Air Conditioner Performance
RV novice here. So please forgive any stupid questions. This may be one. How well should the air conditioners perform during our high heat and humidity here is south Texas?? Yesterday had both uni...
Forum Discussion
Kamphiker wrote:
As far as testing the AC units:
Measuring Intake Air Temp And output air temp (at closest air registrar if you cant measure in the main Plenum) you should see 15 - 20° differential.
Thanks for the replies everyone.
I do want to comment on the 15-20 degree temperature differential though. I am an engineer, sorry I can't help it. I have heard this temperature differential quoted a few times. However, I do not think this is accurate. I think we should be seeing 18 to 20 degrees temp differential -- minimum. This is an educated guess right now based on a knowledge of how home AC is designed. I have been trying to find design info about our RV AC units but have not laid my hands on any yet. But I think most AC units are designed to achieve a 20 degree temp differential. Then they allow for a 10% (or 2 degree) loss of cooling due to ducting or other losses. I am certain this is the basis for a home AC.
Background - if you want it.
Several years ago when we purchased a new home the AC was not working well at all. After a saga with the contractor he finally sent a consultant over to take a look. The consultant was a retired lead designer that had worked for Carrier. Everything changed as soon as he walked onto the site. I learned the basis of how the AC system is designed. It should achieve a delta T of 20 degrees measured immediately after the blower fan before going into the ducts. They then allow for the air to gain 2 degrees of heat in the ducts running through the attic. So, you should see at least 18 degrees delta T at each and every duct outlet. If not, something is wrong.
The issues we found in my house:
- The attic was too hot. Not enough ventilation.
- Not enough flow in some ducts. Slow flow allows more heat input from the attic and not enough volume of cool air in that room. Larger diameter ducts needed.
- Some main ducts were very long. Long length allows extra heat into the duct. Larger diameter and double insulation was the cure.
By the end of this saga I learned a lot about AC system design and what we should be seeing to meet what it is designed for.
The question is, is the design basis the same for RV AC's??
