Honeywell 700 User Manual

66-2069—02

10

Vortex coolers (M3204, M3208, M3210, M4025) - Used with 

air cooling canister. Contact your distributor or the factory for 

selection assistance.

Cable restraints (800CR, 700CRLT) - Liquid tight S80X and 

S70X cable restraint versions.   The 800CR includes the 

700CRLT and the 800ACC-RING adapter.

S80X adapter ring (800ACC-RING) - Adapter ring to fit S80X 

viewing heads to 700ACC cooling jacket and 700CRLT liquid 

tight cable restraint.

Right angle adapter (700RAA) - S70X/S80X viewing head 

right angle adapter. 1/2 in. NPTF to 1/2 in. NPTM connections.

Mounting blocks (700DA, 700DA-1, 800DA) - Delrin 

replacement adapter/mounting blocks for S70X and S80X 

viewing heads. All have 1/4 in. NPTF purge air connections.   

Rated for continuous service up to 180F (82C). The 700DA 

and 800DA have 1/2 in. NPTF process connections while the 

700DA-1 has a 1 in. NPTF process connection. For more 1 in. 

NPT accessories that can be used with the 700DA-1, refer to 

the S55XB/BE manual, 66-2064. 

USB to RS422/RS485 Converter (COMMOD) - Protocol 

converter for use with external communication with a remote 

computer.

Fiber Optic System Compatibility - The S70X and S80X 

viewing heads are compatible with the Honeywell FASA fiber 

optic extension products. The S700FOAD and S800FOAD 

adapters are applicable, depending on the application. 

Contact your distributor or the factory for assistance with fiber 

optic selection and pricing.

The S702 and S802 viewing head models use a Germanium 

photodiode, which responds to IR radiation/flicker in the flame. 

Flame flicker is caused by the combustion, or forced air 

injected in to the flame. Combustion air can be mixed with the 

fuel (pulverized coal) or can be introduced separately. In either 

case, forced air is introduced in such a way as to aid the 

combustion process. This air is usually made turbulent by 

causing it to swirl with spin vanes located in the burner throat. 

Flame flicker is created when turbulent air mixes with the 

flame. It is composed of random frequencies and the amount 

of high frequency flicker is dependent on the fuel and the 

burner.

The S702, S702PF and S802 viewing head models respond 

to flicker frequencies above 33Hz while the S702HF, 

S702HFPF and S802HF viewing heads respond to flicker 

frequencies above 155Hz. All flicker frequencies below the 

filters are ignored, so it is important to sight the viewing head 

on the highly turbulent portion of the flame that contains the 

higher frequencies. The location of the higher frequencies can 

be predicted by examining the burner with regard to where the 

turbulent air enters the flame. The optimum scanner location 

is parallel to the burner center line (Fig. 15). The use of a 

swivel mount is encouraged to allow for line of sight.

If a good count ratio between BNR-ON and BNR-OFF cannot 

be obtained when using an IR viewing head—particularly 

when monitoring oil flames—an IR viewing head with the High 

Frequency (HF) filter option is recommended. The standard IR 

viewing head responds to flicker frequencies above 33 Hz; 

with the HF option, the IR viewing head responds to flicker 

frequencies above155 Hz.

The S706, S706PF and S806 viewing head models use the 

UVTron tube, with a spectral response of 185-260nm and 

peak response of 210nm to ultraviolet radiation. The output of 

the detector is a pulse stream of randomly spaced pulses 

whose average rate is proportional to the UV radiation present 

in the flame. The UV radiation is a direct result of the 

combustion process as oxygen combines with hydrocarbons 

in the fuel in the blue part of the flame. The yellow part of 

flames, and the background radiation from hot refractory, do 

not emit UV radiation. 

The spectral range of the UV tube makes it ideal for 

discriminating between flame and glowing refractory. As with 

any UV radiation, it can be absorbed or masked by unburned 

fuel, smoke, oil mist, dirt dust and other impurities in the fuel. 

Care should be taken to select the proper viewing head for the 

fuel used. Additionally, the contaminants that mask UV can be 

diluted by providing a strong flow of air through the sight pipe 

to clear a viewing path through the attenuating material. See 

It may also be desirable to sight the detector at an area 

containing fewer masking agents such as near the burner 

nozzle or near the entrance of the combustion air. Increasing 

the viewing area of the detector by shortening the sight pipe or 

by increasing the diameter of the sight pipe can also reduce 

the attenuating effects of the masking agents.

In general, the UV viewing heads will work well on natural gas 

and light oil flames. The sighting for both oil and gas flames 

should be parallel to the axis of the burner and aimed at the 

root of the flame, as with the IR detector. (See previous 

section, “IR Detector.”) The highest UV intensity occurs near 

the root of the flame (Fig. 16). In addition, the zone of higher 

UV intensity does not overlap the same zones of adjacent or 

opposing burner so that, with proper sighting, discrimination 

can be achieved.

With low NOx gas burners, the UV radiation is usually much 

less in intensity and spread out. Relatively high readings can 

be obtained from all over the furnace when many burners are 

in service. This is particularly true when flue gas recirculation 

is used. There will however, be a relatively stronger signal 

near the “root” of the flame and the more intense spot should 

be located during the aiming or sighting process. This “root” or 

intense spot may be further out than with the standard gas 

burner so it is imperative that a swivel mount be used when 

making sighting adjustments.

Another factor that needs to be considered when aiming the 

viewing head is the load condition of the boiler. The flames 

from a burner can be radically different at different loads. This 

is one of the reasons for choosing an optimum sighting initially 

that will minimize signal swing due to changing loads.