Hamworthy Spetisbury Installation, Commisioning And Maintenance Instructions

Hamworthy Spetisbury Installation, Commisioning And Maintenance Instructions Manual pdf 12 page image

HAMWORTHY HEATING LTD6SPETISBURY 500001118/C8.0 WATER CIRCULATION SYSTEM8.1 GeneralRecommendations for the water circulation system aregiven in BS 6644 and CP 342. The following notes areof particular importance:-1) In a combined central heating and hot water system,the hot water storage vessel must be of the indirectcylinder or calorifier type. The hot water storage vesselshould be insulated preferably with not less than 75mm(3 in) thick mineral fibre, or its thermal equivalent.2) Circulating pipework not forming part of the usefulheating surface should be insulated to help prevent heatloss and possible freezing, particularly where pipes arerun through roof spaces and ventilated cavities.Cisterns situated in areas, which may be exposed tofreezing conditions, should also be insulated. Insulationexposed to the weather should be rendered waterproof.3) Drain valves must be located in accessible positionswhich permit the draining of the whole system, includingthe boiler and hot water storage vessel.4) Each boiler has 4” N.B. Flanged flow and returnconnections located on the rear section of the boiler.Mating flanges are supplied suitable for welding to 4”NB pipe.5) Multiple boilers should be connected by flow andreturn headers. Headers should be connected to thesystem in a "reverse return" arrangement (the waterflow in each header is in the same direction) to ensureequal flow in each module.8.2 Pressure Relief Valve (Safety Valve)The most important single safety device fitted to a boileris its safety valve and each boiler, or in the case of amodular installation, each bank of boilers, must be fittedwith a pressure relief valve to BS 759 or BS 6759 Part 1(ISO 4126) and sized as shown in BS 6644.BS 6644 provides comprehensive information for theselection and location of safety valves and attention isdrawn to the higher capacity requirements of safetyvalves for pressurised hot water systems.8.3 Open Vent and Cold Feed Pipe(See BS 6644 for further information.)Every boiler or group of boilers should have an openvent pipe and cold feed pipe installed between the boilerand the first water isolating valve. The minimum bore(mm) of these pipes per installation are detailed inFigure 8.3.The vent pipe must rise continually, must not be valvedexcept by a design which when closed for maintenancethe boiler is open to atmosphere. The pipe shall beprotected against freezing where this might occur.8.4 Altitude Gauge (Water Pressure Gauge)Every boiler or group of boilers should be providedwith a gauge complete with isolating valve. SeeFigure 15.1 for typical position.7.0 AIR SUPPLYDetailed recommendations for air supply are given inBS 6644. The following notes are intended to givegeneral guidance. In all cases there must be provisionfor an adequate supply of air for both combustion andgeneral ventilation, in addition to that required for anyother appliance.7.1 Air Supply By Natural VentilationThe boiler room must have, or be provided with,permanent air vents directly to the outside air, at highlevel and at low level. For an exposed boiler house, airvents should be fitted preferably on all four sides, but atleast on two sides. Air vents should have negligibleresistance and must not be sited in any position wherethey are likely to be easily blocked or flooded or in anyposition adjacent to an extraction system which iscarrying flammable vapour. Grilles or louvres must beso designed that high velocity air streams do not occurwithin the space housing the boiler.The air supplied for boiler house ventilation shall besuch that the maximum temperatures within the boilerhouse shall be as follows:1) At floor level (or 100 mm above floor level)= 25 °C.2) At mid-level (1.5 m above floor level)= 32 °C.3) At ceiling level (or 100 mm below ceiling level)= 40 °C.Where both low and high level openings are used, thegrilles shall have a total minimum free area of :-Low Level (inlet) 540cm2 plus 4.5cm2 per kW in excessof 60 kW total rated input (gross).High Level (outlet) 270cm2 plus 2.25cm2 per kW inexcess of 60kW total rated input (gross).7.2 Air Supply By Mechanical VentilationAir supplied to the boiler room by mechanical meansshould be as follows :-1) Mechanical inlet and mechanical extract can beutilized providing design extraction rates comply withFigure 7.1.2) Mechanical extract ventilation with natural inletventilation MUST NOT be used.NOTE: For mechanical ventilation systems anautomatic control should be provided to cut off the gassupply to the boiler, in the event of failure of air flow ineither inlet or extract fans.Forced DraughtBoilers Inlet air(CombustionVentilation)Extract air(Ventilation)m 3/s m 3/sVolume 0.9 0.6Flow Rate per 1000 kWFigure 7.1 Mechanical Ventilation Flow Rates