Safety
On a gas valve train there are 2 automatic valves 1 is an operating valve used to turn on and off the appliance. The other is?
What is a safety shut off valve?
Used to protect against system failures
When the Servo regulator diaphragm and the main valve diaphragm have reached a stable opening point where the downstream gas pressure and flow rate are matching the demand of the appliance. this in know as the point of ?
That is "The Point of Equilibrium"?
This valve has an internal ball which moves when subject to horizontal vibration?
What is an earthquake valve?
On a rod and tube gas valve for a gas HWT the main burner is activated by a copper tube with what kind of rod inside it?
What is an invar rod?
The Invar rod has a very low expansion and contraction rate compared to the cu tube. When connected at the ends the high expansion cu moves the invar rod which contacts the switch.
When a combination gas valve has a 2nd automatic safety shutoff incorporated into the valve body it is referred to as?
What is a Redundant valve?
If a pilot flame goes out and both the main burner and pilot valves close, this is referred to as?
100% Safe
Whereas the standard diaphragm Valve is a strictly open and close valve. The Servo gas valve can also?
What is act as a regulator or Regulate the flow?
What is required by code when gas commercial kitchen appliances are protected by a fire extinguishing system?
What is the fire extinguishing system must be interlocked with the gas supply so as to shut off the gas if the system is activated?
What is an ECO?
What is an Energy cut off?
The ECO is wired in series between the thermocouple and the pilot stat. There is a fuse on this wire that will melt braking the mv circuit to the safety valve and shutting of the gas in the event of the tank overheating. PG 71-73
How have redundant combination gas valves been adapted to give them modulating operation?
What is an electric stepper motor
Note: see picture B1 LT4 pg67
A safety shut off valve is held open by?
What is a Thermocouple and electromagnet?
A regulating diaphragm gas valve is also known as ?
What is a "Servo Gas Valve"?
Note: see pictures B1 LT4 pg 53
Solenoids work on what principal?
What is electro-magnetism?
What is a TCO?
What is the Thermal cut off?
Located within the FVIR (flammable vapor ignition resistant system) the TCO will trip and shut off the gas if there is ignition of any flammable vapors such as gasoline inside the combustion chamber. Pg74
With Reference to both the Redundant valve disc(1st) and the main valve disc(2nd) within the redundant gas valve body, where is the intermittent pilot gas tapping located?
What is in between the 2 valve discs.
The pilot coil is energized 1st. this allows gas to flow to the intermittent pilot with the main valve still closed. After the pilot is proven the main valve is then energized. See B1 LT4 pg56 drawing.
Thermoelectric gas valves are powered by DC current supplied by a thermocouple or thermopile. How many millivolts does a thermocouple produce when heated by a pilot flame?
what is 30mv?
Note: Thermoelectric safety shut off valves are often referred to as "Pilotstats"
When in the de-energized state, the Servo Diaphragm is ----- and the main valve diaphragm is -----?
What is open & closed?
Note see B1 LT4 pg 53
A sealed bellows actuator works on which principal?
What is thermal expansion of liquids?
A self energized Honeywell gas valve has a status light which produces a code showing the status of the valve. What is used to power this valve?
What is a Thermopile?
A 750mv thermopile is used to energize the circuit board in this valve. Pg 74-75
With redundant combination gas valves that do not use a pilot what are 2 common direct ignition sources that are commonly used?
What is DSI (direct spark ignition) and HSI (hot surface igniter)
What is FFRT and what is the maximum FFRT for a Propane or Butane gas appliance?
What is Flame Failure Response Time? and the max FFRT for any gas appliance using a gas that is heavier than air is 20 seconds.
Note: For gases lighter than air (NG) it is 90 seconds
What controls the rate at which at which an internal bleed diaphragm gas valve opens?
What is the restricting Orifice?
Note: see picture B1 LT4 pg 50
How does a modulating hydraulic gas valve react on an initial call for heat?
What is it snaps open to a preset minimum input.
What does a FV react to?
What is the ignition of flammable vapors within the combustion chamber?
Some redundant gas valves have incorporated Multi stage input (example: a dual stage furnace). What is added to this gas valve to allow it to produce 2 separate gas pressures?
That is a 2nd servo regular?
Note: Low fire is commonly 1-1.5"wc
High fire 3-4"wc