Gas Fired LTHW Condensing Boiler15kW - 2300 kW

Suggested Engineering Specification

The following text is provided to assist with specification of commercial gas fired condensing boilers with a rated output of between 15 kW and 1,150 kW (2,300 kW for a ‘single flue’ boiler pair). The text is not a full system design and should only be read as a solution for equipment supplied with additional hydraulic design and controls advice coming from the Technical Department of Hoval Ltd at Newark.

Gas Fired LTHW Condensing Boiler

a. The boiler shall be of the UltraGas® type as manufactured by Hoval. The boiler shall be designed to combust natural gas (or LPG) in order to generate hot water for space heating and/or DHW production at a temperature of up to 90 oC, at an operating pressure of up to 3 barg (15-50 kW), 4 barg (70-90 kW), 5 barg (125-300 kW), 6 barg (350-1,150 kW) or 8 barg (models 720 and 1000 only).

b. Twin UltraGas ‘D’ boilers to be available from 250kW to 2300kW, complete with a common flue header.

c. Models (15-70) to have an “A” rated ErP labelling classification.

d. The boiler heat exchanger shall be of stainless steel construction on the waterside in order to minimise the risk of rapid corrosion where specialist water treatment (as required for aluminium heat exchangers) is not maintained.

e. For low maintenance and continuous high efficiency, the boiler heat exchanger shall be designed to be self cleaning in condensing operation, using aluFer® tubes with aluminium fins providing extended heat transfer surface area on the gas side.

f. The boiler shall be of high specific water content design with low water velocity through the heat exchanger delivering the best efficiency gains from cool return water.

g. The boiler shall have low resistance to water flow and have no minimum flow rate, enabling system connection without (or with) a low loss header (and associated primary circulator).

h. The boiler shall incorporate two return water connections to gain maximum efficiency benefit from directly connecting low temperature returns to the boiler, separate from and without mixing with, higher temperature returns.

i. The burner shall be of low NOx UltraClean® design.

j. The burner shall be of the pre-mix type and be fully modulating from 100% to 24% (or lower) of rated output. Twin units shall be able to modulate down to 12% (or lower) of rated output.

k. The boiler shall be designed to have low standing heat losses. The boiler shall be designed for flow isolation and its controls capable of controlling the motorised shut off

valve to avoid flow through an offline boiler once residual heat after firing has been utilised.

l. The boiler controls shall be of the TopTronic® type. The boiler controls shall continuously monitor the boiler operation. The boiler controller shall be capable of sequencing and modulating, in cascade or unison, up to 5 boilers. Each boiler or cascade system shall be capable of providing both weather compensation (with the installation of an outdoor temperature sensor) and room compensation (with the installation of a remote room station). Each boiler controller shall be capable of controlling two variable temperature heating circuits, one constant temperature heating circuit and one calorifier primary circuit. Installation and commissioning shall be made simpler with the availability of a key system to activate heating program settings. The boiler shall have a water pressure sensor linked to the boiler controls. The TopTronic® boiler controller shall display operating data via an LCD display. A large rotary push button shall be used to make navigation as easy as possible.

DESCRIPTIVE SPECIFICATION

Gas Fired LTHW Condensing Boiler15kW - 2300kW

DESCRIPTIVE SPECIFICATION continued

i. The boiler shall deliver a thermal seasonal efficiency of at least 87.5% gross (97.1% net) in non-condensing operation (> 56 °C return water) and at least 96% gross (106.5% net) in full condensing operation (30 °C return water).

ii. The boiler shall deliver low NOx emissions of less than 39 mg/kWh enabling the maximum 3 BREEAM credits to be claimed.

iii. The boiler shall have a specific water content of at least 0.6 l/kW of rated output.

iv. The boiler resistance to water flow shall be 0.8 kPa (8 mbar) or lower at a 20 K temperature differential and the boiler shall not require a constant flow rate.

v. The boiler shall have noise emissions (acoustic pressure level at 1 metre) of less than 75 dB(A).

vi. Standing heat loss, at 70 °C mean water temperature, shall be lower than 0.4% of full output.

vii.The electrical consumption at full output shall be no more than 3.2 W/kW of thermal output.

PERFORMANCE SPECIFICATION

Hoval Ltd, Northgate, Newark-on-Trent, Nottinghamshire, NG24 1JN, United Kingdom

Phone 01636 672 711 Fax 01636 673 532 email boilersales@hoval.co.uk www.hoval.co.uk

November 2017

l. The boiler shall be compatible with renewable energy technologies such as biomass boilers, heat pumps and solar thermal systems. The boiler manufacturer shall be capable of offering advice on system integration.

m. The boiler shall be CE approved and the manufacturer shall hold ISO 9001:2015 certification.

k. The boiler controls shall be compatible with Building Management Systems and have the availability, through additional optional interfaces, to accept a simple enable signal, a 0-10 V signal for set-point adjustment or firing rate control, or a ModBUS signal for full boiler control and interrogation. The boiler must have the capability to run in manual in the event of a controls signal failure.