wa8yxm wrote:
That said. Dash air is not big enough to cool off a 38' Motor home or for that matter a 15' motor home. when it's 90 out in the shade you got to run the roof air's no choice.
I don't know about a large Class A motorhome, BUT ... the above is certainly not true for our 24 foot Class C and it's E450 chassis ... at least with outside temperatures up to what we have driven in so far ~ 108 degrees F. I've learned that an important key to getting the most effective cooling out of a vehicle's cab air system is to run it in it's recirculation mode - as I mention below. That's also how our stick house heat pump runs all the time, whether in heating mode or cooling mode.
This discussion is similar to another related running discussion, so I've lifted my post from that thread since it also applies here:
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Below are just four (4) links talking about the BTU cooling capacity of vehicle cab air conditioning systems ... and a search yields many more articles that reinforce what these links are saying.
The information in the links confirms what I have experienced ... our motorhome's (and our sedan's and our pickup truck's) cab air conditioning systems have terrific BTU capacities (well beyond 13.5K BTUs at typical traveling engine RPMs). Our motorhome's E450 cab air conditioning system is easily capable of cooling our entire Class C when traveling at highway speeds in scorching temperatures - especially using it's MAX AC setting such that the interior air is only recirculated - instead of the cab air conditioning system having to constantly cool new hot air coming in from the outside.
https://www.google.com/search?lr=&hl=en&as_qdr=all&q=cooling+capacity+of+car+ac&sa=X&ved=0ahUKEwi6p_Hs7IDcAhViylQKHQCZBHIQ1QIItQEoAg&biw=1536&bih=737https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3023729/Average_auto_A/C_BTU_rating?https://autoacforum.com/messageview.cfm?catid=2&threadid=20990https://www.quora.com/What-is-the-typical-nominal-cooling-capacity-kw-or-BTU-h-of-a-car-air-conditioning-device
