Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
14 Cards in this Set
- Front
- Back
|
What is a Cad cell? |
Is a flame proving devices that allows current to flow in the presence of light. |
|
|
Your choice of valve depends on What tipical types of valves? |
1. Two wire zone valves (energize to open valves) 2. Two wire zone valves (energize to close the valve) 3. Three wire zone valves that require power from the thermostat to open or close the valve. |
|
|
Safety control devices include? |
Low water cutout, temperature control devices,aquastats, flow switches,high limit control devices. |
|
|
What is the typical voltage for a zone valves? |
24V |
|
|
What is the purpose of a flame rod? |
To detect a burner flame |
|
|
What is LWCO used for? |
To shut off the burner if the boiler water is too low |
|
|
What are the 2 types of aquastats? |
Immersion and surface mount |
|
|
What should be interlocked with the circulating pump in a intermittent circulation system? |
The main gas valve (MGV) |
|
|
A end of travel switch can be used to start which two components? |
Circulation pump and a boiler burner |
|
|
Are end of travel switchs a normally open or normally closed set of contacts? |
Normally open |
|
|
Which system utilizes a high temperature element to ignite the main burner? |
Hot surface ignition |
|
|
What does a single zone system require? |
One thermostat and one or more terminal units |
|
|
What happens to a light sensitive proving device when it is exposed to light? |
Experiences a change in resistance |
|
|
What does a multi zone system require? |
One thermostat and one zone valve for each zone |
