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Old 10-16-2013, 06:41 PM   #1
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Help New Dometic Brisk @ Air freezing up

One of my new Brisk 2 Air ducted AC is freezing up.Ice is forming somewhere on the return air side and on th e blower blades. It did this last night for a short time with water leaking out of the cover and then stopped, It ran fine all day set at 74 degrees. Then a few mins ago I started hearing a noise and Ice was coming out of the cover and water, I turned it off and took off the cover and water on the sides and small chunks of ice on the blower. I waited a while and wiped it down and now running just on fan. Any thoughts, thanks
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Old 10-16-2013, 06:50 PM   #2
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A common cause is an air leak between the return air plenum and the chilled air plenum. Use metal duct tape and insure the return air plenum is completely sealed from air leakage.
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Old 10-16-2013, 06:52 PM   #3
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I have never heard of one icing up except on the evaporator coils. Sorry, can't help you .

IF it is the evap coils. then there are 3 possible issues.

Folks tell me restricted air flow will cause it. (I'm skeptical)

On many units (mine included) There is/should be a Freeze/Frost sensor that is stuck in the evap coils. On mine it is. I have heard of cases where it was not.

Low Freon/refrigerant.
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Old 10-16-2013, 07:09 PM   #4
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A common cause is an air leak between the return air plenum and the chilled air plenum. Use metal duct tape and insure the return air plenum is completely sealed from air leakage.
There were some holes around the wiring that were open a inch or so between the 2 compartments. I have now taped them thanks, I will see if that helps
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Old 10-16-2013, 07:12 PM   #5
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I have never heard of one icing up except on the evaporator coils. Sorry, can't help you .

IF it is the evap coils. then there are 3 possible issues.

Folks tell me restricted air flow will cause it. (I'm skeptical)

On many units (mine included) There is/should be a Freeze/Frost sensor that is stuck in the evap coils. On mine it is. I have heard of cases where it was not.

Low Freon/refrigerant.
Is the evap the coil on the intake side from the coach or the cold side from the AC. I get confussed. I said ice on the return side but to clarify it is on the side where the cold air comes back through the ducks
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Old 10-16-2013, 07:24 PM   #6
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Folks tell me restricted air flow will cause it. (I'm skeptical)


Low Freon/refrigerant.
Low or restricted and bypassing air flow will in fact cause an A/C unit to freeze the coil over. The compressor on these units is a positive displacement type which means it pumps a given volume (cfm) of refrigerant each minute. It the air flow over the evaporator is too low, there is not enough refrigerant being vaporized to satisfy the compressor requirements. Due to the physical properties of the refrigerant, the compressor will lower the pressure to have sufficient refrigerant volume. When the pressure is lowered, the temperature of the refrigerant and coil i lowered. It will eventually drop below freezing and ice will start to form on the coil. Ice can break off the coil and hit the fan at times on a draw through system.

It is possible to be low on refrigerant, but 90% of the RV A/C cooling issues are air flow related. Running the fan on low speed, dirty evaporator, dirty filters, of bypassing air at the unit is the usual cooling problem. The units are hermetically sealed and less prone to leakage unless you break a line or fitting.

Over the years, the manufactures of A/C units and installers have gotten pretty sloppy in sealing the air side properly.

Ken
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Old 10-16-2013, 07:34 PM   #7
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Low or restricted and bypassing air flow will in fact cause an A/C unit to freeze the coil over. The compressor on these units is a positive displacement type which means it pumps a given volume (cfm) of refrigerant each minute. It the air flow over the evaporator is too low, there is not enough refrigerant being vaporized to satisfy the compressor requirements. Due to the physical properties of the refrigerant, the compressor will lower the pressure to have sufficient refrigerant volume. When the pressure is lowered, the temperature of the refrigerant and coil i lowered. It will eventually drop below freezing and ice will start to form on the coil. Ice can break off the coil and hit the fan at times on a draw through system.

It is possible to be low on refrigerant, but 90% of the RV A/C cooling issues are air flow related. Running the fan on low speed, dirty evaporator, dirty filters, of bypassing air at the unit is the usual cooling problem. The units are hermetically sealed and less prone to leakage unless you break a line or fitting.

Over the years, the manufactures of A/C units and installers have gotten pretty sloppy in sealing the air side properly.

Ken
Its brand new about 2 months.
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Old 10-16-2013, 07:46 PM   #8
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Is the evap the coil on the intake side from the coach or the cold side from the AC. I get confussed. I said ice on the return side but to clarify it is on the side where the cold air comes back through the ducks
The evaporator coils are the ones you can see when you remove the air filter and look up thru the hole above the control unit. This is the "return" side ... the air is flowing up towards the roof. In other words, it is closest to the windshield (front). The condenser can be viewed on the roof after removing the A/C top cover.

In all likelihood you have an air leak between the return side (the front half above the filter) and the ducted output side (the area toward the rear of the A/C) The other possibility is collapsed or poorly taped ductwork ... this is not as likely in a 2005 vehicle (pretty common in pre-2000).

Do you have a "dump" register (a grille with sliding vents) in the rear half of the white ceiling trim/cover ?

Did you install the new A/C yourself or did someone else install it?
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Old 10-16-2013, 08:04 PM   #9
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The evaporator coils are the ones you can see when you remove the air filter and look up thru the hole above the control unit. This is the "return" side ... the air is flowing up towards the roof. In other words, it is closest to the windshield (front). The condenser can be viewed on the roof after removing the A/C top cover.

In all likelihood you have an air leak between the return side (the front half above the filter) and the ducted output side (the area toward the rear of the A/C) The other possibility is collapsed or poorly taped ductwork ... this is not as likely in a 2005 vehicle (pretty common in pre-2000).

Do you have a "dump" register (a grille with sliding vents) in the rear half of the white ceiling trim/cover ?

Did you install the new A/C yourself or did someone else install it?
Yes it was freezing on the ducted side at the rear. I did find some open spots between the 2 sides and taped with aluminum duct tape so that is done.

Yes I have the dump register and that is where the ice came from,
No I had them installed. Its running again on 74 degrees so I will see what happens thanks
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Old 10-16-2013, 08:27 PM   #10
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Yes it was freezing on the ducted side at the rear. I did find some open spots between the 2 sides and taped with aluminum duct tape so that is done.

Yes I have the dump register and that is where the ice came from,
No I had them installed. Its running again on 74 degrees so I will see what happens thanks
Ok ... don't assume the installer did a good job. The tape you added may fix it.

If not, the white cover is held with six screws ... four are accessible by removing the air filter ... screws are in corners. The other 2 screws are under white plastic plugs about the size of a half dollar ... remove plugs with a knife tip. Remove the entire cover .... this should expose the output chamber by looking thru the rectangular hole above the dump register. Look left and right and you should see the entrances to the ductwork. They should not be collapsed and should be tightly sealed to the frame sides with aluminum tape.

If you go here you'll see links to photos of collapsed ductwork ...
A/C Ductwork collapse and rehab

page #9 shows correctly taped ductwork. The new supports (the aluminum frame) was necessary in my older RV but just correct taping should be OK in yours. It is not unusual for an installer to NOT EVEN LOOK AT THE DUCTWORK DURING AN INSTALL.

It is not unusual for tape to fail in 5 years. It doesn't last forever.


As TXICEMAN has said ... at least 90% of icing issues are airflow related. I'm guessing it's more than 90%.
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Old 10-16-2013, 09:16 PM   #11
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Ok ... don't assume the installer did a good job. The tape you added may fix it.

If not, the white cover is held with six screws ... four are accessible by removing the air filter ... screws are in corners. The other 2 screws are under white plastic plugs about the size of a half dollar ... remove plugs with a knife tip. Remove the entire cover .... this should expose the output chamber by looking thru the rectangular hole above the dump register. Look left and right and you should see the entrances to the ductwork. They should not be collapsed and should be tightly sealed to the frame sides with aluminum tape.

If you go here you'll see links to photos of collapsed ductwork ...
A/C Ductwork collapse and rehab

page #9 shows correctly taped ductwork. The new supports (the aluminum frame) was necessary in my older RV but just correct taping should be OK in yours. It is not unusual for an installer to NOT EVEN LOOK AT THE DUCTWORK DURING AN INSTALL.

It is not unusual for tape to fail in 5 years. It doesn't last forever.


As TXICEMAN has said ... at least 90% of icing issues are airflow related. I'm guessing it's more than 90%.
The ducts are not collapsed but I did tape good arou7nd the edges and all of the leak areas between the sides. We are expecting a cool night so I will keep it on 74 and see what happens . Thanks everyone I will followup am
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Old 10-17-2013, 09:49 AM   #12
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The ducts are not collapsed but I did tape good arou7nd the edges and all of the leak areas between the sides. We are expecting a cool night so I will keep it on 74 and see what happens . Thanks everyone I will followup am
No more issues through the night but it was fairly cool outside so the AC was not working that hard. I have tape the areas between the return and cold air discharge and there are no opens between the sides now. I als taped arond the duct openings and so there is a clear shot to the duct and they are not collapsed. the filter is clean and I will see what happens as the weather warms back up and the humidity increases here on Galveston Island in next day or so, Thanks for the input and help. Comforting to know that someone is there to offer help and suggestions when a problem comes up. I will followup
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Old 10-17-2013, 11:19 AM   #13
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No more issues through the night but it was fairly cool outside so the AC was not working that hard. I have tape the areas between the return and cold air discharge and there are no opens between the sides now. I als taped arond the duct openings and so there is a clear shot to the duct and they are not collapsed. the filter is clean and I will see what happens as the weather warms back up and the humidity increases here on Galveston Island in next day or so, Thanks for the input and help. Comforting to know that someone is there to offer help and suggestions when a problem comes up. I will followup
Sound like you are good 2 go ... we'll be optimistic!
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Old 10-17-2013, 12:41 PM   #14
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Sound like you are good 2 go ... we'll be optimistic!
I spoke with my RV shop that installed the AC and the tech wanted me to look for a sensor wire with a metal tip that should be inserted between the coils. I found it
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He told this should regulate the coil temp and prevent freezing on the coils.It appears to be in place but I have not checked the other end to see where or if it is attached. I send them the picture and I am waiting on a call back.

Another question, the unit is off and with the ceiling cover removed I can feel cool air coming from the exhaust cool air side with the blower. It is cool outside today so this is outside air. Is that normal
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