Cambridge Engineering S950 - 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

M
Mark McgrathAug 5, 2025
How to troubleshoot no blower operation in Cambridge Engineering S950?
- J
  jwheelerAug 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).
K
Kimberly PotterAug 9, 2025
What to do if Cambridge Engineering S950 modulating valve does not modulate and runs on continuous high fire?
- M
  Mitchell PhillipsAug 9, 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 ?.
A
Alejandro HamiltonAug 13, 2025
What to do if Cambridge Engineering S950 Heater blower runs, but there is no heat and flame safety relay locks out?
- L
  Lisa WeaverAug 13, 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.
D
Danielle SilvaAug 18, 2025
Why Cambridge Engineering S950 blower runs, unit heats, but will not cycle off?
- R
  Rebecca SmithAug 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.
M
Mark KirkAug 22, 2025
What to do if Cambridge Engineering Heater modulating valve does not modulate and runs on continuous low fire?
- D
  Deborah WallerAug 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
Jessica AndradeAug 27, 2025
What to do if Cambridge Engineering S950 blower runs, but there is no heat and flame safety relay doesn’t lock out?
- L
  Lisa FrostAug 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.
J
Jeffrey RodgersAug 30, 2025
How to fix erratic or pulsating flame in Cambridge Engineering S950 Heater?
- C
  Carolyn HernandezAug 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 Procedures

Thru Wall Mounting Procedures

Vertical Mounting Procedures

Gas Piping and Electrical Wiring

Essential steps for gas supply and electrical connections.

Start-Up Instructions

Initial Equipment Checks

Verifying voltage, pressure, blower rotation, and amp draw.

Gas System Verification

Procedures for gas train and valve leak checks.

Calibration Procedures

Control System Calibration

Operating Instructions

TSS Controller Operation

Troubleshooting Instructions

Troubleshooting Guide Overview

Comprehensive guide for diagnosing and resolving operational issues.

Damper Motor Service

Reference Diagrams

Electrical Wiring Schematics

Diagrams for control enclosure and external connections.

Gas Train Diagrams

Illustrations of gas piping configurations for different models.

ANSI;ASHRAE;IESNA Standard 90.1

Compliance Requirements Overview

Cambridge Engineering S950 Specifications

General

Model	S950
Category	Heater
Input BTU/hr	950, 000
Fuel Type	Natural Gas or Propane
Phase	3

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