This video shows how to properly pipe a drain on a fan coil. We cover traps, cleanouts, vents, pitch and switches for condensate drains. Read all the tech tips, take the quizzes and find our handy calculators at www.hvacrschool.com
Helpful video. Before I knew about the need to have a vent to break the vacuum I connected a garden hose to a rooftop unit to drain the unit over the edge of the roof. I think the drain was plugged up inside. The 15 ton packaged unit was located over a big dining room with a 20 foot ceiling. The result was that the drain pan over flowed and severely damaged the ceiling. It took a lot of special work to repair including using scaffolding and blocking off part of the dining room. My question is how does that drain function properly after a winter if it is not again filled with water to prime the trap?
The unit drain trap will self prime 99.9% of the time, it's rare to have a priming issue. but when a trap dries out, now you have dirt/debris caked into the trap that needs to be cleaned out or it could clog up. That's why you should clear the drain line every spring, clean the primary drain pan and especially the outlet where trash likes to build up. I prefer to use unions on the pan outlet and the trap outlet, so it can be removed and cleaned.
@@awesomeaustin2348 Unions make a lot of sense! I can't count the times I've had to cut glued PVC just to clean the drain line. I always install unions for the very reason you mentioned!
Agreed with everything but breaking Y. This can cause continual short cycling. Either break R or C (if applicable) going to the thermostat so if nothing else the thermostat goes out on time delay allowing the pressures the level. Thanks for the content you provide.
Great video! I'm sure the guy in the video knows this. I found it difficult to explain what I'm trying to say below, but it explains what's going on with drains, traps, and vents. To be clear, the name "vapor lock" might be the correct name used in the trade, but the phenomenon has nothing to do with vapor, and it doesn't really result in a lock. The problem arises if there are two traps within the drain. One you intended on, and another due to pipe sag (I call a, sag-trap). Let's say that each of the two traps in my example result in 3in of vertical water level per trap. With a vent between the two traps, the water entering the vertical pipe before the real trap, only needs to fill to a level of 3.1" (above the trap water level) to move water through the first trap. That same 3.1" of water will be enough to push water through the second trap. The water in each trap is dealt with in order. One, then the other. If there is no vent between the two traps, the two 3" vertical columns of water are connected by air that can not escape. This means there has to be 6.1" of water in the vertical pipe before the first trap in order to build up enough pressure to move the water in both traps simultaneously. No vent means the water in both traps have to move together. This requires higher head pressure to accomplish. Certainly, make sure the vertical pipe leading to the first trap from the unit, can contain a height of water that is greater than the water level in the real trap. If you have multiple sag-traps, that first vent may not save you. Sag-traps are bad!
I'm a home inspector and I routinely watch videos like this for this purpose: I was inspecting a home that just had a brand new HVAC (heat pump) installed within the part couple weeks. I found 5 discrepancies to put on my report with the HVAC alone, the condensate drain being one of them.
Glad you do your job well. Oklahoma inspectors do the bare minimum and will flag things that aren’t even an issue so they can say they did something. 👀
much to the point and understandable, if you could please post a link of the blueprint image you show? that's really all I need but I didn't find the exact image on Google I would prefer to have it stationary instead of having to use RU-vid to look at that
I like to put the clean out at the bottom of the trap, in a T. Then the vent at the top of T, and the outlet at the side of the T. I also like to hook up with a union.
My Bryant evaporator box has a recommended air flow direction which the installer didn’t follow. I’m just wondering why would that matter? Great video thank you very much.
Unrelated I believe Florida used A standard all in one test for the A and B HVAC license in the past. Although this was many years ago I seem to remember our instructors telling us to apply for the higher class license because there was only one test. Does anyone know if this is correct. Thank you in advance for any information. Great channel keep up the great work.
I am redoing my primary drain in a HVAC /Furnace combo. There are air vents on the current install that are both before and after the p-trap. Both are uncapped. I believe my system is a POSITIVE airflow system since when the blower is on, there is air coming out of the uncapped vent before the trap (nearest the unit). There is little to no air coming out of the vent after the trap. My question is, should both vents be uncapped as it is today? Does it matter if the vent after the trap is capped or not? Any advice would be appreciated!
Please my system has those 2 pipes hoses. But i dont know why the vent pipe is the one close to the unit and also the one elevated. It is good to poor the vinegar in the vent pipe in that case?
Great video. I just had a new 95% efficiency system installed. My drains are basically at the floor in the room and I'm unable to install a trap due to no more height. I have a crawl space where the contractor ran the line under the house and adapted 2 inch pvc trap set up in the crawl space and vented it outside the foundation. We failed inspection even though the inspector liked the idea. He also said that if we had no other option that this method would actually pass but in the same breath mentioned the reason for failure was that the outlet or the trap inside the crawl space could freeze. My point was it can only be run through the crawl before it goes outside so it could freeze anyway. Besides cutting the floor open or having the entire furnace reinstalled and lifted to clear room to create a trap, what other options do i have for installing a condensate pump? Thank you.
And your findings how many times have you seen the float switch kill a fan motor, a contactor, or some other component in the system. Happened to me several times just during maintenance. Just testing the float switches I’ve had a cnotactors , motors shortEspecially with carriers I’ve noticed more so than others. Could be we have a lot of carriers though. It has happened to some other units as well like Lennox and Goodman as well as a trane. Standard float switches not touching any metal with no issues before arrival. I did have a couple for the motor sounded kind of off at first then they failed. They were all wired in series breaking red. Thanks Jerry!
Right , I questioned this myself on numerous occasions and has also happened to other techs. Although not as much. My guess is it’s giving it some sort of power surge when it’s kicking in on and off. The same thing is happening to motors when they’re having brown outs. Due to power issues with FPL. We show up and there’s all sorts of issues like every unit needs a capacitor. There’s at least one down fan motor and or circuitboard etc. occasionally condenser fan motors and compressors as well. Do you know something went wrong to win the pool pump is bad or it blew the cap.
@@jerrylockhart3069 in theory if you interrupted load power just momentarily and then reapplied it you could cause something like the compressor to get "hung up" (can't recall the correct term) and of course the LRA goes up each time the motor initially starts back up but I wouldn't think the LRA is a factor. Admittedly I am more familiar with residential 220 in Alabama so I can't speak much to three phase commercial/brownouts but I would expect that improper voltage along with the float switch would probably have adverse affects. Hopefully we may get a response from Brian and in light of your last response, I take back my precious "literally can't happen comment lol.
My Bosch air handler has a trap, but not a clean out tee. I bought a tee to add but I don’t understand if I need to be concerned about positive positive or negative pressure. I don’t think so. There’s no vent either, but I thought just adding a tea would be a safe bet to help me clean it more regularly from the top instead of just the bottom.
I just moved into a brand new apartment (new construction)- 1st floor, new unit and I'm finding water in the floor and coming out of intake. I can see the drain lines for my unit and the others are DRY like nothing is coming out. I've called maintenance and no one will get back with me. Don't know what to do?
Missed one setup. When a horizontal furnace and coil are installed in the attic or an upflow furnace and coil are installed upstairs you can actually run the secondary drain straight into a secondary drain line that would stub out on an exterior wall above a window. This way when the primary becomes clogged, the water would then drain out the secondary where the homeowner would see it and know something was wrong. This was code and the way we used to do it on housing tracts in Southern California back in the 80's before condensate switches were popular.
I see new construction homes today do the same thing with the secondary drain dripping into the garage, usually above the door into the home. Very hard to miss that!
@@sed6 Actually sounds like a great place to put it. Most people are in their garage daily and the concrete floor should withstand it well. Would not be good if you use your garage for any kind of storage. Any kind of organic material that gets constantly wet in a dark warm environment like a garage is inviting a serious mold problem!
Thanks, really informative. I couldn't find a definitive answer to that question: Do you need a p-trap on a positive pressure system (furnace)? I'd say yes because cold air would be pushed out. Most said you don't because it's positive pressure. Any code article stating one or the other?
I don't know code requirements. If you think about it, you're paying to heat or cool all the air going through the air handler. Even though it's a very small percentage, by allowing some conditioned air to blow out the drain line, you're wasting that small amount of energy. Technically, you wouldn't be losing that energy if the unit is installed in a basement or other internal conditioned areas of the house. If the air handler is in the garage or attic.. you are.
I came upon a VERTICAL AIR HANDLER ABOVE THE WATER HEATER, where there was a plastic container below the a/h, it was a particular RHEEM. drain on LEFT SIDE, but you could not run the line lower, as it would be covering accseee door, so they has a. Street elbow, line then ran horizontal to drain access in the wall, HOWEVER IT NEEDED A LEAST 6” DROP, to get over the NEGATIVE I got some pipe & a n EZ TRAP, BUT made the drop 12” as there was lots of space to get to pipe in wall, lady said it ALWAYS LEAKED , you should have seen how much snot was in that drain pan! I guess the installer either did NOT READ about the 6” minimum drop , Or did NOT UNDERSTAND ! That was about 20 years ago in MIMAMAR FL CHEERS 🇺🇸🇺🇸🇺🇸🇺🇸
It seems like my primary drain from the furnace is routed to a bathroom sink drain in the floor below, and the secondary drain line is routed outside the house. Is this setup correct, or at least ok? Lastly, would it be best to tap into the primary or secondary furnace drain for the drain from a dehumidifier? Thank you!
@hvacschool Am I wrong or did you have a video on the configurations for condensate drain lines on positive and negative pressure units for horizontal applications? Because i can't find it
Bryan has another one similar to this called 'A Few Condensate Considerations' at ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE--JSdAMuwbig.html. Excellent videos by others showing air & water behavior in both are here... 'Condensate Drain Traps - Correct sizing: by KHS Engineering Topics' at ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-5ZijpU7tHVc.html and one for a unique system is by 'CostGardTM Condensate Drain Seal' but the LAB VIDEOS are awesome! At ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MS-KdN3MWHU.html
I have issue with wiring the water over flow switch to turn off R. I have found keeping the blower running will help keep the condensate suspended long on the evaporated coil. And not overflow the evap pan. So we wire to turn off the Y. We are on the gulf of mexico in texas high humidity. Please explain.
Breaking Y can let the unit short cycle depending on how long it takes for the switch to close. Residentially thats how you fry a compressor if your outdoor board doesnt have its own time delay
I'm trying only picking brains. Let stay with residential systems. Got a service call about 20 years ago. Ac not cooling. Customer said i feel air but not cooling, Should I turn the unit off. I told no I'll be there in about 15mins. Got there the lady turner of thermostat off. Fan was auto. Water over flowed the pan onto her sheet rock. Water over flow switch was cutting y. what I've seen happen is the blower keeps the water suspended in the evaporator coil. When the air flow stoped water ran down into the pan and over flowed. I don't remember how high the pan was. After that on residential attic i cut y. Any comments. I've been do HVAC-R for 45 years. But i can always learn something new. Commercial i will read the install manual see what people that made the thing say about it
Since there are differing codes and requirements depending on which country or region you are working in, you should probably make it clear which one you are in that this applies to. What is allowed/required in the UK may be different than what is allowed/required in the US (or in a specific state in the US) or Germany, or Japan, etc.
I don't think so. A vent before the trap will allow the unit to suck air from the vent and might prevent the condensate from draining. The reason for the trap is to block air from being sucked into the system so the vent should be placed after the trap.
So confused about the P trap. We bought our 2-story condo with an AC in a closet at the top of the stairs. A white PVC pipe comes out of it that angles down and out of sight. That PVC pipe has one of those shut off floats cut into it, but no P trap. Another pipe comes out which is covered in a black pool noodle cover, heads along a parallel path with the PVC pipe but at a height above it. Again, no P traps. Was this old school, or incompetent work? The AC works with no leaks. Do all ACs need this P trap? The shut off float I described is also the only way to pour in vinegar or bleach to clean the drain pipe. Does that matter?
If it is not trapped where your air handler is it should be trapped outside wherever your drain lines run to, typically it will be next to the outdoor unit
agreed. It's similar to the vent pipes you see that go up through the roof of your house. It's to allow gravity drain liquids to flow downward without the effect you get when putting your thumb over the top of a straw with soda in it. If you don't allow the vacuum to vent, the soda stays in the straw. @@johnwhite2576
You didn't mention anything about the configuration of a "draw" fan unit trap construction or a "pull" fan trap construction. One requires a much deeper trap than just top of pipe to bottom of the other. Otherwise the water WILL be sucked out.
I read my manf guide and yes they wanted the trap at a min 2" deeper than the outlet of the trap meaning I couldnt use those prefab ceap running trap from home d but had to MAKE A TRAP.
Don't use elbows, use 45's and make the trap as shallow as possible, never had a problem with high static. Also insulate the trap to keep from freezing and cracking otherwise great video. If you can help it never ever use elbows on a condensate trap, double up 45's to make and elbow, your clogging problems pretty much non existent.
@@dustyflair Who writes those manuals? My understanding it's usually the engineer that nobody wants to work with and ain't real whippy. It's also pretty obvious that you're not out there in the real world where s*** doesn't always work like it does in a conditioned lab.
