Why so few A/C vents in Toy Haulers?

[azdryheat]

We've been looking at new 5th wheel toy haulers and regular 5th wheels. The Bighorn 3010RE we looked at today has 6 A/C vents in the kitchen and living room area and four vents in the bedroom. We next looked at a Cyclone 3010 toy hauler and found one A/C vent in the kitchen area, none in the bedroom and one in the garage. Both the Bighorn and Cyclone units we looked at have dual A/C units and both are fully ducted.

Question is: Why do toy haulers have fewer A/C vents than 5th wheels? If I were to purchase a Cyclone could I tap into the A/C system and add vents?

 

[campn8r]

Isn't the A/C unit in the Master Bedroom only for the Master? Which means you wouldn't need vents in the master bedroom?

Mark

 

[Rickhansen]

AZDRYHEAT, Good Morning,
I can't directly answer your question, but I can at least provide some food for thought.

First off, you have to consider the original design criteria by room. The engineer may have not intended that the garage area have the same amount of cooling, or had planned on lower internal heat gain in that area, as say a kitchen would have. Another criteria might be the noise. More vents doesn't mean more airflow, it does change the air velocity, which has an effect on noise levels and the force that you feel the air blowing out of each register.

Second, the airflow is sized dependent on the design requirements of each A/C unit. The two A/C's in each model may be different sizes, with different airflow characteristics. For my 3670RL, the rear A/C is a 15kbtu Dometic, the front is a 13.5kbtu. Dometic's troubleshooting guide specifies that a (model specific) 15kbtu A/C has no less than 4 and no more than 8 outlet vents, of a certain size. My rear A/C is ducted and has 8) 5" vents, or about 157 square inches of outlet. It also has about 112 square inches of return grille. My Front A/C is not ducted, so is not included in these numbers. Too few vents and your A/C coil will be frozen all the time.

Your observations of the 3010RE, sounds within reason, given that the front and rear A/C's are ducted together. This, of course assumes similar equipment and diffusers as my rig. What you describe in the Cyclone 3010, only 2 vents for 2 A/C's, makes no sense, assuming similar 5" vents. I suggest that there is something else going on there.

The basic answer to your question is yes, you can easily cut in additional vents, where you have ductwork already installed. It does not change the capacity of a properly installed system, and may have negative effects as well such as the ability to get cooling elsewhere. You should proceed with caution in doing so. Another option is to cut in addition vents that can be closed down, so that you have flexibility to balance the system later.

I think you may have missed something in your assessment of the Toy Hauler A/C system. Assuming similar mechanical sizing, those 2 vents would be at least 8" diameter each to achieve airflow in a acceptable range. There is not enough ceiling space to run ductwork of that size either.

Again, food for thought.