07/21/11 AERCO International, Inc.
•
100 Oritani Dr.
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Blauvelt, NY 10913
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Ph: 800-526-0288
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187
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200
GF-5080
TAG-0046_0A
Commercial Laundry Sizing Guide
THE AERCO INNOVATION COMMERCIAL LAUNDRY HOT WATER HEATER SYSTEM
The AERCO Innovation system recommended for commercial/industrial laundries (i.e. hospital or hotel laundries) is
illustrated in Figure 1 (single unit) or Figure 2 (multiple units). Because laundries are subjected to periodic surge flows,
supplementary storage is usually required to keep the maximum load on a gas-fired water heater within the heater’s
maximum capacity.
PRINCIPAL OF OPERATION
BTUs are stored in a stratified storage tank on a constant temperature-variable volume (of hot water) basis, i.e., the
system depends on an absolute minimum of mixing of cold water and hot water in the tank. The discharge to the
system is taken from the top of the tank and/or the heater. The supply of hot water in the upper portion of the tank is
replenished at a constant rate by the heater operating at its maximum capacity. Tank storage must be large enough to
accommodate the cumulative surge flows that occur in the maximum usage period.
Sizing and selection of the components is covered in the following explanation and example. System set up and
adjustment consists simply of setting the system final outlet temperature and adjusting one balancing cock to set the
circulating pump to operate at the correct point on its curve.
DETERMINATION OF LAUNDRY HOT WATER REQUIREMENTS:
AVERAGE HOURLY HOT WATER RATE (AHHWR)
Commercial laundry equipment generally uses two gallons or less of 180°F water per pound of cloths or linens
washed. This figure is recommended by most machine manufacturers. Most “heavy” work requires a nominal one hour
wash cycle, inclusive of loading and unloading the machine, and is based on a 50-60 second fill time. The use of the
shorter 30 second fill time will shorten the total cycle only 3 to 4 minutes.
The shorter cycles more commonly used are not shorter because of shorter fill time, but, instead, are achieved by the
elimination of a suds- or rinse-cycle or both. These are generally employed with synthetic fabrics which also use lower
water temperatures. Thus, the figure of two gallons/pound of fabrics being washed can be considered to be two
gallons/pound of machine capacity for determination of the AHHWR.
If a 30 second fill cycle is standard for the entire laundry operation, this figure might be increased 6 to 7% to 2.14
gallons/pound of machine capacity. However, the figures used are conservative enough to preclude this necessity.
Average Hourly Hot Water Rate (AHHWR) = (2) • (total machine capacity in pounds)
SIZING THE INNOVATION SERIES GAS-FIRED HEATER
Heater Capacity (recovery rate) in GPM
=
AHHWR
=
2GPH • total machine capacity in pounds
60 mins.
60 minutes
(See Chart A for heater selection)
SIZING THE STRATIFIED STORAGE TANK
Approximately ⅔ of the water usage in the normal laundry machine occurs in a 20 minute time period (⅓) hour. During
this period, the heater can make only half of this required amount or ⅓ of the hourly requirement.
The stratified storage tank must provide the other half or ⅓ of a full hour requirement. Stratification within the tank
precludes 100% usability. Standard practice has shown that the tank is able to deliver between 60% and 80% of its
total capacity without excessive temperature degradation. AERCO recommends using 70% of the total capacity of an
un-baffled vertical tank piped as shown in Figure 1.
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