04 Journey - Black Tank Smell coming through HVAC

phinneyj · 09-13-2015, 01:25 PM

Okay, now I am perplexed. I have checked all normal sources of black tank gas coming into the coach. It only happens when the AC kicks on and pushes the smell out the vents. Anyone have this happen and what was the solution?

Ranger Smith · 09-13-2015, 01:50 PM

you might have a bad vacuum vent under one of the sinks or a trap without water in it.

1ciderdog · 09-13-2015, 05:24 PM

You have basement air - could a critter have gotten into the duct near where the duct attachés to the basement air and perhaps nested or something? Very strange.

phinneyj · 09-13-2015, 05:39 PM

I did have to retape the plenum in the back because it was split. I need to call Winnebago and see if I can get the build plans and look for areas where that could be possible.

1ciderdog · 09-14-2015, 09:58 AM

On my 39K the air comes out the rear of the basement unit and goes up the inside of the rear cap. I'd think if you look up from the bottom you could see possible damage. Other than that -beats me!

DancinCampers · 09-14-2015, 03:19 PM

The air conditioner produces a negative pressure in the coach when running. Try opening a window and see if the smell goes away.

Potential areas for air being pulled from the waste tanks are:

-air vents for the sinks and shower
-if you have a washing machine, the air vent and stand pipe if p-trap empty
-the gasket where the roof vent pipes enter the tanks.
-the gasket where the toilet enters the tank.

The tanks, over time, tend to droop on the tops. The roof vent pipes are usually attached to a nearby frame member. It is possible that the tank has separated slightly from the vent pipe.

Jupiter · 09-16-2015, 01:29 PM

I agree, Dan, with your good suggestions regarding potential sources for odors. But, with due respect, I don't agree that running the A/C creates a negative air condition. The evaporator fan typically "pulls" air from the coach through some type of return air filter and then "pushes" the same volume of air through the evaporator coil which removes the heat and sends it into the coach via the supply diffusers.

Given that a single fan (typically a squirrel cage fan) both returns and supplies the cooling air, it would not be possible to create a negative condition unless there is external issues such as a break in the supply duct which causes a loss of supply air to the outdoors. The single fan cannot possibly move more CFM's (cubic feet per minute) on the return side than CFM's on the supply side. If you DO experience a negative condition in the coach then you should check your ductwork or your rooftop evaporator coil plenum for leakage on the supply side.

Hope this is helpful.
Joopy

NoMoreAZ · 09-16-2015, 02:40 PM

Unit in question, RVP Heat Pump a.k.a. Basement Air, as mentioned above, has 2 cages for squirrels. Indoor and outdoor. Works fine when working. Better than roof units.

DancinCampers · 09-17-2015, 08:41 AM

Hi Joopy
I believe the ceiling ductwork is designed to restrict the airflow. The indoor fan tries to pull in more air than the ducts will allow. If you crack open a window slightly you will feel the outside air being pulled in.

1ciderdog · 09-17-2015, 10:02 AM

Jeff, Have you tried turning on the galley exhaust fan to see if it pulls that smell in. If it does I'd think that would indicate a poor seal in the commode. Other wise still a mystery.

Jupiter · 09-17-2015, 08:37 PM

Quote:

Originally Posted by DancinCampers

Hi Joopy
I believe the ceiling ductwork is designed to restrict the airflow. The indoor fan tries to pull in more air than the ducts will allow. If you crack open a window slightly you will feel the outside air being pulled in.

Hi Dan. I don't doubt that happens. But if it does happen, then there has to be an air loss on the supply air side of the fan (positive pressure) whether it's a rooftop or basement air system. Otherwise the "return" fan could not continue to bring in more and more outside air into the coach unless the supply air could relieve somewhere downstream of the fan. Although the fan will have substantially different pressures on either side of the fan housing (both positive and negative pressure), each side must move exactly the same volume of air.

For example, look inside a typical rooftop unit at the fan housing gaskets and seals and you'll likely find gaps for cold air leakage and it's at the highest air pressure point in the system. Same goes for basement air but I'd sooner expect duct leakage for losses on that system. So your right on, Dan... a loss of supply air to the outside will cause a negative condition inside.

cheers,
Joopy