Honeywell 7800 Series Burner Controls: A Complete Buyer's Guide for Technicians and Facilities Managers
Published by James S. on Feb 2nd 2026
If you've ever stood in front of a malfunctioning commercial boiler trying to decode which relay module you're looking at — or spent twenty minutes on hold trying to figure out whether the part you need is discontinued — this post is for you.
The Honeywell 7800 Series is one of the most widely deployed families of flame safeguard controls in North American commercial and industrial combustion equipment. These microprocessor-based relay modules are installed in boilers, process heaters, furnaces, kilns, industrial ovens, and dozens of other burner-based systems. And while Honeywell has done an excellent job building reliable hardware, the product family is large enough and the part numbering specific enough that buying the right unit — or figuring out what you have — can be genuinely confusing.
This guide covers five key 7800 Series relay modules available at ACR4Sale: the RM7823A1016, RM7838B1013, RM7890A1015, RM7890B1030, and RM7895A1014. We'll explain what each one does, how they differ from each other, and how to figure out which one you actually need.
First: Understanding How the 7800 Series Is Structured
Before diving into individual part numbers, it helps to understand the system architecture. Every 7800 Series installation is made up of at least three components:
The relay module is the brain — the microprocessor-based unit that runs the sequence logic, monitors interlocks, supervises the flame signal, and handles safety lockout. The part numbers covered in this guide (RM7823, RM7838, RM7890, RM7895) are all relay modules.
The wiring subbase is the terminal block that the relay module snaps into. It provides the physical wiring interface between the relay module and the burner's electrical system. The Q7800A or Q7800B Universal Wiring Subbase is required for all of the units in this guide. Importantly, the newer 2000-series relay modules (which includes the RM7895A1014) require the Q7800A2005/U subbase specifically and are not compatible with older 1000-series subbases.
The flame signal amplifier is a color-coded plug-in module that mounts on the relay module itself. It interprets the raw signal from the flame detector (UV tube, infrared sensor, or flame rod) and converts it into a flame present/absent signal for the relay module. The amplifier must match the type of flame detector installed. Common 7800 Series amplifiers include the R7847, R7848, R7849, R7851, R7852, R7861, and R7886.
Some relay modules require a fourth component — a purge timer card (ST7800A) — when prepurge capability is needed. We'll call that out where it applies.
None of the relay modules in this guide include the subbase, amplifier, or purge timer. Those must be ordered separately.
With that foundation in place, let's look at each unit.
RM7823A1016: The Flame Detector Relay (Not a Primary Control)
SKU: RM7823A1016 | View Product →
The RM7823A1016 occupies a unique position in the 7800 Series family: it is not a primary burner control. This is one of the most important distinctions to understand before purchasing.
Most of the relay modules in the 7800 Series — including the RM7890 and RM7895 families covered later in this guide — are full primary burner controls. They handle the entire flame safeguard sequence: safe-start check, burner sequencing, ignition, flame supervision, safety lockout, and load switching.
The RM7823A1016 does none of that. It is a flame detector relay only. Its sole function is to provide relay action from two single pole, double throw (SPDT) relays in response to flame presence or absence. When a flame signal is detected by the connected amplifier, the relays switch. When the flame signal is lost, they switch back. That's it.
This makes the RM7823A1016 a component within a larger system rather than the heart of one. It is used in applications where a separate, suitable primary burner control is already handling safe-start, safety lockout, and load switching — and an additional relay output based on flame status is needed for annunciation, interlocking, or control purposes.
Like all 7800 Series relay modules, it can be fitted with any compatible 7800 Series amplifier (R7847, R7848, R7849, R7851, R7852, R7861, or R7886), which means it supports UV, infrared, and rectification flame detection depending on which amplifier is installed.
Key specs: 120 VAC, -40°F to +140°F operating range, 2000 VA maximum connected load, three status LEDs (power, flame, alarm), nonvolatile memory, shutter drive output.
Who needs this: Technicians and engineers adding secondary flame-status relay outputs to existing flame safeguard systems, or building custom control panels where a separate primary controller is already present. If you are looking for a complete burner control that handles the full startup and supervision sequence, this is not the right product — see the RM7890 or RM7895 sections below.
RM7838B1013: Manual-Start Industrial Programmer for Semi-Automatic Applications
SKU: RM7838B1013 | View Product → (Discontinued — New Old-Stock Available)
While most of the 7800 Series relay modules are designed for fully automatic burner operation, the RM7838B1013 is purpose-built for semi-automatic, manual-start industrial applications. This distinction alone narrows its use case significantly.
In a fully automatic system, a thermostat or process controller calls for heat, and the burner control handles the entire startup sequence without any operator involvement. In a semi-automatic system — which is common in large industrial boilers, process furnaces, kilns, and certain institutional heating plants — an operator must manually initiate each burner cycle by pressing a Start button. The control then handles the automated portion of the sequence (prepurge, pilot ignition, flame proving, main valve opening) but only after the human has pressed the button.
This design is deliberate. In large industrial combustion systems, having an operator physically present and consciously initiating each start cycle is an additional safety layer that the relevant codes and insurance standards often require.
The RM7838B1013 supports LHL-LF & HF proven purge sequencing, meaning it can handle both low-high-low fire (LHL) and low fire/high fire (LF & HF) sequencing through the purge cycle. It also includes an interrupted pilot with lockout interlocks — the pilot is established during startup and then extinguished once the main flame is proven, and lockout interlocks prevent a restart until the fault has been manually cleared.
The selectable pilot flame establishing period (4-second or 10-second PFEP) and the built-in S7800A Keyboard Display Module — which is included with this unit, unlike most other relay modules that sell it separately — make it well-suited for larger, more complex combustion systems that need on-board diagnostics and fault history access.
A few important notes for anyone sourcing this unit: The RM7838B1013 was discontinued by Honeywell, which means the units we have in stock are new old-stock. No factory reorders are possible. If you're maintaining a fleet of equipment that uses this control, now is a practical time to buy spares while they're still available new.
Key specs: 120 VAC, manual start, LHL-LF & HF proven purge, interrupted pilot, selectable 4-sec or 10-sec PFEP, 10-sec or intermittent main FEP, lockout interlocks, 2000 VA max connected load, 10W power consumption, S7800A KDM included. Requires: Q7800A/B subbase, compatible flame signal amplifier, ST7800A purge timer card.
Compatible amplifiers: R7847, R7848, R7849, R7851, R7852, R7861, R7886
Who needs this: Facilities engineers and maintenance technicians responsible for large industrial boilers, commercial heating plants, process furnaces, or multi-fuel combustion systems where manual-start, semi-automatic operation is required by code, system design, or standard practice. Also anyone replacing a failed RM7838B1013 in an existing installation — this is the only way to get a new unit.
RM7890A1015: The Workhorse On-Off Primary Control
SKU: RM7890A1015 | View Product →
If the RM7823A1016 is a specialty component and the RM7838B1013 is an industrial-grade programmer, the RM7890A1015 is perhaps the most straightforward unit in this guide: a clean, capable on-off primary burner control for single-burner applications.
The RM7890 series handles everything a complete flame safeguard system needs from a primary control perspective. Safe-start check? Yes. Automatic burner sequencing? Yes. Flame supervision? Yes. Safety lockout on flame failure? Yes. Fault annunciation via LED? Yes. The RM7890A1015 replaces the older RM7890A1007 and is the current production unit for applications requiring a straightforward on-off intermittent pilot primary control without prepurge.
The absence of prepurge is actually the defining characteristic of the RM7890 series relative to the RM7895 series. A prepurge cycle uses the blower to flush unburned fuel from the combustion chamber before ignition — it is required by some codes and equipment designs and not by others. The RM7890A1015 does not include prepurge capability. If prepurge is required by your application or local codes, the RM7895A1014 (covered below) is the correct choice.
What the RM7890A1015 does offer is a selectable pilot flame establishing period (4-second or 10-second PFEP via site-configurable jumpers), intermittent pilot operation (pilot fires at startup and shuts off once main flame is proven), and a selectable relight or lockout on loss of flame — meaning you can configure the control to either attempt an automatic re-ignition or go straight to lockout if the flame signal is lost during the run cycle, depending on your application requirements.
The five-status LED display (Power, Pilot, Flame, Main, Alarm) and the Power LED's fault-code blink function make troubleshooting straightforward without needing to plug in a display module, though the optional S7800A1142 Keyboard Display Module adds programmable postpurge and full fault history access when needed.
Key specs: 120 VAC, 50/60 Hz, intermittent pilot, selectable 4-sec or 10-sec PFEP, intermittent main FEP, no preignition, -40°F to +140°F, 1 lb 13 oz. Replaces RM7890A1007. Requires: Q7800A/B subbase and compatible flame signal amplifier. Display (S7800A1142) sold separately.
Who needs this: Commercial boiler technicians, HVAC service contractors, and facilities maintenance teams replacing a failed on-off primary control in systems where prepurge is not required. It is widely used in commercial boilers, hot water heaters, rooftop units, and similar single-burner applications.
RM7890B1030: The Shutter Drive Variant — and What That Actually Means
SKU: RM7890B1030 | View Product → (Discontinued — New Old-Stock Available)
The RM7890B1030 sits alongside the RM7890A1015 in the same product family but adds two specific features that some applications require: built-in shutter drive capability and an audible alarm that sounds when the Reset button is pushed.
Understanding why shutter drive capability matters requires a brief explanation of how UV flame detectors work in certain configurations. Some UV scanners — such as certain Honeywell C7027 and C7035 Minipeeper models — can be installed with a motorized shutter that periodically blocks the UV sensing tube's view of the flame. This allows the detector to perform a rudimentary self-check: if the tube still shows a flame signal when the shutter is closed, the tube or amplifier may have failed in the "flame present" position, which is a potentially dangerous failure mode. The shutter drive output on the relay module powers this shutter mechanism.
The RM7890A1015 does not have a shutter drive output. The RM7890B1030 does. If your flame detector installation uses a shutter-equipped UV scanner, the B1030 is the correct module; the A1015 is not.
One installation detail worth noting: the shutter drive output on the RM7890B1030 requires a 220-240V to 120 VAC, 10 VA minimum stepdown transformer to power the shutter mechanism. This transformer is not included and must be provided separately at installation.
The audible alarm on reset is a more subtle difference. On the A1015, pressing Reset is silent. On the B1030, it produces an audible alert — a useful feature in larger commercial or industrial plant environments where lockout events need to be clearly communicated.
The RM7890B1030 was discontinued by Honeywell on April 8, 2022. The current active replacement for new installations requiring shutter drive output is the RM7890B1048. However, for anyone maintaining existing equipment where the B1030 is installed, the functional and wiring footprint remains the same and new old-stock units are the only source for a like-for-like replacement.
Key specs: 120 VAC, 50/60 Hz, intermittent pilot, fixed 4-sec or 10-sec PFEP, intermittent main FEP, no preignition, shutter drive output, audible alarm on reset, -40°F to +140°F, 2.75 lbs. Discontinued April 8, 2022. Requires: Q7800A/B subbase, compatible flame signal amplifier, 120 VAC/10 VA stepdown transformer for shutter (if used).
Who needs this: Technicians replacing a failed RM7890B1030 in an existing installation, or anyone replacing a shutter-equipped UV scanner primary control and needing a like-for-like replacement with shutter drive capability.
RM7895A1014: The On-Off Primary Control with Prepurge
SKU: RM7895A1014 | View Product →
The RM7895A1014 is the natural next step up from the RM7890A1015. Functionally, it is very similar — it's an on-off primary burner control with intermittent pilot, selectable 4-second or 10-second PFEP, and the same general feature set. The critical difference is one word: prepurge.
The RM7895A1014 adds a timed prepurge cycle before every ignition attempt. Before the pilot fires, the combustion air blower runs for a defined period to flush any accumulated unburned fuel from the combustion chamber. This purge cycle is controlled by the ST7800A Plug-in Purge Timer Card, which sits in the wiring subbase alongside the flame signal amplifier.
That purge timer card is the most important thing to understand when buying this unit. It is a third required component that the RM7890 series does not need. Many buyers familiar with the RM7890 family overlook it because the relay module and subbase form the obvious two-part system — but without the ST7800A purge timer card installed, the RM7895A1014 will not operate correctly. It is not included, and it must be ordered separately.
The RM7895A1014 is also the designated replacement for two legacy Honeywell controls: the R4795 and R7795 Primary Controls. If you're modernizing a system that runs either of those older units, the RM7895A1014 with the appropriate subbase and amplifier is the correct upgrade path.
Several other distinctions from the RM7890A1015 are worth noting. The RM7895 series includes an airflow switch check that can be configured via site jumper JR3 — the control can be set to verify that the combustion air blower is actually running before proceeding past prepurge. It also includes a recycle-through-prepurge on flame loss behavior: if the flame signal is lost during the run cycle, the control doesn't simply go to lockout — it recycles back through a full prepurge cycle before attempting re-ignition. Failure to establish flame after recycling results in lockout.
There is also an important subbase note: the RM7895A1014 is a 2000-series relay module and requires the Q7800A2005/U subbase. Older 1000-series Q7800 subbases are not compatible and the module cannot be installed on them.
Key specs: 120 VAC, 50/60 Hz, intermittent pilot, selectable 4-sec or 10-sec PFEP, intermittent main FEP, prepurge via ST7800A purge timer card, airflow switch check (configurable), 10W power dissipation, 2000 VA max connected load, 15A fast blow fusing, -40°F to +140°F, 4 lbs. Replaces R4795 and R7795. Requires: Q7800A2005/U subbase, compatible flame signal amplifier, ST7800A purge timer card.
Who needs this: Commercial boiler technicians and HVAC service contractors working on systems where prepurge is required by equipment design, local codes, or insurance underwriting requirements. Also anyone replacing an R4795 or R7795 Primary Control in an existing installation.
Choosing the Right Unit: A Quick Reference
If you're trying to narrow down which of these five units fits your application, this summary should help:
You need a flame relay output only, not a full primary control → RM7823A1016. You already have a primary control; you just need relay output based on flame status.
Your system requires manual operator start before each burner cycle → RM7838B1013. You're in a semi-automatic industrial application where full automation isn't appropriate or code-compliant.
You need a complete on-off primary control, no prepurge, no shutter drive → RM7890A1015. This is the clean standard choice for the majority of commercial single-burner applications.
You need a complete on-off primary control with shutter drive capability → RM7890B1030 (discontinued, new old-stock) or RM7890B1048 (current production). Your UV scanner uses a motorized shutter that needs to be powered by the relay module.
You need a complete on-off primary control with prepurge → RM7895A1014. Your application, equipment, or code requires a timed prepurge cycle before ignition. Don't forget the ST7800A purge timer card and the Q7800A2005/U subbase.
The Three Questions to Ask Before You Order
Working with flame safeguard controls over the years, the most common ordering mistakes come down to three things:
1. Do you need a primary control or a relay-only module? The RM7823A1016 is frequently confused with primary controls because it looks similar and lives in the same product family. If your system doesn't already have a primary control, the RM7823A1016 won't work as a standalone replacement. You need an RM7890 or RM7895.
2. Does your application require prepurge? If the answer is yes — either because codes require it, the equipment manufacturer specified it, or the existing control has it — then the RM7895A1014 is the correct choice over the RM7890A1015. The two modules look nearly identical and have similar part numbers, but the RM7890 cannot be field-converted to add prepurge functionality.
3. Do you have all required components? Every unit in this guide requires a subbase and amplifier at minimum. The RM7895A1014 additionally requires a purge timer card. The RM7838B1013 also requires a purge timer card. It's worth double-checking what's in your existing installation before ordering — a missing amplifier or the wrong subbase generation will prevent the new control from operating.
A Note on Discontinued Units
Two of the five units in this guide — the RM7838B1013 and RM7890B1030 — have been discontinued by Honeywell. This is increasingly common across the 7800 Series as Honeywell transitions its line, and it creates a practical problem for anyone maintaining older equipment that still runs these controls perfectly well.
New old-stock units are often the best option for like-for-like replacements in existing systems. Swapping to a different model — even within the same product family — can require wiring changes, subbase replacement, amplifier changes, or reprogramming, which adds labor cost and system downtime. When a new unit of the original spec is still available, it is almost always the right call.
Stock levels for discontinued units fluctuate and won't be replenished once depleted, so if you're responsible for equipment that uses the RM7838B1013 or RM7890B1030, buying a spare while inventory exists is worth considering.
About the 7800 Series Amplifiers
One topic that comes up frequently in the context of all these relay modules is amplifier selection. The relay module and the amplifier are separate components, but they must be matched to the flame detector type used in the installation.
The amplifiers compatible with the relay modules in this guide — R7847, R7848, R7849, R7851, R7852, R7861, and R7886 — each support a different detector type or feature set:
- R7847 / R7848 / R7849 — Ultraviolet (UV) amplifiers for use with C7027, C7035, and similar Minipeeper UV detectors
- R7851 — UV amplifier with dynamic self-check capability for use with self-checking UV detectors
- R7861 — Dynamic self-check amplifier specifically for use with the C7061 Purple Peeper detector family
- R7852 / R7886 — Infrared and combination amplifiers for infrared and rectification flame detection applications
If you're replacing a relay module in an existing system, the existing amplifier can typically be reused as long as it is compatible with the new module — which in most cases it will be, since the plug-in amplifier format is standardized across the 7800 Series family.
Final Thoughts
The Honeywell 7800 Series has been in production long enough that many of the relay modules in this guide have already gone through one or more part number revisions, and some have been discontinued entirely. That longevity is itself a testament to how widely deployed this platform is — there are 7800 Series controls running in boiler rooms and industrial plants that have been in service for decades, and the platform remains the industry benchmark for microprocessor-based flame safeguard controls in commercial and industrial applications.
Understanding the differences between a flame relay and a primary control, between a prepurge and a non-prepurge module, and between a manual-start industrial programmer and a fully automatic controller is the foundation for buying the right part the first time. Hopefully this guide makes that a little easier.
All five units — RM7823A1016, RM7838B1013, RM7890A1015, RM7890B1030, and RM7895A1014 — are available at ACR4Sale. Questions about compatibility or application? Call us at 1-800-349-4360.