HVAC primary drip pan overflows beginning every summer


  #1  
Old 06-10-24, 12:49 AM
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HVAC primary drip pan overflows beginning every summer

Why is the main drain line entrance HIGHER THAN THE DRIP PAN (IE: WATER LINE) inside the AHU? How can water drain this way?

I believe HVAC techs have us on a repeat cycle to come yearly vacuum the drip pan of mold/mildew/water and collect a fee whereas it does not appear that the water in the drip pan can ever reach the drain line the way it's setup. Am I missing something?
  1. We clean our intake filter (permanent one) often: IE: Every 1 or 2 months with vacuum and/or hose depending
  2. We also hose down and down shoot grass clippings at the outside compressor unit.
  3. We are POOR and need this problem eliminated instead of paying $300 or so each year to have techs come vacuum and clean it up.
  4. DRIP PAN is FULL and Secondary drip pan beginning to take on water. See photos of secondary drip pan below. COIL main drip pan photo will be posted later.
  5. Why would the main drain line entrance be sitting an inch ABOVE the lowest grade on the coils drip pan inside the AHU?
  6. In the photos below - shouldn't there be a P-Trap or 2???
  7. Should I have left the tape over the PVC hole?









 

Last edited by XSleeper; 06-10-24 at 04:30 AM.
  #2  
Old 06-10-24, 02:07 PM
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I'm guessing that air handler is in the attic.

The A/C drain or drip pan is inside the air handler.
The pan under the air handler is an overflow pan in case the drip pan overflows.
Technically you should have two drains lines....a primary and an overflow pan.
There should normally not be any water in the overflow pan.

There are two drain connections on the air handler. One is slightly lower than the other.
The lower fitting is primary drain. The upper fitting is the overflow drain.
In your case..... the drains are on the incoming or vacuum side of the blower.
You should have two traps. The primary trap goes to the drain line. The secondary goes to the pan.

OR you should have a float switch in the overflow side to detect internal pan overfill.
 
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Old 06-10-24, 02:12 PM
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Continuing on..... do you want to know what you should do ?
It will require cutting PVC pipe and gluing in fittings.
I'll tell you what to do if you are going to do it.... otherwise you now what the problems are.

Since there is no drain connection to the overflow pan.... you do not want water getting there.
 
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Old 06-10-24, 08:46 PM
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Pete (PJMax) - Thank you very much for your time.

YES - I want to know what to do, and I'm very capable. You have my consent. Living where we do, we've had to know how to do "EVERYTHING" from cars, mowers, appliances, computers, etc... our whole lives. IE: Technical ability: I can also wire up a home for electricity. In any case tell me what to do and if I don't do it, then I will likely make the HVAC company come here and do it for on their time/bill since they've been here several times for this issue, they should fix it right.

I would still like to know the answer to my 1st question:
Why is the main drain line entrance HIGHER THAN THE DRIP PAN (IE: WATER LINE) inside the AHU? How can water drain this way? IE: The drip pan is BELOW BOTH drain fittings. Both drain fittings are ABOVE the drip pan.

Answers to your questions:
1. Yes, it's in the attic. Only part of the unit in the living room is the air intake cavity and thermostat.
2. Yes, I know that pan under the AHU is the secondary "EMERGENCY" drain pan.
3. The secondary (overflow) drain pan DOES HAVE a drain (not in the photos) that is on the opposite side of the unit that runs out to an eave vent.
4. Yes, I know there shouldn't be any water in the overflow pan under the AHU.
5. You said: "There are two drain connections on the air handler. One is slightly lower than the other." - but yet this is not the case.... both drain connections on the AHU are parallel at the same level.
6. You said: "The lower fitting is primary drain. The upper fitting is the overflow drain." - but yet again see my answers in #5. The drains are both at parallel levels ABOVE the main drip pan.
7. Yeap, as you saw - no PTraps.
8. Float Switch for detecting overflow - Dunno what that would look like or where it should be sitting, but I doubt we have one.

9. Do I have a negative or positive pressure system setup?
10. So I am correct then..... there's no real DRAIN for the main drip pan based on what I've shown you? There's no "MAGIC VACUUM" effect going in the AHU that makes the water climb UP into the PVC main drain pipe?

 
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Old 06-11-24, 05:39 PM
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Yellow arrows are airflow. Blower is in the right side of the air handler.
That means the coil (orange) and drains are in the suction side of the blower.
Negative air pressure = suction on the drains.

The drain lines may look even.... they are not. One must be lower than the other.
The dark blue is the drip pan.
The light blue is the normal water level and drains out the primary drain.
When the primary is blocked the water level (red) rises and comes out the secondary fitting.



This is exactly what you want to do. The lines just go towards the right.
The secondary p trap drain into the pan since the pan has a drain.
The primary pipe is not covered. The secondary is.
When it's time for cleaning...... shut off the air handler.
Take the cap off the secondary pipe and put it on the output side of the secondary p trap.
Pour several cups of bleach into the secondary pipe followed by a gallon of warm/hot water.
The bleach will go into the pan and drain into the primary drain and get flushed with the warm water.
When done.... remove cap from bottom of secondary p trap and put back on top.
The drain lines rarely clog. The clogs typically occur just inside the primary drain fitting inside the pan.
So flushing just the primary drain line is not effective.

condensate drain video
 
  #6  
Old 06-11-24, 05:41 PM
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5. You said: "There are two drain connections on the air handler. One is slightly lower than the other." - but yet this is not the case.... both drain connections on the AHU are parallel at the same level.
Response only to this comment. Sometimes the secondary drain "fitting" has a half plug in it such that with two even drain holes, condensation will only flow out of one unless there is a blockage in the primary (This is how my Trane is arranged). Water then rises above the half block and flows out the secondary. You can't see this because you have pipe connected.
 
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Old 06-11-24, 05:45 PM
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That is a possibility but I've always seen them at different heights.
It doesn't have to be much.
 
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Old 06-12-24, 09:49 PM
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(Moderator note: Numbered bullets are not showing up properly and line spacing isn't either when trying to use the numbered bullets.)

Pete Thank you for sticking with me (and anyone else too)!!!

I really appreciate you taking the time to do custom photos too, but I think you missed that there are only 2 pipes in play here, but in the side photo it looks like it's 3.

I spent some time last night in the attic thoroughly cleaning out the drip pan to the best of my ability. I have a couple of realizations to make.

I will post more photos too after this post.
  1. 1. When I open the unit (safely of course; turned off power/breakers) what I noticed right away was a drip pan full to the top with water.
  2. 2. Upon looking closer, while the pan was full, it was full on the non-drain side and while there was funk and junk and mildew in the tray near the drain the water level barely reached the drain, yet again was up to the top of the tray level on the opposite non-drain end.
  3. 3. Looking closer on the far corner under the drip tray there is a pvc pipe covered in black mold underneath the tray that is propping up the tray on that corner with the intent to move the water back towards the main drain.
  4. 4. Secondary drain - So while I see there is a pvc running from the overflow pan west edge to the eave outside, I see no where else inside or outside the unit where water could make it to the overflow tray/pan.... and from what I can tell typically water in the overflow pan is coming from "screw holes" at the edge of the unit and/or from under the bottom wall insulation area...... this would explain why sometimes the wet makes it as far as underneath and into the electric box compartment where the breaker is behind the blower motor..... because it simply has no overflow exit point from the main drip pan to outside overflow drip pan.
  5. 5. This also explains why the bottom AHU insulation layer (inside AHU immediately below the main drip pan) is so damn chock full of black mold.

    SOOOOO...... that small old dingy short looking PVC pipe sticking up (the one I had silver tape over, but removed it).... is that simply intended to point at the overflow drain below to be the "overflow drain pipe"????? or should that small pvc pipe that's facing upwards be sucking in ATTIC AIR? CAN somebody just tell me that is correct and for what reason? Because I am thinking this was intended to be the overflow drain pipe and should be pointing downward to the overflow tray.
  6. 6. Using my phone to photo everything "funky" before cleaning, I now know why I was questioning why the main drain line would be a lil higher (possibly 1/8" to 1/4" higher) than the base level of the main drip pan.... because it doesn't make sense to me that you'd always want a small short pool of water to ALWAYS be there in the drip pan.
  7. 7. Why is the base of the coil situated to sit in a pool of water on it's bottom edge?
    I mean this seems like poor design to me. Seems you'd want the coil at least top height of the drip pan so it's never sitting in a pool of water or muck.
  8. 8. In the photo I edited a lot above:
    PVC Line I have edited with blue text = Main Drip Pan Drain Line = which to you is Primary (P) drain

    PVC Line I have edited with GREEN CIRCLED text I think should be = Overflow Drain = which to you is Secondary (S) - and I am thinking I should turn that pipe downward to the overflow drain, otherwise the only way water will ever make it to the overflow pan in event the main pan fills up again is to overflow inside the unit and drain through and between screw holes (not wanted).

    PVC line I have edited labeled with red and white text as "Service Pipe" = P main maint line for pouring bleach down it, but this bothers me because the bleach will never reach the elbow in the main drain line just before the "Service Pipe" = which is essentially a big CAP.
  9. 9. I did not remove the blackened PVC pipe that a tech obviously put propped under the main drip tray, and instead I put a prop under it's parallel opposing side to send water back towards the P drain line inside the tray. I'm going to pop the AHU cover off sometime soon to see how the flow is doing due to this.

  10. 10. I see your AIR FLOW arrows, but I must be missing something because I don't see how air is going to the RIGHT and making it into the rest of the ducts because to the right I thought there was just a metal wall, but I guess I'll look again when I go up there because I want to have a good understanding of all this for the future and put notes in my computer.
  11. 11. I'm starting to wonder if they didn't put "P Traps" because of "space" issues below the drain pipe(s) and how it might require lifting and leveling the whole AHU UPWARDS a few inches. I guess I'll have to measure and look at the store to see the shortest PTrap available and see if it can be done. If there isn't enough room to add them, then I would suspect this is why they aren't there, because it would be an insane labor cost to add new walling and blocks to lift the whole unit upwards to just add the PTraps.
    This makes me wonder if there is another CHECK VALVE special solution to resolve this issue if there isn't enough space below the drain line to put a PTrap.
  12. 12. Does the coil have to come out to remove the drain pan in order to replace the bottom wall insulation that is caked with black mold? - To me right now this is the most important thing after I resolve the drainage issues.
  13. 13. I read the rest of what you said in post 3012346 about PTrap setup and proper flushing routine. THANK YOU!!!!!!!!!!!!!!
Will post back. Gonna add photos in a few minutes.
 

Last edited by searcherrr; 06-12-24 at 10:01 PM. Reason: Numbered bullets not showing up properly on finished post
  #9  
Old 06-13-24, 10:42 AM
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No need to get fancy or use many words. I get the point quickly.

To the left is the return duct that looks to go down to a ceiling register in the second floor ceiling.
The flex lines to the right are your supply lines to the rooms.
The air flows from left to right.

The air handler needs to be mounted level so that the water goes to the drains.
I always tip my units slightly more towards the drains.
Yours sounds like it's tipped away from the drains.

The tall piece of pipe was installed as a place to pour chemical to clean the drain line. As I have previously mentioned the clogs are 99% inside the air handler.... not the drain line. You will no longer be using that tall white pipe.

I'm not a fan of sitting the air handler directly in an overflow pan on the floor.
I either raise the unit off the floor or suspend from the roof rafters.
You may have to cut a hole in the flooring for the trap to fit into. Below the floor should be at least 8".

The coils sits in the drip tray. The coil would need to come out as it can't be lifted high enough.
That would mean removing the refrigerant and cutting the coil out.
Then it would need to be reconnected and recharged.

. Do you under stand the diagram I have left you ? That is how I would pipe that unit.

 
 

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