Hydronics 7

Generally, for a two-pipe system, the connections to risers, branches, or terminal units are taken off the top of the main at either a 45° or ___ angle from the horizontal plane.

90°

A trunk or trunk line is a smaller pipe taken off from the main to supply other smaller branch lines or terminal units.

False

A two-pipe direct return system is preferred over a two-pipe reverse return system because the direct return system is easier to balance.

False

A vertical branch connection from a main to a terminal unit is sometimes termed a runout.

False

In a direct-return system, the first terminal unit taken off the supply main is the last to return to the boiler.

False

In a one-pipe system, the supply connection to the terminal unit must be downstream from the return connection.

False

The temperature of a secondary loop HTF is not sufficient to provide the proper heat transfer needed for the terminal unit supplied by the tertiary loop.

False

Where unit heaters comprise either all or part of the heating units in a hydronic system, it is generally recommended that they be installed on a one-pipe system rather than a two-pipe system.

False

A secondary circuit or loop is a separate piping configuration connected to the primary loop and supplies HTF to separate heat transfer loads or terminal units.

True

A single main system is a hydronic piping system in which a single main, or primary circuit, provides HTF to terminal units that are each connected to the main by a separate secondary loop or circuit.

True

General piping layout should be as simple as possible.

True

In a manual changeover system when there is a relatively low pressure drop through an average boiler, the pump will tend to circulate excessive quantities of HTF, causing velocity noises and possible overloading of the pump motor.

True

In a single main system, flow in the main will not be affected by reducing or stopping flow in individual terminal units as in the series loop system.

True

In a single main system, if proper air control equipment is installed at the heat source, further venting should not be necessary.

True

In an automatic changeover system, the tees that connect the chiller or boiler to the system piping are placed as close together as possible to keep the pressure drop between them to a minimum.

True

In two-pipe systems, the size of the main is reduced as branches are taken off the main.

True

The two types of one-pipe systems are the series loop system and the single main system.

True

Most of the problems associated with manual changeover heating and cooling systems are eliminated by the use of ____________________ changeover systems.

automatic

____________________ connections should not be used on the return piping of divided circuits to the heat source.

bull-head

A ___ valve changeover is the most commonly used changeover method using two three-way valves connected to the terminal unit or zone piping on a four-pipe system.

conventional three-way

There are two main styles of ____________________ fittings in use: the Monoflo® fitting developed by Xylem, Inc. and the Venturi Fitting developed by Taco.

diversion

In a four-pipe system, a ___ valve is generally recommended when high differential pressures are encountered.

double-seated two-way

A ___-pipe system is used where each terminal unit or zone may heat or cool independently of all other units or zones.

four

In a(n) ____________________-pipe system, each terminal unit is controlled by two-position valves that are operated by a thermostat.

four

The ____________________ line is the large pipe that distributes HTF from the heat source or chiller to smaller branch pipes.

main

A(n) ____________________ hydronic system is a piping system in which a single main line serves as the hot supply and hot return piping to and from the heat source.

one pipe

In ___ is when two or more circuits or branches have a common starting and ending point.

parallel

A diversion fitting is a fitting that creates a greater-than-normal ___ in a line in order to divert flow to another line.

pressure drop

The ___ circuit or loop is the piping directly connected to the heat source or chiller inlet and outlet and to which the compression or pre-charged expansion tank is connected.

primary

A tee-shaped fitting is a carefully engineered device which introduces just the right amount of ___ to ensure a proper diversion of HTF to terminal units.

resistance

In a(n) ____________________ system, the first terminal unit taken off the supply main is the first to connect to the return main.

reverse-return

____________________ are vertical mains or large vertical branches from which smaller branch lines are taken off to provide HTF to terminal units.

risers

____________________ circuits in the single main system are connected to the primary circuit by diversion or diverter fittings.

secondary

A ___ system is a piping system that circulates HTF through a single main in which each terminal unit serves as a portion of the main.

series loop

Expansion and contraction occurring in system piping will also occur in the ____________________, and thus expansion and contraction protection will be critical.

terminal unit

A(n) ____________________ loop is an additional loop taken off of a secondary loop to provide HTF to an additional terminal unit.

tertiary

____________________ valves are silent, efficient, nonelectric control valves that provide reliable temperature control for hydronic terminal units.

thermostatic

A(n) ____________________-pipe system permits any zone or building space to be heated or cooled independently of any other zone, although all zones are supplied by the same piping.

three

In a ____________________-pipe system, a hot supply main is run from the heat source to terminal units, and a chilled supply main is run from the chiller to the same units.

three

The ___ line is the section of the main in a multiple circuit system that carries the combined capacity of the circuits.

trunk

A single loop system can serve ___ circuits.

two

In a correctly designed ___-pipe system, the pressure in the supply main is higher than that in the return main, and a slight variation in the distances of the supply and return connections from the heat source is usually not an important factor.

two

A ___ hydronic system is used where the terminal units, such as unit heaters and convection units for heating and cooling, have very high pressure drops.

two-pipe

A ___ is a section of a building that is controlled by one HVAC controlling device.

zone

____________________ allows for the independent control of separate building spaces, which will, in turn, help to reduce energy costs by using only the energy to heat or cool a zone when and where it is needed.

zoning