| Bob Pietrangelo 2005-07-31, 8:21 pm |
| udarrel,
I use several design programs, and each one prints me out a list of what my
equipment will do at certain OD temps and wetbulbs. I always design for a
20 differential. You are right in what you are saying. We use primarily 2
stage, and variable speed Trane equipment. It is asstounding what your
sensible capacity is at certain OD temps and wetbulbs. We use Tranes perf
program and I have to constantly play with combinations to get it right.
And you no what, you are never 100% right. We just gotta get it as close as
possible for comfort. Those perf reports are a savior in sales sometimes.
--
Bob Pietrangelo
bobp3@comcast.net
bob@comfort-solution.biz
www.comfort-solution.biz
On Time or Your Service Call is FREE
Preventive Maintenance Specialist
"udarrell" <anonymous@anonymous.com> wrote in message
news:42ecfae6_3@newspeer2.tds.net...
> Unless the system is sized properly, -- SEER ratings become meaningless.
> (Arguments?) (These are merely my opinions -- up for discussion.)
>
> Concerning air conditioning BTU per hour and EER ratings
>
> Air conditioning condensing and evaporator matching systems are rated at
> 95°F outdoor and 80°F indoor with a 67 degrees Fahrenheit wet bulb or
> around 50% relative humidity. At all other temperature and relative
> humidity conditions, the BTU per hour will be different from the
> specified manufacturers' ratings.
>
> With an outdoor temperature of 95°F, indoor temperature of 80°F and a
> relative humidity of 80%, the evaporator heatload output will be above
> the units BTU per hour rating.
> http://www.udarrell.com/air_return_...enser_split.jpg
> In the event of indoor low temperature and low humidity, the Btu/hr will
> drop way off.
>
> When down sizing a system the best way to get the most BTU per hour is
> to have the return air come from the ceiling area and the blower CFM at
> 425 ft.³ per minute in order to get an optimal heatload on the
> evaporator recoil. The amount of CFM will depend on the indoor air
> temperature and the amount of its relative humidity.
>
> At normal thermostat settings of 76°F to 72°F, most air-conditioning
> systems do not put enough heatload on the evaporator coil to achieve the
> refrigerant boiling and heat absorption capacity of the coil. When the
> evaporator is very much under heatloaded it is not achieving anywhere
> near its BTU per hour or its EER rating.
> Air-conditioning service technicians should always check the airflow and
> approximate latent and sensible heatload on the evaporator coil "BEFORE"
> adjusting the charge on the system. It is impossible to get an accurate
> charge on the system unless you first have the proper heatload going
> through the evaporator coil.
>
> I wrote this post with "Dragon Naturally Speaking 8" voice recognition
> software, with a few corrections.
> - udarrell
>
> --
> Factors in the Correct Sizing of Residential Air Conditioning Systems -
> Recommended Procedures for Proper Duct Sizing of Residential Air
Conditioning Systems
>
http://www.udarrell.com/proper_cfm_...ng_systems.html
|