Anyone here with HVAC knowledge (relating to funky smells)?

[Spec A!]

So over the summer our upstairs AC went out on us, and we had the original 15yr old Carrier 2 ton unit and upstairs coils replaced with a Trane XL-14i 2 ton and new coils. Works like a charm. Now that we are out of the constant need for AC, there have been a handful of days/nights where it's gotten warm enough upstairs to turn it on (mainly to cool it off for the kids). Well since it's been off from constant summer use, when we have had to use it occasionally, there's a horrific smell now. I've read up, and it could possibly be the DSS- dirty sock syndrome. There's two main questions I have:

Does it not seem coincidental that since the new coils were installed we've had this issue? Never had the problem with the old system.

How should the condensate drainage be hooked up? From what I can tell it is just a straight pipe that hooks into what I think is the upstairs bath ventilation/drainage. It does not appear to have a trap in the line, but there is a T in the line that I have poured bleach though upon recommendation from the HVAC company that installed it. They said the smell is normal when the system hasn't been used in a while and then turned on- the solution is to our bleach through the drain line via the T. Well it hasn't fixed the problem, and I don't think I should be pouring bleach through there everytime I need to occasionally turn the AC back on.

FYI we don't have the smell when the heat is on. The evap coils are brand new, I suppose it's possible that they've grown some mold on it, I just hve a hard time believing that they already need to be cleaned after only a few months, especially when the old system and coils never had this issue. Which leads me to think- how should the condensate drain be hooked up, should there be a trap of some sort in the line, did the HVAC company hook something up wrong?

Anyone with any advice would be greatly appreciated! thanks!

[Adorable]

When is the last time you changed your air filter?

[klynam]

No smell w/ heat...new coil installation...did the HVAC co hook something up wrong...quite possibly, or the work they did exposed another problem that was "stable" before being disturbed by the work.

From there start the process of elimination...

After the AC has run a while, take off the coil cover and observe (look and smell.)
Is the condensation pan leaking or overflowing (getting some surface below it wet)?
The drain must have a definite downward slope - did they mess that up?
If the pan is draining well, the bleach is good but you also need to "blow out" the drain - as in using compressed air - to be sure nothing is actually partially clogging the line further down.

My guesses in order are...

1. The drain pan is leaking down onto something below which is moldy
2. The drain pan itself is moldy
3. The drain pipe is partially clogged and moldy

All of these will "recur" when new condensation (water) re-wets the problem and releases the smell again.

If the case is no.1, you have some work on your hands to tear our (and replace) whatever moldy surfaces are down there.

If the case is no.2/3 then just replace the pan/drain line. The pan will have to be ordered. The drain line is just PVC and you can do it yourself. A trap isn't necessary. Just rebuild what is already there with new PVC pipe, making sure you have a slight downward slope from the pan for proper drainage. The entire cost should be <$30.

Are there other possible reasons for the smell, yep...

[kenw]

ok, hopefully I can help.

there are 2 condensate drains. the primary/ 1st is connected to the bottom/side of the coil. normally this goes to a nearby vent stack or sewer pipe connection. Sometimes it just goes outside. As you suspect this is probably where the problem is, no guarantees but let's check it first. in a minute...

The 2nd drain is a BACKUP drain that is connected to the pan which sits under the coil. It is an open pan, not atached to (usually) the box that the coil is inside of. If the 1st one get plugged (they do, more on that later), the coil overflows and the pan catches it. In many cases this drain is routed so that it drains thru a soffit over a door or window so that you can see it dripping. If you can see it dripping you therefore know that the coil drain (the 1st) is plugged and that you need to clean it out.

You can disconnect the 1st drain at the coil box and poke around a bit to see if water is able to flow out. There may be some air pressure if the fan is on, that's a good sign. When you disconnect that pipe, be prepared for some water to blow or leak out (have rags ready). That air pressure also can push a lot of crud (pet fur, carpet fibers, lint, etc) into that drain line. Take a whiff of the drain pipe after you disconnect it. Is that the smell? if so, lift it so that it drains completely thru the other end and take it outside and force water (garden hose, etc) thru it to completely flush it. Your bleach may be the right idea but it really won't get rid of the crud, only the algae that's already there. In a few hours, more will grow to replace it's fallen comrades.....you've got to completely clear out that pipe. In my case, it was easier to just replace it; it's cheap and cuts with a utility knife.

It is important that the 1st drain have a p-trap (aka j or elbow) that stays full of water and keeps fumes from the sewer or vent stack from being sucked into the coil's airflow. Check this line to see that it has a p-trap. There will /should not be a p-trap on the 2nd drain. It is easy to confuse the 2 drains, make sure that you are looking at the right one. The one you are looking for is NOT the one that is connected to the pan that sits in the open below the coil. The one you ARE looking for is connected to the lower side of the sheetmetal box that the coil is inside of.

The reason it doesn't smell when the heater runs is that the heater isn't making condensate for the algae to grow in, and possibly that the heat is sufficient to kill any that might hang around.

let me know what you find, I've done a lot of work on these over the years and fixed a lot of bonehead installer mistakes. The stories I could tell....

[kenw]

addendum: a p-trap IS most certainly necessary on the 1st drain, even if not connected to a sewer or vent. Without it lots of cold / hot air will be blown outside your house (or down the sewer). The p-trap blocks this air loss as well as prevents sewer gas intrusion; it works both ways.

[Spec A!]

Ok- you guys rock.

Air filters are brand new- changed seasonally

In response to Kevin: #1- nope, #2- nope, new pan with new system, #3- possibly.

In response to Ken- I'm pretty sure the 1st drain is not clogged as I do not see signs of
drainage into the pan below. My downstairs AC unit has this problem (I believe) as over the summer the pipe that the pan drains from out of house and a little above the master bath window (1st floor) dripped quite alot, and also rust stained my siding. That's another mess but one I'm 99% sure I know why and how to fix.

The Drain pan on the upstairs AC is new along with the system, and shows no obvious signs of water. The pvc pipe with the T connection I poured bleach into is indeed from the 1st drain, as it comes off the bottom of the coil box. It is on a downward slope and I'm pretty sure it drains into the sewer or vent pipe- not 100% sure as it gets buried in insulation near the roof line but it heads straight for the upstairs bath. I'll have to check outside but I'm pretty sure there are not any soffet pipes on that side of the house (there are on the back of the house though). There is most definitely not a p-trap on the line out of the coil box, just a 90deg horizontal elbow and a straight pipe down towards the bath. The only thing it has is that T connection, and none of the typical looking p-traps I've seen pictures of on the interweb.

So chances are better that the smell is coming from the drain rather than the coil?

[kenw]

if there is no p-trap on the coil drain, then the smell is likely coming from the sewer that it is connected to, it is being sucked into the airflow thru the drain pipe. Very common problem, you can buy a p-trap and install one yourself. HD, Ace and Lowe's carry them.

[JohnT]

This is very interesting. During the fall, when the temps are up and down, some days I run the heat and other days the AC. When I run the AC, I notice a very pungent (read: stinky) odor in the air. I had this checked out by a tech, and he said that he couldn't find a source to my "problem." No issue during the summer months, when the AC is all that is on.

[kenw]

leaving out the p-trap is probably one of the most common installer mistakes.

John, I'll bet you don't have one either......

[Spec A!]

John I'm pretty sure you are in the same boat as me- check your drain pipes for the p-trap.

Ken- Thanks! Would you happen to know if it's code for a p-trap to be installed? I hate to pay for a mistake the HVAC installer made....

[JohnT]

Cool. I'll check it out.

Thanks for posting about this, Anthony.

[kenw]

Code? In Harris county? Don't bet on it......seriously, I have no idea.

trust me, fixing it yourself will take 20 minutes and less than $10. Code or not it probably isn't worth the hassle to get them to fix it depending on your comfort level with this sort of thing.

[Kalrog]

I have done p-traps in a kitchen sink installation with a new garbage disposal - very easy to do if it is the same process.

[Spec A!]

Originally Posted by kenw

Code? In Harris county? Don't bet on it......seriously, I have no idea.

trust me, fixing it yourself will take 20 minutes and less than $10. Code or not it probably isn't worth the hassle to get them to fix it depending on your comfort level with this sort of thing.

Montgomery Co, but I figured as much. I know what I'm doing this weekend!

Thanks again guys!

[KJ Smith]

Anthony,

You can buy pre-formed p traps that are made for this. You would just cut the line and glue it in with couplings, or some of them are pre-swedged for you.

You need to install the p trap after the T. Not between the T and coil.

The T is there to relive the air pressure when the fan is running.
If it is not there it can keep the condensate from draining.

This assumes your coil is up stream of the furnace. ( most common ).

You can also buy a product from an A/C supply house called bio ?
Can't remember the name, it comes in gallons or a spray bottle. You spray it into the return air with the fan on and it flows through the system and kills all the odor making mold ect. It is odorless and really does a great job.
If I can think of the name I will post it later, otherwise it will be after Christmas before I can look it up.

I have also heard of people mixing bleach and vinegar in a pan and setting it in th return air with the fan running. You are supposed to get the same result, but it really stinks up the house.

There are a couple A/C supply houses behind the golf cart place on 45 in Conroe.
I think there is a Johnson and a Baker. Baker carries the Bio product and should know what your looking for if you ask.

Kevin

ON EDIT : The product name is Bio-Fresh CD. I use it and recommend it.

http://www.nucalgon.com/nucalgon/web...1?OpenDocument