Flame Detection Problem

[mickyb0]

Hello All,

I have "inherited" a small industrial gas fired air heating system which locks out, on average, about once a week. The control unit is a Satronic MMI 810 Mod.45.which has a UV cell as a flme detector. I have no information on this controler, apart from an inscription on the bottom of it, saying that it must not be used with a UV cell !!! I am, therefore assuming that it should be connected to a flame rectification detector.
As this unit works most of the time can anyone tell me if the flame detection currents produced by the two different systems are similar and also if this could be the source of my problem.

Thankyou.

 

[DougMSOE]

First off, gas flames ARE detected by a UV cell. Some of the older types are of gas tube design. Not only is the intensity used as detection, but also the frequency of the flame for detection. This is done so discrimination between the furnace walls and the flame is accomplished. Suggest that you look at the signal with an "o" scope and do some research (in the library) how the older systems work.

 

[mickyb0]

Thankyou for your reply but I am afraid I may not have explained myself well enough. I am well aware of the reasons for using a UV cell and have used them for many years on various applications.
My question was, basically, is the output from a flame ionisation, or flame rectification, detector similar to that of a UV detector. As I said, this control unit is working happily with the UV detector even though the inscription says it must not!

 

[DougMSOE]

I believe that it is the ionisation. It has been a few years.

 

[hacksaw]

some one must have modified the circuit. about the only change would be the coil voltage required on the detection relay.

the flame rods used 115 v at one time, and produced enough current to pull in a relay.

conversion to a uv det. would require a bit of re-wiring. the one issue that could cause you some grief is that the uv systems generally have a fail-safe timer that drives a shutter assy. if the time delay in the output relay is not set right, you can get a drop out. make certain that your are not having burner problems, you want a safe system.

if you are having problems with it, replace or upgrade. otherwise your have to trace out your circuit to sort out what was done.