TM

Installation & Service Manual

11 Operating information

General

How the water heater operates

The Shield water heater combines an advanced stainless steel heat exchanger, electronic control module, and tank that allows fully condensing operation. The blower pulls in air and pushes flue products out of the heat exchanger and flue piping. The control module regulates blower speed to control the water heater firing rate. The gas valve senses the amount of air flowing into the water heater and allows only the right amount of gas to flow. An internal pump circulates the water between the tank and heater and mixes the incoming water to provide maximum efficiency.

Temperature control

Modulation

The Shield water heater is capable of modulating its firing rate from a minimum of 20% to a maximum of 100%. The firing rate is dictated by the hot water draw and various other temperature limitations.

Night setback

The controller may be programmed to reduce the tank set point during a certain time each day. A start and stop time can be programmed for each day of the week.

Flame current support

To prevent nuisance shutdowns when the water heater is firing at minimum rates, the control will increase fan speed when the flame signal drops too low.

Protection features

Outlet temperature, flue temperature, and temperature rise limiting

The heat exchanger outlet temperature is monitored by the heat exchanger outlet temperature sensor. When the heat exchanger outlet temperature exceeds 190°F, the unit will reduce the fan speed. If the heat exchanger outlet water temperature exceeds 198°F the control will shut the unit down until it cools off.

The control module monitors the flue temperature by a sensor located in the flue exhaust. If the flue temperature exceeds 215°F the control will reduce the maximum fan speed. If the flue temperature exceeds 240°F the control will shut the unit down. The unit will restart automatically once the flue temperature drops 25°F and the minimum off time has expired.

The control monitors the temperature difference between the heat exchanger inlet and the heat exchanger outlet sensors. If this difference exceeds 25°F the control will reduce the fan speed. If the temperature difference exceeds 30°F the control will shut the unit down. The unit will restart automatically once the temperature difference has dropped below 25°F and the minimum off time has expired.

Freeze protection

DO NOT install the water heater in a room likely to freeze.

The following integral feature of the electronic control module provides some protection for the water heater.

• The electronic control module provides freeze-up protection as follows when the water heater water temperature drops below 45°F:

Below 45°F, the internal pump operates constantly.

Below 37°F, the burner turns on.

The burner and pump will turn off if water heater water temperature rises above 45°F.

￿ CAUTION This feature of the electronic control module does not eliminate the possibility of freezing.

The installation must still use recognized design, installation and maintenance practice to prevent freeze potential for the water heater.

Monitor external limits

Connections are provided on the connection board for external limits. The electronic control module will shut off the burner and inhibit relighting whenever an external limit opens.

Runtime and alarm outputs

The water heater provides dry contacts for indicating when the water heater is running, and when it is unable to operate.

Error logging

The control will hold in memory the last 10 faults. The date and time of the occurrence will be recorded as well. Only the 10 most current occurrences will be held in memory.

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Lochinvar SNA285-125, SNA500-125 Operating information, General, How the water heater operates, Temperature control

SNA400-125, SNR150-100, SNA285-125, SNR200-100, SNA500-125 specifications

Lochinvar has established itself as a leader in the realm of high-efficiency heating solutions, and its line of condensing boilers, including the SNA500-125, SNR200-100, SNA400-125, SNA285-125, and SNR150-100, exemplifies the brand’s commitment to innovation, efficiency, and reliability.

The SNA500-125 model stands out with its impressive heating capacity, designed for larger commercial applications. Featuring advanced modulating burners, it can precisely adjust its output based on real-time demand, significantly enhancing energy efficiency. The stainless steel heat exchanger ensures robust durability and improved thermal performance, while the integrated controls offer advanced diagnostic capabilities and user-friendly operation.

Next in the lineup, the SNR200-100 serves as a versatile option for mid-sized applications. Its compact design allows for flexible installation, making it a valuable choice for facilities with limited space. The boiler incorporates a high-efficiency combustion system that maximizes fuel utilization, while its low NOx emissions technology aligns with environmental standards, reducing the carbon footprint of users.

The SNA400-125 delivers a robust solution for diverse heating needs, equipped with state-of-the-art modulation technology that not only optimizes efficiency but also offers quiet operation – a crucial feature for facilities where noise reduction is paramount. This model also includes built-in redundancy options, enhancing reliability during peak operational periods.

The SNA285-125 provides a balance of performance and efficiency for smaller commercial settings. Its innovative control system offers precise temperature management and easy integration with existing systems. Energy Star certified, this model is not only cost-effective but supports sustainability efforts in various industries.

Lastly, the SNR150-100 is ideally suited for light commercial applications, featuring a compact footprint and excellent heat transfer capabilities. The user-friendly interface and robust safety features make it an excellent choice for operators prioritizing both ease of use and reliability.

All these models incorporate Lochinvar's commitment to superior design and advanced technologies, setting a benchmark in the high-efficiency heating market. With a focus on long-term performance and compliance with modern environmental standards, Lochinvar continues to deliver top-tier solutions tailored to meet diverse customer needs. Whether for large-scale operations or smaller settings, these boilers represent a significant advancement in commercial heating technology.