Flame Rectification

Question 1

What was the major weakness of early, AC conductivity flame detection systems?

Answer 1

Carbon deposits created by flame impingement could create a “bridge” between the electrodes that had a similar resistance/conductivity as the flame. Thus creating an unsafe situation.

Question 2

What is the minimum and preferred ratios of ground electrode to flame electrode?

Answer 2

• Minimum 4:1
• Preferred 10:1

Question 3

Where is the ground electrode usually located?

Answer 3

In the burner head

Question 4

What is rectification?

Answer 4

The conversion of an alternating current to a direct current

Question 5

How does a diode work?

Answer 5

It operates like a check valve. It has low resistance in one direction and high resistance in the other

Question 6

What is identified by the flame safeguard to prove that a flame is present?

Answer 6

The imbalance of current flow. In this way the flame safeguard can distinguish between a short to ground and a flame

Question 7

What are the three characteristics of a premix pilot?

Answer 7

• Strong
• Stable
• Higher flame propagation
  (A raw gas pilot is the opposite of these)

Question 8

How quickly can a flame rod amplifier detect the loss of flame?

Answer 8

Within microseconds

Question 9

What must be done when setting a pilot burner/flame rod system?

Answer 9

A pilot turndown test must be performed

Question 10

On an in-shot burner the flame rod should be position above the burner.

TRUE / FALSE

Answer 10

False

Question 11

What are the two main advantages of flame rod systems?

Answer 11

• Quick response to flame failure
• Flame rods cannot be bypassed or defeated

Question 12

Flame rods can be used with fuel oil systems.

TRUE / FALSE

Answer 12

False

Question 13

Flame rods can be used to supervise pilot only, main flame only or pilot and main flame.

TRUE / FALSE

Answer 13

True

Question 14

What do you use to clean a flame rod?

Answer 14

A Scotch Brite pad