Originally Posted by glenn Taylor
Thanks for the info gents! it is going to take me a while to figure out what to buy with that info in mind. Maybe that should have been my question. What's a good AC system for a 12x24 building with two rooms. There will be two windows on 1 of the long sides 3 feet from each end. Whats good? A window unit, split system, package unit, Mr Slim? I am in Florida. It's a swamp for 5 months a year starting in about 2 weeks.
It depends - what are the uses of the spaces involved?
If one is a control room and the other a tracking room - then the HVAC needs are very different -
HVAC is based on a few different design requirements - he first being Sensible Loads the other being Latent Loads.
Sensible loads are loads based on mechanical and electrical items that introduce heat into the space but do NOT introduce humidity.
Examples of this would be your lighting - computers and recording gear, thus your board - your compressors, amps - powered speakers, etc.
Typically you will have a ton more gear in the control room putting out heat than you will in the tracking room.
Latent loads are loads that introduce both heat AND humidity - so people, fresh air, in homes that would include kitchens (cooking, washing dishes, etc) bathrooms - etc., etc.
IN a control room people are generally relaxed and seated - whereas in the tracking room they are usually working their butts off - and putting out a lot of heat and humidity.
This is one of the reasons that it is difficult to provide a single HVAC system to handle both rooms......
The amount of heat that people put out varies tremendously depending on what they are doing, for example:
To accurately calculate the Btu output of a person, you first have to
determine their BSA (Body Surface Area). To determine this, you could
use one of several mathematical models available. I prefer the Mosteller
formula, but other popular methods exist. My reason for preferring
this formula over the others only has to do with the ease of use this one
presents. The calculations can be performed with a simple handheld
The Mosteller formula is:
BSA (m2) = ([Height(cm) x Weight(kg)]/3600)* .5
A person 5'-10" tall (177.8cm) weighing 180.78 pounds (82kg) would
have a BSA of 2.02594m2
BSA (m2) = ([177.8cm × 180.78kg ]/3600)* .5 = 2.02594m2
To convert meters2 to feet2, simply multiply it times 10.7639104. So this person would have a BSA of 21.807 feet, and let’s call him Mr. “A.”
Mr. “A” will produce (in a typical office setting) 482.81Btu/h (22.14Btu/h × 21.807 feet2) (141.48watts/h ).
A person who is working hard has a Met Rate of about 3.0 - and I know when I am jamming my ass off it is as physical as anything i do - so using this Met Rate Mr "A" is going to produce 353.56w/hr or about 1207 Btu/h.
That's roughly 2 1/2 times as much heat output. But not just heat - it is Latent - containing humidity.
When you design using standard commercial split system it's easy - you simply choose the system you want based on the latent / sensible loads that meet your needs and are listed as a part of the manufacturer's design.
But - this info does not exist for mini-split, through the wall or window type air conditioners - they are a generic sort of one size fits all - which is why people end up needing to add either humidification or dehumidification or sometimes both depending on whether or not fresh air is an issue.
So (in my mind) everything begins with what your real needs are.......... is this going to be a serious project studio - or just a place where you jam and occasionally make a 1/2 way decent demo tape?