Hydronics Controls, Valves, And Parts Flashcards
Electric Controls for Boilers:
- What do Operating Controls do? and give 2 examples
- What do actuators do?
- what are Limit and safety controls for? give 3 examples
Electric Controls for Boilers:
_ Operating Controls: measures changes in variable conditions ex: Thermostat or Aquestate
- Actuators: Regulate Flow (Primary Controls, and Final control element)
- Limit and Safety Controls: High limit, low limits, and safety switches. Detects dangerous conditions
Mechanical Controls:
- list 5 types
Mechanical Controls:
- Safety Relief Valve
- Pressure reducing valve
- Gauges
- Manually operated devices (isolation and drainage valves)
- Expansion Devices (such as cushion tanks and diaphragm tanks)
Safety Relief Valves (Pressure relief valve):
- Is it required on every type of boiler?
- What are the symbols associated with it?
- What 2 factors are used to size it?
- Are valves aloud down stream of the PRV?
- How large does the drain have to be?
- Max and Min Air brake are?
- Are threads aloud on the drip tube
Safety Relief Valves (Pressure relief valve)
- At least 1 on every individual boiler
- Symbol is “V” or “VH”
- Sized using both the input rating and the maximum allowable pressure
- No valve on the drain of the valve
- Drain must be at least the same size as the relief valve
- Max air brake from floor is 12” and Minimum Air brake is 6” off floor
- No threads on outlet pipe (drip Tube)
High (Safety) Limit Control:
- What does a High limit control do when activated?
- At what temperature must it activate at?
- Does it work with or separate from other boiler controls?
High (Safety) Limit Control:
- A Fired hot water boiler Must have a safety limit control (High limit Control) that will cut off fuel supply.
- It is activated when temperatures exceed 121°C (250°F)
- It doesn’t operate with other boiler controls, but will shut off the gas if other controls fail (Last line of defense)
Operating Control (Boiler temp control):
- what is the purpose of a Operating control
- at what temp must a Operating control activate?
- What are the 3 types
Operating Control (Boiler temp control):
- Each Fired hot water boiler must have a control that will cut off the fuel supply when the water temp reaches the desired operating limit
This limit is below the Maximum allowable temp of 121°C (250°F)
Examples of these are:
- Aquastat: not very common
- Indoor-outdoor control: common, and adjusts boiler supply temp based on outdoor air
- Microprocessor controller
Valves Part 1:
Isolation Valves:
- What 2 valves are used for this?
- What is there purpose?
Isolation Valves
- Gate valves and Ball valves
- Used to isolate a section of piping for repairs
Valves Part 2:
Balancing Valves:
- What are they used for?
- What type of valve is used?
- Do they go on supply or return?
- What should be done with the handle once its properly balanced?
Balancing Valves
- Used to balance the heat requirements of different zones and to stop short circuiting from happening, They also help to encourage proper, balanced flow
- Globe valve can be used but there are also specialty balancing valves
- Can be on either supply or return, (preferably on the return)
- It is good practice to remove the handle once properly balanced, this prevents tampering
Valves Part 3:
Radiator (Rad) Valves:
- Used for?
- What are the 2 types?
Radiator (Rad) Valves
- Stops or regulates flow to a Rad
- there are Two types: Sleeve and Disc Types
(See papers for more info)
Valves Part 4:
Zone Valves:
- What is it used for?
- What device are they usually hooked up to?
- Powered by how many V?
- Comes in N.O or N.C or both?
- What does power do to a Normally open valve?
- What does power do to a Normally closed valve?
- What is a 4 wire zone valve used for?
Zone Valves:
- Allows flow to specific areas (Zones)
- Are almost always connected to a thermostat
- Can be either electric or pneumatic (air control)
- Powered by low voltage (24V)
- Come in either normally open or normally closed
- Normally open: power causes valve to close
- Normally closed: power causes valve to open
- 4 wire zone valves have a end switch that will activate and tell the boiler to fire up when needed, or could send power to open other valves
Valves Part 5:
Flow Control Valve:
- where is it usually installed?
- What is it used for? and what does it prevent?
- Does it have to be placed a specific direction?
Flow Control Valve:
- Installed close to boiler
- When circulator is on flow runs regularly, but when circulation is off it prevents the circulation sometimes caused by gravity
- Must be installed in the correct direction
Boiler Feed Piping part 1:
Backflow Preventer: (Check Valves):
- Why must every boiler have this?
- What do these stand for and what severity level are they used for?: DCAP, DCVA, and RP
Backflow Preventer: (Check Valves)
- Every boiler must have a Backflow preventer so that there is no cross contamination between a potable water system and hot boiler water
- Several devices for different degrees of severity:
-DCAP: Duel check with atmospheric port (Low degree of hazard)
- DCVA: Double check valve assembly (Moderate degree of hazard)
- RP: Reduced pressure principle backflow preventer (Severe degree of hazard)
- Residential boiler feeds typically have a shutoff valve, backflow preventer, and a PRV. and the Backflow preventer would be either a DCAP or DCVA.
Boiler Feed Piping part 2:
Residential Boiler water Feed:
- What is a isolation valve for?
- PRVs are set to what psi?
- Read card for more
Residential Boiler water Feed (Components)
- Isolation Valves (Shut off valve)
- PRV: Pressure reducing valve, can be set to 15 psi for low pressure applications
- Boiler feeds are often piped to connect to a tee, the lower side leads to a expansion tank and then above is a air eliminator dives that is ran inline with the boilers hot supply pipe
Boiler Feed Piping part 3:
Commercial Boiler Water Feed:
- what is another word for this water make up assembly?
- see Q-card for order of valve train
Commercial Boiler Water Feed:
- Boiler water feed called a “Valve Train”
See Q-Card on Valve trains for Order of appliances on a valve train
Boiler Feed Piping part 4:
Expansion Tank:
- What is it used for in a hydronic system?
- how much does water expand? (%)
- what has happened if the Pressure relief valve is leaking?
- how can you tell a tank needs replacing?
- What is the expansion tank pressure set to based on the PRV
- where do you install it in relation to the pump?
Expansion Tank:
- Provides room for water to expand in a closed hydronic loop
- Water expands about 1/23 or 5%
- If PRV is leaking the expansion tank may be to full
- if you tap on air side and you head a dual sound the tank is water logged
- Expansion tank pre-charge = same pressure set by the PRV
- Always install the expansion tank upstream of the Pump/Circulator
If the pump is on the other side it could cause the pressure to be lowered to a point where the water would boil at the inlet to the impeller and cause cavitation
- Thermal expansion of water: Total Gallons x 0.00023 x (change in Temperature)
Air separator and Air eliminator part 1:
Air separator:
- what does it do?
- 3 different types?
Air separator: separates water and air
- Boiler fitting
- Line Scoop (Air Scoop)
- Micro-Bubble Resorber
