Hamworthy Wessex 220 M SeriesHigh Efficiency, Fully Modulating, Pre-mix Gas Fired Modular Boilers Outputs 220kW, 440kW and 660kW

up to

Gross efficiency(100% Nett)

91%

BU

ILDING REGULATION

S

PA

RT

L COMPLIANT

2

High Efficiency, FullyModulating, Pre-mix GasFired Modular Boilers Natural Gas or LPG

Wessex 220 M Series

Since the early 1980’s Hamworthy hasled the way in development of highefficiency pre-mix modular boilers.The latest in the line is the newWessex 220 M Series which builds onthe success of the innovative Wessex100 M Series.The output of each module has beenincreased from 200kW, on Wessex HEboilers, to 220kW on the Wessex 220M Series and the burner is now fullymodulating, packing in more powerand increasing the control to matchthe load even closer.Designed to meet the requirements ofnew build and refurbishment projects,the Wessex is a well proven, reliableBritish product, which has come ofage with the latest amendments to theBuilding Regulations (2001). TheHamworthy Wessex range has beenachieving efficiency performancebeyond these latest regulations forover twenty years and throughinvestment in product developmentand continuous improvement, theevolution in design has maintained itsposition at the forefront of boilertechnology.The Wessex 220 M Series usesbuilding blocks of 220kW modules ina matrix configuration which enablesboilers to be assembled in one, two orthree high arrangements andpositioned closely together side byside.There are three models in the series,M220, M440 and M660 with outputsof 220kW, 440kW and 660kWrespectively.

Fully Compliant with Building Regulations Part L

Qualifies for Enhanced Capital Allowances*

Closely matches heat load to demand

Rapid response and ultra low standing losses

Extremely economical with space

Ease of handling on site

Reduced installation costs

Pipework Kits for fast turnaround BE

NE

FIT

S

OptionsModulating sequencecontroller

LPG - propane

Pipeworks kits

The Wessex M Series of high efficiency

boilers exceed the requirements for the

latest Building Regulations, (Amendment

2001), Part L (England & Wales) and Part J

(Scotland)

*on loads over 400kW

2 Wessex 220 M660 boilers with manifold kits fitted

3

High Efficiency SystemThe central component to theHamworthy design is a heat exchangerthat can generate a highly efficient gasto water heat transfer, through acylindrical extended surface heatexchanger constructed from finnedcopper tubes. To ensure an equal flowthrough each tube, sectioned endplates are incorporated into thedesign.

Your solution to meeting Part L (Part J in Scotland)Using high efficiency boilers is a simple reliable solution to meeting Part L inrefurbishment projects.More often than not, the original heating system design was based on 80°C flowtemperature from the boiler. This does not fall within the normal operating rangeof condensing boilers, therefore, unless the entire heating system is redesigned,then it is unlikely that the full benefits of a condensing boiler will be achieved.The Wessex range of high efficiency boilers from Hamworthy produces exceptionalperformance, with full load efficiency up to 84% gross (93% nett) and part loadefficiency up to 91% gross (100% nett).This level of performance enables the designer to use the energy performance ofthe boiler to compensate for a lower level of performance in the building fabric,such as insulation or glazing, and yet easily comply with the requirements of thelatest Building Regulations.

System Temperature

50°C

High

High

Bo

iler

Eff

icie

ncy

Condensing

Traditional

High Efficiency

The Wessex 220 M Series boilersfeature a fully modulating premixburner control system. An electronicthermostat monitors the boileroperating conditions andautomatically adjusts the output tosuit. The gas/air ratio control systemensures that clean and efficientcombustion is maintained throughoutthe maximum modulation range,down to a minimum of 20%.Fully automatic ignition is achievedutilising a hot surface ignition system.This highly effective and reliable formof ignition requires less maintenancethan conventional spark ignition andeliminates the electrical interferencesometimes associated with that typeof system. Flame proving is achievedusing a flame rectification probe.The controls are housed within afabricated steel enclosure, whichfeatures a visual display allowing theuser to monitor the current operatingstatus of the boiler.All boilers are fitted as standard with

volt free contacts, which allow forremote monitoring of the boiler status,indicating boiler run, lockout & hightemperature conditions.The compact design achieves up to880kW output per square metrefloorspace, which significantly reducesthe plant room size when compared totraditional cast iron boilers.Wessex 220 M Series boilers aresupplied fully assembled from thefactory therefore eliminating boilerbuilds on site. The assembled boilercan be easily manoeuvred using apallet truck and will pass through astandard single doorway.

Gas to Water Heat TransferThe copper finned tubes of theWessex heat exchanger provide theperfect ratio of eight times moresurface area on the gas side comparedto the water side. In addition to this,copper is an ideal heat exchangermaterial being 8.5 times moreconductive than cast iron or steel. It isalso compatible with system waterand offers resistance to flue gascorrosion.

Rapid ResponseThe superior rate of heat transfer ofthe Wessex boilers means that theremoval of that heat requires anincrease in the flow rate of water. Thisresults in a smaller boiler with reducedwater content. The combination ofthis low volume and high watervelocity not only keeps solids insuspension, but increases the speed atwhich the boiler responds.

Water flow through multi-pass copperfinned heat exchanger Access via a single door

4

Heat ExchangerAll Wessex models have a highlyefficient cylindrical primary heatexchanger constructed from copperfinned tubing. The tubes areexpanded at each end into cast irontube plates. These tube plates aresectioned to provide even flowthrough each tube in a multi-passarrangement.The relatively large 22mm diametertubes combined with the high waterflow velocities considerably reducesthe risk of blockage in comparisonwith alternative heat exchangerdesigns, which have smallerwaterways.

BurnerA cylindrical woven fibre burner ispositioned centrally within the primaryheat exchanger. This design of burnerallows for good flame stability at lowturndown rates. The woven fibreconstruction of the burner also resultsin lower flame temperatures beingachieved and thus lowers NOxemissions.

Low NOxAn area crucial to the success ofreducing NOx emissions is the burnerdesign and its ability to evenlydistribute the excess air requiredduring the combustion process.In designing the burner, Hamworthytook consideration of the requirementfor low NOx production, and anyanticipated EC legislation.Here the correct air/gas mixture isachieved before entering the burnerbar, and can effectively provide flamesthrough the 360° of it’s surface.By pre-mixing the air and gas prior toignition, the excess air required isevenly distributed achieving a moreeven temperature. This process resultsin low NOx production and is furtherassisted by the superior heat transferqualities of the copper fins which keepthe combustion chamber cool.Hamworthy Wessex boiler NOxemissions are low, achieving Europeanclass 5 performance.

Specification

Section of primary heat exchanger tube

Water SystemThe Wessex is designed toaccommodate high rise applicationsand has a maximum working pressureof 10 bar.Each module is supplied with aconnection for fitting a pressure andtemperature relief valve, (notHamworthy supply).Where the boiler feed water has ahigh degree of hardness, it isrecommended that the water betreated to prevent precipitation ofscale or sludge in the boiler waterpassageways.

The Gas TrainA zero governor gas valve is used toprecisely control the mixture of gasand air entering the burner as thefiring rate modulates. This is achievedby measuring the pressure drop acrossa venturi at the fan inlet and adjustingthe gas pressure accordingly.

FlameTemperature

Premix

Combustion Air IntakeIncoming combustion air is pre-heatedby directing the flow through theinnovative casing design, contributingto the efficiency performance. Theflow of combustion air also serves toinsulate the boiler casing panels andremoves the need for insulationmaterial in the casing.

ThermostatsAll Wessex 220 M Series boilers arefitted with a manual reset limitthermostat, which has a range of 90-110°C. This will normally be factoryset to 95°C.An electronic temperature controlthermostat regulates the boiler flowtemperature up to a maximum of90°C. The control thermostat alsooperates as a push button on/offswitch.To accommodate multiple boilerinstallations the limit thermostat isadjustable up to a maximum of 110°Cwhere the boiler control thermostatsare to be set higher than 83°C,adequate system pressure must beavailable either by gravity head orsystem pressurisation.For further details of multiple boilers,system pressures and temperaturesplease refer to Hamworthy publication500002194, Energy Efficient MultipleBoiler Systems.

Hot Surface IgnitionThe Wessex M Series boilers have afully automatic direct burner ignitionsystem that employs a hot surfaceignition element. Using hot surfaceignition eliminates the electricalinterference sometimes associatedwith traditional spark electrodes. Inaddition it also requires lessmaintenance than a spark electrode.

Hot surface ignitor and flame probe.

5

Pipework manifold kitsAs with all Hamworthy products, thepipework kits are designed with thecomplete solution in mind. TheWessex 220 M series is available withoptional pipework kits to make theboiler installation quicker and easier toenable the contractor to save time inthe plant room during installation.

Contrary to popular practice, thepipework can be installed before theboilers are put in place. This reducesthe possibility of damage to the boilercasings during pipework installationand gives the contractor more roomto work in the plant room.

The M440 and M660 water and gasmanifold pipework kits are freestanding and incorporate all necessaryvalves, inter connecting pipework, andflexible flow and return connections.

The water manifold kits are for hotwater heating installations up to100°C maximum temperature and allcomponents are pressure tested priorto despatch from our works.

The water manifold kits are intendedfor use in reverse return configuration.The Wessex 220 M Series boilers havea low water content and water flowrates must be maintained at or abovethe levels shown in the technical datatable for the boilers. A suitablepressure relief valve (not Hamworthysupply) must be fitted to each boilermodule before connecting the watermanifold assembly.The main pipework kit is designed forease of handling and is delivered to

site in a kit form which utilises a steelbase arrangement similar to the boilerfor ease of handling and to facilitatealignment with the boiler.

Our BS EN ISO 9001 accreditationensures that our products aredesigned and manufactured to ourconsistently high standard.

All Hamworthy boilers have EuropeanCertification and bear the CE mark,the customers assurance of conformitywith European standards.

Power SupplyAn independent isolator and fusedelectrical supply is recommended foreach module, to enable each moduleto be shut down without losing theentire boiler output.230 volt, 50Hz single phase.

Remote SignallingVolt free contacts are fitted asstandard to all models to indicateboiler lockout, high limit lockout and

normal run. The contacts are BMScompatible and allow the boiler toconnect to a Building ManagementSystem to monitor boiler operationand status.

Condensate DischargeDue to the high thermal efficiency ofthe boiler, condensation will occurwithin the boiler casing during firingfrom cold conditions. A drain with anintegral trap is fitted to the rear centreof each module to enable the disposalof the condensate.The connection to the trap is Rp1/2”.The drainpipe must be manufacturedfrom a non corrosive material and beat least 22mm diameter. The pipeworkshould be installed with at least a 3°fall (approximately 50mm per metre)and connect via a tundish to a drain.In addition to the boiler condensatedrain, the M440 and M660 modelshave a condensate drain connectionfitted to the close-coupled flue header.This is a 22mm diameter drain stubwhich should be connected in asimilar manner via a suitable trap.

Low weight designThe boiler’s lightweight design,compared with traditional cast ironsectional boilers, offers perfectsolutions for roof top installationswithout the need for excessivestructural reinforcement. Around one-third of the weight ofconventional boilers, the Wessex 220M series weighs in at approximately1kg per kW output.Its compact dimensions and basedesign enable it to be easilymanoeuvred, using a standard pallettruck, through a normal sizeddoorway

PumpsHamworthy Heating is now the exclusive distributor of Biral pumps in the UK.With a wide range of models available, you can closely match pump performanceto suit your requirements.

The high quality design with innovative features include:• Unique Can system – no seals to leak• Low, medium and high speed ranges• High torque starting• Ultra low power consumption• Flat performance curves – less system noise• Operating pressures up to 16 bar• Temperatures from -20°C to 140°C• Whisper quiet pump operation

Talk to HAMWORTHY BIRALyour new partners in pumps

6

Sequence ControlUsing a number of smaller boilers(modules) in order to accurately matchthe required load is acknowledged asan excellent approach to heatingsystem design. In order to get the fullbenefit from a multiple boilerinstallation it is essential to fit someform of sequence control to regulatethe firing of each module.The Milton sequence control panel hasbeen specifically designed to controlfully modulating boilers such as theWessex 220 M Series.

The Milton can control the operatingpattern of up to 9 modules firing infully modulating mode. The unit isenclosed in a compact lightweightcasing and is designed to be installedon a boilerhouse wall or any otherlocation within the building.In addition to providing sequencecontrol the Milton is also capable ofdirect weather compensation andoptimised boiler start. These featuresrequire optional external and roomsensors to be fitted, and enablefurther energy savings to be achieved.

DeliveryWessex 220 M Series boilers aresupplied fully assembled from thefactory. The assembled boiler can beeasily manoeuvred using a pallet truckand will pass through a standardsingle doorway.The M440 and M660 models aresupplied with a separate close-coupledflue header, which has to be fitted tothe boiler on site.

Electrical detailsSupply 230V 50Hz, single phase. Wiring external to the boiler must beinstalled in accordance with I.E.E.regulations and any local regulationswhich apply. Wiring must becompleted in heat resistant 3 corecable, ( size 1.0 mm2 c.s.a.). Fasciafuse rating is 2 amp. An isolatorcorrectly fused at 5 amps should besited close to the boiler, for eachmodule.

Time clock controlWhere boilers are operated from timeclocks, to avoid overheating andprogressive calcium deposition at zeroflow conditions, provision should bemade for a 5 minute circulating pumpover run after the last boiler hasceased firing.

Enhanced Capital AllowancesAs part of the Climate ChangeProgramme the Government introducedEnhanced Capital Allowances (ECA) inApril 2001, coinciding with theintroduction of the Climate Change Levy.Companies that are liable to paybusiness or corporation tax may benefitfrom Enhanced Capital Allowancesthrough improved cash flow as a resultof a reduced tax demand in the firstyear of investment in qualifying plant.The normal method of a reducingbalance capital allowance would spreadthe benefit over a longer period, wheretypically 95% of the cost would berelieved in a period of 8 years. TheEnhanced Capital Allowance enables100% of the allowance to be claimed inthe first year.

This benefit should encourage designersto specify more energy efficient boilersfor their client. All Hamworthy Wessexboilers are eligible for the allowancewhere specified on loads over 400kWoutput, and other costs directlyassociated with the provision of theboiler may be included in the ECAclaim.For further details on the EnhancedCapital Allowance scheme, please referto Hamworthy publication AAG 001, or visit the GovernmentECA web site at www.eca.gov.uk

Milton sequence controller for fullymodulating boilers

Flue SystemEach of the boiler variations isdesigned for direct connection to aflue system. M440 and M660 modelsare supplied with a separate close-coupled flue header, and the outletsfrom more than one boiler may beconnected to a single chimney.A fixed draught diverter is notrequired in the flue system, however, adraught stabiliser is recommended forsome installations.Refer to page 15 for further details.

The Wessex 220 M Series complements the range of high efficiency boilersmanufactured by Hamworthy, satisfying the high output end of the range.Mid-range there is the Wessex 100 M Series, which utilises 100kW modules in thesame compact design.To satisfy the smaller outputs, Hamworthy has designed the Sherborne wall hunghigh efficiency fully modulating pre-mix boiler (65kW output), which can be openflued or fitted with a room sealed balanced flue.For further details of Wessex 100 M Series boilers please refer to publication500002184, and for Sherborne boilers refer to publication 500002216.

7

Technical dataWessex 220 M Series - Performance and General Data Information - Natural Gas

Boiler output - maximum kW

Btu/h x 1000

220

750

M220

1

Boiler Model

Number of Modules

M440

2

M660

3

440

1501

660

2252

262

894

524

1788

787

2685

236

805

472

1610

708

2416

44

150

Boiler input (gross) - maximum kW

Btu/h x 1000

Boiler input (nett) - maximum kW

Btu/h x 1000

Module output - minimum kW

Btu/h x 1000

System design flow rate across boiler @ 11°C ∆T rise l/s

Water content (not including headers) litres 17 34 51

4.78 9.56 14.33

3.50 7.01 10.51

64

34.5

10

24.99 49.97 74.96

20

25

329 659 988

135

G21/2” male

R1”

230V AC 50Hz 1Ph

250 500 750

Minimum flow rate @ 15°C ∆T rise l/s

Waterside pressure loss @ 11°C ∆T rise mbar

Waterside pressure loss @ 15°C ∆T rise mbar

Maximum water pressure barg

Gas flow rate natural gas (G20) - maximum m3/hr

Nominal gas inlet pressure natural gas (G20) mbar

Maximum gas inlet pressure natural gas (G20) mbar

Approx. flue gas volume @ 8.7-9.3% CO2 m3/hr

Approx. flue gas temperature °C

Water flow/return connections

Gas inlet connection pipe thread size

Normal supply voltage

Power consumption - maximum W

Nominal flue diameter (I/D) mm

inches

153

6

254

10

305

12

En

erg

yW

ater

Gas

Flu

eC

on

nec

tio

nE

lect

rics

1.07

220 430 635

Module start and run current Amp

Approx. shipping weight kg

NoX

Emission (DAF) mg/kWh

ppm

<51

European Class 5 <29

8

Dimensional DetailsWessex 220 M Series - Boiler Dimensions/Clearances

70050

700

900

600

400

400

865

700

666 30

128

6F

low

Ret

urn

1088

Flue153 I/D

583

80540

Flue (M220 only)

254 I/D

1549

1406

301

827

Flo

wR

etur

n

1454 223

325

499

611

541

crs.

1946

FlowG2 /2” Male

Return

R 3/4” PressureRelief Valve(1 per module)Valve Not HHL Supply

2085

305 I/D

301

Flo

w

Rp1” Gas(1 per module)

23 DIACondenseDrain(1 per module)

1368

Ret

urn

Flue

2 x M440 880kW

2 x M660 1320kW

2 x M220 440kW

3 x M220 660kW

1320kW3 x M440

3 x M660400

for access

1980kW50

M220

M440

M660

9

180

747 TYP

SIDE VIEWFRONT VIEW

REAR OFBOILER

Flow & returnconnection 150 NBPN16 flange (BS4504)

1946

BO

ILE

R O

UT

LIN

E

568

179270

1595

1775

844

644

120BOILER

C

700 BOILER OUTLINE

FLOW

2" BSP Gas connection

GAS PIPE

RETURN

700 BOILER OUTLINE

FRONT VIEW

566

1406

BO

ILE

R O

UT

LIN

E

BOILER

747 TYP

FLOW

2" BSP Gas connection

179270

RETURN

SIDE VIEW

644

844

180

1054

1234

REAR OF BOILER

Flow & returnconnection 150NB PN16 flange (BS4504)

120

GAS PIPE

74776

844

644

680Boiler outline

Dimensional DetailsWessex 220 M Series Water Manifold Kits

PLAN

10

Application & System dataThe installation of all boilers MUST bein accordance with the relevantrequirements of the Gas SafetyRegulations, Building Regulations,I.E.E. Regulations and the bye-laws ofthe local water undertaking. It shouldalso be in accordance with anyrelevant requirements of the local gasregion, local authority and relevantrecommendations of the followingdocuments:

British StandardsBS7074: Application, selection andinstallation of expansion vessels andancillary equipment for sealed watersystems.Part 2: Code of practice for low andmedium temperature hot watersystems.BS6644: Installation of gas fired hotwater boilers – 60kW to 2MW.BS6700: Design, installation, testingand maintenance of services supplyingwater for domestic use.BS6880: Part 1, 2 & 3: Code ofpractice for low temperature hotwater heating systems of outputgreater than 45 kW.BS EN 60335: Part 1. Safety ofhousehold & similar electricalappliances. BS 3456: Part 201: ElectricalStandards.CP 342: Centralised hot water supply.Part 2: Buildings other than individualdwellings.

I.Gas E. PublicationsIGE/UP/1 Soundness testing andpurging of industrial and commercialgas installations.IGE/UP/1A Soundness testing anddirect purging of small low pressureindustrial and commercial natural gasinstallations.IGE/UP/2 Gas installation pipework,boosters and compressors in industrialand commercial premises.IGE/UP/10 Installation of gasappliances in industrial andcommercial premises Part 1 fluedappliances.

Boiler AccessoriesWessex boiler modules are supplied with control and high limit thermostats. The followingitems (not supplied) should be fitted to the boiler pipework system to satisfy BritishStandards. Each isolatable module or arrangement of modules, should have a drain cock atthe lowest point, a pressure relief valve and an open vent, (or high/low pressure switcheson closed systems). An altitude gauge and temperature gauge should be fitted to the flowmanifold beyond the entry of the last module but before any branches to different circuits.If a sequence control panel is fitted, the flow temperature sensor should be fitted in asimilar position.

Boiler baseWessex boilers should be positioned on a level non combustible surface that is capable ofadequately supporting its weight (when filled with water) and any ancillary equipment.Adequate space for installation and servicing should be considered. Clearance details areprovided on page 6.

Water systems - Modular installationsWessex modular boilers are suitable for installation in both open vented and closedsystems. Irrespective of the type of system, the water flow and return headers should beconnected in a “reverse return” arrangement (i.e. the water flow in each header followsthe same direction) thus providing equal flow through each boiler. This also ensures thatpressure loss across any number of boilers will never be greater than the head loss acrossone boiler plus local pipework losses.

Flow

Return

Module 1 Module 2 Module 3

Adequate water flowHamworthy Wessex modular boilers are designed as high efficiency, rapid response,low water content units. Care must be taken with initial system design and layoutto ensure that there is adequate waterflow through each module, and that theinfluence of the system control does not adversely affect that flow at any time.A minimum flow rate equal to 80% of the quoted design flow must be maintainedat all times when the burner is firing.

System feed water qualityIf the boiler feed water has a high degree of hardness, it is recommended that thewater be treated to prevent precipitation of scale or sludge in the boiler waterpassages. Details of additives can be obtained from any specialist water treatmentmanufacturer or local water authority.When Wessex units replace boilers in an existing system, it is important that theexisting system is thoroughly flushed through tfitted with isolating valves andinspected regularly after commissioning.

Wessex modular boilers in “reversereturn arrangement”

Guidance Note PM5 Health andSafety Executive This note states that “hot waterboilers should have an automaticcontrol apparatus to cut off fuel tothe burners of gas fired plant whenthe water at or near the boiler flowoutlet rises to a pre-determinedtemperature. This should provide amargin of at least 17°C below thetemperature of saturated steamcorresponding to the pressure at thehighest point of the circulation systemabove the boiler.” To comply with thisrecommendation, the minimumsystem pressure is dependant onsystem design flow temperatures andin the case of modular installations,the temperature rise across eachmodule.

Single installationsThe minimum pressure must be equalto the gauge pressure equivalent tothe saturated steam temperatureobtained by adding 17°C to therequired boiler flow temperature. Thehighest point of the circulation systemabove the boiler should never be lessthan 2m (6.5ft).

Required flow temperature 90°CSafety margin 17°CEquivalent saturated steam temperature 112°C

From steam tables correspondinggauge pressure - 0.50 bar (7.3 psi)- 5.1m (16.7ft) head of water.

Modular installationsThe minimum pressure should beequal to the gauge pressure equivalentto the saturated steam temperature.This is obtained by adding 17°C to thesum of the required mixed flowtemperature plus the temperature riseacross the modules.

Required mixed flow temperature 82°C Temperature rise acrossmodules at minimum flow rate 11°C Safety margin 17°CEquivalent saturated steam temperature 110°C

From steam tables correspondinggauge pressure 0.42 bar (6.1 psi) -4.3m (14ft) head of water.

CommissioningHamworthy Heating stronglyrecommends that all boilers arecommissioned by their servicedepartment. On completion,Hamworthy will issue a boiler log bookwhich will provide details of the initialoperating settings. The log bookshould be used to record any futuremaintenance and service work.For more information oncommissioning contact HamworthyHeating Service Department:01202 662555

Air supply and ventilationAn adequate supply of fresh air forcombustion and ventilation must beprovided in accordance with BS 6644.The air supply should be free fromcontamination such as buildingdust and insulation fibres fromlagging. To avoid unnecessarycleaning and servicing of the boilermodules, we recommend that theboilers are not fired whilstbuilding work is being undertaken.

The air supply should be achievedusing:

Natural ventilation supplying air with a low level opening and discharge through a smaller sized high level opening.

A fan to supply air to a low level opening with natural discharge through a high level opening.

A fan to supply air to a low level opening and discharged by means of a fan at a high level.

Note: Fans must be selectedsuch that a negative pressure isnot created in the boilerhouserelative to outside air pressure.The air supplied for boiler houseventilation should be such that themaximum temperatures within theboiler house are as follows:At floor level 25°C (or 100mm above the floor level) At mid level 32°C(1.5m above floor level)At ceiling level 40°C(or 100mm below ceiling level)

Where natural ventilation is usedsuitable permanent openings at lowlevel and high level connected directlyto the outside air should be provided.These openings must be fitted withgrilles that cannot be blocked orflooded.

The free area of the grilles should beas follows:Low Level (Inlet) 540cm2 plus 4.5cm2 per kW in excessof 60kW total rated input. High Level (Outlet)270cm2 plus 2.25cm2 per kW in excessof 60kW total rated input.

11

System Head

Open vent pipe and cold feed pipe

Boiler Open vent size Cold feed size

<60kW 25mm (1in) 19mm (3/4 in)

60kW-150kW 32mm (11/4 in) 25mm (1in)

150kW-300kW 38mm (11/2 in) 32mm (11/4 in)

300kW-600kW 50mm (2in) 38 (11/2 in)

660kW 55mm 50mm

Pressure relief valveEach boiler, or in the case of a modular installation, each bank of boilers mustbe fitted with a pressure relief valve to BS759 or BS6759 Pt.1 and sized asshown in BS6644.BS6644 provides comprehensive information for the selection and location ofsafety valves and attention is drawn to the higher capacity requirements ofsafety valves for pressurised hot water systems.

12

System DesignThe installation of modular boilers in commercial and industrial heating and hot water systemsoffer a wide choice of design options and applications. The following systems shown are typicaland should be considered for general guidance.

Example 1Heating only; with separatetemperature compensation on eachzone.

Example 2Combined heating and domestic hotwater with diverting valve on DHWand mixing valve on heating.

Example 3Split system. Completely separateheating and DHW systems. Multipleboilers under direct temperaturecompensation and a decoupledheating circuit, which may have avariable flow. DHW generated bydirect gas fired water heaters.

WATER SENSOR

FLOW

RETURN

CO

MM

ON

HE

AD

ER

MIXINGVALVE

ZONEPUMP

MIXINGVALVE

ZONEPUMP

HEATINGLOAD

(ZONE 1)

HEATINGLOAD

(ZONE 2)

BOILERPRIMARY

PUMP

BOILER1

BOILER2

BOILER3

MILTONSEQUENCER

21 3COMPENSATOR

COMPENSATOR

CO

MM

ON

HE

AD

ER

WATER SENSOR

BOILERPRIMARY

PUMP

BOILER1

BOILER2

BOILER3

MILTONSEQUENCER

21 3DIVERTING

VALVE

MIXINGVALVE

HEATINGPUMP

DHWPUMP

BYPASS

HEATINGLOAD

POWERSTOCKCALORIFIER

FLOW

RETURN

CO

MM

ON

HE

AD

ER

WATER SENSOR

BOILERPRIMARY

PUMP

BOILER1

BOILER2

BOILER3

MILTONSEQUENCER

21 3

DHW FLOW

DHW RETURN

COLD FEED

DORCHESTER DIRECT GAS FIRED

WATER HEATER

HEATINGPUMP

HEATINGLOAD

OUTSIDE AIR SENSOR

13

FLOAT VALVE

FEEDPIPE

EXPANSIONPIPE

FEED & EXPANSION TANK

VENTED TANK

HEATING LOAD ETC.FLOW

AUTOMATICAIR VENT

MAINSWATER

PUMPRETURN

BOILER

1BOILER

2BOILER

3

FLOW

TEMPERATURE GAUGE

PRESSUREGAUGE

TEMPERATURE GAUGE

SAFETYVALVE

2

3

BOILER 1

PUMP

(ROOF TOPAPPLICATION)

WATER SENSOR

AIRSENSOR

MILTONSEQUENCE

CONTROLLER

DRAIN DRAIN

DRAIN

DRAIN

DRAIN

MAINSWATER

PERMANENTLYCONNECTED DOUBLECHECK VALVE ASSY

COLD FILL CONNECTION

(REMOVE IMMEDIATELY

AFTER FILLING)

ANTIGRAVITY

LOOP

LOCKSHIELD VALVELOCKSHIELD

VALVE

LOCKSHIELD VALVE

LOCKSHIELD VALVE

HAMWORTHYPORTLAND

PRESSURISATIONUNIT

PORTLANDEXPANSION

VESSEL

DRAIN

DRAIN 230 V.A.C.1PH.50Hz

ISOLATED SUPPLY

HEATING LOAD ETC.FLOW

AUTOMATICAIR VENT

AUTOMATICAIR VENT

PUMPRETURN

BOILER

1BOILER

2BOILER

3

FLOW

TEMPERATURE GAUGE

PRESSUREGAUGE

TEMPERATURE GAUGE

SAFETYVALVE

2

3

BOILER 1

PUMP

(ROOF TOPAPPLICATION)

WATER SENSOR

AIRSENSOR

MILTONSEQUENCE

CONTROLLER

DRAIN DRAIN

DRAIN

DRAIN DRAIN

DRAIN

Example 4Boiler installation (typical)vented system.

Example 5Boiler installation (typical)unvented system.

General notesIn any single or modular system, it isimportant that the water flow ratethrough each firing boiler does not fallbelow the minimum required flow ratefor that size of boiler (see table page 7).In applications where the minimumflow rate will not be met a shunt pumpshould be installed, sized to provide theminimum stated flow rate per boiler atthe equivalent boiler pressure drop pluspipework resistance.Both heating and shunt pumps shouldbe controlled to provide an overrunperiod to dissipate residual heat.

VENTED SYSTEM

UNVENTED SYSTEM

14

Wiring DiagramsWessex 220 M series

L

N

LOC

KO

UT

VO

LT F

RE

E

CO

NTA

CT

CO

NN

EC

TIO

NS

OV

ER

HE

AT V

OLT

FR

EE

CO

NTA

CT

CO

NN

EC

TIO

NS

CO

NTA

CT

CO

NN

EC

TIO

NS

NO

RM

AL

RU

N V

OLT

FR

EE NOT UTILISED

TIME CLOCKREMOTEFUSED ISOLATOR

CONTROLSSAFETY INTERLOCK

BOILER SITE WIRING TERMINALS

ROTARY SWITCHSW1

1) SINGLE BOILER INSTALLATION, FULLY MODULATING OPERATION VIA REMOTE TIME CLOCK CONTROL.NOTE: ROTARY SWITCH 'SW1' ON BOILER CONTROL PANEL MAIN PCB - POSITION '0' SETS BOILER TO FULLY MODULATING OPERATION.

VOLT FREE SIGNALINPUTS RATED UPTO 230V

LOW VOLTAGESIGNAL OUTPUTS

230V AC 50HzSUPPLY

BOILER NUMBER 1 BOILER NUMBER 2 BOILER NUMBER 3

2) MULTIPLE BOILER INSTALLATION, FULLY MODULATING SEQUENCED OPERATION VIA HAMWORTHY HEATING LIMITED MILTON BOILER SEQUENCE CONTROL.NOTE: ROTARY SWITCH 'SW1' ON BOILER CONTROL PANEL MAIN PCB - POSITIONS '1' THROUGH '9' SETS BOILER TO MILTON SEQUENCED OPERATION, AND SETS THE BOILER FIRING ORDER.

BOILER SITE WIRING TERMINALS230V AC 50Hz

SUPPLY

ROTARY SWITCH - SW1

SUPPLY230V AC 50Hz

BOILER SITE WIRING TERMINALS

SUPPLY230V AC 50Hz

BOILER SITE WIRING TERMINALS

ROTARY SWITCH - SW1 ROTARY SWITCH - SW1

LOW VOLTAGESIGNAL OUTPUTS

LOW VOLTAGESIGNAL OUTPUTS

LOW VOLTAGESIGNAL OUTPUTS

TO HAMWORTHY HEATING LIMITED MILTON BOILER SEQUENCE CONTROL (REFER TO MILTON INSTALLATION MANUAL FOR FURTHER DETAILS)

NOTE: VOLT FREE CONTACTTERMINALS NOT SHOWN FOR CLARITY

NOT

INTERLOCKCONTROLS

FU

SE

D IS

OLA

TOR

L N

SAFETY

UTILISEDNOT

FU

SE

D IS

OLA

TOR

NL

UTILISED

FU

SE

D IS

OLA

TOR

NOT

L N

UTILISED

CONTROLSINTERLOCK

SAFETY

CONTROLSINTERLOCK

SAFETY

BOILER SITE WIRING TERMINALS230V AC 50Hz

SUPPLY

ROTARY SWITCH - SW1

SUPPLY230V AC 50Hz

BOILER SITE WIRING TERMINALS

SUPPLY230V AC 50Hz

BOILER SITE WIRING TERMINALS

ROTARY SWITCH - SW1 ROTARY SWITCH - SW1

BOILER NUMBER 1 BOILER NUMBER 2 BOILER NUMBER 3

3) MULTIPLE BOILER INSTALLATION, HIGH/LOW SEQUENCED OPERATION VIA NON HAMWORTHY HEATING LIMITED BOILER SEQUENCE CONTROL.NOTE: ROTARY SWITCH 'SW1' ON BOILER CONTROL PANEL MAIN PCB - POSITION 'A' SETS BOILER TO TO HIGH/LOW SEQUENCED OPERATION.

LOW VOLTAGESIGNAL OUTPUTS

LOW VOLTAGESIGNAL OUTPUTS

LOW VOLTAGESIGNAL OUTPUTS

FU

SE

D IS

OLA

TOR

FU

SE

D IS

OLA

TOR

FU

SE

D IS

OLA

TOR

L L LN N N

CONTACT TERMINALSNOTE: VOLT FREE BLR 1 ON/OFF BLR 2 ON/OFF BLR 3 ON/OFF

CONTACT CONTACT CONTACT

SEQUENCER SEQUENCER SEQUENCER

NOT UTILISED NOT UTILISED NOT UTILISED

CONTROLS CONTROLS CONTROLSINTERLOCK INTERLOCK INTERLOCK

SAFETY SAFETY SAFETY

SEQUENCER SEQUENCER SEQUENCERBLR 1 HIGH/LOW BLR 2 HIGH/LOW BLR 3 HIGH/LOW

CONTACT CONTACT CONTACT

NOT SHOWN FORCLARITY

15

Flue SystemGeneral RequirementsThe Wessex is designed for directconnection to a flue system and flueoutlets from more than one boilerwhich may be connected to a singlechimney, providing the relevantrequirements of the current BuildingRegulations are adhered to.The Wessex has a low draughtrequirement and is therefore able tooperate with a low chimney,improving the aesthetic appearance ofthe building exterior.The flue system should be designed tomaintain atmospheric pressure or aslight suction at the module flueconnection at all times. If at any time the suction islikely to exceed 0.1 mbar (0.04in wg), it is recommended thata draught stabiliser be fitted tothe flue system.Because of their high operatingefficiency Wessex modular boilershave a correspondingly low exhaustgas temperature (125°C - 135°C). Theflue gas temperature provides themotive force in overcoming flueresistance, therefore this temperaturemust be maintained. It isrecommended that twin walled orinsulated flue ducts incorporating astainless steel inner skin are used onall Wessex installations.NOTE: Where twin walled insulatedflues are used, minimum draughtcondition at the furthest module will

be obtained with all modules firingunder summer ambient (20°C)temperature. Maximum draughtcondition will be obtained with onemodule firing under winter ambient(0°C). Both conditions should bechecked and a controller(s) fitted if thedraught exceeds 0.1 mbar (0.04 in wg).Wessex boilers are suitable forconnection to a fan diluted flue system,refer to British Gas publication IM/11‘Flues for commercial and industrial gasfired boilers and air heaters.’

Flue CondensationAs a result of the high thermalefficiency of Wessex modules, the fluegas temperature is low (135°C) andcondensation is likely to be producedwithin the flue system during start-upand low load conditions. Care shouldbe taken to ensure that each flue isinstalled with a minimum slope of 3° inthe direction of the condensate drain,and that all joints are shaped to directcondensation to a drain pipe. Longerlengths of flue should be provided witha separate drain connection.Each boiler casing is fitted with a drainconnection. The drain pipe must be22mm ID minimum, having a fall of atleast 3 degrees (approx. 50mm permetre), and consist of non-corrodiblematerial led to a gully via a waste trap.

Boiler and flue packagesHamworthy boiler flues are specificallydesigned to complement theirextensive range of boilers and otherindustrial and commercial heatingequipment.Flue solutions can be engineered innatural draught, fan assisted or fandilution applications, offering singleskin, twin wall with an air gap or twinwall with an insulated gapconstruction.Hamworthy offer a comprehensiverange of flue equipment from stockfor supply only contracts, oralternatively provide a full design andinstallation service incorporatingsizing, site survey and drawings forapproval, (where necessary) prior tomanufacture.Engineered flue solutions fromHamworthy may well result in areduction in sizes providing anefficient system at lower cost. Please refer to brochure500002009 or contact HamworthyFlue & Chimney Systems forfurther details.

For more information on

Hamworthy HeatingFlue & Chimney

SystemsContact:

0121 360 7000

Hamworthy flue components

500002265 B

Poole OfficeHamworthy Heating LimitedFleets Corner, Poole, Dorset BH17 0HH EnglandMain switchboard tel: 01202 662500

Enquiries and quotations 01202 662552 01202 662550

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Birmingham OfficeHamworthy Heating LimitedShady Lane, Great Barr, Birmingham B44 9ERMain switchboard tel: 0121 360 7000 fax: 0121 325 2309

General enquiries 0121 360 7000

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