How to size washer-extractors

Motels/Hotels and Resorts

• one bed per room in economy hotel:
  • 8 lb./day x rooms x 7 days x occupancy % / 40 hours = lb./hr.
• two beds per room in economy hotel:
  • 14 lb./day x rooms x 7 days x occupancy % / 40 hours = lb./hr.
• one bed per room in luxury hotel or resort:
  • 11 lb./day x rooms x 7 days x occupancy % / 50 hours = lb./hr.
• two beds per room in luxury hotel or resort:
  • 20 lb./day x rooms x 7 days x occupancy % / 50 hours = lb./hr.

With larger facilities, increase poundage because of pool, spa, fitness, banquet and/or dining facilities used by both guests and non-guests.  Assume laundry to process 1.5 loads per hour.

Nursing Homes

• 50 lb./bed/week x number of beds / 37.5 hr. = lb./hr
• This includes patient clothing in the average home.
  If a higher number of incontinent patients, increase the per bed per week poundage to 60 lb. 

Assume laundry to process 1.3 loads per hour.

Hospitals

• 15 lb./day x number of beds x 7 days / 37.5 hr. = lb./hr
• For the division of work, assume 60% flat work (i.e.: sheets), 40% fluff/dry.

Assume laundry to process 1.3 loads per hour.

Correctional Facilities

• 6 lb./day x number of inmates x 7 days / 50 hours = lb./hr.

Assume laundry to process 1.3 loads per hour.

Shirt Laundry / DryCleaning Plant

• 1/2 lb. x number of shirts/day x 6 days / 40 hours = lb./hr.

Assume washer to process 1.5 loads per hour.

How to size dryers

Dryer should be of larger capacity than corresponding washer-extractor. Estimate between 1.4 and 1.5 times washer-extractor capacity. (i.e.: a 50 lb. washer requires approximately a 75 lb. dryer).

Average loads per hour:
gas fired = 2;  steam heated = 1.5;  electric heated = 1

How to size gas water heaters

To determine the quantity of hot water requirements per hour:

• Figure about 2.5 gallons per pound washed.
• Figure about 70% of the water to be hot.

Determine temperature of incoming water. Subtract this from the desired hot water level to arrive at the degree of rise.

Formula: gallons hot/hr x 8.3 (lb./gal) x degree rise / .6 = BTU/hr

Example:
100 gal/hr x 8.3 (lb./gal) x 100 F rise / .6 = 138,333 BTU/hr

If heating with steam, divide by 33,500 BTU/BHP.  Storage capacity should equal from 1/2 to 1 hour’s demand.

How to size water softener

Determine grain hardness (3 grains acceptable without softening).
Determine total gallons of water to be used per hour.
Multiply grains hardness x total gallons x hours of operation between regeneration (backwashing).

Example:
20 grains x 1000 gallons x 24 hours = 480,000 grain softener

Check the flow rate of softener, and make sure it is adequate.

How to size air compressors

Add up CFM requirements on all air driven equipment.
Add an additional 25% to CFM.
Tank size should be 3 to 5 times the CFM output in gallons of storage.

Example:
Required 20 CFM + 25% = 25 CFM
Tank should be 75 - 125 gallon size.

How to size boilers

Find the BHP rating on each piece of equipment in the operation that requires steam. If pounds of steam consumption is known (in place of BHP), divide by 34.5 to get BHP.

To all BHP requirements, add 10% of the total for heat loss/radiation and divide by .7 (this allows for efficiency factor and keeps you from operating the boiler at full capacity, which is both costly and harmful to the boiler).

How to size drain troughs

Determine the total number of gallons to be dumped at one time by all present and future machines. Use high level rinse figures to get this total.

Divide total gallons by 7.48 gallons/cubic foot to get the total cubic feet required.

Example:
300 gallons / 7.48 = 40 cubic feet of trough area

The trough depth should usually be 12 inches, and the width 14 inches.
In the example above, assume a 12 inch deep and 14 inches wide trough:

14" x 12" = 168 sq. inches

168/144 (one sq. ft.) = 1.166 sq. feet (trough area)

40 (cubic feet required) / 1.166 = 34.3 feet (length of trough)

Drain trough should slope 1/4" per linear foot to the outlet drain. On long troughs, this can be decreased to 1/8" per linear foot to keep the depth from becoming too great.

Facility Check List

A 10 point check list to consider when laying out your new laundry.