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Old 06-26-2010, 07:36 PM   #1
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Smell coming from all floor registers.


There is a smell like cat urine coming out of every floor register when the air conditioner is on. This started about a week ago. This is the first time we have had this problem.

Any suggestions will be greatly appreciated.

We have a 2,000 square foot, single story ranch style brick house on a crawl space.

All duct work is in the crawl space along with the indoor heat pump coil (with UV light), gas furnace, blower and two stage filter unit (fan fold element and activated charcoal element). The entire HVAC/duct system is 3.5 years old. The main supply trunk line is 16” metal, running along the north and east ends of the crawl space. All ducts to the floor registers are 6” flex. The return duct is 18” flex.

The floor of the crawlspace is covered with heavy plastic – part of our radon mitigation system. The plastic goes to the walls and part way up them, where it is sealed to the cinder block with adhesive. A duct, under the plastic, runs the length of the crawl space (west to east) and terminates at a pipe that goes through the foundation wall and connects to a fan and exhaust stack. The radon mitigation system is 2.5 years old – and in good working condition.

There are air vents in the crawl space walls on three sides of the house (north, west and south).

Recent changes:

1. Last fall, our contractor replaced a leaking indoor coil – and – the manufacturer’s rep (Goodman) fixed a vibration problem (too much Freon in the system) and changed the blower settings to factory spec (higher speed than before).

2. Just before the smell started, about a week ago, a very hot and humid summer hit us early and hard.

Checks and observations:

1. The crawl space smells like cat urine, but there are no openings that a cat could get through and the smell started at least a month after the last time I had the crawl space door open.

2. All the floor vents and the return register smell fine, so the smell is not getting into the system from inside the house.

3. After the crawl space door has been open for an hour or two, the smell goes away – and it no longer comes up into the house from the floor vents. This lasts about 24 hours, and then the smell comes back.

4. I checked all the duct work for critter damage and found nothing. No dead animals anywhere in the crawl space.

5. I opened all units in the system – no smell or mold inside – and none coming from the main return or leaving out the main supply duct.

6. With the system on, and the blower going full speed, I did a smoke test all around the outside of the active components and the entire length of the return duct. There is no air being sucked into the system that I could see.

7. There is no urine smell at any of the vents, on the outside of the house.

8. There is no significant air flow in/out of the drain line from the indoor coil, and no smell. The drain is working normally.

9. I found small puddles of water across the north and east ends of the crawl space, mostly within a few feet of the main supply duct. In some places, it was obvious the puddles had come from dripping condensation off the supply duct. Some of the puddles were clear, some were slightly yellow. The yellow puddles did not smell like urine.

10. There was no single spot that smelled really bad. I’m pretty sure that the smell is worst where the puddles are, along the path of the main supply duct, which is along the north and east ends of the crawl space.
Attached Thumbnails
Smell coming from all floor registers.-full-crawlspace-system.jpg   Smell coming from all floor registers.-return-duct-meets-filter-end-unit.jpg   Smell coming from all floor registers.-16-inch-hard-metal-supply-duct.jpg   Smell coming from all floor registers.-return-plenum-front-back.jpg  

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Old 06-26-2010, 08:52 PM   #2
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Smell coming from all floor registers.


It may be that a cat got into the crawlspace this past winter and its only now that I'm smelling it because the humidity has gone up so much.

I'm still puzzled about why/how the smell comes out through the floor registers. I'm sure the urine is not inside the duct work. I guess a little urine smell goes a long way - somehow managing to get sucked into what seems to be a very tight system.

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Old 06-26-2010, 09:12 PM   #3
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Smell coming from all floor registers.


2,000 square foot ranch and a single return?! Am I missing something?
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Old 06-26-2010, 10:19 PM   #4
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Smell coming from all floor registers.


Lots of ammonia smell comes from cat urine. I would try an experiment. Go to Safeway or a pharmacy or HDepot and get that highly concentrated Nilodor product which is in drops in a small bottle. Use 1 or 2 in those puddles and wait to see if the smell gets sucked into the house. My installers use silicone where the air filter attaches to the furnace etc and even a small leak on those joints if not siliconed can suck in a smell.
http://www.petmarket.com/nilodor-tapadrop-p-1340.html
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Last edited by yuri; 06-26-2010 at 10:22 PM.
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Old 06-26-2010, 11:26 PM   #5
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Smell coming from all floor registers.


Quote:
Originally Posted by yuri View Post
Lots of ammonia smell comes from cat urine. I would try an experiment. Go to Safeway or a pharmacy or HDepot and get that highly concentrated Nilodor product which is in drops in a small bottle. Use 1 or 2 in those puddles and wait to see if the smell gets sucked into the house. My installers use silicone where the air filter attaches to the furnace etc and even a small leak on those joints if not siliconed can suck in a smell.
http://www.petmarket.com/nilodor-tapadrop-p-1340.html

Yuri,

Thanks for the tip. I will get some and try it.
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Old 06-26-2010, 11:43 PM   #6
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Smell coming from all floor registers.


Quote:
Originally Posted by gena View Post
2,000 square foot ranch and a single return?! Am I missing something?
1,800 square feet in the house proper use that return. There is another 200 square foot room, in the garage, that has its own return back to the main return.

Since the Goodman rep increased the blower speed, the grill you see makes a singing sound. Even with the grill removed, there is still a rumble from the constriction (choke point picture is attached) where the air passes through the floor.

The original contractor set the blower to a lower speed to minimize both noises. Last fall, the Goodman rep helped us with another problem, but also checked all the DIP switch settings. He said two of them were wrong and he changed them. The result was a greatly increased air flow rate, and a return of the grill noises.

The original contractor should have increased that opening through the floor. There were other troubles with him, and we have gone to a new company for our service work.
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Old 06-27-2010, 09:53 AM   #7
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Smell coming from all floor registers.


wet insulation has ammonia smell
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Old 06-27-2010, 10:48 AM   #8
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Smell coming from all floor registers.


Mr. Polk gets the "Cupie" doll, IMO. John-you state that you are in AL. which I will take to be Alabama= high humidity this time of year as it is here. I fought this exact same problem some years back and found it to be high humidity under the home. I have plastic on the ground and was finding puddles of water directly under the main A/C lines but not the return line (yes, gena-one return for a 1960 sq.ft. living space home). Further investigation found that all of my insulation was wet and dripping from humidity-cold air vs. warmer high humidity air under the home. At that time a friend of mine who does HVAC work got me a squirrel-cage type fan from a split unit and we adapted it to fit one of my foundation vents. I wired this in on timer to run twice a day to bring in air from outside. This air may be high in humidity but is dryer than what is under the house after testing with hydrometers. So-new A/C duct insulation, running the vent fan two times/24 hrs. solved that problem and got rid of some mold on my floor joists. Now there are two businesses in my area that go under homes and put de-humidifiers under there to control humidity under the home. David
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Old 06-27-2010, 10:54 AM   #9
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Smell coming from all floor registers.


Seal the crawlspace. Install a small portable dehumidifier in the crawlspace. With a hose to drain outside.
Set it for 55%RH. It won't have to run often. And will also prevent moisture from getting into the house.
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Old 06-27-2010, 10:57 AM   #10
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Smell coming from all floor registers.


You can reduce the noise in your grilles by upgrading to a new type of vent cover
the ones you have are stamped steel with and open area of 3/8"
change over to the bar type grille that as more free air space

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