MAKING MODERN LIVING POSSIBLE Technical brochure Capacity regulators (hot gas bypass) PMC and CVC The PMC and CVC is used for capacity regulation in refrigeration, freezing and air conditioning plant for ammonia and fluorinated refrigerants. The PMC is a servo-operated regulator with screwed-on pilot valves. PMC and CVC can be used in all types of refrigeration plant: With direct expansion With pump recirculation With natural circulation The function of the capacity regulator is to match the fixed output of the compressor and the varying load on the system. This function is obtained when the PMC and CVC is installed in a bypass line between the discharge and suction sides of the compressor. If the load on the evaporator, and with it the load on the compressor, falls, an "artificial" load in the form of hot gas from the high pressure side of the compressor is applied to the evaporator or compressor. Features Accurate regulation High capacity and operating range Independent of condensing pressure variations High flexibility Screw in pilot Simple adjustment and build-up Materials Gaskets are non-asbestos Valve body EN-GJS-4-18-LT Danfoss A/S (AC-MCI/MWA), 213-2 DKRCI.PD.HM.A3.2 / H35 1
Contents Page Features... 1 Materials... 1 Technical data... 3 Ordering... 4 Sizing... 5 Hot gas capacity... 6 Design/Function... 8 Dimensions and weights... 1 2 DKRCI.PD.HM.A3.2 / H359 Danfoss A/S (AC-MCI/MWA), 213-2
Pressure Equipment Directive (PED) The PMC and CVC valves are approved in accordance with the European standard specified in the Pressure Equipment Directive and are CE marked. For further details / restrictions - see Installation Instruction. PMC and CVC valves Nominal bore DN 25 (1 in.) Classified for Fluid group I Category Article 3, paragraph 3 Technical data Type Refrigerants Opening diff. pressure Dp bar P-band Temperature of medium Max. working pressure PS 1 ) bar Max. test pressure p ' bar With PMC 1 and PMC 3 Applicable to built-on CVC: 5 +12 42. HCFC, HFC, Approx..2 bar CVC and R717 (Ammonia) 5 +12 17/ 26.5/42. EVM 5 +12 35 46. a.c.: 1W d.c.: 2W a.c.: 21 d.c.: 14 1 ) Max. working and test pressures refers to the high pressure side connection (PS: and p': 42 bar) and reference pressure (PS: 17 and p': 26.5 bar) which must be connected to the low pressure side of the system. Danfoss A/S (AC-MCI/MWA), 213-2 DKRCI.PD.HM.A3.2 / H35 3
Ordering PMC main valves PMC 1 PMC 3 Size EN-GJS-4-18-LT EN-GJS-4-18-LT PMC 5 27F3 27F349 PMC 8 27F346 27F35 PMC 12 27F347 27F351 PMC 2 27F348 27F3 Valve size 1 ) The k v value is the water flow in m 3 /h at a pressure drop across the valve of 1 bar (ρ = 1 kg/m 3 ). The code nos. stated apply to main valve type PMC incl. flange gaskets and bolts. Pilot valves Rated replacement capacity in kw 1 ) The code no. stated apply to pilot valve type CVC incl. pilot signal connector. 2 ) Without coil. Please see the technical brochure "Coils for solenoid valves" (PD.BS.A). k v value R22 R134a R44A R12 R R717 m 3 /h 1 PMC 5 19 2 34 1.7 PMC 8 35 37 61 1 3.2 PMC 12 82 47 88 51 83 244 4.2 PMC 2 14 74 1 78 13 7 6.5 The rated capacity is given for an evaporating temperature of t e = 1, a condensing temperature of t c = +32 and an offset (= suction t s ) of 4 K. Description Range Code no. Pilot valve type CVC Pilot valve type EVM. bar 7 bar 4 bar bar 27B17 1 ) 27B87 NC 27B112 2 ) NO 27B113 2 ) Flange sets Valve type Flange type Weld flange set Solder flange set in. Code no. 1 ) in. Code no. 1 ) mm Code no. 1 ) 3 / 4 27N122 7 / 8 27L1223 22 27L1222 PMC 1 and 3 12 1 27N1225 1 1 / 4 27N123 1 ) Code no. applies to a flange set consisting of one inlet flange and one outlet flange. Example PMC 3 size 12, code no. 27F1 + 1 in. flange set, code no. 27N1225 + CVC, code no. 27B17 + EVM, code no. 27B112 2 ) + 6.5 / 1 mm pressure gauge connection, code no. 27B235. Accessories Description Pressure gauge connector Ø 6.5 / Ø 1 mm weld / solder Pressure gauge connector ¼ in. flare (self-closing) Must not be used for ammonia Pressure gauge connector, cutting ring connection 6 mm 1 mm 1 1 / 8 27L12 27L12 Code no. 27B235 27B241 27B263 27B264 Pressure gauge connector ¼ NPT 27B262 External pilot connection 27F148 4 DKRCI.PD.HM.A3.2 / H359 Danfoss A/S (AC-MCI/MWA), 213-2
Sizing Suction pressures in the table relates to suction pressure / suction temperature after the reduction. If a smaller offset than 4 K is required, multiply the capacity found at t s = 4 K by a correction factor k. If the correction factors are not changed as a function of the suction t s, the proportional band of the regulator is fully utilized. The proportional band of the regulator is approx..2 bar. Q h =. m b (h 2 -h 4 ) (kw) where Q h = hot gas capacity or replacement capacity. m b given in table in kw = flow through PMC in kg/s h 2 -h 4 = enthalpy difference in kj/kg The stated PMC hot gas capacities assume that the hot gas is injected ahead of the evaporator. The thermostatic expansion valve compensates for the heat the hot gas transfers to the evaporator by increasing liquid injection. In this way the superheat at the evaporator outlet is kept more or less constant. Capacities are thus made up of the PMC regulator capacity + expansion valve compensation. Capacities are given for an offset (= suction t s ) of 4 K. Selection example An R134a unit for compressed air drying must be capacity regulated from 1% to % using hot gas injection direct into the evaporator after the expansion valve. The compressor has no internal capacity regulation. Compressor capacity, Q c = 12 kw at t e = and t c = +3. Min. suction temperature, t s min. =. Max. off-set, t s max. = 2 K. Min. evaporator load, Q e min. = kw. Necessary PMC replacement capacity, Q h = 12 = 12 kw. From the capacity table, it can be seen that PMC size 5 produces 19 kw at t s =, t c = +3 and t s = 4 K. Correction factor k for off-set t s = 2 K is given as.7. The final replacement capacity Q h for PMC size 5 thus become 19.7 = 13.3. A PMC size 5 will therefore produce the same as the compressor, i.e. 12 kw at an off-set a little lower than 2 K. Danfoss A/S (AC-MCI/MWA), 213-2 DKRCI.PD.HM.A3.2 / H35 5
Hot gas capacity Hot gas / replacement capacity for suction temperature reduction, off-set t s = 4 K. Type PMC 1 and PMC 3 Size 5 8 12 2 +1-1 -2-3 -4 +1-1 -2-3 -4 +1-1 -2-3 -4 +1-1 -2-3 -4 Correction factor k for different off-set (suction s) R22 +1-1 -2-3 -4 Type PMC 1 and PMC 3 Size 5 8 12 2 +1-1 -2-3 +1-1 -2-3 +1-1 -2-3 +1-1 -2-3 kg/s Condensing temperature t c 2 3 4 5 2 3 4 5.111.14.14.138.137.137.192.257.257.253.253.251.239.348.348.343.339.339.335.53.537.53.464.9.184.182.181.181.17.18.337.333.333.333.33.33.5....447.4.688.694.694.694.53.399.232.231.231.231.2.2.425.424.424.424.424.397.574.5.5.5.538.393.885.885.885.3.568.41..9.9.9.9.9.534.532.532.532.532.397.2....1.4 1.112 1.112.922.715.5.414 23 38 49 18 18 18 99 89 89 89 89 9 13 14 14 14 17 8 kw 83 83 82 82 82 77 111 111 111 111 14 77 1 1 1 14 18 78 R22 55 55 55 11 11 11 11 11 76 139 139 139 139 12 75 216 216 1 14 18 t c = 2 and 3 t c = 4 and 5 Suction Dt s k 1 2 3 4 1 2 3 4.4.5.5.4.4.3.19..92.92.92.35.161.169.169.169.47.23.2.2.2.76.264.332.332.278.7.9.9.7.7.6.122.12.118.118.118.224.22.218.218.218.32.9.4.4.4.421.46.5.43.32.9.9.9.8.156.1.1.151.151.5.1...278.385.38.378.378.332.594.587.584.466.358 kg/s kw Condensing temperature t c 2 3 4 5 2 3 4 5.194.192.192.192.192.358.3.353.353.353.484.478.478.478.359.747.9.6.55.374 Correction factor k for different off-set (suction s) Refrigerant Refrigerant R 134a +1-1 -2-3.6.5.5.5.4.4 3 15 15 15 15 5 26 7 33 37 37 37 12 42 55 55.9.7.7.7.6.7 19 19 19 19 19 34 35 35 35 35 46 47 47 47 47 74 66.9.9.9.8.8 24 24 24 24 24 43 44 44 44 44 58 58 6 6 89 9 91 56 t c = 2 and 3 t c = 4 and 5 R134a 113 113 77 57 Suction Dt s k 1 2 3 4 1 2 3 4.1.4.8.4.8.3.7.9.4.7.9.3.6.8.3.6.8.3.6.8.3.6.8.2.6.8.2.5.8 6 DKRCI.PD.HM.A3.2 / H359 Danfoss A/S (AC-MCI/MWA), 213-2
Hot gas capacity (continued) Hot gas / replacement capacity for suction temperature reduction, off-set t s = 4 K. Type PMC 1 and PMC 3 Size 5 8 12 2 +1 1 2 3 4 +1 1 2 3 4 +1 1 2 3 4 +1 1 2 3 4 kg/s kw Condensing temperature t c 2 3 4 5 2 3 4 5.151.184.182.1.178.178.266.337.333.3.3.3.333.4.449.443.443.443.435.688.694.685.9.511.235.234.233.231.23.23.43.427.425.425.425.425.577.5.575.575.574.53.871.892.886.886.713.557.5.4.2.1.1.1.3.539.5.535.535.535.4..5.5.5.4 1.132 1.125 1.118.9..556.3.37.8.7.7.7.685.68.6.6.6.59.927.921.915.915.744.569 1.4 1.418 1.191.941.875.569 Correction factor k for different off-set (suction s) R44A +1 1 2 3 4 23 39 51 49 69 71 14 19 11 17 82 34 63 85 86 88 88 88 125 1 1 1 113 84 43 43 44 43 43 43 78 16 17 17 17 17 15 159 17 17 1 15 82 R44A t c = 2 and 3 t c = 4 and 5 Suction Dt s K 1 2 3 4 1 2 3 4.4.5.5.4.4.3.7.9.9.7.7.6.9.9.9.8.6.5.5.5.4.4.9.7.7.7.6.7.9.9.9.8.8 5 51 51 51 51 51 93 93 94 94 94 82 122 122 122 122 14 193 193 17 1 125 Type PMC 1 and PMC 3 Size 5 8 12 2 +1 1 2 3 4 +1 1 2 3 4 +1 1 2 3 4 +1 1 2 3 4.5.57.55....87.12.11.1.1.1.19.139.137.135.135.11.144.213.211.27.1.12.77...71.71.71.14.1.133.132.132.115.189.183.181.1.177.122.7.3.2.244.189.121.98.97.94.94.94.94.18.178.1.1.1.1.2.241.234.234.19.13.377.3.2.27.197.126.125.123.121.121.121.121.23.227.224.224.195.137.312..33.266.1.139.48.4.359.27.185.99 Correction factor k for different off-set (suction s) Refrigerant Refrigerant R717 (NH 3 ) Suction temp. t s after temperature reduction +1 1 2 3 4 kg/s kw Condensing temperature t c 2 3 4 5 2 3 4 5 63 111 141 141 141 141 141 139 186 186 186 186 151 184 1 1 1 238 162 1 1 1 1 1 1 244 244 244 244 244 162 356 7 7 324 248 162 R717 (NH 3 ) 124 124 124 124 124 124 23 23 23 23 23 166 313 313 313 313 255 174 475 475 475 356 259 1 t c = 2 and 3 t c = 4 and 5 Suction Dt s K 1 2 3 4 1 2 3 4.4.5.5.4.3.2.8.8.8.6.6.6.9.8.8.8.5.4.4.4.4.2.8.7.6.6.6.6.9.8.8.8.8 158 158 158 158 158 158 2 2 2 2 243 1 383 383 383 3 244 174 583 583 4 346 238 13 Danfoss A/S (AC-MCI/MWA), 213-2 DKRCI.PD.HM.A3.2 / H35 7
Design/Function 1. Valve body 1a and 1b. Channels in valve body 1. Regulating spindle 11. Throttling cone 12. Valve seat 22. Locking ring 24. Servo piston 24 a. Equalizing hole in servo piston 3. Bottom cover. Plug 4. Cover 4 a, b, c and d. Channels in cover 44. Blanking plug for pressure gauge connection 6. Manual operating spindle PMC 1 PMC 3 The PMC regulator is a servo-operated main valve whose function is determined by the pilot valve. The main valve with pilot valve controls refrigerant flow by modulation in accordance with the pilot valve impulse. The degree of opening of the PMC is determined by the pressure difference (differential pressure) between pressure p 2, which acts on the top of the servo piston (24), and pressure p 3, which acts on the underside of the servo piston. Because of the channel (1b) in the valve body, pressure p 3 acting on the underside of the servo piston (24) is equal to the regulator discharge pressure, p 4. If this pressure difference is, the regulator will be fully closed. If the pressure difference is approximately.7 bar or more, the regulator will be fully open. At pressure differences (p 2 - p 4 ) between approximately.3 bar and.7 bar the opening degree of the regulator will be correspondingly proportional. The shape of the throttling hole (11) gives an ideal regulation characteristic to servooperated regulators. The degree of opening of the regulator is thus controlled by applying a pressure, p 2, on the top of the servo piston which is equal to or greater than the discharge pressure, p 4. p 2 = p 4 closed position. p 2 = p 4 +.7 bar completely open position. p 4 p 2 p 4 +.7 bar proportional degree of opening. The maximum pressure, p 2, that can be built up on the top of the servo piston (24) normally corresponds to the pressure, p 1, acting on the regulator inlet side. Inlet pressure p 1 is led, via the drilled channels (1a, 4a, 4b, 4c, 4d) in the valve body (1) and cover (4) through the individual pilot valves and on the top of the servo piston (24). The degree of opening of the individual pilot valves determines the size of pressure p 2 and thus the degree of opening of the regulator, i.e. the equalisation hole (24a) in the servo piston (24) ensures that pressure p 2 is balanced in accordance with the degree of opening of the pilot valve. 8 DKRCI.PD.HM.A3.2 / H359 Danfoss A/S (AC-MCI/MWA), 213-2
Design Function (continued) 43. Gasket 44. Blanking plug for pressure gauge connection A2. Gasket A1. O-ring 13. Banjo fitting 14. O-ring 15. Protective cap 16. O-ring 17. Signal connection 18. Pilot orifice 19. Banjo fitting connector 11. Diaphragm 111. Spring 112. Setting spindle CVC Blanking plug A + B Blanking plug A 1. Coil 2. Armature 3. Armature tube A2. Gasket A1. O-ring 6. Seal ring 7. Spacing ring 8. Nut 9. Locking knob 1. Union nut 11. Valve seat EVM PMC opens when the pressure p s in the signal connection (17) is below set point. The PMC 3 has three connections for pilot valves, two in series (marked "SI" and "SII") and one in parallel (marked "P"). If only two pilot valves are necessary for the required function, the third pilot port must be blanked with the blanking plug provided. Fitting instructions accompany the blanking plug. Danfoss A/S (AC-MCI/MWA), 213-2 DKRCI.PD.HM.A3.2 / H35 9
Dimensions and weights PMC 1 and CVC PMC 3, CVC and EVM Type Size H 1 H 2 H 3 H 4 H 5 H 6 H 7 L L 1 L 5 max. B 1 B 3 without pilot valves Weight with flanges but 1 W 2 W PMC 1 PMC 3 Flangeset PMC 1 mm mm mm mm mm mm mm mm mm mm mm mm mm kg kg kg 5-2 PMC 3 66 162 11 178 117 2 177 16 122 132 75 87 6.5 7. 1.1 Pilot valve type CVC EVM Weight kg.7.5 CVC EVM Pressure gauge connector, ¼ NPT Pressure gauge connector, flare External pilot connection Size A B L M 6 mm 19 14 39 27 1 mm 19 19 4 Pressure gauge connector, cutting ring connection Pressure gauge connector Pressure gauge connector, self-closing 1 DKRCI.PD.HM.A3.2 / H359 Danfoss A/S (AC-MCI/MWA), 213-2
Danfoss A/S (AC-MCI/MWA), 213-2 DKRCI.PD.HM.A3.2 / H35 11
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