Expansion Tank Sizing Calculation (Hydronic System)

Expansion Tank EasyCalc

HYDRONIC SYSTEM EXPANSION TANK CALCULATION (c) 2000 ASHRAE Handbook, HVAC Systems & Equipment, Hydronic Heating & Cooling System Design, Chap.12 MODA GDMW, Engineering Design Branch, Developed by: Edgar I. Lim, EasyCalc Software

®

Equations for Sizing Expansion Tanks: EasyCalc Software Email Address

Job no.:

Date Prep.

5/6/2013

● For Closed Tanks with air/water interface:

Equation (12)

(Sometimes called a plain steel tank)

● Open Tanks with air/water interface: Equation (13)

(i.e., A tank open to the atmosphere & must be located above the highest point in the system)

● For Diaphragm Tanks: Equation (14)

(Flexible membrane between the air & the water. Another configuration is the bladder tank)

REQUIRED DATA FOR CALCULATIONS

Where: Site Altitude-Elevation (m)► vol.of expansion tank, gal (Closed, Open, Diaph) Vt = V s = volume of water in system, gallons t 1 = lower temperature, °F t 2 = higher temperature, °F P a = atm.pres.psia (14.696 psia at sea level) P 1 = pressure at lower temperature, psia P 2 = pressure at higher temperature, psia 3 v 1 = specific vol.of water at lower temp., ft /lb 3 v 2 = specific vol.of water at higher temp. ft /lb Δt = (t2−t1),°F, temperature differential α = linear coef.of thermal expansion, in/in-°F

Expansion Tank Calculation

Data Entry 0

Closed

Open

Diaphragm

►

39

Temp T2 Hi

144

3000

3000

3000

3000

40

40

40

40

220

220

220

14.696

14.696

not reqrd.

220 not reqrd.

4.0

4.0

not reqrd.

4.0

39.7

39.7

not reqrd.

39.7

0.01602

0.01602

0.01602

0.01602

0.01677

0.01677

0.01677

0.01677

180

180

180

180

6.50E-06

6.50E-06

6.50E-06

6.50E-06

(α equals to 6.5 ×10−6 in/in-°F for steel or 9.5 ×10−6 in/in-°F for copper)

` Water Volume in Hydronic System Components (Cooling or Heating) System Hydronic Components

Equipment Data (Sys. Components) Vol. of Water in System Water Content Capacity Liters Gallons

Piping Distribution System 0.0057 Liters per lps of airflow

Total Lps

Air Handling Units

1.2 Liters per Ton of Refrigeration

Total Tons

Chillers

0.7 Liters per Ton of Refrigeration

Total Tons

Fan Coils

Boilers Radiators

1.9 Liters per Kw 2 Liters per m2 of Heat Surface

Total Kw Tot. m2 of H.S

Total Plus safety factor for other components, fittings etc. (%)

0.0%

Grand Total Volume of Water in System eil software 2008

1

11356.25

3000.00

-

-

-

-

-

-

-

-

-

-

11356.25 11356 Liters

3000.00 3000 Gallons Expansion Tank EasyCalc

Expansion Tank EasyCalc

Water Volume Calculation in System Distribution Pipe Works

a

Table 2 Steel Pipe Data (excerpts) (c) 2000 ASHRAE Hndbk, Chap.40 HVAC Sys.& Equipment

Nom. Pipe Size Pipe Length

a

Flow Area. 2

Inch

mm

meters

mm

1/2" 3/4" 1" 1-1/4" 1-1/2" 2" 2-1/2" 3" 4" 5" 6" 8" 10" 12" 14" 16" 18" 20"

15 20 25 32 40 50 65 75 100 125 150 200 250 300 350 400 450 500

4.25

196 344 557.6 965 1313 2165 3089 4769 8213 12907 18639 32280 50870 72190 87290 114000 144300 179400

19 333

822

Liters per

Water Vol.

Water Vol.

Lineal meter

Liters

Gallons

0.196 0.344 0.558 0.965 1.313 2.165 3.089 4.769 8.213 12.907 18.639 32.280 50.870 72.190 87.290 114.000 144.300 179.400

0.8 24.9 720.9 10609.5 11356.25 Liters

0.2 6.6 190.5 2802.7 3000.00 Gallons

Total water volume in distribution pipe works

NOTES: (c) 2000 ASHRAE Handbook, HVAC Systems & Equipment, Hydronic Heating & Cooling System Design, Chap.12

Low-temperature water (LTW) system. Max. allowable working pres. for low-pres. boilers is 160 psig,with a max. temp. limitation of 250°F.

Medium-temperature water (MTW) system. Operates at temperatures between 250 & 350°F, with pressures not exceeding 160 psi.

Usual max. working pres. for boilers for LTW systems is 30 psi

Usual design supply temperature is approx. 250 to 325°F, with a usual pres.rating of 150 psi for boilers & equipment.

High-temperature water (HTW) system.

Chilled water (CW) system. Normally operates w/ design supply water temp.of 40 to

Operates at temp. over 350°F & usual pressures of about 300 psi. Max. design supply water temp.is usually about 400°F, w/ a pres.rating for boilers & equipt. of about 300 psi

55°F, usually 44 or 45°F, & at a pres. of up to 120 psi.

The connected piping in hydronic systems is subject to expansion & contraction due to changes in system temp. especially during initial system fill. Expansion tanks (or compression tanks) are required to protect against thermal expansion of the piping system due to temperature rise. During initial fill the piping system could experience the largest thermal expansion. In good design practice, in order to reduce the size of the expansion tank, it is preferred to install the tank before the system pump. The size of the tank can also be reduced when the tank is installed at the highest point of the piping system where the pressure is the lowest. As an example, the lower temp. for a heating system is usually normal ambient temp. at fill conditions (e.g., 50°F) & the higher temp. is the operating supply water temp. for the system. For a chilled water system, the lower temp. is the design chilled water supply temp., & the higher temp. is ambient temp. (e.g., 95°F or 115oF for KSA hot areas). For a dual-temp. hot/chilled system, the lower temp. is the chilled water design supply temp., & the higher temp. is the heating water design supply temperature.

Pressures at the expansion tank are generally set by the following parameters: 1) The lower pressure is usually selected to hold a positive pressure at the highest point in the system (usually about 10 psig or 24.696 psia). 2) The higher pres. is normally set by the max. pres. allowable at the location of the safety relief valve(s) without opening them. Other considerations are to ensure that (1) the pres. at no point in the system will ever drop below the saturation pres. at the operating system temp. and (2) all pumps have sufficient net positive suction head (NPSH) available to prevent cavitations.

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Expansion Tank EasyCalc

Expansion Tank EasyCalc

Enable/Disable notes on page 2 above yes Example Calculation of Expansion Tanks From 2000 ASHRAE Handbook, HVAC Systems & Equipment, Chap. 12 Example 1. Size an expansion tank for a heating water system that will be operated at a design temperature range of 180 to 220°F. The minimum pressure at the tank is 10 psig (24.7 psia) & the maximum pressure is 25 psig (39.7 psia). (Atmospheric pressure is 14.7 psia.) The volume of water is 3000 gal. The piping is steel. 1. Calculate the required size for a closed tank (plain steel tank) with an air/water interface. Solution: For lower temperature t 1 , use 40°F From Table 3 in Chap. 6 of the ASHRAE Handbook—Fundamentals,

Given Data:

v1 at 40°F = 0.01602 ft3/lb v2 at 220°F = 0.01677 ft3/lb

ASHRAE Data Users Entry Example 2 Data Page1

Vs = t1 = t2 =

3000

3000

40

40

220

220

Pa = P1 = P2 = v1 = v2 = Δt = α= Vt =

14.7

14.696

24.7

4.0

39.7

39.7

0.01602

0.01602

0.01677

0.01677

180

180

6.50E-06

6.50E-06

578

39

Solution: Using Equation (12) , ASHRAE Data in Formula as per Example no.1)

Answers: Volume of Diaphragm Expansion Tank Vt= Vt=

578 39

Gallons (ASHRAE Data as per Example no.1) Gallons ( User's Entries calculation at page 1)

Example 2. If a diaphragm tank were to be used in lieu of the plain steel tank, what tank size would be required? ASHRAE Data Users Entry Example 2 Data Page1 Vs = 3000 3000 t1 = 40 40 t2 = 220 220

Given Data:

P1 = P2 = v1 = v2 = Δt = α= Vt =

24.7

Solution: Using Equation (14) , ASHRAE Data in Formula as per Example no.2)

4.000

39.7

39.7

0.01602

0.01602

0.01677

0.01677

180

180

6.50E-06

6.50E-06

344

144

Answers: Volume of Diaphragm Expansion Tank Vt= Vt=

344 144

Gallons (ASHRAE Data as per Example no.2) Gallons ( User's Entries calculation at page 1)

EXPANSION TANK MINIMUM PRESSURE The expansion tank must be pressurized to provide at least 4 psi (28 kPa) of positive pressure at the highest point in the hydronic piping system. This will also ensure no air is drawn into the piping. The amount of charge pressure in pounds per square inch (psi) that is required in the expansion tank is equal to 4 psi (28 kPa) plus the height (in feet) from the chiller to the highest point in the hydronic system divided by 2.31. Example: The expansion tank elev. is 10 feet. The hydronic system is piped to an air handler on the roof with an elevation of 100 feet. The total pressure required in the expansion tank is: 4 psi + (100 ft – 10 ft)/2.31 = 42.96 psi Thus an expansion tank with a pre-charged pres. at 40 psi from factory will require an additional 3 psi pressure.

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Expansion Tank EasyCalc

Expansion Tank EasyCalc

Boiler System Types: 1. Low Temperature Heating Water Systems: a. 250°F. &Less. b. 160 psig maximum. 2. Medium Temperature Heating Water Systems: a. 251–350°F. b. 160 psig maximum. 3. High Temperature Heating Water Systems: a. 351–450°F. b. 300 psig maximum.

Common Boiler Design Pressures ( psig.) Add 14.696 to get absolute pressure at sea level. 1. 15 Psig 2. 30 Psig 3. 60 Psig 4. 125 Psig 5. 150 Psig

6. 200 Psig 7. 250 Psig 8. 300 Psig 9. 350 Psig

EXPANSION TANKS COMMERCIAL LISTED SIZES (ARMSTRONG) N TANKS LISTED COMMERCIAL SIZES Diaphragm Tank Bladder Tank Configuration Closed Tank liters 29.5 41.3 82.1 127.2 168.1 210.8 257.4 291.5 340.7 416.4 499.7 601.9 798.7

gallons 7.8 10.9 21.7 33.6 44.4 55.7 68.0 77.0 90.0 110.0 132.0 159.0 211.0

liters 200.6 302.8 401.3 499.7 598.1 798.7 999.3 1200.0 1400.6 1597.4 1998.7 2498.4 2998.0 3997.4

gallons 53 80 106 132 158 211 264 317 370 422 528 660 792 1056

liters 56.8 90.8 113.6 151.4 227.1 302.8 378.5 454.2 511.0 662.4 832.8 908.5 1154.6 1116.7 1514.2 1911.6 1987.3

gallons 15.0 24.0 30.0 40.0 60.0 80.0 100.0 120.0 135.0 175.0 220.0 240.0 305.0 295.0 400.0 505.0 525.0

A. Class I Boilers. ASME Boiler &Pressure Vessel Code, Section I: 1. Steam Boilers, Greater than 15 Psig 2. Hot Water Boilers: a. Greater than 160 Psig b. Greater than 250°F. B. Class IV Boilers. ASME Boiler &Pressure Vessel Code, Section IV: 1. Steam Boilers, 15 psig &less 2. Hot Water Boilers: a. 160 psi &less b. 250°F. &less

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Expansion Tank EasyCalc

Hot Water Boilers

Steam Boilers

Chillers

A. Boiler Types: 1. Fire Tube Boilers: a. 15–800 BHP. b. 500–26,780 MBH. c. 30–300 psig. 2. Water Tube Boilers: a. 350–2,400 BHP. b. 13,000–82,800 MBH. c. 30–525 psig. 3. Flexible Water Tube Boilers: a. 30–250 BHP. b. 1,000–8,370 MBH. c. 0–150 psig. 4. Cast Iron Boilers: a. 10–400 BHP. b. 345–13,800 MBH. c. 0–40 psig. 5. Modular Boilers: a. 4–115 BHP. b. 136–4,000 MBH. c. 0–150 psig. 6. Electric Boilers: a. 15–5,000 KW. b. 51–17,065 MBH. c. 0–300 psig.

A. Boiler Types: 1. Fire Tube Boilers: a. 15–800 BHP. b. 518–27,600 Lb./Hr. c. 15–300 psig. 2. Water Tube Boilers: a. 350–2,400 BHP. b. 12,075–82,800 Lb./Hr. c. 15–525 psig. 3. Flexible Water Tube Boilers: a. 30–250 BHP. b. 10,000–82,000 Lb./Hr. c. 15–525 psig. 4. Cast Iron Boilers: a. 10–400 BHP. b. 1,035–8,625 Lb./Hr. c. 0–150 psig. 5. Electric Boilers: a. 15–5,000 KW. b. 51–17,065 MBH. c. 0–300 psig.

A. Chiller Types: 1. Centrifugal: a. 200 Tons &Larger. b. 0.55–0.85 KW/Ton. c. 4.14–6.39 COP. d. Turndown Ratio, 100% to 10%. 2. Reciprocating: a. 200 Tons &Smaller. b. 0.90–1.30 KW/Ton. c. 2.70–3.90 COP. d. Turndown Ratio, Staged or Stepped based on nos of cyl.& unloadingcontrol. 3. Rotary Screw: a. 50–1100 Tons. b. 1.00–1.50 KW/Ton. c. 2.34–3.50 COP. d. Turndown Ratio, 100% to 25%. 4. Absorption (Steam or Hot Water): a. 100 Tons &Larger. b. 18,750 Btuh/Ton; 0.64 COP 1-Stage. c. 12,250 Btuh/Ton; 0.98 COP 2-Stage. d. Turndown Ratio, 100% to 10%. 5. Absorption (Gas or Oil): a. 100 Tons & Larger. b. 11,720 Btuh/Ton; 1.02 COP Gas. c. 12,440 Btuh/Ton; 0.96 COP Oil. d. Turndown Ratio, 100% to 10%.

Low Temperature Heating Water Systems: Chilled Water Systems: 1. Leaving Water Temperature (LWT): 180–200°F. 1. Leaving Water Temperature (LWT): 40–48°F. 2. ΔT Range 20–40°F. (60°F.Maximum) 3. Low Temperature Water 250°F. & less; 160 psig maximum 2. ΔT Range 10–20°F. Medium &High Temperature Heating Water Systems: Low Temperature Chilled Water Systems 1. Leaving Water Temperature (LWT): 350–450°F. (Glycol or Ice Water Systems) 2. ΔT Range 20–100°F. 1. Leaving Water Temperature (LWT): 20–40°F. 3. Medium Temperature Water 251–350°F.; 160 psig maximum (0°F. minimum) 4. High Temperature Water 351–450°F.; 300 psig maximum 2. ΔT Range 20–40°F. Dual Temperature Water System Types:

Condenser Water Systems:

1. Leaving Cooling Water Temperature 40–48°F. 2. Cooling ΔT Range 10–20°F. 3. Leaving Heating Water Temperature: 180–200°F. 4. Heating ΔT Range 20–40°F.

eil software 2008

1. Entering Water Temperature (EWT): 85°F. 2. ΔT Range 10–20°F. 3. Normal ΔT 10°F. Water Source Heat Pump Loop 1. Range: 60–90°F. 2. ΔT Range 10–15°F.

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Expansion Tank EasyCalc

Expansion Tank EasyCalc

AC Condensate Flow: 1. Range: 0.02–0.08 GPM/Ton 2. Average: 0.04 GPM/Ton 3. Unitary Packaged AC Equipment: 0.006 GPM/Ton 4. AHU (100% outside Air): 0.100 GPM/1,000 CFM

5. AHU (50% Outdoor Air): 0.065 GPM/1,000 CFM 6. AHU (25% Outdoor Air): 0.048 GPM/1,000 CFM 7. AHU (15% Outdoor Air): 0.041 GPM/1,000 CFM 8. AHU (0% Outdoor Air): 0.030 GPM/1,000 CFM

AC Condensate Pipe Sizing 1. Minimum Pipe Sizes are given in the following table. AC Tons of Refrigeration 0-20 21-40 41-60 Minimum Drain size (inch) 1" 1-1/4" 1-1/2"

61-100

101-250

251 &Larger

2"

3"

4"

Expansion Tanks &Air Separators A. Minimum (Fill) Pressure: 1. Height of System + (5 to 10 psi) or 5–10 psi, whichever is greater. B. Maximum (System) Pressure: 1. 150 Lb. Systems: 45–125 psi 2. 250 Lb. Systems: 125–225 psi C. System Volume Estimate: 1. 12 Gal./Ton 2. 35 Gal./BHP The sizing of low-temperature hot water pipes is usually based on a pressure drop of 1 to 3 ft per 100 ft of pipe length. For a small low-temp. hot water heating system, an open-type expansion tank is often used. An open expansion tank has the disadvantage of allowing air to enter the system via absorption in the water. A diaphragm tank is often used for a large system. On-line circulating pumps with low head are often used. Table 1 Standard Atmospheric Data for Altitudes to 10 000 m Altitude,

Pressure,

Atmospheric Data Calculation For Different Altitudes Altitude,

Pressure,

m

kPa

psia

m

kPa

psia

−500

107.478

15.588

555

94.833

13.754

0

101.325

14.696

500

95.461

13.845

1 000

89.875

13.035

1 500

84.556

12.264

2 000

79.495

11.530

2 500

74.682

10.832

3 000

70.108

10.168

4 000

61.64

8.940

5 000

54.02

7.835

6 000

47.181

6.843

7 000

41.061

5.955

8 000

35.6

5.163

9 000

30.742

4.459

10 000

26.436

3.834

(c) 2005 ASHRAE Handbook, Fundamentals, Chapter 6

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nds per

pressure.

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Expansion Tank EasyCalc

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Expansion Tank EasyCalc

0–48°F.

0–40°F.

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ASHRAE Fundamentals Table 3 Thermodynamic Properties of Water at Saturation Temp., °F 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59

Specific Vol. ft3/lbw 0.01747 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01602 0.01603 0.01603 0.01603 0.01603 0.01603 0.01603 0.01603 0.01603

Temp., °F 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87

Specific Vol. ft3/lbw 0.01604 0.01604 0.01604 0.01604 0.01604 0.01604 0.01604 0.01605 0.01605 0.01605 0.01605 0.01605 0.01606 0.01606 0.01606 0.01606 0.01606 0.01607 0.01607 0.01607 0.01607 0.01608 0.01608 0.01608 0.01608 0.01609 0.01609 0.01609

Temp., °F 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115

Specific Vol. ft3/lbw 0.01609 0.0161 0.0161 0.0161 0.01611 0.01611 0.01611 0.01612 0.01612 0.01612 0.01612 0.01613 0.01613 0.01613 0.01614 0.01614 0.01614 0.01615 0.01615 0.01616 0.01616 0.01616 0.01617 0.01617 0.01617 0.01618 0.01618 0.01619

Temp., °F 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143

Specific Vol. ft3/lbw 0.01619 0.01619 0.0162 0.0162 0.0162 0.01621 0.01621 0.01622 0.01622 0.01623 0.01623 0.01623 0.01624 0.01624 0.01625 0.01625 0.01626 0.01626 0.01627 0.01627 0.01627 0.01628 0.01628 0.01629 0.01629 0.0163 0.0163 0.01631

Temp., °F 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171

Specific Vol. ft3/lbw 0.01631 0.01632 0.01632 0.01633 0.01633 0.01634 0.01634 0.01635 0.01635 0.01636 0.01636 0.01637 0.01637 0.01638 0.01638 0.01639 0.01639 0.0164 0.0164 0.01641 0.01642 0.01642 0.01643 0.01643 0.01644 0.01644 0.01645 0.01646

172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205

0.01646 0.01647 0.01647 0.01648 0.01648 0.01649 0.0165 0.0165 0.01651 0.01651 0.01652 0.01653 0.01653 0.01654 0.01654 0.01655 0.01656 0.01656 0.01657 0.01658 0.01658 0.01659 0.01659 0.0166 0.01661 0.01661 0.01662 0.01663 0.01663 0.01664 0.01665 0.01665 0.01666 0.01667

206 207 208 209 210 212 214 216 218 220 222 224 226 228 230 232 234 236 238 240 242 244 246 248 250 252 254 256 258 260 262 264 266 268

0.01667 0.01668 0.01669 0.01669 0.0167 0.01671 0.01673 0.01674 0.01676 0.01677 0.01679 0.0168 0.01682 0.01683 0.01684 0.01686 0.01688 0.01689 0.01691 0.01692 0.01694 0.01695 0.01697 0.01698 0.01700 0.01702 0.01703 0.01705 0.01707 0.01708 0.01710 0.01712 0.01714 0.01715

270 272 274 276 278 280 282 284 286 288 290 292 294 296 298 300 302 304 306 308 310 312 314 316 318 320 322 324 326 328 330 332 334 336

0.01717 0.01719 0.01721 0.01722 0.01724 0.01726 0.01728 0.01730 0.01731 0.01733 0.01735 0.01737 0.01739 0.01741 0.01743 0.01745 0.01747 0.01749 0.01751 0.01753 0.01755 0.01757 0.01759 0.01761 0.01763 0.01765 0.01767 0.01770 0.01772 0.01774 0.01776 0.01778 0.01780 0.01783

338 340 342 344 346 348 350 352 354 356 358 360 362 364 366 368 370 372 374 376 378 380 382 384 386 388 390 392 394 396 398 400 405 410

0.01785 0.01787 0.01789 0.01792 0.01794 0.01796 0.01799 0.01801 0.01804 0.01806 0.01808 0.01811 0.01813 0.01816 0.01818 0.01821 0.01823 0.01826 0.01828 0.01831 0.01834 0.01836 0.01839 0.01842 0.01844 0.01847 0.01850 0.01853 0.01855 0.01858 0.01861 0.01864 0.01871 0.01878

415 420 425 430 435 440 445 450 455 460 465 470

0.01886 0.01894 0.01901 0.01909 0.01918 0.01926 0.01935 0.01943 0.01952 0.01961 0.01971 0.01980