Originally Posted by Jolly Roger
In my experience as an HVAC installer whether using steam,180deg.water for heat or 40deg. Water for A/C the manufacturer regardless of names always had the hottest/coldest on the leaving air side.
That was to heat or cool a building?
It does depend on coil position and is dependent on what you are trying to do?
Maybe exhaust fans drawing air in from the air skirt blowing into the coil or cowl induction for each coil?
I don't know the answer?
But to me if you made a cowl inducted hood and duct it between each box(depending on your arrangement ) the coolest air comes in and passes through box. If the first box is the hottest then the second box is warm and the third box tempered. As the air spends time passing through each box it loses a little bit/or alot of temp depending on the space it is trying to heat/cool? But sometimes you want outside air and sometimes you don't? And is all dependent on the outside air temp?
And our computer geeks on here might be able to suggest some 12v controllers/temperature regulator's that might/could control a temperature damper in a cowl induction hood on the side of a skoolie? To regulate space temps???
for efficiency you want the Least-conditioned space air hitting the MOST extracted conditioning medium... for instance in heating.. I take the Coldest space return air and run it over the Heat exchanger just before the heat (in my case exhaust gasses fro ma furnace) is exhausted to the outside..
for cooling you get the Most humidity removal by the air being Cold.. if you temper the air first by running it over the coils closest to the suction line.. then you give your main heat exchanger a chance to cool that air way down.
with A/C, the actual air temperature over the coild plays a big part in how well the humidity is handled.. so if I run the CFM of air up (hugh speed, high volume) then that air is never going to be cooled-down to the point of removing the humidity(and it wont be as cold).. its not a matter of that air not having time to get cold.. its a matter the volume of air being moved is over-loading the heat exchanger...
those of you that have newer home A/C systems will notice in very humid weather your system fan will slow down.. the air coming from the vents is reduced bt is very cold.. the humidity is reduced at the expense of there becoming hot and cold spots in the rooms...
I employ a technique in my house for cool but very humid days where I run the coil temperature very cold, (right above freezing) and then I bypass a certain percentage of the air.. (it never hits the coils).. so I get a nice dry but temperate air from the vents... again its not the TIME that air needs to spend over those coild to condense the water.. its a matter of not expecting my heat exchanger to do more than what its designed to do..
as for the bus skirt A/C airflow.. I have no idea wich way the air flowed when those conditions were right... all i know is enough air flowed over the coils that the fans never turned on.. it couldve been negative pressure on the side of the bus due to traffic, wind, etc. . so the air may have flowed "under bus to skirt and out the left side".. or it couldve flowed in the same way that the fans intended which was in the skirt and out under the bus..
I NEVER hit a time when the air-flow was so backwards that the fans failed to move enough air.. I never tripped my High head pressure switch.. (and it was a manual reset type on purpose)
my new condenser is going to be fully under-bus so im guessing I'll always have to run a fan or 2 or 3 depending on the interior system load..
though I will note what it does once I get it installed and running...