Specifying High-Efficiency Water Heaters for Food Service

Transcription

1 Specifying High-Efficiency Water Heaters for Food Service May 14 th, 2010 Presented by: Don Fisher

2 Water Heater Selection and Specification Selection Efficiency Economics Myths & Limitations Tank versus Tankless Sizing To Meet Food Safety Regulations Recommendations

3 System Efficiency

4 Favorable Economics for Condensing Storage

5 Myth #1 Standby Heat Loss Standby losses can be as high as 30% with storage heaters in residential applications Solution energy benefit of tankless in residential applications will translate to similar savings in restaurants -- FALSE Water Use Storage Heater Standby Heat Loss (gal/d) Standard Efficiency High Efficiency Residential 60 30% 23% QSR % 2.7% FSR % 0.5% Large FSR % 0.3%

6 Myth #2 Tankless is Less Expensive to Operate A fundamental difference: A tank-type heater will always deliver water at or above its thermostat setpoint A tankless heater will always deliver water at or below its thermostat setpoint Field monitoring by FSTC has shown that water supplied by tankless is approx. 10 F below the temperature supplied by a storage heater Thus at the same setpoint, the tankless will inherently use less energy by doing less work

7 Limitations Storage Can run out of hot water during heavy usage if undersized

8 Limitations Tankless Startup sequence creates an additional lag in hot water delivery A couple of seconds before it wakes up seconds before its close to set temperature Cold water sandwich effect Difficulty working with door-type dishwashers and low flow aerators on hand-washing sinks

9 Limitations Tankless Doesn t work well with recirculation systems w/o expansion of system Most heaters are not designed to modulate down to accommodate a 5 to 15 F temp rise May nullify or shorten manufacturer s warranty Making it work requires additional investment Plumbing recirculation line to one sacrificial unit in a multi-unit system may be an option

10 Limitations Filling a 3-compartment sink Faucets typically flow at 15 gpm The 3-comp sink is one of the most demanding hot appliances in QSR and coffee shops Tank-type may fill two 40-gal sinks in 4 minutes One standard eff. tankless takes 14 min in winter At best cond. tankless in summer can fill in 15 min The additional fill time can effect behavior of staff At ~4 gpm flow (199 kbtu/h) several tankless units are needed to meet demand

11 Tank vs. Tankless = 1 condensing tank = 2 condensing tankless Without recirc system Quick-service restaurant

12 Tank vs. Tankless = 2 tanks = 4 tankless+storage tank+pump+controller With recirc system Full-service restaurant

13 Water Heater Sizing for Food Safety Sizing to meet a minimum recovery rate at the highest temperature rise encountered in winter

14 Fixture Types and Fixture Counts Fixture Type Deli QSR Small FSR Large FSR Bathroom sinks Hand sinks Compartment sink Dishmachine Door-type Conveyor Pre-rinse valve 1 1 Mop sink Utility and Prep sinks Dipper well 1

15 Flow Rate Guidelines Fixture Type Tankless (gpm) Tank (gph) Bathroom sinks Hand sinks comp. sink (18 X 18 ) comp. sink (bar) 2 18 Door-type dishwasher 4.4* 30** Conveyor dishwasher Pre-rinse spray valve Mop sink 2 15 Utility sink 2 5 Utensil pre-soak sink 2 5 Dipper well *Rate of rinse flow for door-type rated at 0.74 gal/rack, 58 racks/h and 10 seconds of rinse/rack **Door-type maximum rinse consumption of 43 gph x 0.7 (rack loading factor) = 30 gph

16 Tank-Type Heater Sizing Recovery Rate (gph) Deli QSR Small FSR Large FSR Bathroom sinks Hand sinks compartment sink Dishwasher Pre-rinse spray valve Mop sink Utility or pre-soak sink Dipper well 30 Min. recovery rate (gph)* 54** 66** Minimum input rate (Btu/h) 76,000 76, , ,000 Est. Street price $2,000 $2,000 $4,400 $9,200 *Minimum recovery 90 F temp. rise **Discount factor of 20% for using single service utensils

17 Tankless Heater Sizing Tankless Flow Rate (gpm) Deli QSR Small FSR Large FSR Bathroom sinks Hand sinks compartment sink Dishwasher Pre-rinse spray valve Mop sink Utility or pre-soak sink Dipper well 0.5 Minimum flow rate (gpm)* Minimum input rate (Btu/h) 200, , ,000 1,000,000 Number of condensing heaters Est. street price w/recirculation $1,750 $3,500 $7,000 + $1700 $9,750 + $1700 *Smaller facilities require hot water at 120 F equating to a 70 F temp rise in winter (condensing heater at 5.3 gpm). In larger facilities, a 90 F temp rise is required (4.1 gpm).

18 Number of Occurrences FSR Daily Hot Water Consumption Average = 2100 gal/day Daily Hot Water Consumption (gal)

19 Hot Water Flow (gal/min) 24-Hour Flow Rate Profile min data 6 per. Mov. Avg. (5 min data) 3741 gallons After hours cleaning 550 gal/h :00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 Time

20 Water Heater Sizing Recommendations Cleaning practices can heavily sway these requirements, ballooning the minimum recovery rate of storage heaters Sizing for cleanup practices or for redundancy (in case one heater fails) improves the operating life of storage heaters Hosing down a full-service restaurant at 15 gpm requires 450 gallons of hot water over the ½-hour use phase. Two 100 gallon (240,000 Btu/h) heaters are needed to meet this load at a 70 F temperature rise. Approximately 1.5 to 3 times the designed input rate is required to meet the after hours cleanup load.