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G e o t h e r m a l H e a t i n g a n d C o o l i n g

Tranquility

30 Digital (TE) Series IOM - 60Hz HFC-410A

R e v. : 2 9 M a y, 2 0 1 5 J

Multiple Unit Piping and Flushing

Often projects require more than one heat pump. Where
possible, it makes sense for multiple units to share a common
ground loop. Common ground loops for multiple units bring
new challenges including the need to avoid backward

through inactive units, increased pumping requirements,
and more complex

ushing needs. Three types of multiple

unit systems are described below along with guidelines for
installation of each type.

vFlow

™

internal variable

ow technology is a great assist

for systems with multiple units. vFlow

™

is available in three

different con

gurations:

1. Internal variable-speed pump for closed loops
2. Internal modulating valve for closed loops
3. Internal modulating valve for open loops

The internal modulating valve for closed loops version is a
low system pressure drop valve that in most cases is not
suitable for open loop systems.

The internal modulating valve for open loops version is a high
system pressure drop valve that in most cases is not suitable
for closed loop systems.

To determine if these valve versions are appropriate for the
available pumping refer to the Tranquility

30 Digital (TE)

Series IOM part number 97B0045N04 for performance
characteristics of the valves.

The internal variable speed pump version of vFlow

™

includes

an internal variable speed circulator controlled by the DXM2
microprocessor, internal 3-way

ushing valves, an internal

bladder type expansion tank, and front-mounted pressure
ports that allow access to the pressure drop across the
coaxial heat exchanger only. The pump includes an internal
check valve. The pump curves are shown in Figures 13 and
13a. The internal expansion tank will operate as a pressure
battery for the geothermal system. It will absorb

uid from the

loop when loop pressure rises and inject

uid into the loop

when loop pressure falls. In this way the expansion tank will
help to maintain a more constant loop pressure and avoid

loops due to seasonal pressure changes in the loop.

When using the internal variable speed pump as the loop
pump in multiple unit installations it is important to ensure
that the variable speed pump can provide adequate

through the heat pump against the loop head when all units
are operating.

Units with UPM Geo pumps should not be combined with
units with Magna Geo pumps on the same loop. UPM Geo
units are best suited for small applications with a single
geothermal heat pump.

It may be possible to

ush a multiple unit system through

the unit’s

ushing valves. Flushing pressure drop of the

valve may be calculated to determine if it is acceptable.
Engineering data for the 3-way

ushing valves can be found

in Table 2.

For example, if a system includes two 2-ton units and four ¾
loop circuits we can calculate the

ushing pressure drop as

follows. From Table 1 we know that it will take 4 gpm to

ush

each ¾” circuit. If there is no provision to isolate the circuits
for