Herrmidifier Load Calculator - Manual (Page 16)

L o a d C a l c u l a t i o n G u i d e
L o a d C a l c u l a t i o n G u i d e
16 w w w. h e r r m i d i f i e r- h v a c . c o m
Process Reduction
From measurement or design data, determine the amount of
moisture vapor being given off by any sources in the plant,
such as hot water washes, steam curing, etc. This will de-
crease the maximum demand load for humidification when-
ever the process is in operation. Be sure it is effective at all
times that the maximum demand load for humidification is
being experienced.
People Reduction
People present in an area will give off moisture and, if enough
people are present, can affect the maximum humidification
load. People give off moisture at a rate of approximately .2
pounds per hour per person if seated and .9 pounds per hour
per person if active. This moisture can be deducted from
the maximum humidification demand load. Be sure these
people are present at all times when the maximum humidi-
fication demand load exists, because when they leave, the
maximum humidification demand load will increase by that
amount and if the humidification system was designed for
the load with people present, it will be undersized and un-
able to maintain the desired level of R.H. which could result
in product damage.
Maximum Demand Load For Humidification
THE MAXIMUM DEMAND LOAD FOR HUMIDIFICATION
for a plant or building consist of: the Heating or Cooling load,
whichever is greater, plus or minus the Product load (if any),
minus the Process reduction (if any) and the people reduc-
tion (if any). There are several other factors and pitfalls to be
aware of. These will be discussed next.
HELPFUL GUIDE LINES
1. Area to be humidified must be isolated from non- humidi-
fied areas as moisture travels to dry area by Dalton’s Law of
Partial Pressures. Open doors, elevator shafts, etc. will allow
moisture to escape.
2. WHen a common air handling system is in use and the
area to be humidified is served by a part of the system, you
must consider the air and moisture lost to non-humidified ar-
eas in figuring demand load, or you must humidify all the air
delivered to the humidified areas by the system; also, this
moisture loss to other areas can cause problems in those
areas if not properly controlled.
3. Be sure the structure will handle the level of relative hu-
midity desired without damage due to condensation, etc.
Moisture migration into wails with no vapor barrier can cre-
ate problems. Vapor barriers must be installed properly to
be effective in preventing moisture migration from humidified
areas. All barrier joints must be air tight.
4. Consider the dew point of the humidified atmosphere and
be aware of condensation problems that can occur on cold
surfaces such as: steel roof deck, single glazed windows,
aluminum window and door frames, etc. Dew point is the
temperature at which condensation will begin to occur when
the humidified air is cooled to that level.
5. Check the psychometrics and be sure the volume of air
can absorb the amount of water vapor you will be adding.
(DO NOT EXCEED 100% R.H.)
6. Cold air is difficult to humidity as it does not give up heat
as readily. Special equipment must sometimes be used.
7. Cold fresh air make-up can cause condensation problems
in ducts. Be careful where humidity is introduced.
8. “Free Cooling” using cold outside air can be costly by add-
ing greatly to the maximum demand load for humidification.
It is usually more economical to recirculate the humidified air
and cool it, as required, using air conditioning or refrigeration
equipment.
9. Be sure adequate services are available, or can be ob-
tained; i.e., water, water pressure, electrical, compressed air,
steam, etc.
10. It is critical to understand your water prior to selecting a
humidification system. Forward a complete water analysis or
water sample to Herrmidifier and we can help you optimize
your equipment selection or suggest water pretreatment to
minimize maintenance and maximize performance.
11. For ducted applications, atomization systems require
special application considerations to insure complete evap-
oration and no duct wetting. Proper selection of controls,
modulation technique and installation location is critical to
satisfactory performance. Please contact Herrmidifier for a
copy of our “Herrmidicool Technical Manual” prior to design-
ing your system.
12. Consider first cost, operating cost, installation cost and
the equipment’s ability to maintain your design conditions
under your system psychrometric limitations. Water quality is
vitally important as well. Simply using DI or RO water with a
system does not eliminate potential water problems!
13. Any humidification system must be accessible for main-
tenance, especially periodic cleanings.
Energy consumed in humidifying is of great importance.
Be sure to consider the efficiency of the equipment you
select.