Section 3 060203a-db Flashcards
(88 cards)
Name the two types of hydronic systems
Gravity systems
Forced flow systems
How do gravity systems work
Circulation relied on natural convection with the heated water rising in the supply and the denser, cooler water dropping in the return piping
What are the 2 major drawbacks to gravity systems
Large diameter piping
Slow response time
What are forced flow systems
Addition of circulator
What are the two advantages to forced flow systems
Very Efficient
Smaller pipe diameters
What are the 4 types of forced flow systems
Monoflow systems (one pipe system)
Reverse return (two pipe systems)
Direct return (two pipe systems)
Series loop (one pipe system)
What does a monoflo system have that others don’t
Venturi tee
What does a Venturi tee do?
Reduces pressure at the outlet of the Venturi causing a flow of fluid from the convector into the header (typically on the outlet side)
What are the advantages and disadvantages of monoflo systems?
ADVANTAGES: less piping, and each unit can be controlled individually.
DISADVANTAGES: limited sizes of Venturi tees,temp of fluid decreases after each unit, and heat transfer units with high resistance don’t work well with this system
What is a direct return system
First supply, first return
What are the advantages and disadvantages of direct return systems
ADVANTAGES: all units get the same temperature, and size of piping can be reduced as flow requirement is reduced.
DISADVANTAGES: unequal length of each circuit, prone to short circuits, and must have balancing valves.
What is a reverse return system
First supply last return
The distance for each unit on a reverse return is the nearly the same (true/false)
true
What are the advantages and disadvantages of a reverse return system?
ADVANTAGES: easy to balance, individual units can be controlled.
DISADVANTAGES: more piping, expensive to install.
What is a series loop?
All fluid flowing through the circuit flows through each series-connected baseboard.
What are the advantages and disadvantages of a series loop?
ADVANTAGES: reduces the amount of piping.
DISADVANTAGES: first convector gets the highest temperature fluid, downstream units may have to be increased.
What kind of valves are used for isolation
Gate and ball valves are a good choice
What valve is used for balancing
Globe valve
Where are balancing valves installed in a heating system?
Either the supply or return (preferably on the return)
Stem on valve has to be installed with the valve stem in a ___________ position to prevent air from being trapped.
Horizontal
What is a wild loop
A connection between the supply and return piping that allows for continuous flow
When using a wild loop what is required to prevent dead-head
A bypass
What are radiator valves
Used to stop or reduce circulation at each heat emission unit.
What are zone valves
Allow flow to specific areas or zones