Enertech EAV060 - Enertech Recommendations for All EAV Unit Applications

Enertech Global 
EAV - EME/EMD Rev. A Models
Installaon and Operaons Manual

Almost all air-to-water and water-to-water heat pumps
require a buer tank. With the introducon of variable speed
compressors, the requirements have changed and are addressed
in this secon. The purpose of a buer tank is primarily to keep
the heat pump running long enough to prevent short cycling
when the hydronic load is much smaller than the heat pump
capacity. Another important use of the buer tank is to decouple
the ow rate required for the heat pump from the ow rate of
the hydronic system, which is typically much less than the heat
pump requires. Heat pumps with single speed and two-stage
compressors almost always need more ow rate than the design
ow rate of the hydronic system, especially if only one zone is
calling for heang or cooling.
Variable speed heat pumps can operate at much lower
ow rates when capacity is reduced using a variable speed
compressor and variable speed pump. With the installaon of a
pressure dierenal bypass valve or hydraulic separator, even a
small radiant oor heang zone (three or four 1/2” PEX circuits,
2 to 3 gpm), can allow a variable speed heat pump to operate
without the use of a buer tank. In order to maintain the
minimum ow rate required for the heat pump (about 4 gpm),
part of the ow is returned to the heat pump through the bypass
valve, and the remainder is delivered to the hydronic zone. This
approach works well for radiant oor zones. Very small loads
will cause the heat pump to cycle, but the minimum ow rate
for the refrigerant circuit is always maintained. If a hydraulic
separator is used, full ow to the heat pump is achieved since
the separator decouples the hydronic system ow rate from the
heat pump ow rate, much like a buer tank.
Systems that require cooling must ulize fan coils that are large
enough to allow sucient run me to provide adequate latent
capacity. Fan coils smaller than two tons could cause the heat
pump to cycle too oen, not allowing the system to maintain a
coil cold enough to provide good dehumidicaon. Therefore,
Enertech recommends that fan coils two tons and larger are
used with variable speed heat pumps. A buer tank is required
when using smaller fan coils.

Based upon Enertech’s experience with variable speed heat
pumps, purging air from the system is one of the biggest
challenges to a successful installaon when a buer tank is not
used. Besides prevenng short cycling and decoupling pumping
systems, a buer tank funcons as an air separator. Single speed
and two-stage heat pumps with buer tanks do not typically
experience problems with air in the system because water ow
to/from the unit is simply owing through a small amount of
piping from the heat pump to the buer tank. Any air in the
system ends up at the top of the buer tank (the buer tank is
an air/dirt separator). Even if air is in the hydronic piping (other
side of the buer tank, opposite the heat pump-- radiant oor
zones, fan coils, etc.), the heat pump does not experience ow
issues because it is isolated from the system by the buer tank.
A buer tank is typically not needed for variable speed
heat pumps (see “Recommendaons” secon, below), but
uctuaons in ow rate or even an air-locked pump can occur if
there is sll air in the system when a variable speed heat pump
is installed without a buer tank.
Based upon experience, some piping arrangements are
nearly impossible to properly purge air, especially when using
undersized PEX tubing. Fan coils are parcularly dicult to
purge. If piping to a fan coil is insuciently sized, it’s dicult to
get enough ow rate to purge the coil. For example, when a 1”
pex pipe feeds a tee with 1” branches, the inability to get the
proper ow for purging will occur. This is especially true if a zone
valve is located at a fan coil and isolaon valves are far away
from the tee. There are many more examples of piping systems
that either lack air separators or that are dicult to purge due to
the piping conguraon/sizing.


Based upon exisng installaons, Enertech recommends that all
EAV variable speed air-to-water installaons include a hydraulic
separator to help lessen issues with air in the system and
isolate the heat pump from the hydronic system (radiant oor
manifolds, fan coils, etc.).  shows typical piping when
a hydraulic separator is incorporated into the design.
Following is a detailed list of recommendaons for variable
speed heat pumps:
 System should include
a hydraulic separator (Figure 12b).
 System should
include a buer tank (Figure 12c).
: All zone piping should be “Home Run” style (Figure
12e) to assist with purging air and to maintain lower pressure
drop.
 System should include a boiler trim
kit that includes an expansion tank, air separator/automac
air vent, pressure reducing valve, and backow preventer.
In addion, an automac air vent should be located at the
highest point in the piping system. Note that a factory-installed
expansion tank is included with the Indoor Module.
 All systems must include anfreeze in the hydronic
piping and Fernox F1 inhibitor or approved alternate (this is a
warranty requirement). Heang only systems do not require
anfreeze in the hydronic piping (except those that have exposed
piping) but must include Fernox F1 inhibitor or approved
alternate (this is a warranty requirement).
⚠⚠




 System should include ush valves as shown in
Figures 12b and 12c to facilitate purging of air.
