Requirement
Supply and install Condensing Heating Hot Water Generators as shown on drawings and as scheduled.
Installation
Install units to operate in accordance with the following:
- Hot water generator manufacturers instructions
- AGA
- AS 5601
- AS 3814
- AS 1797 Installation of Hot Water Boilers (Section 8.9)
- AS 1228
Type
Provide packaged water tube type having a stainless steel furnace, heat exchanger and casing and completely factory equipped with forced draught burner equipment, fittings and trim, electronic combustion controls and safety interlocks, electrical wiring and devices, refractory insulation, etc, and suitable for operation on Natural Gas.
Manufacturer
Supply condensing hot water generators from an approved manufacturer with certified rating data equal to Rendamax.
Construction
Incorporate high quality stainless steel finned tube waterways providing a three pass arrangement with the flue outlet at the rear . The stainless steel pre-mix burner should be water cooled. The boiler should be constructed so as to provide ultra low heat loss emissions and where necessary it should be insulated with 50 mm high temperature mineral wool. Provide a casing with an attractive enamellised finish of approved colour or a polished aluminium finish.
Auxiliaries
Provide all auxiliaries not specifically mentioned herein but required for a safe and fully operating installation and to comply with all applicable codes and regulations.
Controls
Provide each unit with in-built instrument and control panel(s) containing the following:
- Fully Modulating control
- Weather-compensated regulator
- Control thermostat
- High limit thermostat
- Flow water temperature gauge
- Return water temperature gauge
- Altitude gauge
- Burner operating and safety controls
Emmissions
The minimum standard for emmissions are:
- NOx – 53 mg/KWh
- CO – 19 mg/KWh
- Noise level – 59 db (A)
Efficiency
53 mg/KWh 19 mg/KWh 59 db (A)
The minimum efficiency standard is 96% using the Gross Calorific Value of natural gas with a return water temperature of 50 degrees C.
Energy Input Interlock
For automatic boilers, continuously circulate system water through the heating hot water boiler while it is in operation. Interlock the energy input system to prevent ignition or combustion in a liquid or gaseous fired heating hot water boiler unless water is circulating.
Efficiency
Select water heaters with a thermal efficiency of not less than 92% from full load down to 25% M.C.R. under modulating control.
Capacity Adjustment: Adjust minimum low fire capacity at commissioning to minimise condensation.
Tools
Provide a set of tools for the maintenance and cleaning of the heaters.
Flues
Provide a metal flue sized in accordance with the heater manufacturer’s recommendations and as required by the relevant authorities. Fully self support discharge flues without guys transmitting weight to the heater or roof. Fit the low points with flanged clean-out openings, drained to waste.
Expansion Joint: Provide a restrained stainless steel double tied expansion joint similar to the Jord 400 DTEJ-100-FFl assembly, or approved equal, where shown on the drawing.
Flexible connection: Provide a fabric flexible connector in each flue similar to the Jord EJ/STG or approved equal.
Fittings and Installation: Fit flues with draft regulators and clean out doors, plugged test points for flue gas analysis tests and a socket to accept a flue gas temperature gauge. Provide draught regulators if recommended by the manufacturer or if necessary for the efficient operation of the heater. Arrange flues to expand and contract and fit with flashing skirts where they penetrate the roof.
Construction: Fabricate from 304 stainless steel and insulate with 50 mm high temperature type insulation fixed with wire lacing and metal sheathed as detailed in section “Pipework”. Provide an approved discharge.
Gas Firing Equipment
Provide fully-automatic gas firing equipment complying with all relevant Codes and Regulations. Gas Train: Factory-fitted and test the gas train before dispatch to site.
Burner: Manufacture burner with a hinged body for access to the burner head without removing burner from the unit.
Features: Incorporate the following features into the gas-firing equipment:
- Pre-purge before ignition.
- Limit ignition cycle to approximately 15 seconds.
- Shutdown burner in the event of failure to ignite – manual reset.
- Shutdown on flame failure – manual reset.
- Stop burner on momentary power failure and resume starting cycle. Shutdown on power failure.
- Stop burner on low water level – manual reset.
- Stop burner on excessive leaving water temperature – manual reset (hi-limit stat).
- Stop burner if fan air flow stops.
- Post-purge for approximately 1 minute on shut-down or flame failure or failure to ignite.
- Stop burner on abnormal gas pressure – manual reset.
- Indicating light for each safety shut-down condition.
- Shutdown on failure of water flow with pump enabled.
- Hot water boiler status.
- Hot water boiler availability isolation switch.
- Shutdown and lock out of gas supply on failure of the plantroom ventilation system.
Integral Pipework
Expansion or Vent Pipe: Design the pipe connecting each boiler to an expansion vessel or open vented head tank so that the rise of pressure in the boiler due to the maximum expansion rate of the water is not more than 106 percent of the design pressure.
Safety Valve: Where a safety valve is fitted to the expansion vessel, design the connecting pipe so that under maximum discharge conditions of the safety valve(s) the heater pressure does not rise to more than 106 percent of the design pressure.
Vent/Expansion Pipe Connection: Provide a separate vent pipe from the pipe supplying the make-up water from the head tank. Where necessary take precautions against freezing.
Flow Restriction: Do not fit a shut-off valve, cock, or other obstructions to flow between the heater and an open vented head tank or expansion vessel, unless the boiler safety valve(s) are fitted directly to the heater shell.
Make-Up Water Systems
Make provision for the supply of make-up water to the system. Where a pump is provided for filling while the heater or system is pressurised, take precautions to avoid water-hammer during filling with cold water. Maintain an effective alarm while make-up water is required, where automatically controlled pumps are used.
