Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
RV Trip Planning Discussions

Go Back   iRV2 Forums > RV SYSTEMS AND TECHNOLOGIES FORUMS > RV Systems & Appliances
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 05-18-2022, 07:31 AM   #1
Junior Member
 
Join Date: Oct 2020
Posts: 17
Roof AC will not drain while fan is on problem

Hello! I have a 1990 class a with two Coleman super Mach model: 6799-808. Both units have been looked at and I have made sure all the drain routes I can see are clean and free of debris.

The problem I have is that when the rear unit is running, it will not drain condensate from the unit. Once I turn the unit off, all of the condensate drains out onto the roof and down the rv as expected. Does anyone know what can cause this and how to fix it? It's causing excess humidity and eventually begins to drip inside through the air vent unless I shut the unit off every so often for a few minutes to allow it to drain.

Any help would be greatly appreciated!
Slm32123 is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 05-18-2022, 09:05 AM   #2
Senior Member
 
Join Date: Aug 2019
Location: Eastern outskirts of Dallas, TX
Posts: 1,643
You need to relook the condensate drains in the units.

If the drain is open to atmosphere then when the fan runs, it will suck air up thru the condensate drain and prevent the condensate from draining out. Eventually the condensate pan fills with water to the point that some may drip out the drain and the rest may just spill over the drain pan and into the coach.

Once the fan is turned off, the air flow stops in the drain, and gravity takes over allowing the condensate to drain out the drain.

The solution isn’t easy on MoHo’s as there usually isn’t enough room to install a p-trap at the drain (note the condensate drain on your home AC unit if you have one AND it’s installed per the UMC or similar).
So, the objective is to figure out how to put a flap of sorts under the drain that sucks up against the bottom of the drain due to air pressure, but will drop away somewhat under the weight of the condensate to allow it to drain away.
And it’s very possible the OEM has recommendation as to how they intended their drain system to work. Yours being a 1990, maybe what they intended is no longer there. And even with a unit that old, the design of the units hasn’t evolved so much that something used today or more recent past can’t be implemented into an older unit.
__________________
Ď91 Ultrastar Champion
Ď02 Georgie Boy Landau 8.1l Workhorse - Ď03 Jeep Wrangler TJ 2018 Jeep Wrangler JK toad
MrMark52 is offline   Reply With Quote
Old 05-18-2022, 03:41 PM   #3
Senior Member
 
Join Date: Dec 2021
Posts: 124
Some models use a "slinger" fan that slings the condensate water on to the condenser fins - Helps increase the cooling efficiency.

If so, you often won't see much condensate draining out until after you shut off the unit - Takes a while for any remaining condensate to drip off the condenser before it drains out.
__________________
2021 Casita Spirit Dlx - San Antonio, TX
Skibane is offline   Reply With Quote
Old 05-18-2022, 04:28 PM   #4
Senior Member
 
Join Date: Aug 2019
Location: Eastern outskirts of Dallas, TX
Posts: 1,643
Quote:
Originally Posted by Skibane View Post
Some models use a "slinger" fan that slings the condensate water on to the condenser fins - Helps increase the cooling efficiency.

If so, you often won't see much condensate draining out until after you shut off the unit - Takes a while for any remaining condensate to drip off the condenser before it drains out.
You make a good point about the slinger (didnít think anyone did that any more for the other problems it creates) - but the issue remains that the condensate canít get out of the drain pan thru the drain hole, whether the path is to a pan under the condenser fan or to allow drainage to the roof.
__________________
Ď91 Ultrastar Champion
Ď02 Georgie Boy Landau 8.1l Workhorse - Ď03 Jeep Wrangler TJ 2018 Jeep Wrangler JK toad
MrMark52 is offline   Reply With Quote
Old 05-18-2022, 11:23 PM   #5
Senior Member
 
Gulf Streamers Club
Ford Super Duty Owner
Join Date: Aug 2015
Location: Memphis, TN
Posts: 3,244
99% says problem is a dirty COIL if will not drain while running, and drains are clear. IF Motor has been replaced or serviced, there MIGHT be a remote possibility fan is running backwards, but usually, (with squirrel cage fan) that just gives reduced airflow (about 40% air volume drop)
__________________
(TerryH.) 2000-GS Conquest Limited 6266 Class-C 99-E450SD V10
THenne1713 is offline   Reply With Quote
Old 05-25-2022, 07:47 AM   #6
Junior Member
 
Join Date: Oct 2020
Posts: 17
Quote:
Originally Posted by MrMark52 View Post
You need to relook the condensate drains in the units.

If the drain is open to atmosphere then when the fan runs, it will suck air up thru the condensate drain and prevent the condensate from draining out. Eventually the condensate pan fills with water to the point that some may drip out the drain and the rest may just spill over the drain pan and into the coach.

Once the fan is turned off, the air flow stops in the drain, and gravity takes over allowing the condensate to drain out the drain.

The solution isn’t easy on MoHo’s as there usually isn’t enough room to install a p-trap at the drain (note the condensate drain on your home AC unit if you have one AND it’s installed per the UMC or similar).
So, the objective is to figure out how to put a flap of sorts under the drain that sucks up against the bottom of the drain due to air pressure, but will drop away somewhat under the weight of the condensate to allow it to drain away.
And it’s very possible the OEM has recommendation as to how they intended their drain system to work. Yours being a 1990, maybe what they intended is no longer there. And even with a unit that old, the design of the units hasn’t evolved so much that something used today or more recent past can’t be implemented into an older unit.
I believe this may be the problem, if I put the unit into Low cool mode, the slowest fan speed, it seems to have no issue with draining properly onto the roof and down the side of the coach. I'll have to do some more looking to find diagrams from coleman of the unit as it is intended to be assembled and will compare to my unit after doing so.
Slm32123 is offline   Reply With Quote
Old 05-25-2022, 08:44 AM   #7
Senior Member
 
Join Date: Aug 2019
Location: Eastern outskirts of Dallas, TX
Posts: 1,643
Quote:
Originally Posted by Slm32123 View Post
I believe this may be the problem, if I put the unit into Low cool mode, the slowest fan speed, it seems to have no issue with draining properly onto the roof and down the side of the coach. I'll have to do some more looking to find diagrams from coleman of the unit as it is intended to be assembled and will compare to my unit after doing so.
Excellent! Your experiment of reducing the fan speed to low has proven the physics of what the problem is. A very, very, hard situation for most people to understand.

The means to block air from being drawn thru the condensate drain when there isnít room for a p-trap varies. It could be nothing more than a rubber flap covering a drain hole that draws closed under negative air pressure (a poor manís check valve) - yet allows a trickle of water to escape as the weight of the condensate on the flap pushes the flap down enough to allow the escape.

Keep us posted on what you find!
__________________
Ď91 Ultrastar Champion
Ď02 Georgie Boy Landau 8.1l Workhorse - Ď03 Jeep Wrangler TJ 2018 Jeep Wrangler JK toad
MrMark52 is offline   Reply With Quote
Old 05-25-2022, 01:29 PM   #8
Senior Member
 
Join Date: Mar 2019
Posts: 788
Quote:
Originally Posted by MrMark52 View Post
Excellent! Your experiment of reducing the fan speed to low has proven the physics of what the problem is. A very, very, hard situation for most people to understand.

The means to block air from being drawn thru the condensate drain when there isnít room for a p-trap varies. It could be nothing more than a rubber flap covering a drain hole that draws closed under negative air pressure (a poor manís check valve) - yet allows a trickle of water to escape as the weight of the condensate on the flap pushes the flap down enough to allow the escape.

Keep us posted on what you find!
I never thought about why they were there, but my condensate drains have duckbills on the end of them.

Now I know why they are there.
bentjm is offline   Reply With Quote
Old 05-25-2022, 02:06 PM   #9
Senior Member
 
Join Date: Aug 2019
Location: Eastern outskirts of Dallas, TX
Posts: 1,643
Quote:
Originally Posted by bentjm View Post
I never thought about why they were there, but my condensate drains have duckbills on the end of them.

Now I know why they are there.



__________________
Ď91 Ultrastar Champion
Ď02 Georgie Boy Landau 8.1l Workhorse - Ď03 Jeep Wrangler TJ 2018 Jeep Wrangler JK toad
MrMark52 is offline   Reply With Quote
Old 05-25-2022, 03:05 PM   #10
Senior Member
 
ernieh's Avatar
 
Join Date: Jul 2009
Posts: 1,700
If your drain "LINES" have duckbills on them it's for a completely different reason, "critters". You most likely have a condensate pump as well.
__________________
ernieh
2019 Phaeton 37BH
ernieh is offline   Reply With Quote
Old 05-25-2022, 04:03 PM   #11
Senior Member
 
Join Date: Aug 2019
Location: Eastern outskirts of Dallas, TX
Posts: 1,643
Our WorkHorse dash AC unit condensate drain has what I would call a "duckbill" on it as does does our '03 Wrangler TJ and prior '03 Grand Cherokee - it never occurred to me how much they look like "duckbills" until "bentjm" said it.


Never seen a condensate pump on a MoHo or mobile rooftop unit - but that doesn't mean it doesn't exist.
__________________
Ď91 Ultrastar Champion
Ď02 Georgie Boy Landau 8.1l Workhorse - Ď03 Jeep Wrangler TJ 2018 Jeep Wrangler JK toad
MrMark52 is offline   Reply With Quote
Old 05-25-2022, 07:53 PM   #12
Senior Member
 
Join Date: Mar 2019
Posts: 788
Quote:
Originally Posted by ernieh View Post
If your drain "LINES" have duckbills on them it's for a completely different reason, "critters". You most likely have a condensate pump as well.
I have a 2005 Newmar Mountain Aire 4032 DP.

Could be for "critters". No pump. There are grated drains under each rooftop AC. The lines run through the roof to the rear and drain down both sides in the back. I do flush them everytime I pressure wash the roof.
bentjm is offline   Reply With Quote
Old 05-26-2022, 01:31 PM   #13
Senior Member
 
ernieh's Avatar
 
Join Date: Jul 2009
Posts: 1,700
Quote:
Originally Posted by MrMark52 View Post
Our WorkHorse dash AC unit condensate drain has what I would call a "duckbill" on it as does does our '03 Wrangler TJ and prior '03 Grand Cherokee - it never occurred to me how much they look like "duckbills" until "bentjm" said it.


Never seen a condensate pump on a MoHo or mobile rooftop unit - but that doesn't mean it doesn't exist.
You need to look a little harder. Almost every mid to upper range coach built in the last 10 years for sure has them.
__________________
ernieh
2019 Phaeton 37BH
ernieh is offline   Reply With Quote
Old 05-26-2022, 02:48 PM   #14
Senior Member
 
Join Date: Aug 2019
Location: Eastern outskirts of Dallas, TX
Posts: 1,643
Quote:
Originally Posted by ernieh View Post
You need to look a little harder. Almost every mid to upper range coach built in the last 10 years for sure has them.
Uhhhhhmmmmm - weíre too poor to own one that fit into either one of those classes of coach, nor do we have any friends who have one either.

And unless the OPís coach was Uber, Uber, high end in 1990 or as somehow retrofitted with a condensate pump and drain - the issues posed by a condensate pump are mute.

__________________
Ď91 Ultrastar Champion
Ď02 Georgie Boy Landau 8.1l Workhorse - Ď03 Jeep Wrangler TJ 2018 Jeep Wrangler JK toad
MrMark52 is offline   Reply With Quote
Reply

Tags
fan, problem, roof



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Replacing the Fan-tastic fan with RVLovent Fan jlotze Class A Motorhome Discussions 7 02-02-2022 12:52 PM
Fan-Tastic Bath Fan, broke fan :( Bmaintz8 iRV2.com General Discussion 11 09-01-2019 06:20 PM
To drain or not to drain toilet while cruising down the road AllanK Class A Motorhome Discussions 25 11-09-2018 11:51 AM
to run refrig while not in use or not while parked fxdave MH-General Discussions & Problems 29 11-02-2010 08:09 PM
Choosing a Powered Fan (MaxxAir MaxxFan vs. Fan-Tastic Vent 6600 + MaxxAir Fan/Mate) TrailerFool iRV2.com General Discussion 6 11-22-2008 05:06 AM

» Featured Campgrounds

Reviews provided by


All times are GMT -6. The time now is 03:33 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.