Lochinvar NOBLE NKC 110-199

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100275091_2000533998_Rev R

FIRE TUBE

™

Noble Fire Tube Boiler and Combi

Installation & Service Manual

NKC 110 - 199

NKB 80 - 150

This manual must only be used

by a qualified heating installer

/ service technician. Read all

instructions in this manual before

installing. Perform steps in the

order given. Failure to comply

could result in severe personal

injury, death, or substantial

property damage.

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The Noble Fire Tube Boiler and Combi is a high-efficiency heating appliance designed for residential and commercial applications. It utilizes a fire tube heat exchanger for maximum heat transfer and protection against flue gas corrosion. The unit is available in various models, including NKC 110-199 (Combi) and NKB 80-150 (Boiler only), with inputs ranging from 8.3 MBH to 199 MBH.

Function Description

The Noble Fire Tube Boiler and Combi operates by pulling in air and gas through a venturi, mixing them in the blower, and pushing the mixture into the burner for combustion. The heat exchanger then transfers heat to the system water. The control module modulates the firing rate based on internal and external signals, including temperature sensors and external demands.

Key components and their functions:

Heat exchanger: Specially designed coils for maximum heat transfer and flue gas corrosion protection.
Blower: Pulls in air and gas, mixes them, and pushes them to the burner.
Gas valve: Senses negative pressure from the blower, allowing gas flow only when powered and combustion air is flowing.
Venturi: Controls air and gas flow to the burner.
Flue gas sensor: Monitors flue gas exit temperature, modulating or shutting down the boiler if temperatures are too high.
Boiler outlet/inlet temperature sensors: Monitor water temperatures to adjust firing rate.
Electronic LCD display: Provides five buttons and a liquid crystal display for adjustments and status readings.
Burner: Metal fiber and stainless steel construction, uses pre-mixed air and gas for a wide range of firing rates.
Boiler control module: Responds to internal/external signals, controls blower, gas valve, and pumps.
Air pressure switch: Detects blocked conditions.
Pump (Combi Only): Provides flow for space heating and domestic water, serving as both boiler and DHW pump.
Diverter valve (Combi Only): Diverts boiler water between heating loop and DHW heat exchanger.
DHW Flow switch (Combi Only): Detects DHW draw and signals the boiler to fire.
DHW sensor (Combi Only): Monitors DHW temperature to adjust firing rate.
Condensate trap: Sized for a 3/4" PVC outlet connection pipe (factory-installed on Combi, field-installed on Boiler).

Important Technical Specifications

Input MBH:
- NKB80N: 8.3 (Min) - 80 (Max)
- NK(B,C)110N: 11 (Min) - 110 (Max)
- NK(B,C)150N: 15 (Min) - 150 (Max)
- NK(C)199N: 20 (Min) - 199 (Max)
AFUE: 95.0% for all models.
Boiler Water Content: 1.2 to 2.7 gallons depending on model.
SH Water Connections: 1" NPT (Combi) / 1" Sweat (Boiler).
DHW Water Connections (Combi Only): 3/4".
Gas Connections: 1/2".
Vent/Air Size: 3" for all models.
Maximum Working Pressure: Located on the rating plate.
Altitude Operation: Standard units operate from sea level to 4,500 feet (de-rate 4% per 1,000 feet above sea level). High altitude units (3,000 to 9,600 feet) de-rate 1.7% between 5,000 and 9,600 feet, with an additional 4% per 1,000 feet beyond 9,600 feet.
Vent Piping Lengths: Minimum 7 equivalent feet, maximum 100 equivalent feet for both combustion air and vent. (Add 5 feet for each 90° elbow, 3 feet for each 45° elbow).
Vent Materials: Approved PVC, CPVC, Polypropylene, or Stainless Steel.
Condensate pH: Typically 3 to 5 (acidic).
Boiler Water Chemistry:
- Dissolved Solids: < 2000 ppm
- pH Level: 6.5 to 9.5
- Chloride: < 150 ppm
Freeze Protection: Inhibited propylene glycol solutions specifically formulated for hydronic systems. Automotive antifreeze (ethylene glycol) is toxic and should NEVER be used.

Usage Features

Direct Venting Options: Can be vented sidewall or vertically through the roof using two-pipe or concentric vent systems.
Optional Room Air: For commercial applications, a single pipe can carry flue products outside while using indoor combustion air (requires specific room air kit).
Mounting: Designed for wall mounting (not floor installation) on cement, brick, block, or 16" on-center wooden studs, capable of supporting at least 200 pounds.
Gas Conversion: Units are factory-shipped for natural gas but can be converted to LP gas by installing an LP venturi.
System Control:
- Outdoor Air Reset: Advanced non-linear outdoor reset curve to improve system efficiency by reducing boiler water set point as outdoor temperature warms up.
- Space Heat Rate Limiting: Limits maximum modulation during space heating calls.
- DHW Priority (Combi): Prioritizes DHW calls over space heating.
- Combi Pre-Heat (Combi Only): Maintains boiler water at an elevated temperature to improve DHW performance and comfort.
- DHW Respond (Combi Only): Helps eliminate cold water sandwich issues by maintaining ignition readiness after DHW demands.
- Cascade Operation: Multiple Noble Fire Tube units can be wired together for cascade control (up to 8 boilers) for space heating demands.
Safety Features:
- Overheat Protection: Flue gas and outlet water sensors monitor temperatures, reducing firing rate or shutting down the unit if limits are exceeded.
- Low Water Cutoff Protection: Boiler modulates or shuts down if flow rate is too low or outlet temperature too high.
- Low Voltage Blocking: Prevents ignition attempts during temporary low line voltage conditions.
- Error Logging: Stores the last 10 lockouts with date and time.

Maintenance Features

Annual Service (by qualified technician):
- Address reported problems.
- Inspect interior, clean, and vacuum.
- Clean condensate trap.
- Check for leaks (water, gas, flue, condensate).
- Verify flue and air lines are in good condition and sealed.
- Check system water pressure, piping, and expansion tank.
- Check fill water meter.
- Test boiler water, clean system water if needed.
- Check control settings.
- Check ignition electrodes (sand off deposits, clean, reposition).
- Check wiring and connections.
- Perform start-up checkout and performance verification.
- Inspect flame (stable, uniform) and flame signal (at least 10 microamps at high fire).
- Clean heat exchanger if flue temperature is more than 54°F above return water temperature.
- Inspect and clean DHW flow switch filter and sanitary bypass filter (Combi only).
- Clean burner using compressed air if needed.
Owner Maintenance:
- Daily: Check boiler area, pressure/temperature gauge.
- Monthly: Check vent/air piping, termination screens, relief valve, condensate drain system, air vents.
- Periodically: Test low water cutoff (if used), reset button (low water cutoff).
- Every 6 months: Check boiler piping (gas and water) for leaks, operate relief valve.
- End of season: Shut down boiler (unless used for DHW).
Condensate Disposal: Requires a 3/4" plastic drain line, potentially with a neutralizing filter due to acidic condensate. A condensate removal pump is needed if the boiler is below the drain.
Heat Exchanger Cleaning: Detailed procedure for removing top plate, gas valve, fan, and venturi assembly to access and clean the heat exchanger.
Brazed Plate Heat Exchanger Cleaning (Combi Only): Procedure for flushing the DHW heat exchanger.
DHW Flow Switch Filter Cleaning (Combi Only): Procedure for removing and cleaning the filter.