methods for determining heat/cooling(?) loads
methods for determining heat/cooling(?) loads
(OP)
all,
this question is directed to skilled engrs whom practice hvac. i've studied hvac (college) and extensively worked in the hvac industry, but have not done any hvac design work. so i am inquisitive!
this question is realted to arch5599 post on 05-01-03.
i heard of engineers determining heat loads (or cooling loads?) based on a Btu/hr-sq.ft and by ASHRAE standards (fundamentals handbook) - determining overall room/bldg U based on design of bldg. i understand that there is a difference in construction (residential and commercial), and considering what tools are available,...
Please clarify which method is actually practiced most often and for what reasons (client specified?)
for what reasons is the Btu/hr-sq.ft method used?
the Btu/hr-sq.ft method seems too simple and can provide results which lead to over/undersized equipment (example of air conditioners running 100% of time during summer months in houston, tx and not keeping apt. rooms adequately cooled).
which method provides results that are realistic - i understand that in the hcav world, results can vary >10%, depending upon method used.
it seems to me that determining heating and cooling loads as stated in the ahsrae fundamental handbook )or by other recognized industry stds) is the more appropriate and professional method.
thanks!
-pmover
this question is directed to skilled engrs whom practice hvac. i've studied hvac (college) and extensively worked in the hvac industry, but have not done any hvac design work. so i am inquisitive!
this question is realted to arch5599 post on 05-01-03.
i heard of engineers determining heat loads (or cooling loads?) based on a Btu/hr-sq.ft and by ASHRAE standards (fundamentals handbook) - determining overall room/bldg U based on design of bldg. i understand that there is a difference in construction (residential and commercial), and considering what tools are available,...
Please clarify which method is actually practiced most often and for what reasons (client specified?)
for what reasons is the Btu/hr-sq.ft method used?
the Btu/hr-sq.ft method seems too simple and can provide results which lead to over/undersized equipment (example of air conditioners running 100% of time during summer months in houston, tx and not keeping apt. rooms adequately cooled).
which method provides results that are realistic - i understand that in the hcav world, results can vary >10%, depending upon method used.
it seems to me that determining heating and cooling loads as stated in the ahsrae fundamental handbook )or by other recognized industry stds) is the more appropriate and professional method.
thanks!
-pmover





RE: methods for determining heat/cooling(?) loads
When we get estimates from building owners prior to our design, they are almost always suprised to find that their estimates are low. They are usually based on a contractor's rule-of-thumb estimate. These estimates almost never account for the impact of ventilation on the cooling load.
ASHRAE's published methods essentially require you to employ a computer program. If you want to run a cooling/heating load for a building, and don't want to shell-out the big money, I recommend getting Carrier's "System Design Manual Part 1: Load Estimating". It guides you through a hand calculation procedure and would be good for simple jobs. I still use it and have never had a problem with over/under-sizing equipment. In the same vein, ASHRAE's method for Residential load analysis (Fundamentals Ch. 27) works well too.
RE: methods for determining heat/cooling(?) loads
i.e to determine the project cost. But it should never be used for selecting the equipment for actual installation.
There are many Heatload software available in the market the best is carrier's E-20 II, which gives you energy analysis also.
RE: methods for determining heat/cooling(?) loads
your responses confirms what i suspected.
-pmover
RE: methods for determining heat/cooling(?) loads
i investigated carriers web site and was not able to find it. is the manual discontinued?
-pmover
RE: methods for determining heat/cooling(?) loads
RE: methods for determining heat/cooling(?) loads
To comply in New York State for any rebates you must use manual J speciifications. This was instituted to reduce the tendency for installers to oversize units for a "safety" factor. Oversizing tends to utilize too much power, and due to shortcycling, is not able to properly dehumidify the space.
RE: methods for determining heat/cooling(?) loads
could u get the carrier systems design manual.
I too need a copy can u help
reg
grnblr
RE: methods for determining heat/cooling(?) loads