Understanding your furnace's combustion & safety processes

illustration by Ben Hirsch

This illustration should give you an idea of what we do to insure your safety while providing efficient and optimal combustion in your furnace. Please see the description of each of these components below.
We at Wet Dog Glass take safety seriously. Generally, when a studio meets NFPA (National Fire Protection Association) standards, a higher safety level exists. The higher your safety level, the better you sleep at night. What's more is that many insurance companies look for NFPA compliance as a safety minimum. We are proud to supply the components required to comply to these safety standards.

Control:
[A] Regulator ($95.00-$150.00) maintains stable gas pressure over full range of required gas flow.
[B] A programmable controller reads one of two [C] type-S or type-R
thermocouples ($250.00-$285.00; price fluctuates due to current platinum value; includes protective
ceramic tube; type-r is more accurate at lower temperatures) and activates an
[D] actuator motor ($525.00) which opens/closes the [E] butterfly valve ($75.00-$115.00).
As the air pressure changes, the [F] proportionator ($145.00-$175.00) proportionally adjusts the gas flow.
Safety:
[G] Flame monitoring unit ($512.50) energizes [H] spark ignition transformer ($82.00) only after
purging the atmosphere inside the furnace with fresh air. It then initiates a trial-for-ignition period of 15 seconds during which the [I] spark plug (standard) fires and the main gas valves allow gas flow to the burner. If the [J] U.V. Scanner ($150.00) sees a flame, the valves stay open and the spark plug is de-energized. Otherwise the valves close and a manual reset is required.
[K] The Redundant Automatic Shutoff Valves or DMV-DLE (price range: $860.00 - $1,300.00; mandatory on furnaces over 150KBTU/HR) shut off the gas immediately if any of the following incidents occur:
1. Loss of blower pressure sensed by [L] air pressure switch. ($76.00)
2. Excessive fluctuations in gas pressure sensed by [M] gas pressure switch ($87.50) and [N] closure proven indicator (62.50).
3. Loss of flame (detected by [J] U.V. Scanner)
4. [O] Hi Limit switch ($145.00) reads an unsafe temperature value (higher than that at which the furnace
can operate safely) from [P] second thermocouple.
Optional [Q] automatic dialer can be programmed to call three numbers three times each if temperature drops below or rises above given set-point and if gas valves shut.

Prices and options vary greatly, so feel free to contact us regarding a particular installation.