DHM Service Manual
Contents
1. DHM 5 xx MODULE SHOWN EXHAUST MANI FOLD PLAN Module 3 xx 4 xx 5 xx 6 xx 7 Xxx Notes l 1 Low fire is with only one of the five burner modules running Height 910 1155 1400 1645 1890 2 Maximum Ambient Temperature 25 C 3 Maximum Gas Inlet Pressure 60mbar 2 2 Performance Data Rea Input a Psa aa 55 oes 7 es 2 os os er HeatOutut Max w 300 0 soo oo woo o soo 750 900 1050 Heat Input Min 11 1 16 3 Heat Output Min 10 0 15 0 Heat Input Max Heat Output Max Heat Input Min Heat Output Min Power Input Start Current Run Current Min air flow rate Weight Fig 1 Pre ssure Test Point Gas Inlet 80 0 100 0 120 0 0 140 0 0 120 0 160 0 0 on ee on AC OETEOEAEA 200 0 0 ee 20 0 38 0 a o o 240 0 280 0 a e o a a a a a 2 3 Gas Controls Schematic 1st Main Gas Safety Shut off Valve 2nd Main Gas Safety Shut off Valve Main Gas Governor 1st Main Gas Safety Shut off Valve 2nd Main Gas Safety Shut off Valve Main Gas Governor 1st Main Gas Safety Shut off Valve 2nd Main Gas Safety Shut off Valve Main Gas Governor 1st Main Gas Safety Shut off Valve 2nd Main Gas Safety Shut off Valve Main Gas Governor 1st Main Gas Safety Shut off Valve H 2nd Main Gas Safety Shut off Valve2. Main Gas Governor Pressure Test Point Pressure Test Point Pressure Test Point Pressure Test Point Pressure Test Point To Burner To Burner To Burner To Burner To Burner DHM 5 xx MODULE SHOWN Table 1 Injector Sizes amp Burner Pressure Natural Gas Group H G20 Net CV Hi 34 02M m Gas Rate Max Burner Pressure Injector size wm o ee sa vor en sar om a_i ieee mm a Gas Rate Max Burner Pressure mbar Injector size Table 2 10 6 at each burner mm oo o A E 10 0 at each burner Injector Sizes amp Burner Pressure Propane G31 Net CV Hi 88 00MJ m Gas Rate Max Burner Pressure mbar Injector size mm 2 6 3 General Requirements 3 1 Related Documents The installation of the module must be in accordance with the rules in force and the relevant requirements of the Gas Safety Regulations and the E E Regulations for Electrical Installations 3 2 Electrical Supply The module requires 230V 1ph 50Hz fused at 5A The method of connection to the main electricity supply must facilitate the complete electrical isolation of the module The isolator must have a contact separation of at least 3mm in all poles See the accompanying wiring diagram for the module electrical connections 3 3 Gas Connection A servicing valve and downstream union must be fitted at the inlet to the module gas controls assembly
3. Fig Rectification electrode om Sy SY Ye 8 9 10 5 3 1 DS w 2 Burner Assembly Reverse side of Gas Valve Ignition 7 electrode Governor adjustment screw Pressure switch impulse pipe Pressure Switch Full Sequence Control DN Earth electrode Burner Body gt l lt 3 5 4 5mm Front view of electrode assembly Swirler Injector re Burner Burner Assembly Release the single securing screw retaining the full sequence control to the gas valve assembly and pull off the full sequence control Pull off the electrical leads to the pressure switch on the burner concerned Remove the screws securing the gas inlet flange to the gas manifold Pull the burner out from the primary tube and clear of the gas manifold Check that the electrodes and swirler plate are in good condition Replace if necessary Check that the primary tube is clear internally Access is available if required to the outlet end of the secondary tube Remove the cover plates at the right hand side of the bulkhead and then remove the appropriate access plate from the internal manifold Reassemble burner in reverse order and a new cork gasket on the manifold flange Repeat for the remaing burners in the module Replace heat shield if fitted Exhaust Fan Remove the heat shield if fitted situated between the exhaust fan and burners contols section Remove electrical connections t
4. to facilitate servicing The gas supply to the module must be completed in solid pipework and be adequately supported Warning When completing the final gas connection to the module do not place undue strain on the gas pipework of the module 3 4 Combustion Air Supply If the duct heater or air handling unit is installed internally in buildings having a design air change i 24 0 ateach burner rate of less than 0 5 h and in heated spaces having a volume less than 4 7 m kW of total rated heat input grilles shall be provided at low level as follows The total minimum free area shall not be less than 270cm plus 2 25 cm per kilowatt in excess of 60 kW rated heat input The air vent s should have negligible resistance and must not be sited in any position where it is likely to be easily blocked or flooded or in any position adjacent to an extraction system which is carrying flammable vapour Where the duct heater or air handling unit is to be installed in a plant room there must be permanent air vents communicating directly with the outside air at high level and at low level Where communication with the outside air is possible only by means of high level air vents ducting down to floor level for the lower vents should be used Air vents should have negligible resistance and must not be sited in any position where they are likely to be easily blocked or flooded or in any position adjacent to an extraction system w
5. CE DHM Range Commissioning And Servicing Instructions WARNING THIS APPLIANCE MUST BE EARTHED DHM Range C amp S Issue 6 September 2002 1 INTRODUCTION The Powrmatic DHM range are multiple tube heating modules designed for insertion into duct heaters air conditioning plant and similar units Each module comprises a number of gas fired forced draught burners and a single exhaust gas fan venting into a closed flue system Each burner tube assembly in a module is rated at 40 kW 20kW 15kW or 10kW output DHM X 20 units are certified for use on Natural Gas Group H G20 and Propane G31 and are Cat Il 435 Note Conversion from one gas to another is factory completed DHM X 10 DHM X 15 and DHM X 40 units are certified for use only on Natural Gas Group H G20 and are Cat 2 Technical Data 2 1 Dimensions 2740 DHM40 2280 DHM15 20 1630 DHM10 E Cea 20 2300 DHM40 1800 DHM15 20 1160 DHM10 URNER ASSEMBLY ry 6 6 A ie 6 6 See below INN AIAN wi LJ hol ho Ly ei Fin ty a REAR HEADER TUBE FRONT GAS MANIFOLD BURNER END Gas connection size R1 i gt 7 EXHAUST FAN ASSEMBLY
6. Section 2 If necessary adjust the burner gas pressure by turning the adjustment screw on the side of the valve See Fig 2 5 Turn OFF the main electricity supply remove pressure gauge and refit sealing screw in pressure test point Repeat for the remaining burners in the module With all burners running check the CO2 content of the flue gases which should be in the range of 7 5 8 5 7 Turn OFF the main electricity supply and refit flue sample point cover plug OD 4 4 Final Soundness Test 1 After making final gas rate checks all joints on the gas controls assembly must be tested for soundness using leak detection fluid 4 5 Flame Safeguard 1 Whilst the burner is in operation close the gas service valve The burners should go to lockout within 1 second 4 6 User Instructions The Users instruction supplied with the module are for the end customer and must be supplied with the module 5 Servicing The DHM unit should be serviced once per year WARNING Always switch off and isolate the incoming electrical supply and close the gas service valve before carrying out any servicing work 5 1 General Full maintainance should be undertaken not less than once per year After any service work has been completed or any component replaced the unit should be recommissioned as detailed in Section 4 5 2 Burners 1 Remove the heat shield if fitted situated between the exhaust fan and burners contols section
7. f each burner a Connect pressure gauge to the inlet pressure test point on the gas manifold b Open gas service valve and allow pressure to stabilise before shutting it again The valves are sound if no pressure drop is observerved If a pressure drop is observed do not proceed until the fault has been rectified Remove pressure gauge and refit sealing screw in pressure test point 4 3 2 Sequence Check 1 Ensure that the gas service valve is closed and that the main electrical supply to the module is switched off 2 Aei that all external controls are calling for eat 3 Turn ON the main electrical supply and check that the following sequence of events occurs i Exhaust fan runs Then for each module i Ignition spark is heard ii Main gas valves open iii Burner goes to lockout as there is no gas supply Reset from lockout 4 Switch off main electricity supply 4 3 3 Final Adjustment 1 Remove the sealing screw from the pressure test point located on the gas valve of the first burner and attach a pressure gauge Remove the sample point cover plug from the outlet flue length and insert a CO2 measuring instrument 2 Turn ON the main electricity supply via the duct heater air handler controlsand check that the following sequence of events occur i Exhaust fan runs ii Ignition spark is heard iii Main gas valves open iv Main gas flame is established 3 Check that the burner gas pressure agrees with that in
8. hich is carrying flammable vapour Grilles or louvres should be so designed that high velocity air streams do not occur within the plant room The basic minimum effective area requirements of the air vents are as follows a Low Level inlet For heaters of total rated heat input 60 kW or more 540 cm plus 4 5 cm per kilowatt in excess of 60kW total rated input b High Level outlet For heaters of total rated heat input 60 kW or more 270 cm plus 2 25 cm per kilowatt in excess of 60kW total rated input 4 Commissioning amp Testing Gas Safety Installation amp Use Regulations 1994 It is law that all gas appliances are installed adjusted and if necessary converted by qualified persons in accordance with the above regulations Failure to install appliances correctly can lead to prosecution It is in your own interests and that of safety to ensure that the law is complied with e g Corgi Registered 4 1 Electrical Installation Checks to ensure electrical safety must be carried out by a competent person 4 2 Gas Installation The whole of the gas installation including the meter should be inspected and tested for soundness and purged in accordance with the recommendations of IM 16 1988 4 3 Lighting the Module 4 3 1 Gas Controls Assembly Soundness Check 1 Ensure the gas service valve at the inlet to the gas controls assembly is shut 2 TO prove soundness up to the first main safety shut off valve o
9. ng replacement thermostat NOTE Only the limit circuit is used and the limit set point is 100 c Fig 3 Honeywell L4064N Limit Thermostat Fan Circuit Set Point Dial Limit Circuit Summer Limit Reset Winter Switch Fan Circuit Limit Circuit J umper Location Action A UJ N e eNe amp WwW Nr Check that there is a main electrical supply present Check that all external control circuits are completed Check that high limit thermostat has not tripped reset Check that mains voltage is present at fan motor change fan if faulty Check full sequence is not at lockout reset Check full sequence controls for mains supply change if necessary Check that exhaust fan and burner air pressure switches are activated Check spark electrode and spark gap Check rectification electrode lead signal Check gas supply is ON Check overrun thermostat Refer to Powrmatic Ltd for the details of any parts not listed here ITEM Gas Valve SIT 830 Tandem 0833033 1 2 BSP Full Sequence Control SIT 503EFD Thermostat Limit Honeywell L4064N Thermostat Exhaust Fan RS 331 540 Exhaust Fan AD 90BWTLG90 x 40 modules Exhaust Fan AD 71DTXL x 20 modules Exhaust Fan AD 52BTXL x 10 amp x 15 modules Pressure Switch Kromschroder DL5K Pressure Switch Honeywell C6065A1028 2 Electrode Rectification Johnston Controls Electrode Ignition Johnston Controls Rela
10. o the exhaust fan overrun thermostat situated on the fan casing Remove the electrical connections from the exhaust fan motor Remove the pressure switch impulse pipe Disconnect flue system from exhaust fan outlet Remove the four set screws securing the fan inlet tube to the fan and the two screws ae the fan support bracket to the bulk ead re 8 Gas Inlet Inspect the fan blades and if necessary remove any deposit build up using a stiff brush Reassemble in reverse order 5 4 Replacement of Faulty Components 5 1 A 2 ro e w Sow S w NEU S w O ON A A 1 Full Sequence Control Remove the single screw retaining the control to the gas valve Remove the top of the contol and pull off the electrical connection plugs and the spark and rectification leads Remove the control from the gas valve by pulling upwards Refit replacement in reverse order 2 Electrode Assembly Release the screw retaining the top cover of the associated gas control Remove the top of the contol and pull off the Spark and rectification leads Remove the screw on the front face of the electrode assembly and remove assembly Refit replacement in reverse order 3 Gas Control Valve Burner Injector Complete steps 5 2 1 to 5 2 5 Remove the screws securing the pressure switch bracket to the gas valve Seperate the burner end cap injector holder from the body of the burner Unscrew the cup burner and remove the b
11. urner end cap from the injector Remove the injector from the gas valve Remove the inlet pipe from the gas valve Reassemble in reverse order using new items as required and a new cork gasket on the 8 5 l 2 manifold flange Replace heat shield if fitted 4 4 Exhaust Fan Complete steps 5 3 1 to 5 3 7 Reassemble in reverse order using replacement fan 5 4 5 Exhaust Fan Overrun Thermostat 1 Pull off the electrical connections from the thermostat 2 Remove the two securing screws 3 Reassemble in reverse order using new thermostat 5 4 6 Exhaust Fan Pressure Switch 1 Remove the impulse pipe from the pressure switch 2 Remove the pressure switch cover and disconnect the wiring 3 Remove the screws securing the pressure switch mounting bracket to the controls panel 4 Remove the bracket from the pressure switch 5 Reassemble in reverse order using replacement pressure switch NOTE Impulse pipe is connected to suction tapping Pressure switch set point is 2 0mb 6 Fault Finding Fault Cause Exhaust fan does not run Electrical No spark ignition Electrical Burner will not light Electrical Exhaust fan runs continuously Electrical 7 Short List of Parts 5 4 7 Limit Thermostat 1 Remove the single screw securing the thermostat cover 2 Remove the electrical connections 3 Remove the screws securing the thermostat to the bulkhead and withdraw the thermostat 4 Reassemble in reverse order usi
12. y Finder 60128230 PART NUMBER 142400444 145601045 143000303 147600001 140201504 140201502 140210500 145604643 146522170 142400625 142400625 143000813 BSI Registered Firm wrmatic lt 6 Ind amp Comm Air Heaters Air Moving Equipment Es y a Flues amp Chimneys Natural F 8 Powered Supply amp extract G V ow Fans amp By stems 0 lt gt HEATING DIVISION Winterhay Lane Ilminster Somerset TA19 9PQ Tel 01460 53535 Fax 01460 52341 Every effort is made to ensure accuracy at time of going to press However as part of our policy of continual product improvement we reserve the right to alter specifications without prior notice
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