Product Spotlight
What Additional Components Are Needed for a Honeywell RM7800 Series Burner Control?
Oct
The Honeywell RM7800 Series is one of the most trusted flame safeguard systems in commercial and industrial burner applications. Known for its reliability, self-diagnostics, and modular design, it provides safe sequencing and protection for gas, oil, and combination-fuel systems. However, the RM7800 relay module alone is not a complete system — it requires several key companion modules to operate properly. Below, we break down all the essential Honeywell RM7800 burner control components, including subbases, flame amplifiers, keyboard display modules, and purge timers — with links to each product.
🧱 Core Honeywell RM7800 Burner Control Components
According to Honeywell Installation Manual 32-00142, each RM7800 relay module requires the following accessories for proper operation
1️⃣ Wiring Subbase
Models: Q7800A1005, Q7800B1003, Q7800B1011, Q7800A2005, Q7800B2003, Q7800B2011
The wiring subbase provides all electrical connections for line voltage, limits, and interlocks. It forms the physical foundation for the relay, allowing easy plug-in installation and service replacement.
🔹 Subbase Options
Q7800A1005 – Two-sided subbase for panel-mount applications
Q7800B1003 / Q7800B1011 – Four-sided subbases for burner or wall-mount installations
🔹 Series 2000 Updates
Honeywell introduced new subbases for the latest RM7800 controls:
Q7800A2005, Q7800B2003, and Q7800B2011
Designed for all models with a “2” in the part number (e.g. RM7800A2012)
Easily identified by the standing grounding pin in the corner
💡 Note: 1000-series and 2000-series subbases are not interchangeable.
2️⃣ Flame Amplifier Modules
Models: R7824, R7847, R7848, R7849, R7851, R7852, R7861, R7886 series
The flame amplifier detects the flame signal from the scanner or flame rod and tells the RM7800 whether a stable flame is present. If no signal is detected, the amplifier forces a lockout to prevent unsafe operation.
Each amplifier must match the type of detector (UV, IR, optical, or rectification).
🔍 Common Amplifier Models and Applications
| Amplifier Model | Detection Type | Compatible Sensors | Typical Application |
|---|---|---|---|
| R7847A1025 / R7847A1033 / R7847A1074 / R7847A1082 | Rectification | Flame rods, C7012A/C | Gas or oil burners using flame-rod detection |
| R7847B1023 / R7847B1031 / R7847B1064 / R7847B1072 | Rectification (AMPLI-CHECK®) | Flame rods, C7012A/C | Dynamic self-check models for enhanced safety |
| R7847C1005 | UV (Self-Check) | C7012E/F | Self-check ultraviolet detection |
| R7848A1008 / R7848B1006 | Infrared (Lead Sulfide) | C7015 | IR flame detection in oil or coal systems |
| R7849A1015 / R7849A1023 | UV (Minipeeper) | C7027, C7035, C7044 | Compact UV detection for on/off burners |
| R7849B1013 / R7849B1021 | UV (Minipeeper, AMPLI-CHECK®) | C7027, C7035, C7044 | Dynamic self-check UV flame detection |
| R7851B1000 / R7851B1018 | Optical (UV/IR/Visible) | C7927, C7935, C7915, C7962 | Multi-fuel optical flame detection |
| R7851C1008 | Optical (Self-Check) | Same as above | Self-check optical for continuous operation |
| R7852A1001 / R7852B1009 | Infrared (Lead Sulfide) | C7015 | IR detection for oil or coal flames |
| R7861A1026 / R7861A1034 | Ultraviolet (Self-Check) | C7061A | Continuous-duty UV detection for industrial burners |
| R7886A1001 | Ultraviolet (Dynamic Self-Check, Adjustable Sensitivity) | C7076A/D | High-temperature UV detection for large burners |
⚙️ Amplifier Highlights
Plug-in design for quick installation
Self-check circuitry tests amplifier and detector up to 12 times/minute
Flame-failure response time (FFRT): 0.8 – 3.0 seconds
Flame-signal range: 0 – 5 V DC
Color codes: 🟢 Rectification 🟣 Ultraviolet 🔴 Infrared ⚪ Optical 🔵 Adjustable UV
3️⃣ Keyboard Display Module
Models: S7800A1001 (1st Gen), S7800A1142 (2nd Gen), S7800A2142 (3rd Gen)
The Keyboard Display Module (KDM) serves as the interface for setup, operation, and diagnostics. It shows real-time status, flame signal strength, timing, and lockout codes directly on the control.
🧩 Generation Breakdown
| Model | Generation | Display Type | Key Features |
|---|---|---|---|
| S7800A1001 | 1st Generation | 7-segment LED | Original KDM design for early RM7800 units — basic sequence and fault display. |
| S7800A1142 | 2nd Generation | VFD (Vacuum Fluorescent Display) | Brighter text-based display with expanded diagnostics. Common on RM7800L and RM7840 controls. |
| S7800A2142 | 3rd Generation | LCD | Modern LCD screen with backlight, multilingual text, and flame-signal history. Designed for 2000-series controls. |
All KDMs are backward compatible and plug directly into the relay face.
🧠 Key Functions
Displays burner sequence status (Purge, Pilot, Main Flame, Run, Post-Purge)
Shows flame-signal voltage (0 – 5 V DC)
Stores lockout history and fault codes
Allows adjustment of purge timing and valve-proving
Provides onboard diagnostics for troubleshooting
💡 For modern installations, choose the S7800A2142 for the best readability and compatibility.
4️⃣ Purge Timer
Models: ST7800A and ST7800C Series
The purge timer determines how long the burner’s blower motor operates before ignition (pre-purge) and after shutdown (post-purge). This ensures unburned fuel vapors are safely cleared from the combustion chamber.
Honeywell’s ST7800 timers plug directly into the subbase alongside the RM7800 relay and are available in various timing configurations.
🔹 ST7800A Series
| Part Number | Product Link |
|---|---|
| ST7800A1005 | Standard purge timer |
| ST7800A1013 | 10-second purge |
| ST7800A1021 | 30-second purge |
| ST7800A1039 | 60-second purge |
| ST7800A1047 | 90-second purge |
| ST7800A1054 | 120-second purge |
| ST7800A1062 | 180-second purge |
| ST7800A1070 | 240-second purge |
| ST7800A1088 | 300-second purge |
| ST7800A1096 | 360-second purge |
| ST7800A1112 | 420-second purge |
| ST7800A1120 | 480-second purge |
| ST7800A1138 | 540-second purge |
| ST7800A1146 | 600-second purge |
🔹 ST7800C Series
| Part Number | Product Link |
|---|---|
| ST7800C1003 | Custom purge configuration |
| ST7800C1011 | Alternate timing configuration |
| ST7800C1037 | Extended purge cycle |
| ST7800C1052 | Adjustable purge range |
| ST7800C1136 | Custom factory timing |
⚙️ Purge Timer Highlights
Adjustable purge durations from 2 seconds to 30 minutes
Post-purge capability up to 60 minutes (via KDM)
Plug-in design for quick configuration
Compatible with RM7800 and EC7800 controls
🧠 Final Thoughts on Honeywell RM7800 accessories
A complete Honeywell RM7800 system includes:
Correct Wiring Subbase
Compatible Flame Amplifier & Detector
Keyboard Display Module (S7800A1001 / A1142 / A2142)
Purge Timer (ST7800A or ST7800C series)
Each module plays a vital role in safe burner operation, flame supervision, and service diagnostics. Using genuine Honeywell components ensures long-term reliability and compliance.
Disclaimer: This article is not intended to serve as a guide for selecting burner control components. Each system has unique requirements, and configuration should always be performed by an experienced burner control technician.
