Sizing of Water Heaters
Transcript of Sizing of Water Heaters
-
7/30/2019 Sizing of Water Heaters
1/40
SIZING OF
WATER
HEATERS
-
7/30/2019 Sizing of Water Heaters
2/40
Randy L. AmanCivil EngineerRegistered Master PlumberReal Estate Broker
PSPE National Auditor
PSPE Camarines Chapter President 2008
NAMPAP National Director 2004 & 2006NAMPAP Camarines Naga City Chapter President
2003
PICE Naga City Chapter President 2004
-
7/30/2019 Sizing of Water Heaters
3/40
WATER HEATING
Water heatingis a thermodynamic processusing an energy source to heat water aboveits initial temperature.
Typical domestic uses of hot water are forcooking, cleaning and bathing.
Domestically, water is traditionally heated invessels known as kettles, cauldrons and pots.
-
7/30/2019 Sizing of Water Heaters
4/40
TRADITIONAL WATER HEATERS
Kettle cauldron pot
http://aa.wrs.yahoo.com/_ylt=A0WTf23v9NRKvTcBNSq.Rwx./SIG=130pqf4v5/EXP=1255556719/**http:/farm2.static.flickr.com/1165/1371910755_1cd410f1cc.jpg?v=1189720733http://aa.wrs.yahoo.com/_ylt=A0WTf2n489RKHNoAC92.Rwx./SIG=13mg4po1h/EXP=1255556472/**http:/spicetreegraphics.biz/Illustrations/Holidays/Halloween/LargeThumbs/CauldronWitch-Thumb2.jpghttp://aa.wrs.yahoo.com/_ylt=A0WTf2n489RKHNoA8Ny.Rwx./SIG=12o0h5sje/EXP=1255556472/**http:/www.clipartheaven.com/clipart/holidays/halloween/cauldron.gif -
7/30/2019 Sizing of Water Heaters
5/40
In industry, both hot water and water heated to
steam have many uses.
Appliances for providing a more-or-less
constant supply of hot water are variously
known as water heaters, boilers, heat
exchangers, calorifiers, or geysers.
These are Mechanical Engineers task.
-
7/30/2019 Sizing of Water Heaters
6/40
TYPES OF WATER HEATERS
1. Conventional or storage water heater
2. Solar water heater
3. Storage and heat pump water heater
4. On-demand or tankless or instataneous
water heater5. Pool water heater
-
7/30/2019 Sizing of Water Heaters
7/40
Conventional or Storage Water Heater
Electric Gas-fired Oil-fired
-
7/30/2019 Sizing of Water Heaters
8/40
Solar Water Heater
Passive Type with Active Type with
Evacuated Tube Collector Flat-plate Collector
-
7/30/2019 Sizing of Water Heaters
9/40
Storage and Heat Pump Water Heater
Storage tank Heat pump
-
7/30/2019 Sizing of Water Heaters
10/40
On-demand or tankless or
Instataneous Water Heater
Single Point Multi-point
-
7/30/2019 Sizing of Water Heaters
11/40
Pool Water Heater
Electric Solar
http://www.solar-pool-heaters.us/1-468240-B000A4WPVS-Sunheater_Solar_Pool_Heating_System_Above_Ground_Pool_System_421A.html -
7/30/2019 Sizing of Water Heaters
12/40
Before buying a new water heater,
you need to consider the following:
1. Size or FHR (First Hour Rating)2. Energy efficiency
3. Fuel type and availability
4. Costs
http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800 -
7/30/2019 Sizing of Water Heaters
13/40
IMPT. FACTORS OF WATER HEATER
The Energy Factor
Energy Factor (EF) is an overall efficiency
rating of the water heater. The higher the EF,
the more efficient the model. Water heaters
with high EF ratings may cost more initially
but save energy and money in the long run.
Eventually, they will pay for themselvesthrough a lifetime of energy savings.
-
7/30/2019 Sizing of Water Heaters
14/40
First Hour RatingAnother important factor in choosing a water heater.
The 1st Hour Rating is an indicator of how much hotwater a particular model can provide. The rating, ingallons of usable (desired temperature) hot water isreached by combining the amount of usable hotwater stored in the tank plus how many gallons ofusable hot water the water heater can generate inone hour of operation. For example, if a 40-gallonnatural gas water heater will store 31 gallons ofusable hot water and can deliver 41 gallons of usablehot water in the first hour, its 1st Hour Rating is 72gallons. 1st Hour Ratings are included in the EnergyFactor charts.
-
7/30/2019 Sizing of Water Heaters
15/40
ENERGY SOURCES FOR HEATING WATER
Natural gas or liquefied petroleum gas
Oil or solid fuels
Electricity
Solar energy
Heat pumps
Hot water heat recycling Geothermal heating
-
7/30/2019 Sizing of Water Heaters
16/40
WATER HEATING IN SOME COUNTRIES
Geothermal heating and hot water heat recycling
http://en.wikipedia.org/wiki/File:Hot_water_heat_recycling_unit.jpg -
7/30/2019 Sizing of Water Heaters
17/40
SIZING OF STORAGE WATER HEATER
Basic Equation:
Q = W x cp xt
Where:
Q = time rated heat transfer, Btu/hr
W = weight of heated water, lbs/hrcp = specific heat of water at standard
condition, say 1 Btu/lbF
t = change of heated temp of water F
http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800 -
7/30/2019 Sizing of Water Heaters
18/40
The British thermal unit(BTU or Btu) is a
traditional unit of energy. It is approximately
the amount of energy needed to heat onepound of water one degree Fahrenheit. One
Btu is equal to about 1.06 kilojoules. It is used
in the power, steam generation, heating andair-conditioning industries.
Farenheit/Celsius Convertion Formula:C = (F 32) x 5/9 F = C x 9/5 + 32
-
7/30/2019 Sizing of Water Heaters
19/40
SAMPLE PROBLEM
Design the water heater of a 4-storeyhotel with 60 guestrooms.
SOLUTION:Hot water loads of a hotel
1. Guest rooms demand
2. Food service demand3. Laundry demand
http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800http://www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12800 -
7/30/2019 Sizing of Water Heaters
20/40
ASSUMPTIONS:
Number of Person per Room:
Convention hotel 1.5 person/room
Business/travellers hotel 1.5 person/room
General occupancy hotel 2 person/room
Peak Demand Period:
Convention hotel 1 hour peak
Business/travellers hotel 1 hour peakGeneral occupancy hotel 2 hours peak
-
7/30/2019 Sizing of Water Heaters
21/40
GIVEN:
no. of guestroom 60 rooms
no. of person/room 1.5 (assumed)
% of guests shower at
peak time 70% (assumed)
ave. shower time 5 min (assumed)
max. flow of shower 2.5 gpm
supply water temp 68 F or 20C
hot water temp 105 F or 40.5C
Note: hot water to be stored at 140F or 60C
and delivered to guest room at 105F or 40.5C
-
7/30/2019 Sizing of Water Heaters
22/40
COMPUTATION FOR STORAGE WATER HEATER:
Total no. of guests = 60 rms x 1.5 guest/room
= 90 guests
% of guests showering per hour = 90 x 0.70
= 63 guests per hour
Vol. of hot water = 63 x 5min/guest x 2.5gpm
= 787 gal of 105F at peak
Since stored water is 140F; equivalent volume isVol = (105 68) x 787 gal = 364 gal
(140 68)
-
7/30/2019 Sizing of Water Heaters
23/40
Q = 364gal/hr x 8.33lb/gal x 1Btu/lbF x (140-68)F
= 218,313 Btu/hr
If Energy Factor of Water Heater is 0.90 then
Q = 218,313 = 242,570 Btu/hr
0.90
In KW: 242,570 Btu/hr = 71 KW3,413 Btu/KW.hr
-
7/30/2019 Sizing of Water Heaters
24/40
Properly size supply and recirculation system is
necessary for efficient and economical operation
Over sizing the system will cause increased
installation costs for equipment and materials,
and create additional heat losses, lesseningefficiency.
Under sizing the system will seriously hampereffective circulation, which means adequate
hot water will not be available at all fixtures.
-
7/30/2019 Sizing of Water Heaters
25/40
SIMPLE METHOD FOR SIZING
RECIRCULATING PUMPS
1 gpm for 20 fixtures units
0.5 gpm for each or 1 riser
1 gpm for each 1 or 1 riser
2 gpm for each 2 riser
-
7/30/2019 Sizing of Water Heaters
26/40
SIZING OF SOLAR WATER HEATERFACTORS OF SOLAR WATER HEATER:
1. Economics
2. Geographic location and solar resource
3. Correct system size
4. Building structure
ACTIVE SOLAR WATER HEATER:
- Storage tank as per requirement per day
- 1.5 gal per square foot of collector
-
7/30/2019 Sizing of Water Heaters
27/40
SIZING OF SOLAR WATER
HEATER
PASSIVE SOLAR WATER HEATER:
Storage Tank:
30 gal cap 1 to 2 persons60 gal cap 2 to 3 persons
80 gal cap 3 to 4 persons
Collector Area for Tropical Countries:
- 20 ft for first two family members- add 8 ft for each additional family
members
-
7/30/2019 Sizing of Water Heaters
28/40
COMPUTATION FOR SOLAR WATER HEATER:
Total no. of guests = 60 rms x 1.5 guest/room
= 90 guests
Vol. of hot water = 90 x 5min/guest x 2.5gpm
= 1,125 gal of 105F at peak
Since stored water is 140F; equivalent volume is
Vol = (105 68) x 1,125 gal = 578 gal
(140 68)Collector Area = 578 gal = 385 ft
1.5gal/ft
-
7/30/2019 Sizing of Water Heaters
29/40
SIZING OF HEAT PUMP WATER HEATER
Heat pump water heaters require installation inlocations that remain in the 40F 90F(4.4C 32.2C) range year-round andprovide at least 1,000 cubic feet (28.3 cubic
meters) of air space around the water heater.
In sizing the water heat pump requirement, usethe Btu/hr or kW capacity of the water heatpump but do not use the peak load alone,use a whole day hot water requirement.
COMPUTATION FOR SOLAR WATER HEATER
-
7/30/2019 Sizing of Water Heaters
30/40
COMPUTATION FOR SOLAR WATER HEATER:
Total no. of guests = 60 rms x 1.5 guest/room
= 90 guestsVol. of hot water = 90 x 5min/guest x 2.5gpm
= 1,125 gal of 105F at peak
Since stored water is 140F; equivalent volume isVol = (105 68) x 1,125 gal = 578 gal
(140 68)
Q = 578gal/hr x 8.33lb/gal x 1Btu/lbF x (140-68)FQ = 346,661 Btu/hr
In KW: 346,661 Btu/hr = 101 KW
3,413 Btu/KW.hr
-
7/30/2019 Sizing of Water Heaters
31/40
FACTORS OF DEMAND (TANKLESS OR
INSTANTANEOUS) WATER HEATER
Advantages of Tankless:Continuous hot water
Uses energy only when hot water is
demanded
Lower energy costs (11% - 60% energy
savings)
Designed to last 20 years
Smaller than hot water tank units, saving
floor space
-
7/30/2019 Sizing of Water Heaters
32/40
FACTORS OF DEMAND (TANKLESS OR
INSTANTANEOUS) WATER HEATER
Disadvantages of Tankless: Must size the unit correctly to avoid losing hot water
May need more than one tankless unit to heat water for
more than one shower
More expensive than hot water tank units
May need to limit the flow of water to properly heat
water (for example, to fill a tub)
Existing gas and water lines may need to be increased in
size
Need to be serviced periodically (to clean scale build-up)
More complex/difficult to service than standard water
heater
-
7/30/2019 Sizing of Water Heaters
33/40
SIZING OF DEMAND (TANKLESS OR
INSTANTANEOUS) WATER HEATER
Demand (tankless or instataneous) waterheaters are rated by the maximumtemperature rise possible at a given flowrate. Therefore, to size a demand waterheater, you need to determine the flow rateand the temperature rise youll need for itsapplication (whole house or a remote
application, such as just a bathroom) in yourhome.
-
7/30/2019 Sizing of Water Heaters
34/40
SIZING OF DEMAND (TANKLESS OR
INSTANTANEOUS) WATER HEATER
Typically, a 70F (39C) water temperature rise ispossible at a flow rate of 5 gallons per minute
through gas-fired demand water heaters and 2
gallons per minute through electric ones.Faster flow rates or cooler inlet temperatures
can sometimes reduce the water temperature
at the most distant faucet.To reduce flowrates, install low-flow water fixtures.
-
7/30/2019 Sizing of Water Heaters
35/40
ARISTON INSTANTANEOUS WATER HEATER SPECIFICATION
Specifications GL 2.5 GL4 GL6 PLUS
Tank Volume 2.5 Gallons 4 Gallons 6 GallonsDimensions 14x14x 10" 14x14x12 17x17x 14
Recovery at 8 GPH* 10.5 GPH* 12.5 GPH*
90F RiseWaterConnections inch NPT inch NPT inch NPT
Relief Valve installed installed included*Gallons Per Hour - First Hour Recovery
All Units:Voltage 110/120 Volts Phase Single Amperage
12.5 amps Temperatures 65 - 145F Heating Capacity
1500 Watts Operating Pressure 150 psi
-
7/30/2019 Sizing of Water Heaters
36/40
MOST INSTANTANEOUS WATER HEATER SPECIFICATION
Power Rating = 4,500W or 4.5kW
Convert kW to Btu/hr = 4.5 x 3,413 = 15,358.5 Btu/hr
Q = W x cp x t
then W = Q = 15,358.5_
cp x t 1 x (105 -68)
Q = 415 lbs = __415 lbs/hr_ = 49.82 gal/hr
8.33lbs/gal
Q = 49.82 gal/hr = 0.83 gpm
60min/hr
-
7/30/2019 Sizing of Water Heaters
37/40
SIZING A GAS OR HEAT PUMP
SWIMMING POOL HEATER
Gas pool heaters are rated by Btu (British
thermal unit) output. Outputs range from
75,000 Btu to 450,000 Btu.
Heat pump pool heaters are rated by Btu
output and horsepower (hp). Standard
sizes include 3.5 hp/75,000 Btu, 5hp/100,000 Btu, and 6 hp/125,000 Btu.
-
7/30/2019 Sizing of Water Heaters
38/40
Calculating Approximate Size Determine your desired swimming pool
temperature. Determine the average temperature for the
coldest month of pool use.
Subtract the average temperature for thecoldest month from the desired pooltemperature. This will give you the temperaturerise needed.
Calculate the pool surface area in square feet. Use the following formula to determine the
Btu/hour output requirement of the heater:
-
7/30/2019 Sizing of Water Heaters
39/40
Btu/Hr = Pool Area x Temp Rise x 12
This formula is based on 1 to 1.25F
temperature rise per hour and a 3.5
mile per hour average wind at the
pool surface. For a 1.5F rise multiply
by 1.5. For a 2F rise multiply by 2.0.
-
7/30/2019 Sizing of Water Heaters
40/40
Thank you