Cambridge Engineering S1850 - User Manual

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S-TM7-02-18

S400-S3200 REV. F

S-SERIES

DIRECT GAS-FIRED

INDUSTRIAL BLOW-THRU

®

SPACE HEATER

TECHNICAL MANUAL

mWARNING:

Improper installation, adjustment, alteration, service or maintenance can cause property dam-

age, injury or death. Read the installation, operating, and maintenance instructions thoroughly

before installing or servicing this equipment.

FOR YOUR SAFETY

The use and storage of gasoline or other flammable vapors and liquids in open containers in

the vicinity of this appliance is hazardous.

FOR YOUR SAFETY

If you smell gas:

1. Open windows.

2. Don’t touch electrical switches.

3. Extinguish any open flame.

4. Immediately call your gas supplier.

®

90.1

ASHRAE

ASHRAE

COMPLIANT

COMPLIANT

Made in the USA

®

Table of Contents

Questions and Answers

A
andersonericAug 5, 2025
How to troubleshoot no blower operation in Cambridge Engineering S1850?
- J
  Joe LeeAug 5, 2025
  If the Cambridge Engineering Heater blower isn't running, first ensure the unit isn't in reset by turning it OFF and then ON again. Check that the heater disconnect is ON. Verify the mode selector switch on the RCS is in the correct mode and adjust the operating thermostat if needed. Make sure the blower service switch is in the REMOTE position. Examine the control and Class 2 transformers, checking the disconnect, supply fusing, and supply voltage. Also, inspect the multi-functional PC board, checking the voltage in the RCS. Other potential causes include the damper motor (adjust damper stroke), motor protection/starter/motor (check primary power source or replace starter), blower (replace bearings), or belts (tighten belts).
N
Nathaniel RileyAug 9, 2025
What to do if Cambridge Engineering S1850 modulating valve does not modulate and runs on continuous high fire?
- M
  Mark MitchellAug 10, 2025
  If the Cambridge Engineering Heater's modulating valve is stuck on continuous high fire, try reinstalling the wire on the amplifier (A1014, A1044, or AD1014). You might also need to clean the Discharge Air Temperature Sampling Tube for the discharge temperature sensor (TS114J or TS144). For Series 44 models, replace the space temperature selector if resistance exceeds specified values (7,000 ? for T244; 5,500 ? for TS244; or 2,250 ? for TD244). For Series 14, recalibrate or replace the space thermostat. If using a remote heat adjust (TD114 or CEI 4175-0-960), replace it if resistance between terminals 1 and 3 is less than 6,000 ?.
M
Mrs. Alexandria Collins DDSAug 14, 2025
What to do if Cambridge Engineering S1850 blower runs, but there is no heat and flame safety relay locks out?
- H
  hartdebraAug 14, 2025
  If the blower runs but the Cambridge Engineering Heater doesn't heat and the flame safety relay locks out, start by checking the igniter current. Also, check the gas supply for low or no gas pressure using the high or low gas pressure switches. Inspect the gas valve, verifying the FSR output to the R1 relay during ignition. Finally, adjust the minimum fire on the modulating valve.
R
Randy BakerAug 18, 2025
Why Cambridge Engineering S1850 blower runs, unit heats, but will not cycle off?
- C
  cbakerAug 18, 2025
  If the Cambridge Engineering Heater blower runs, the unit heats, but it won't cycle off, first check the thermistor wiring and consider replacing the thermistor for the operating thermostat. Ensure the burner service switch is in the REMOTE position. Inspect the auxiliary circuit wiring and contacts. Consider reviewing the control system's operational characteristics to ensure proper understanding.
J
Jeffrey BeckerAug 22, 2025
What to do if Cambridge Engineering Heater modulating valve does not modulate and runs on continuous low fire?
- H
  hintonvalerieAug 22, 2025
  If the Cambridge Engineering Heater's modulating valve is stuck on continuous low fire, start by checking for a short in the modulating valve coil using the Class 2 transformer. If the valve coil resistance is less than 40 ? or greater than 85 ?, replace it. With the wire removed from terminal 3 of the amplifier, replace the amplifier if the valve voltage doesn't exceed 18 Volts DC. Replace the discharge temperature sensor (TS114J or TS144) if the resistance at terminals 1 and 2 on TS114J is less than 8,000 ?. Also, replace the space temperature selector (T244 or TS244/TD244) if the resistance is less than 5,000 ? for the T244, 3,500 ? for the S244, or 1,950 ? for the TD244.
J
james79Aug 27, 2025
What to do if Cambridge Engineering S1850 blower runs, but there is no heat and flame safety relay doesn’t lock out?
- J
  Jeffrey BlackAug 27, 2025
  If the Cambridge Engineering Heater blower is running but there's no heat and the flame safety relay isn't locking out, first, ensure the mode selector switch is in the HEAT position. Then, check that the burner service switch is in the REMOTE position. After that, check the voltage in the RCS using the multi-functional PC board. You may also need to reverse the motor direction on the airflow switch. Finally, check the wiring of the flame safeguard relay.
E
Emily WardAug 30, 2025
How to fix erratic or pulsating flame in Cambridge Engineering S1850?
- K
  Kenneth JonesAug 30, 2025
  To address an erratic or pulsating flame in your Cambridge Engineering Heater, start by enlarging the vent piping size or reducing the vent piping length for the high-pressure regulator. Then, adjust the sensitivity control dial on the amplifier counter-clockwise. For the space temperature selector (T244 or TS244/TD244) and remote heat adjust (TD114 or CEI 4175-0-960), use shielded, twisted pair wiring.

Summary

Hazard Summary

Hazard Identification

Installation Instructions

Roof Top Mounting

Thru Wall Mounting

Under Roof Mounting

Vertical Indoor Mounting

Vertical Outdoor Mounting

Gas Piping

Electrical Wiring

Start-Up Instructions

Start-Up Procedure

Outlines the sequence of checks before and during initial heater operation.

Visual Inspection of Equipment

Verifies equipment condition and accessory installation before operation.

Electrical Supply Voltage Verification

Confirms supply voltage matches heater requirements.

Gas Supply Pressure Verification

Checks gas supply pressure against nameplate specifications.

Burner Manifold Pressure Adjustment

Adjusts the gas manifold pressure to the correct operating level.

Minimum Fire Adjustment Procedure

Sets the minimum gas input rate for stable burner operation.

Calibration Check

Verifies and adjusts temperature control settings for accurate operation.

Gas Valve Leak Check

Tests the gas valve seats for tightness to prevent leaks.

Final Heater Preparation

Final checks and settings before operating the heater.

Calibration Procedures

EDL Control Systems

Calibration steps for EDL systems, focusing on discharge temperature.

EDSM and EDSM;TP Control Systems

Calibration steps for EDSM/TP systems, adjusting amplifier and sensor.

EDR Control Systems

Calibration steps for EDR systems, involving remote heat adjustment.

Operating Instructions

Operating Sequence

Describes the step-by-step process of the heater's operation.

Electronic Thermostat

Setting Temperatures

Temperature Calibration

TSS Controller

Overview of the TSS controller's features and capabilities.

Setting Schedules

Maintenance Instructions

Gas Train Leak Check

Procedures to check the gas train for leaks.

Troubleshooting Instructions

Troubleshooting Guide

A guide to diagnose and correct common operational problems.

No Blower Operation

Blower Runs; No Heat; Flame Safety Relay Locks Out

Modulating Valve Does Not Modulate

Erratic or Pulsating Flame

Damper Motor Replacement & Adjustment

Damper Motor Replacement & Adjustment

Individual Component Descriptions

Gas Control Systems

Cambridge Engineering S1850 Specifications

General

Model	S1850
Category	Heater
Type	Unit Heater
Fuel Type	Natural Gas or Propane
Voltage	115/1/60
Motor Type	PSC
Mounting	Suspended

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