Dynamically Variable Capacity Automatic Backup Heater For Inline Integration w/
Hydronic Heat Pumps (Reverse Cycle Heat Pump Chillers)
output is modulated in real time from 0-18,760 BTU (0-5.5 kW) in 1% increments
to avoid overshoot and maximize the percentage of total heat provided by the higher
COP heating source (the compressor).
V18 dynamically variable capacity inline (tankless) backup heater is designed
for use with intelligent variable capacity hydronic (air-to-water) heat pumps
such as the Chiltrix CX34.
The V18 variable capacity backup heater automatically adjusts its BTU (Watts)
output to target an exact match to any shortfall of heating, in real time.
The V18 backup heater provides between 0 - 18,766 BTU, depending on the
requirements of the moment.
on your location, building envelope values, and other factors such as weather,
you may need to consider an integrated backup heat solution.
backup heat is needed in your climate, the V18 backup heater will save energy
compared to the typical options, by providing only the amount of backup heating
V18 dynamically variable backup heater maximizes the percentage of
compressor-generated high efficiency heat (COP ~2.5 to 3.5 or higher) and
reduces the consumption of less efficient resistance backup heat (COP
a fully integrated and automatic system, the V18 also avoids the need for
unsafe "portable" heaters, has a tiny footprint and little pressure
with your Chiltrix sales engineer or HVAC professional to see if backup heat is
needed for your application and location.
to the Standard Air To Water Backup Heating Approach:
Prior to the introduction of the
V18, the typical and globally-accepted standard backup heat solution for air-to-water
(hydronic) heat pumps has been to mount a small electric water heater tank,
with thermostat & element, in series on the supply side of the loop, to add
extra heat when the heat pump cannot keep up with the load. In this example a
controller enables the tank thermostat/heating element when loop temperature
goals are not met. While this works and is the common global technique for
hydronic backup heat, thermal lag in the backup heat tank and hysteresis of the
element/thermostat generally cause significant overshoot and undershoot of the
temperature settings, with swings of up to 10 ºF above or below the target
While providing capability to supply
heat under conditions where the heat pump compressor cannot by itself handle
the heating load, in the standard solution, comfort is acceptable but
efficiency is lower than it could be due to temperature over-shoot. For
example, when the tank-type backup heater overshoots, any extra heat provided
(low-efficiency resistance heat) unnecessarily lowers the overall system
efficiency by providing heat that could have been provided by the compressor at
a much higher efficiency.
Modulating tankless heaters have
also been tested for radiant and hydronic backup applications but severe
pressure-drop issues have proven them to be an undesirable alternative.
Further, commercially available tankless heaters are not compatible with cold
water running through them during the cooling season and as a result, they
suffer condensation problems.
New & Different About The V18 Variable Backup Heater?
The patent-pending V18 dynamically
variable inline (tankless) backup heater solution avoids overshoot or
undershoot issues by matching its output to a capacity shortage (BTU
shortfall). For example, if a certain BTU is needed, the V18 targets exactly
that amount of BTU. The V18 can dynamically adjust its output in real time. As
the load changes, and heating shortfall changes, the V18 changes with it
dynamically, reconfiguring its BTU output to match the load shortfall. The V18
is always targeting the precise amount of extra heat needed, allowing the
compressor to provide the highest possible percentage of the heating
requirement and providing stable heat values in the hydronic loop. So
aside from not requiring the footprint/space needed for a backup tank and
avoiding the excessive pressure drop and condensation issues of a tankless
heater, the V18 saves a lot of energy by keeping the loop temperatures stable
and allowing the compressor to provide the highest possible percentage of the
The patent-pending V18 uses a
special long-life and replaceable Incoloy resistance heating element rated at
up to 5,500w (18,766 BTU). The element is installed in a linear configuration
inside a 2" stainless steel tube with 2" NPT female threaded
connections on each end. The tube is heavily insulated and wrapped by a
stainless steel outer cover. A special solid state relay controller is used to
vary the watts of the element from 0w to 5500w in increments of around 1%. The
solid state relay is controlled by information from the heat pump to accurately
target the BTU shortfall. The element output can be adjusted on the fly, for
example at 55w (187 BTU), 110w (375 BTU), 165w (562 BTU), and so forth up to
the full power of 5500w (18,766 BTU) as needed to match the requirement. The
Chiltrix heat pump, which is a variable capacity unit, modulates its capacity
based on continuously recalculating and adjusting its output to match the load.
In this control process, the Chiltrix unit is also aware of any heating
shortfall, and knows the BTU amount of such shortfall. When controlled by the
Chiltrix heat pump, the V18 can be targeted to match its output closely to any
BTU shortfall in real time.
In all heat pump systems including
Chiltrix, ultimately the "return" water temperature (or buffer tank
temperature) directly or indirectly generates a call for a capacity increase or
decrease. If a backup heater overshoots its target as is common with the
standard tank approach, return water is at that time artificially higher,
causing the heat pump to think the load has decreased, causing the heat pump to
slow or stop. This action recursively creates the need for more backup heat and
ultimately means a much higher than needed percentage of heat comes from the
low efficiency backup unit than would be used if overshoot did not occur.
The V18 dynamically modulating heater
eliminates this problem by avoiding overshoot.
This allows the higher efficiency heat source (the compressor) to provide a
much larger percentage of total heat during this time and minimizes the amount
of lower efficiency of resistance heat applied by the backup source which
raises the average system COP significantly.
The V18 heater has a small footprint
in a compact tubular form factor ~19" in length and ~6" in diameter
and is connected to a small low voltage control unit measuring approximately
5" x 5" x 1.5". The design of the V18 is such that it cannot
operate if there is no heating shortfall, if outdoor temperature is above a
predefined setting, if water flow is below a minimum GPM required, or if the
water temperature (or the unit itself) rises above a maximum set point. Low
voltage controls in communication with the Chiltrix heat pump send power
modulation signals to the solid state relay. Within the V18 there is a thermal
overload safety switch that will interrupt power to the backup heater and must
be manually reset if a maximum backup heater internal temperature is reached.
The Incoloy heating element, the solid state relay, and the thermal over-limit
switch are all UL Listed. Assembly by a qualified and licensed installation
professional is required.
Requires >/= 25a circuit with GFCI breaker, 208-240v. Multiple V18
units can be installed with a single heat pump if needed.
Practically No Pressure Drop:
@ 7 GPM = 0.000427775 ft.
@ 14 GPM= 0.001438843 ft.
Click Here - V18