Chapter 105 Flashcards
A low gas pressure cut off switch will shut down the burners due to?
Low gas pressure
A thermal element, used on hot water boilers is capable of sending temperature and?
Converting it into a pressure signal
What are the three distinct methods of burner operation control?
On-off, modulating, high-low
What is the pressure control device used for on steam boilers?
Starts and stops the burner to maintain the pressure within set limits
What kind of boilers are on-off controls most commonly used?
Low capacity boilers
The operating pressure of a on-off device is controlled by what?
The tension of the large spring (increase in tension will raise operating pressure)
To reduce cycling (starting and stopping of on-off device) what is installed?
A second spring (differential adjustment)
What must be adjusted in direct proportion to the firing rate of the burner to maintain the proper fuel-air ratio?
Air to the furnace
A damper positioning switch is used on boilers with a high-low fire control that has three positions:
Automatic, low, high
A high pressure fuel cut-off switch open when?
Gas pressure it too high
High limit control is used to shut down the fuel supply in the event of an elevated change in?
Steam pressure
Automatic firing boilers that aren’t under constant supervision must be installed with a high limit control that shuts of the fuel supply to ensure pressure doesn’t raise above?
100 kPa
The low air pressure fuel cut-off switch should be checked when air flow is?
Maximum
The high gas pressure switch can be tested?
During the operation of the boiler
The bottom of the bellows is connected to a sensing bulb by means of a what?
Capillary tube
