17
c l i m a t e m a s t e r.c o m
Tranquility
®
30 Digital (TE) Series IOM - 60Hz HFC-410A
R e v. : O c t o b e r 5 , 2 0 2 1
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 flow
through inactive units, increased pumping requirements,
and more complex flushing needs. Three types of multiple
unit systems are described below along with guidelines for
installation of each type.
vFlow
™
internal variable flow technology is a great assist
for systems with multiple units. vFlow
™
is available in three
different configurations:
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 flushing 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 fluid from the
loop when loop pressure rises and inject fluid into the loop
when loop pressure falls. In this way the expansion tank will
help to maintain a more constant loop pressure and avoid flat
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 flow
through the heat pump against the loop head when all units
are operating.
Units with the standard head pump should not be combined
with units with high head pumps on the same loop. Standard
head pumps are best suited for small applications with a
single unit.
It may be possible to flush a multiple unit system through
the unit’s flushing valves. Flushing pressure drop of the
valve may be calculated to determine if it is acceptable.
Engineering data for the 3-way flushing 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 flushing pressure drop as
follows. From Table 1 we know that it will take 4 gpm to flush
each ¾” circuit. If there is no provision to isolate the circuits
for flushing, we will have to flush with a minimum of 4 circuits
x 4 gpm/circuit = 16 gpm total. A check of other piping sizes
used must be done to ensure that 16 gpm total flow will flush
all piping.
Pressure drop through the flushing valve can be calculated
using the following formula.
ΔP = (GPM/Cv)
2
where,
ΔP = pressure drop in psi through the valve while flushing
GPM = flushing flow in gallons per minute
Cv = valve Cv in flushing mode
We know from Table 2 that the Cv for the flushing valve in
a TE026 is 10.3 in the flushing mode (90° flow). Therefore,
ΔP = (GPM/Cv)
2
= (16/10.3)
2
= 2.4 psi per valve (there are
two flushing valves). So long as the flushing pump is able to
provide 16 gpm at the flushing pressure drop of the loop plus
the 2.4 x 2 valves = 4.8 psi of the flushing valves, the internal
flushing valves may be used. If the flushing pump is not able
to overcome the pressure drop of the internal flushing valves,
then larger external flushing valves must be used.
Unit Configuration
Multiple vFlow
™
units with internal variable-speed flow
controller and check valve, piped in parallel sharing a
common loop MUST
be configured for ‘VS PUMP PARALLEL’
in Installer Settings Menu.
Installer Settings
System Config
Unit Config
Loop Config
Table 2: Internal 3-Way Flushing Valve Data
Model
Flushing
Connection
Straight
Flow Cv
90°
Flow Cv
TE026 - 038
3/4" FPT
25
10.3
TE049 - 072
1" FPT
58
14.5
UNIT CONFIGURATION
CURRENT CONFIG TE026
HEAT PUMP FAMILY TE
HEAT PUMP SIZE 026
BLOWER TYPE ECM
LOOP CONFIG VS PUMP
PARALLEL
SELECT OPTION
PREVIOUS SAVE
TE026
TE
