9
Once the HydroBox and heat pump has been connected to the heating
system, it must be filled, purged and pressure-tested.
The following points must be observed when filling the system:
• Untreated filling water and make-up water must be of drinking water
quality (colorless, clear, free of sediments)
• Filling water and make-up water must be filtered (max. pore size 5
µm).
Scale formation in domestic hot water heating systems cannot be avoided,
but in systems with flow temperatures below 140°F (60°C), the problem
can be disregarded. With high-temperature bivalent systems (heat pump
+ boiler combination), flow temperatures of 140°F (60°C) and more can be
achieved. The following standard values should therefore be adhered to
with regard to the filling and make-up water according to EPA 40 CFR 143.3
or VDI 2035, sheet 1: The total hardness values can be found in the table.
Minimum Heating Water Flow Rate
The minimum heating water flow rate through the heat pump is maintained
by the integrated variable speed heat pump circulating pump (M16) and
ensures proper flow across all operating states of the heat pump system. If
the minimum heating water flow rate is not reached, the heat pump will go
into a blocked status.
The specified nominal flow rate (see “Device information”) must be assured
in all operating statuses. The installed flow rate monitoring is used only for
switching off the heat pump in the event of an unusual and abrupt drop in
the heating water flow rate and not to monitor and safeguard the nominal
flow rate.
A method of manual drainage should be provided for heat pumps which
are exposed to freezing temperatures or the system piping needs to be
filled with an appropriate percent mixture of a propylene glycol antifreeze
suitable for hydronic system use and based on the minimum outdoor
design temperature. The freeze protection function is automatically
enabled whenever there is power at the HydroBox to make sure there is
flow through the heat pump outdoor unit at low temperatures. The system
HVAC System Connection
There are six 1" female NPT connections extending from the top of the
HydroBox. If looking from the front of the HydroBox, going left to right,
the first two are the supply and return for the indirect domestic hot water
tank (DHW). The middle two are the supply and return to the house's
HVAC distribution system (Heating / Cooling Circuit or HCC). The right
two connections are the supply and return to the Heat Pump outdoor unit.
Note that the heat pump circulator (M16) is on the return side of the heat
pump (pumping through the heat pump) and the hot or chilled water coming
from the heat pump enters the indoor unit through the heat pump supply
connection (see fig. 11). When making connections to the HydroBox make
sure to use a backwrench at the top outlet connections so as to not bend or
twist the piping manifold.
HydroBox Components
The HydroBox includes two Taco 0034e high efficiency ECM variable speed
circulators which control the flow between the HydroBox and domestic hot
water tank respectfully. Each of the circulators is controlled via a 0-10 VDC
signal and their operation is controlled and optimized by the on-board heat
pump manager. The Hydrobox includes a 30 gallon buffer tank for thermal
storage and additional thermal mass when used on an air based distribution
system with an integrated 6KW immersion heater for temperature boost
during low outdoor temperature operation. The HydroBox has shut-off
valves to isolate the pumps and individual circuits, a 2.1 gallon expansion
tank, and a 30psi relief valve and backflow combination valve piped to a
drain pan. The drain pan has a 1/2" NPT connection which should be piped
to a floor drain or other means of water collection/dispersement as required
by code. A Taco 4900 Air Separator is internal to the piping and a Taco Hy-
Vent is connected at the top of the buffer tank. Both provide secondary air
elimination within the HydroBox. Both vents are shipped closed and should
not be relied upon for main purging of the distribution system. Additional
vents should be located at the high points of the system. The entire piping is
fully insulated to reduce condensate accumulation during cooling operation.
(see fig. 2)
The HydroBox is a complete turn-key system able to provide either heated
of chilled water out to the HVAC distribution system and hot water to an
indirect DHW tank. The necessary system distribution equipment (e.g.
pumps, valves, heating/cooling emitters) and the associated controls and
required safety devices are supplied by the installing contractor.
Abb. 6.1:Guideline values for filling and make-up water in accordance with VDI 2035
For systems with an above-average specific system volume of 50 l/kW, VDI
2035 recommends the use of fully demineralized water and a pH stabilizer
to minimize the risk of corrosion in the heat pump and heating system.
1. This value lies outside the permissible value for heat exchangers in heat pumps.
Caution:
With fully demineralized water, it is important to ensure
that the minimum pH value of 7.5 (minimum permissible value
for copper) is complied with. Failure to comply with this value can
result in the heat pump being destroyed.
Heating / Cooling Circuit (HCC) Piping / Connection
There are no special requirements for piping the heating / cooling circuit
(HCC). Heated or chilled water will be supplied to the “System Supply”
outlet connection at the top of the HydroBox and once distributed to the
system’s terminal output units (radiant floors, radiators, fan coils, etc.) it
will return to the HydroBox at the “System Return” piping inlet connection.
The distribution system can be completely independent of the System M
indoor and outdoor unit control or an optional Heating / Cooling Circuit (HCC)
pump (M13) can be controlled using a 0-10vDC signal from the HydroBox’s
wiring hub. It is recommended that this option be used when a domestic hot
water indirect tank is part of the overall system design. Operating the HCC
pump in a variable speed manner also maximizes system operation and
operational efficiency. Proper sizing of the HCC pump is up to the installing
contractor based on the distribution design and head/flow requirements.
However, we recommend the use of an ECM-driven pump and it must be
able to accept a 0-10vDC signal from the HydroBox. Line voltage power to
the pump is field supplied.
Total
heat output
in kW
Total
Alkaline earths in
mol/m
3
and/or mmol
Specific system volume
(VDI 2035) inl/kW
< 20
> 20 < 50
> 50
Total hardness in °dH
< 50
< 2.0
< 16.8
< 11.2
< 0.11
1
50 - 200
< 2.0
< 11.2
< 8.4
200 - 600
< 1.5
< 8.4
< 0.11
1
> 600
< 0.02
< 0.11
1
% Propylene
Glycol Solution
10%
15%
20%
25%
30%
35%
40%
Burst Protection
Temperature°F/°C
22°F /
-6°C
15°F /
-9°C
11°F /
-12°C
-1°F /
-18°C
-18°F /
-28°C
-46°F /
-43°C
-60°F /
-51°C
Multiplier for
Pressure Drop
1.02
1.04
1.08
1.13
1.21
1.26
1.47
Multiplier for
Capacity Factor
0.994
0.992
0.986
0.972
0.960
0.950
0.928
must be protected or drained if the heat pump is taken out of service or in
the event of a power failure. The heating circuit should be operated with a
suitable freeze protection method if heat pump systems are implemented
in buildings where a power failure cannot be detected (holiday home). See
Note 4 under section 11 to see capacity impacts for different antifreeze
mixture percentages. Because of the heat transfer penalties of using glycol
in the system we recommend selecting the proper concentration based on
the burst rating. Follow the glycol manufacturer's recommendations for
maintenance and testing, which is usually yearly, to maintain the correct pH
of the system fluid.
Freeze Protection
