C7027A

What does this device do in a burner management or flame safeguard system?

It detects ultraviolet (UV) radiation emitted by a combustion flame and provides a flame signal to a compatible Honeywell flame safeguard control/amplifier. When correctly sighted, it helps the control confirm flame presence during ignition and operation.

What fuel types and burner applications is it typically used for?

It is commonly used for flame supervision on gas, oil, or combination gas-oil burners where UV flame detection is appropriate and a clear line-of-sight to the flame can be achieved.

How is it mounted to the burner or combustion chamber?

The detector has an integral collar with 1/2-14 NPSM internal threads designed to mount onto a 1/2-inch sight pipe or suitable fitting. The sight pipe location and angle are typically set during commissioning to achieve a stable flame signal.

Does it require a direct line-of-sight to the flame?

Yes. UV detectors must “see” the flame to generate a reliable signal. The sight pipe and detector position should be arranged so the detector views the target flame area without being exposed to non-flame UV sources.

What are common non-flame UV sources that can interfere with operation?

UV detectors can respond to UV from ignition spark, welding arcs, certain lamps, and very hot refractory surfaces. Installations are typically arranged so the detector does not view ignition spark and does not have an excessive view of hot refractory.

What are the typical wiring requirements and lead identification?

It uses two colour-coded leadwires. In standard Honeywell wiring practice for these UV detectors, the blue lead is connected to the F terminal and the white lead to the G terminal at the flame safeguard control/amplifier. Maintaining correct polarity is important for proper flame supervision.

Can the detector wiring be run in the same conduit as ignition transformer wiring?

It is generally avoided. Routing detector leads separately from high-voltage ignition wiring helps reduce electrical interference and preserves flame signal strength.

What ambient temperature limits should be considered during installation?

Depending on the specific model variant, the ambient operating temperature rating is typically either 0°F to 215°F (-18°C to 102°C) or -40°F to 215°F (-40°C to 102°C). Confirm the exact rating for the unit/variant being installed.

What is the maximum pressure rating for the housing when installed on a sight pipe?

Properly installed, it is pressure rated up to 5 psi (34.5 kPa) for typical applications.

Can two detectors be wired in parallel to improve flame sighting reliability?

Yes. Up to two UV detectors of this type may be connected in parallel in difficult sighting applications to reduce nuisance shutdowns. When wiring in parallel, background signals add together and minimum ambient temperature limits at the detector may need to be increased depending on the detector’s low-temperature rating.

How is the flame signal measured and what levels are generally expected?

Flame signal is commonly measured at the flame safeguard control/amplifier using the control’s flame test points/jacks and an appropriate meter. Acceptable minimums depend on the specific Honeywell control/amplifier; typical minimum steady flame current levels are often in the 1.5–3.5 microamp range for many systems, while some systems use a DC voltage flame signal output.

What should be checked if the flame signal is low or unstable after installation?

Typical checks include verifying correct detector aiming (sighting), confirming correct lead polarity (F/G), ensuring detector leads are routed to minimise electrical noise, checking for excessive heat at the detector location, and confirming the detector is not viewing ignition spark or other UV sources. If a consistently adequate signal cannot be obtained, replacement of the detector (for example, Honeywell C7027A) may be required.

Is there an accessory to help with high sight-pipe temperatures?

Yes. A dedicated heat block accessory (Honeywell 136733) can be used to insulate the detector from elevated sight-pipe temperatures (up to 266°F / 130°C at the sight pipe in the referenced application guidance), helping keep the detector within its ambient temperature limits.

Are there best practices for sight pipe selection and positioning?

A black iron sight pipe is commonly recommended. The pipe is usually kept as short as practical, often angled slightly downward to reduce build-up inside the pipe, and positioned so the detector views the most stable flame zone across firing rates while avoiding line-of-sight to ignition spark.