower ) I just hope they haven't neglected to place what should be there. I read on one site that all AC drains should have a p-trap. Although my drain outside I has a short hose connected so that it doesn't constantly drain near the foundation and that hose at the end does go up through my fence then drains into the back yard. Essentially what I saying is it's a faux trap but far down the line. The water does actually drain all day though ( I'm in hot South Florida ) although I recently had that clogged with slime at the opening from the pan and it wouldn't drain at all and kept triggering the float to shut off the condenser. What are your thoughts on this and how can I prevent that slime from blocking that in the future? I can't unscrew my connector from the drain because it's in such a tight space. I was wondering if I could somehow drop in condensate tabs through the opening so that it can fall into the pan. Sorry this is long but I've been having cooling issues and aside from the usual things like dirty filters or coils, would the fact that there's no p-trap mean I'm losing all that clod air through all the drain to the outside and could be an issue for me? Or would it not change a thing since it may push the water and air through?

Glad it can help, understanding how stuff works helps make repairs easier

@@thehvachacker I have a P-trap but no clean out! I tried to vacuum it from outside the house below, but I think I’ll put a little cleanout tee in there. I see some people adding vents, but I don’t think I’ll mess with that.! I have about an 1/8th inch of water in my secondary pan - not enough to drain out of the secondary. Sincerely Mr. clueless, but determined

you ought to do a video to show how to do it

It’s why I put out vids

Best way to explain is with video

I think it’s only when it’s negative pressure meaning the air sucked over the coils instead of pushed as in positive pressure. A positive pressure trap does not need to be primed

Yes only negative pressure does it need a trap to make a vapor barrier. If not it will pull air through the drain line. Preventing the water from draining. Possible overfilling the drain pan.

@@thehvachacker well positive pressure I believe still needs a trap. I just don’t think it needs to be primed. They typically self prime. Isn’t that correct?

Yes they self prime. Inspectors in many municipalities require the trap on positive pressure drains. Even though it doesn’t effect how the system drains

​@@thehvachackerSo when you start running AC after the months of having it off, should you make sure water is in the trap before you turn it on again?

Thanks

Steve M the problem with your video is you have it backwards. The water is the by product of lowering the temperature of the air being drawn through the evaporator core. Which squeezes the moisture out of the air. The colder the air the less moisture it can hold.

Should I do more videos like this or stick with just my repair jobs

@@thehvachacker I love what you're doing with your videos but yeah it would be nice to stick in a couple of tech tips every now and then that would be awesome. Keep up the great job you're doing. I found your Channel about 3 weeks ago and I really enjoy what you're doing. You keep videoing and I'll keep watching. Thanks for everything. Peace brother

Your fan speed wasn’t set correctly or ductwork is too small if the blower is sucking the water out of the trap. Or the trap was too shallow. I always do a static check when starting up a system. You will know if their is an airflow problem.

Yes usually the trap can fill itself

Trap really wouldn’t be needed. Yet most inspectors fail jobs without. Air pushed the water out the drain on positive pressure drains.

Happy to help

did you not watch the video??? YES!!!!!!!!!!!!!!!

The return should not be undersized. Ductwork needs to be properly sized or corrected so it is. Or an air conditioning/ heating system will never operate correctly. Dirty filters won’t suck the water back in. The trap is a vapor barrier

Very little air is lost through the drain tube. The trap does prevent air going through the drain

S man, I was going to ask the same question, seems my 20 year old Ruud R22 also has positive pressure. When put 90 ell with a short stub to another 90 ell and 20 feet of horizontal pipe, it would never drain. Maybe P trap is still needed. The HVAC Hacker what do suggest?

Depends on what side of the blower motor the drains on. Without on negative side it holds water in. On positive it will still push the water out. It’s not needed on the positive side yet in nj the inspectors want it

No context. What do you attribute that to?

@@reggiereseller8252 It depends on amount of humidity in the air and static pressure of the system.

No.... a vent located AFTER ( downstream-water flow) the "U"-tube trap is perfectly fine...... DO NOT put the vent BEFORE the ""U"-tube" trap ( air-handler side). Capping is OK especially if you want to clean the trap using a shop vac at the end of the condensate line....this method is sometimes used to suck out the gunk. When done cleaning, you can leave the vent capped ( making it useless as a vent) or open....but in either case will not affect the function of the trap or the draining that occurs while the unit is running.

@@TheWilferch you seem very knowledgeable on AC units I had a 3 ton unit installed 5 years ago brand new it's it's installed vertically. Even though it says 70° in my house it was really really humid. You did Humanity was really high.. it never felt cold. And it seemed like the unit was constantly running.. this is a smaller house. I still had my window units in it and just started using them as they kept it colder than the central AC. I had the superheat subcooling and all that checked on my unit and the freon level. It all checked out good. I took the access panel off of the coil and the insulation was soaking wet on the inside of the panel. I noticed there wasn't a P-trap on the drain line. Could this be my problem? Can't get anyone to really work on it they all want to replace my unit I bought the unit brand new it probably only has two weeks of use on it. Any help is appreciated.

@@tommytaylor7523 ...I am not an expert but by profession I was trained as an engineer. I had AC problems and decided to learn what I needed myself, because local techs were clueless. I can't help on all issues but for sure, let me say this about the wetness. Wetness can only occur 2 ways....1.) the coil inside the "Air handler" cabinet ( that piece that is inside your house....the other main piece is the condenser which is outside the house)....the coil inside the air handler creates the cold and condenses water on its surface that drains into a drain-pan inside the air handler unit. The pan could be missing , leaking, or damaged, or too-high air flow "carries" the water further downstream inside the unit to cause moisture accumulation. The other possibility is the problem I had....the air handler is located in my hot attic, and the "cold" was condensing on the outside surface of the air handler. I bought poly insulation sheets and glued this onto the entire outside surface of the entire air handler cabinet....to gain more insulation to the lousy 1/4" stuff they have on the inside of the cabinet. So far that works. Then there is this VERY important part. The air handler creates water as said....and it drains into the drain pan. IF THERE IS NO U-TUBE ON THE DRAIN LINE , THE PAN WILL FILL AND OVERFLOW, AND WILL ONLY DRAIN WHEN THE UNIT SHUTS OFF. FOR IT TO DRAIN "WHILE RUNNING", YOU NEED THE U-TUBE attached to the drain line....see here for a better description of how/why this works---> ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-vWGLVe-X550.html. I hope some of this helps.

@@TheWilferch thanks

Now a vent should not be before the trap. Vents are not always needed. Depends how the drain is ran and terminated. Yet a clean out tee like what’s in this video should be before the trap.

Yes the pan is slopes toward the drain. Only time a trap is when the drain is on the positive side of the blower. When on the negative side of the blower, (meaning blower motor is before the evaporator coil) the trap is a vapor barrier. The negative side is sucking in air before it pushes the air. The negative pressure creates a suction that holds water in the pan. Most towns want traps by code on both sides, yet positive pressure will push the water out of the drain without a trap

@@thehvachacker is it necessary to make a trap on the fan coil unit pan ? i have never seen before

Its not code to run a drain like that. Yet many just drain the water into a slop sink

You can pull out the float switch inside the house next to the Air Handler Unit and pour around 1/2 cup of Vinegar (Not bleach, bleach can destroy copper tubing and glue on pvc) down the drain line and then flush with hot water (Hotter the better no need to boil though) put float switch back in and if you flipped the float you'll have to wait 5 to 10 minutes. If nothing is on thermostat, Pull out float and wiggle it till thermostat comes back on. Then wait for timer and you should be good to go with a primed clean drain line for months. Just know if you use a vacuum to suck out the line be sure to put water back in it to fill the trap.

It will not self fill. So refill the water yourself, at least the "hand block" trick can work also. The video didn't give the perfect example.

Means your ac is draining and water isn't collecting in your drain pan under the Evaporator coils.

Yes it’s not necessary unless the job will be inspected. Most municipalities want traps on the positive pressure drains. It prevents bacteria and mold from getting into the unit through the drain. Even though bacteria and mold grow in an unmaintained drainline

@@thehvachacker ok, thanks. Have not seen these in Minnesota.

i was just thinking about that.. could that be the reason why other indoor units do not have traps yet they drain smoothly or do they even need them on a positive pressure?...

Positive pressure drains don't need traps yet local codes requires them. I would guess to prevent odors or fumes from traveling into the drain line when the system is off. I never looked into why yet a positive pressure drain seems to drain better without the trap since it pushed the water out

@@thehvachacker Thank you for the quick response sir!....will check out more of your vids in the future

Do you have power at the unit the thermostat is connected to? It seems like a power issue not really a drain issue. Usually if the unit has a condensate pump then I could shut down the power to the stat. You need to see if you have power at the unit. Many variables yet I would start basics and verify line voltage. Also verify low voltage is also between r and c terminals in the unit. If so then look around the unit for a shut off safety. Where are 5e packaged units located?

@@thehvachacker no power to the unit. I was thinking maybe it's a fuse. I haven't yet tried to locate where the fuses are yet.

You have no power to the stat or the actual package unit? Many times fuses are on the main control board

@@thehvachacker I'll try to locate the fuses tomorrow when there is some light. I'll let you know how it goes.

@@thehvachacker i located the fuse on the main control board. I pulled out the 5 amp fuse and it was blown. Then replace it and not even 5 mins it blown again and i replace it 1 more time and samenthing happened. What could be causing it? Oh yeah after replacing the 5 amp fuse twice the display on the thermostat came on and the unit turned on. But didn't last for 5 mins.

William Kennard check out some of my other drain issue vids. Put a clean out t on your trap. You can keep your drain line clear by flushing out the line every year

The HVAC Hacker I installed one. I also found a tablet (small brick) that I purchased and put in the a/c that supposedly eats the bacteria.

is it humid or dry currently where u live. Condensation is the humidity condensing back into water. Does the system cool?

@@thehvachacker not humid right now. It got hotter this week hitting the 3 digit weather, 112 today. System is cooling. I am not sure if I was clear, I am talking about the drip line (I think that's what it's called).

I ment that if it wasnt draining on roof but the drain was tied to the building drain. Thanks

Except if the drain pan might over flow while the system is running causing water to leak through ceiling

@@thehvachacker And if the trap clogs the pan will overflow and drip onto the ceiling.

Yes why I clean them on all maintenances. To me the most important part of an ac maintenance is cleaning and flushing drain, checking temp split on evaporator and cleaning the condenser coil. All other test are a bonus and I still check everything else. Yet the three things I listed here are the main task for preventive maintenance

Unless the unit is on constant fan. Then there is no down time to allow drainage. In really humid climates the condensate will collect faster than the drain pan is designed to hold in its allotted run time for the most part. Drain pan want designed to hold water it was designed to shed water away.

@@calebburns4346 Yes I agree and that is the scenario where a trap is indeed a necessary requirement in a drain, but normal residential units cycle where they will drain in between off and on. In those cases a trap might be a point of restriction and require more attention than a straight flow design with a good gravity pitch.It would depend on each scenario and vary accordingly for sure.

If the end of drain is submerged in water. Not the correct way of doing it. But it makes a vapor barrier

Yup the Pulse is the one with the spark plug and flappers. We don't have a lot of them still around since Lennox a few years ago had all Pulse Furnaces pressure tested heat exchangers and swapping furnaces for free under warranty. It was some kind of recall and Lennox paid for us to scrap most pulse. It was like a purge they wanted all pulse furnaces ripped out and replaced. I still have a few parts on my truck. I use to work on many pulse furnaces. The next time I work on one I will make a video. The plug was always a pain to pull. Usually, the flapper would wear out from vibration or just needed to be cleaned. There used to be a boiler Called the Hydro Pulse that operated on the same concept.

The HVAC Hacker oh man, I cringe when I see one. I have heard that Lennox doesn't even know the correct gaping for those plugs.

Here is a link of the recall. You might be able to sell the owner of a pulse a new furnace since the recall is over. inspectapedia.com/heat/Lennox_Pulse_Furnace_Notice.php

We don’t have water leak issues with these traps. We don’t glue them to make it easy to clean out. These traps are sized properly for these units if not we would size them up or put a deeper trap if the system called for it.

@@thehvachacker Have you seen this product, this is pretty interesting ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MS-KdN3MWHU.html

What will that help me with? I mostly fix plugged drains don’t install many new drain lines. Except for a 4” underground downspout drainline

Good way to reuse the water. If your doing that you might want to clean out your drain pan sometimes. Nasty ness may grow in the pan or drain line yet I doubt it would effect plants

This trap works fine. Never have water backing up or spilling. Trap was dry why water came out after I blocked it for some time. Iran it dry twice I think in vid