Montana Owners Club - Keystone Montana 5th Wheel Forum - View Single Post

jameswbarton · 08-24-2016, 05:30 AM

Hi,
Ours is a pressurized duct system and my understanding is that if we have the correct amount of 14 sq inch free area vents, each vent will output the same cu ft of air. Our 4.750 id vents are about 17.7 sq inches free space with no covers/louvers. The louvers likely cut the vent efficiency by 30%-45%. The specs call for a minimum of 8 ea. up to a maximum of 16 ea.14 sq inch free space vents. With 8 vents and 2 AC each vent should output between 60-80 cuft per minute measured with an air hood. To know how many vents is correct you would need to check the system pressure in the ducting. Our AC's should have a light pressure of .15 inches of water up to .65 inches of water using a AC pressure gauge.

So ideally the cold air should be dispersed as it falls to the floor so a vent that is just a hole will be a cold spot. The vent mentioned earlier do not state their sq inches of free air but wide open have better free space than ours that cannot be seen through at a 90 degree viewing angle. This company rates some f their vents and I have been toying with using their jetport vent or the spaceport vent. http://www.dwincorp.com/products/93/...red-RV-AC-Vent

My distribution on my front living room sounds like yours. Bathroom one vent is always freezing. Hallway outside the bathroom is always hot with no vent. Bedroom is usually at set point of the rear AC and the living room and kitchen are always the hottest. So I was thinking of trying to figure out how to cut in three new vents to add one closer to the hall and two more in the kitchen living area.

If you install too may vents then the pressure will be low and all vents will not have equal airflow out of the vents but if the pressure is too high you system airflow is too low, inefficent and can cause icing of the coils

Mine has been in the shop awaiting parts for weeks so I have not done much with airflow yet. I also posed questions to Dometic but have not yet received answers either. I should not have told Dometic I had a new Montana as they may have more loyalty to Keystone than to answer if Keystone goofed up with too few vents.

08-24-2016, 05:30 AM	#54
jameswbarton Montana Fan Join Date: May 2016 Location: Massillon Posts: 437 M.O.C. #18658	Hi, Ours is a pressurized duct system and my understanding is that if we have the correct amount of 14 sq inch free area vents, each vent will output the same cu ft of air. Our 4.750 id vents are about 17.7 sq inches free space with no covers/louvers. The louvers likely cut the vent efficiency by 30%-45%. The specs call for a minimum of 8 ea. up to a maximum of 16 ea.14 sq inch free space vents. With 8 vents and 2 AC each vent should output between 60-80 cuft per minute measured with an air hood. To know how many vents is correct you would need to check the system pressure in the ducting. Our AC's should have a light pressure of .15 inches of water up to .65 inches of water using a AC pressure gauge. So ideally the cold air should be dispersed as it falls to the floor so a vent that is just a hole will be a cold spot. The vent mentioned earlier do not state their sq inches of free air but wide open have better free space than ours that cannot be seen through at a 90 degree viewing angle. This company rates some f their vents and I have been toying with using their jetport vent or the spaceport vent. http://www.dwincorp.com/products/93/...red-RV-AC-Vent My distribution on my front living room sounds like yours. Bathroom one vent is always freezing. Hallway outside the bathroom is always hot with no vent. Bedroom is usually at set point of the rear AC and the living room and kitchen are always the hottest. So I was thinking of trying to figure out how to cut in three new vents to add one closer to the hall and two more in the kitchen living area. If you install too may vents then the pressure will be low and all vents will not have equal airflow out of the vents but if the pressure is too high you system airflow is too low, inefficent and can cause icing of the coils Mine has been in the shop awaiting parts for weeks so I have not done much with airflow yet. I also posed questions to Dometic but have not yet received answers either. I should not have told Dometic I had a new Montana as they may have more loyalty to Keystone than to answer if Keystone goofed up with too few vents.