ENVIRO-TEMP Commercial / Industrial

ENVIRO-TEMP™
Commercial Heat Recovery Systems
by Turbotec Products, Inc.
Installation, Operation
& Maintenance Manual
Heat Recovery Units from 10 to 200 Tons
Contents
Function and Design
Equipment Mounting Refrigerant Piping Design and Sizing
Single Compressor, Non-Unloading Single Compressor, Unloading 1
Multiple Compressor Systems Segregated Refrigerant Systems 5
Multiple Compressor
Bypass Type HRU 3
4
5
5
5
6
Bypass/ Isolation Circuits Water Piping Design and Sizing 7
8
Single Tank 9
Multiple Tanks, Series 10
Multiple Tank, parallel
11
Multiple HRUs, Parallel Connection 11
Plumbing with Hot Water Systems
13
Electrical Controls
14
Electrical Connection
14
Thermostats
16
16
Maintenance and Troubleshooting
18
Refrigerant Leak Test
20
Cleaning / Descaling Water Tubes
20
Winterization Procedure
20
Pressure Controls
NOTE: Installation of this Heat Recovery Unit (HRU) should be done by licensed
professionals and in accordance with state and local standards and codes.
The manufacturer accepts no
responsibility for failure to follow the applicable standards and codes.
2
FUNCTION AND DESIGN
Application: Enviro-Temp Heat Recovery Units
are designed to heat water, or other fluids, by recovering
a portion of the heat of rejection from refrigerating equipment. By means of conduction and turbulent convection,
this heat is transferred from the higher temperature refrigerant vapor into a lower temperature fluid.
R-717 systems, steel or stainless steel heat exchangers
must be used in place of copper. Enviro-Temp units can
be applied to air conditioning, refrigeration, heat pumps,
and even air compressors. They may be used with air- or
water-cooled equipment.
The Enviro-Temp is designed to remove superheat at condenser, which is usually 20-25% of the heat of
rejection. It is not intended to replace the condenser, but
rather is a pre-cooler, to be connected in series with, and
upstream of, the condenser. Heating capacities and temperatures produced by the HRU are dependent upon the
proper operation of the refrigerating equipment to which it
is applied. Therefore, proper operation of the refrigerating
equipment should be verified prior to installing the EnviroTemp unit.
The most common application for a heat recovery unit (HRU) is domestic water heating or pre-heating. However, there are other applications that can be
very cost-effective. Such uses include hot deck reheat
for humidity control, space heating, and swimming pool or
spa heating. Fluids other than water can also be heated,
providing the refrigerant discharge temperature is greater
than the fluid temperature. (Consult factory for heating of
other fluids, as special pumps and other considerations
may affect application).
Since the Enviro-Temp unit becomes an integral part of the refrigerating equipment, proper sizing and
design will produce a system that not only saves energy
costs from fluid heating, but can also improve efficiency of
the refrigerating equipment to which it is applied. A properly engineered and installed system should provide years
of trouble-free service and savings for the end-user.
Enviro-Temp units can be used with most any refrigerating equipment using reciprocating, rotary, or screw
type compressors. They may be used with halocarbon
refrigerants (R-22, R-134A, R-404, R-407C, R-410A, R500, R-507 ) or ammonia (R-717). When applying to
1
EQUIPMENT MOUNTING
The commercial/industrial Enviro-Temp units
have straight tube heat exchangers manifolded in parallel, and are designed to be mounted horizontally. This is to prevent trapping of refrigerant oil. You will
see that the refrigerant enters at the top of the HRU
and leaves at the bottom, which promotes proper oil
drain in the compressor off-cycle. The HRU, where
practical, should be mounted above the condenser so
that oil and/or liquid refrigerant will drain into the condenser rather than back to an idle compressor.
The circulator pumps in active units are gen-
erally designed for operation with the motor shaft in a
horizontal position. With some circular pumps it may
be permissible for the shaft to be in a vertical position. Consult Enviro-Temp or pump manufacturer for mounting positions other than horizontal.
The HRU should be mounted so that access
is provided for service and repair. “C” model EnviroTemp systems have mechanically cleanable water
tubes, so be certain there is adequate space available
at the cleanable end for the cleaning brush handles.
2
REFRIGERANT PIPING DESIGN AND SIZING
Oversizing hot gas lines will reduce refrigerant velocity,
and may promote oil trapping.
The HRU is normally designed to accept the
full flow of refrigerant vapor discharged from the compressor. As with any component in the refrigerant piping, there is pressure-drop associated with the addition
of components. However, the Enviro-Temp unit, when
properly sized, will keep pressure-drops well within
acceptable limits. It is usual practice not to exceed a
pressure-drop in hot gas lines that corresponds to a 2
degree change in saturation temperature (see charts). The pressure-drop through the HRU must be added to
the pressure-drop in piping, valves, fittings, and components in the hot gas lines so that total pressure drop
does not exceed acceptable limits.
When sizing Enviro-Temp units it is imperative
to use compressor horsepower, rather than tonnage,
due to the difference in horsepower-per-ton requirements of different refrigerants at varying saturated,
suction temperatures. The lower the suction temperature, the higher the volume of refrigerant that must be
circulated per ton. This requires greater horsepower
per ton on mid-temp and low-temp refrigeration than
on high-temp air conditioning.
Once the HRU has been mounted and the
refrigerant piping has been assembled, a nitrogen atmosphere should be present during brazing to prevent
oxidation from taking place on the inside of the piping. It is a good idea to replace refrigerant filter driers at
this time. All braze joints should be pressure-tested
for leaks, and system should be thoroughly evacuated
prior to recharging and restoring the system to operation.
Another factor that must be considered when
sizing hot gas lines is oil transport. Since some oil is
discharged with the refrigerant from the compressor, it
must be returned at the same rate at which it leaves. For oil to be carried by the refrigerant in hot gas lines,
a minimum velocity of 500 fpm in horizontal runs and
1000 to 1500 fpm in vertical upflow lines is required.
3
SINGLE COMPRESSOR, NON-UNLOADING REFRIGERANT SYSTEMS
Where possible, the HRU should be mounted
above the condenser and as close as practical to the
compressor to keep discharge line length and refrigerant pressure-drop to a minimum. This will promote
oil drain-down into the condenser inlet during the compressor off-cycle. If the HRU must be mounted below the condenser, vertical upflow lines greater than 8’
should be equipped with a trap at the “refrigerant out”
stub of the HRU, and the vertical riser should be sized
for a minimum gas velocity of 1000 fpm (see figure
R-101). For systems where oil movement may be a
problem (long discharge line lengths, low temperature
applications, etc.), an oil separator may be required
(see figure R-103). The use of oil separators does not,
however, negate the need for proper line sizing and
design, since they may not be 100% effective.
mounted in an occupied area where compressor noise
could be a critical factor.
Bypass/isolation valves, installed in the discharge
lines, may be a desirable feature. These valves allow
the HRU to be isolated and bypassed so that the HRU
can be cleaned, repaired or replaced (in the event of
a failure), without taking the refrigerating equipment
off-line (see figure R-105). The bypass/isolation circuit
can be factory-installed or field-installed. On field-installed valves, be certain to use refrigerant valves that
are designed and rated for this purpose.
The total pressure-drop of the HRU, fittings,
valves, tubing, and other associated components
should be calculated so that pressure drop is kept
within maximum allowable limits. Charts and schematics are provided in this manual to aid in the design and
sizing of the hot gas circuit. For special systems or
applications, consult Enviro-Temp and/or refrigerating
equipment manufacturer for recommendations.
A vibration isolator mounted in the discharge
line will reduce noise and lessen the chance of tubing
fractures caused by compressor vibration. Gas pulsation noise can be dampened by the addition of a discharge muffler if the HRU is to be
4
SINGLE COMPRESSOR, UNLOADING TYPE CAPACITY CONTROL
REFRIGERATING SYSTEMS
The hot gas circuit and HRU should be sized to
handle the entire discharge of the compressor at fullyloaded conditions without causing excessive pressuredrop. At the same time, proper velocity of refrigerant
should be maintained. If the hot gas line is to have a
vertical riser of 8’ or greater, a double riser should be
used to assure proper gas velocity during part-load operation. (See figure R-107). The small riser should be
sized for a minimum gas velocity of 1000 fpm when
the compressor is operating at its minimum load capacity. The large riser should be sized to handle the
difference between minimum and maximum compressor capacity so that, during full-load operation, the two
risers combined will allow full refrigerant flow within acceptable pressure-drop limits, and with sufficient velocity for proper oil movement. Again, if an oil separator is
used, it does not negate the need for the proper piping
design and sizing.
MULTIPLE COMPRESSOR SYSTEMS
Segregated Refrigerant Systems
ED and SD series are particularly suited to this application when dual compressors are used. These systems,
since they are non-unloading, do not usually pose
complications with respect to piping design and sizing. Each circuit, since it is a separate circuit, should be
treated as a single compressor, non-unloading system
(see Single Compressor, non-unloading refrigerant
systems section).
Many systems use multi-circuited evaporator and condenser coils, each circuit having its own
compressor. This allows for capacity control by offcycling of compressors. This type of system requires
a separate heat exchanger/refrigerant circuit for each
compressor. The water circuits in these heat exchangers are usually circuited in a parallel configuration so that fluid may be heated whether one or all of
the compressors are in operation. The Enviro-Temp
Multiple-Compressor
On multiple compressor arrangements of this
type there may be refrigerant check valves installed on
each individual compressor discharge line to prevent
refrigerant from active compressors from condensing
on the heads of idle compressors. The HRU should be
installed downstream of these valves. As always, good
refrigeration practice and piping design should be followed to minimize pressure-drop and promote proper
oil movement (see figures R-109 and R-110).
Common refrigerant circuit systems may use
a single HRU sized to accept the full hot gas discharge
when all compressors are in operation, or may use
multiple HRUs sized for the full load capacity of each
individual compressor. These systems are usually
manifolded into a discharge header which brings the
refrigerant flow of all the operating compressors into a
single hot gas line. This hot gas line would then connect to the “refrigerant in” line on the HRU. 5
Bypass Type HRU
If partial superheat recovery is desired, a
bypass system using a smaller HRU may be used. This type of installation requires that the hot gas line
be branched, so that the required tonnage is routed
through the HRU with the balance of the system tonnage routed around the HRU to the condenser inlet (see figure R-121). Proper line sizing of the two
branches will maintain proper gas velocity and system
balance. When this type system is applied to unloading compressors, and the HRU is sized to the capacity
at minimum load, a solenoid valve should be installed
in the line bypassing the HRU. This will ensure desired
gas velocity through the HRU for proper oil movement
during part-load compressor operation. This design
will keep the HRU active through all stages of compressor loading (see figure R-123).
R-121
On compressors with multiple steps of unloading,
HRUs sized for each step of unloading may be used. Solenoid valves should be installed on the “refrigerant
in” lines of the HRUs to close off those circuits that are
not needed as the compressor unloads (see figure R125). The method of controlling this solenoid valve will
vary depending upon the type of unloader employed by
the compressor.
Solenoid valve closes when
compressor unloads to
HRUs capacity
R-123
R-121
6
Bypass/Isolation Circuits
three (3) refrigerant valves, one each on the “refrigerant in” and “refrigerant out” lines and a bypass tube
between the “refrigerant in” and “refrigerant out” lines
(see figure R-105). Be certain to use proper size and
type refrigerant valves to keep discharge pressuredrop within acceptable levels.
A bypass/isolation circuit offers the advantage
of being able to bypass the HRU if service or replacement becomes necessary, without having to take the
refrigerating equipment off-line. This can be especially
desirable on multiple compressor, common discharge
systems. This type of circuit requires
7
WATER PIPING, DESIGN AND CONNECTION
Enviro-Temp HRU units are designed for a
water flow rate of 0.4 gpm/H.P. This flow rate will produce optimum performance in most cases. The flow
rate can be varied to meet differing requirements. With
any heat exchanger, as water flow rate is increased,
the total BTU heat exchange will increase, but temperature rise of the fluid will decrease. Greater fluid
temperature rise can be achieved by reducing flow rate
through the HRU.
Plumbing and piping connections should be
made using approved materials and connections for
potable water systems if the HRU is to be used for
domestic water heating or pre-heating. This usually
means a pressure rating of 150 psi. Another issue is
with respect to the solder used in sweat joints. Most
code bodies require low-lead or no-lead content solder. Consult the appropriate code enforcement department
for approved materials.
If the application of the HRU is for spa or pool
heating, heat exchangers and piping should be constructed of a material approved for use with chlorinated
water. Since the acidity of the water can become quite
high, cupro-nickel, stainless steel, titanium, or other
suitable material should be specified. These applications usually require negative suction lift pumps. Consult factory or pump supplier.
In most applications, HRUs are used as preheaters, or supplementary heaters, and are usually
connected to a storage tanks (or tanks). The water
in the storage tank is pumped through the heat exchanger in a closed-loop configuration. Each time the
water is passed through the HRU, its temperature will
be raised. With sufficient passes through the HRU, the
water can be heated to within a few degrees of the hot
gas temperature. As the water temperature in the storage tank increases, a lower BTUH recovery rate will
result. For this reason, a storage capacity of approximately 10 gal/H.P. will usually produce best overall performance of the HRU. If higher water temperature rise,
rather than greater total BTUH recovery, is desired, a
storage capacity of 5 gal/H.P. is recommended.
When making water piping connections between the HRU and the water heater, boiler, or storage tank, there are some considerations that should
be made. First consideration should be given to the
applicable plumbing codes. A great deal of extra work
can be avoided by using approved methods and materials for the plumbing hookup. This information should
be obtained from the proper code enforcement body
prior to installation. Some other factors to consider are
performance of the HRU and serviceability of the system. The best performance of the HRU will result from
pulling the coldest water at or near the bottom of the
tank. This can be accomplished by installing a tee in
the cold water feed to the water heater for the supply
line to the HRU. Most tanks use a dip tube for delivering cold supply water to the water heater. The return
water line from the HRU can be connected to the tank,
by means of a tee, to the bottom drain port of the tank
see figure W-101). The serviceability of the system
can be improved by using unions on pipe connections
and a bypass/isolation circuit on the water lines. This
will enable the HRU to be bypassed in the event of a
need for service, without interrupting the hot water circuit. There are schematics and instructions for various
types of connections within this section of the manual. These examples, by no means, represent all the ways
in which a successful installation can be accomplished. For engineering assistance with special applications,
consult factory.
The water usage should also be considered
when sizing storage tanks. If the HRU is to be used for
domestic water heating, as the water usage increases,
the storage tank temperature will decrease. For applications having short periods of high usage and long
periods of low usage, increased storage capacity (thermal storage) may be used to accomplish the desired
results.
The purpose and design of the heat recovery
project should be to replace as many BTUs as possible
with the heat from the HRU. This design strategy will
usually produce the greatest dollar savings for the enduser.
The pumps used in Enviro-Temp HRUs are
centrifugal circulators designed for potable water. They create differential pressure through the heat exchanger, causing the water to be circulated between
the storage tank and the HRU. The pumps are constructed with either brass, bronze, or stainless steel
volutes (impeller housings or heads) and impellers to
resist corrosion that could contaminate the water supply.
The circulator pumps are available in a wide range of
horsepower and performance characteristics to meet
the various pumping needs of different applications. It
is best to determine the required flow rate and piping
losses of the HRU plumbing circuit to assure that the
proper pump is supplied.
8
Single Tank
There are many different ways in which the HRU can
be connected to a storage tank or water heater. As
a general rule, the best results will be realized if the
coldest water is piped to the HRU. The heated water
is normally returned through the drain port of the tank.
Since heat rises, the hottest water will go to the top of
the tank. Figures W-103 and W-105 illustrate some
typical plumbing connections of HRUs to a single stor-
age tank. When connecting to an existing tank, a thorough flushing of the tank is recommended to remove
sediment that accumulates in the bottom of the tank.
When pulling water form the bottom of the
tank, caution should be taken so that sediment that accumulates in the tank is not pulled into the pump where
it may foul the impeller. This can be accomplished by
9
installing a Y-strainer or fabricating a suction trap (see
figure W-104).
Water lines between the HRU and the storage
tank should be insulated separately with an approved
tube insulation. If these lines are to be direct-buried in
the ground, use an insulation approved for this application so that water will not penetrate the insulation and
reduce the insulating value. Insulating all valves, pipe,
and fittings will reduce line losses and improve energy
savings.
To make the HRU more serviceable, shut-off
valves should be installed on both water lines. These
valves are usually installed at, or near, the storage
tank. When these valves are used, a pressure relief
valve, installed on either water line, between the HRU
and the shut-off valves must be installed. This is to
vent excessive pressure in the event the valves are
closed, trapping water in the heat exchanger while the
refrigerating equipment continues to operate. By add
ing another pair of valves (figure W-103), one valve
tee’d into each water line at the lowest point in each
line, the HRU can be isolated and drained. This design is particularly useful if the HRU is to be drained for
freeze protection during the winter season. Thisalso
provides access to the heat exchanger for chemical
cleaning and descaling. This arrangement is useful in
purging the air from the system and is recommended
on all installations. (NOTE: If system is to be drained
for freeze protection, circulator pump must be electrically disconnected to prevent damage to the pump from
dry-run).Once the plumbing has been completed, any
air trapped in the system must be purged. The circulator pump will not pump if air is trapped in the volute. The removal of air is a simple operation when isolation
and access valves have been installed. By opening
the valve on the “water in” line at the tank and opening
the access valve on the “water out” at the HRU, the
air can be purged from the suction side of the pump. After the air has been removed, close off the access
valve and open the shut-off valve on the “water out”
line at the tank. Automatic air vents may also be used
to remove and keep air out of the system. Continued
operation of any air-locked (dry run) pump can cause
premature pump failure.
Multiple Tanks, Series
When Enviro-Temp units are connected to
multiple tanks in series, it is usually done so that the
first tank provides storage capacity for the HRU and
the last tank in the series is used as a booster or backup heater. This configuration is designed so that water
is preheated in the storage tanks, thereby reducing the
heating load on the booster heater. With this design,
the cold water supply would enter the storage supply
would enter the storage tank at the “cold” water port
and preheated water would leave at the “hot” port. This
preheated water then enters the booster tank at the
“cold” port where it can be boosted to the proper temperature. The heated water leaves the booster heater
at the “hot” port where it is piped to the desired appliance (see figure W-107).
10
Multiple Tank, parallel
In some installations, a parallel piping configuration is desired to increase storage capacity. This
is easily accomplished by manifolding the “cold” ports
and “hot” ports together into common supply and re
turn pipes (figure W-109). This system may be desired
if periodic large volumes of hot water are required with
extended periods between hot water demands. This is
common in wash-down operations.
Multiple HRUs, Parallel Connection
Many applications will have multiple HRUs,
each connected to a separate compressor to reclaim
the heat from several condensers. In these cases, it
is usually easiest to run one supply and one return line
between the storage tank and the HRUs and connect
the HRUs, in parallel, with the two water lines. When
this design is used with active HRUs (units with pumps)
care should be taken to assure that the pumps do not
work against each other. This can be accomplished
by installing a check valve on the “water out” line of
each HRU, upstream of the return line (figure W-110).
Be certain, when using spring check valves, to use
a valve with light spring pressure so that the pump
can overcome the additional head loss. Swing check
valves may also be used. The additional head losses
associated with these valves should be calculated into
the total system head loss when sizing the pump(s).
11
This same design often lends itself to the use
of slave HRUs (units without pumps), using a single
circulator pump (see figure W-111). If using this type
system, be certain to size the pump for the proper flow
rate and head loss for all the HRUs and associating
piping. If no flow through idle is desired, the installation
of a pressure-actuated water flow control valve (Penn
V46 series or equivalent) will stop water flow when the
compressor is idle (figure W-113). These valves can
be set to open at a desired head pressure, thus helping
to maintain head pressure of the refrigerating system
by modulating water flow. A solenoid valve can also
be used to stop flow during the compressor off-cycle.
This type of valve is usually fully-open or –closed, and
does not modulate flow. If this type of valve is used, be
certain that it is rated for the temperature and pressure
that will be encountered with heating water.
12
Plumbing Connection with Hot Water Loops or Solar Systems
It is also possible to connect HRUs to a solar
system. Depending upon the desired use of the HRU,
there are several methods of connection. Some hot water systems will use two pipes
(supply and return) to circulate hot water continuously. This system is commonly used in hotels, where it is
desirable to have hot water instantly available to many
rooms. A pump will circulate water from the water
heater through the hot water loop and return it to the
water heater to be reheated. When installing an HRU
to a system of this type, care should be taken in the
design of the HRU piping so that the two circulator
pumps (HRU pump and Hot Water Loop pump) do not
work against each other. It is best, if possible, to keep
the plumbing connections of the HRU and hot water
loop separate (figure W-111). If the connection must
be made together, check valves and proper line sizing
will allow the two systems to operate properly (figure
W-119).
•
If the HRU is to be used as a booster for the solar
heated water, the HRU should be connected in
series. •
If the HRU is to act as an alternate heat source
when there is little or not sunlight, the HRU
should be connected in a parallel configuration at
the tank. This arrangement will allow water to be
heated by solar or the HRU.
Again, care should be taken in the design to prevent
two pumps (solar and HRU) from working against
each other (see figures W-111 and W-119).
13
ELECTRICAL AND CONTROLS
Electrical Connections
ible. In some cases, (such as 3 phase or higher voltage
systems), 115 VAC pumps may be used, as the available control circuit, be certain the control transformer,
if used, has sufficient capacity to operate the pump
and controls (figure E-104). If the control transformer
is already operating at its rated output, an additional
step-down transformer may be wired into the load-side
of the compressor contractor to supply proper voltage
to the pump (figure E-102).
The Enviro-Temp active HRUs are designed
so that the circulator pump will operate when the compressor operates. The simplest method is to connect
the pump to the load side of the compressor contractor (figure E-101). Each time the contractor closes,
the compressor and HRU pump will be started. Since
pumps are available in different voltages, be certain
the pump voltage and compressor voltage are compat
14
All wiring should be done in accordance with
applicable codes. The HRU pump controls should
be fused separately (normally factory prewired) since
the pump is usually a smaller horsepower motor than
the compressor. The HRU should also be properly
grounded.
relays and pressure or temperature controls, so that the
pump can be activated if any or all of the compressor(s)
are operating (Consult factory for pump modules). Continuous operation of the pump will use
additional energy and increase heat loss through the
piping, and is not recommended for systems with long
compressor off-cycles. Since there are many different methods of control and connection of the HRU, it
is impossible to give examples for every situation in
this manual. However, a thorough knowledge of the
controls and control strategy will be very helpful in determining the best design.
Controlling pump operation may be desirable
in some applications, such as multiple slave HRUs connected to a single supply and return water lines. Timed
operation can be accomplished using a time clock.
Running the pump in conjunction with a compressor(s)
requires a pump control module (figure E-107). The
pump control module can be designed with control
15
Thermostats
There are three thermostats that are commonly used in HRU systems. There are water temperature limit,
freeze protection, and refrigerant temperature thermostats.
Water Temperature Limit Thermostats
domestic water heating, the temperature should be
limited to 160 degrees or less for safety purposes. If a
tempering valve is used on the plumbing circuit, there
will be not need to reduce the temperature setting on
the thermostat unless a redundant limit control is desired.
These thermostats are designed to open on
temperature rise to limit the temperature of the water. The sensor for these thermostats is usually mounted
on the “water in” line of the HRU. When the desired
temperature is achieved, the thermostat opens and terminates pump operation. When the HRU is used for
Freeze Protection Thermostats
These thermostats are designed to close on a
fall in temperature (nearing the freezing point), so that
the pump will be activated, circulating warm water from
the storage tank through the heat exchanger. This thermostat must be wired in parallel around the
other controls to a constant power source such as the
load line side of the compressor contactor (figure E105).
Refrigerant Temperature Thermostats
be used to provide for electrical isolation in conjunction
with freeze protection thermostats (see Figure E-105). These controls are available as options on EnviroTemp commercial / industrial units.
These thermostats are designed to close on
temperature rise and open on fall. They are used to
prevent premature or overcooling of the refrigerant
which can reduce refrigerating effect. They may also
Pressure Controls
ing of the refrigerant may drop head pressure too low,
and reduce refrigerating effect. This situation can be
corrected by installing a pressure control (fan cycle
type) in series with the other controls in the HRUs electrical circuit.
It is important to maintain proper operating
pressures of the refrigerating equipment to maintain
efficiency. In certain situations, such as low ambient
conditions or cold water in the storage tank, overcool
16
The pressure control can be adjusted to open on a fall
in refrigerant pressure, terminating pump operation. Once the pressure has increased sufficiently, the pressure control will again close and start the pump. Most
of these controls offer an adjustable differential which
should be set at a range wide enough to prevent short
cycling of the pump motor (figure E-103).
lowest de sired head pressure setting. As the head
pressure increases, the valve will open wider, allowing
more water flow, which will serve to maintain proper
head pressure. This control is refrigerant-pressure operated, eliminating the need for additional control wiring (see figure W-113).
There are numerous controls and control systems that
can be used with heat recovery systems. A thorough
knowledge of the different controls and desired sequence of operation for the HRU will be very helpful in
the design and application of control systems. Consult
factory for special applications.
Another control that is often used wit the HRU is a
pressure actuated water flow control valve (such as
the V46 series Penn valve). This valve is installed on
the “water out” line of the HRU with the sensor line connected to the refrigerant liquid line (preferably the high
pressure line). The valve should be set to open at the
17
MAINTENANCE AND TROUBLESHOOTING
Performance Testing
After installation of the HRU, a performance
test will confirm the proper operation of the system.
The performance figures obtained from this test on
new equipment can serve as a guideline in the future
as to whether the unit is in need of maintenance or
servicing. When comparing future test figures with the
original test data, be certain that the operating conditions
are reasonably similar so that a valid comparison can
be made (i.e. entering water temperature, water flow
rate, hot gas discharge temperature). If water flow rate
and temperature rise of the water through the heat exchanger are known, the BTUH recovery rate can be
easily determined.
The following formula can be used to calculate the BTUH output of the HRU.
By transposing the equation, flow rate
or gpm can be found.
Q = 500 x GPM x T.D.
Q = BTUH
500 = 60 min./hr x 8.33 lbs./gal.
GPM = Gal per minute
T.D. = Temperature Difference
(Leaving water temp – Entering water
temp)
GPM = Q
500 x T.D.
T.D. = Q
500 x GPM
By installing a flow-setter/indicator, flow rate
can be established at a glance. This is a
very useful component for testing and is inexpensive to include during system installation.
Testing Controls
Since there can be numerous controls that can be installed with the HRU, an explanation of the troubleshooting every possible control is practical. However, a discussion of basic controls is in order.
Water Temperature Thermostat
temperature (closing the contacts) and checking for
electrical continuity. If this procedure is done while a
test thermometer is attached near the thermostat sensor, the accuracy of the thermostat can be determined
by comparing the thermostat setting with the actual
temperature readings.
This control is designed to limit water temperature at some desired setting. This control opens the
circuit when the set point temperature is reached and
terminates the circulator pump operation. The sensor
for the thermostat should be mounted on the “water in”
line of the HRU. This control should be checked by
setting the temperature higher than the water
18
MAINTENANCE AND TROUBLESHOOTING
Freeze Control Thermostat
This control must be wired in parallel around
any other HRU controls and is designed to close on
a fall in temperature. (Figure E-105). When the contacts close, (approximately 35° F) power is supplied
to the circulator pump so that hot water is circulated
from the storage tank through the heat exchanger and
water lines to prevent freezing. This thermostat can
be used to sense either water or air temperature. If it
senses water temperature, it will open when the water
line temperature reaches the limit set point (i.e. L45-10
closes on fall at 35°F and opens on rise at 45°F).
If the thermostat senses air temperature, it will close
on temperature fall and stay closed until the air temperature rises above limit set point.
To test this control, the temperature at the sensor must
be lowered below the closing temperature (35°F) while
checking for electrical continuity. Again, a thermometer should be used to check the accuracy of the control
during the test. The temperature of the sensor can be
lowered by spraying with liquid refrigerant or immersing the sensor in an ice water bath.
Head Pressure Controls
set points of the control. This can be accomplished
by manipulating the head pressure of the refrigerating equipment during actual operation. For air
cooled equipment the head pressure can be raised
by blocking air flow through the condenser or cycling
off of the condenser fan. Head pressure can be
lowered by spraying cool water on the condenser. Check for opening and closing of the control at the
desired pressures and adjust or replace the control as required. If the HRU is installed on water
cooled equipment, pressures can be manipulated
by increasing and decreasing water flow through the
condenser. The two common types of head pressure
controls are operated by refrigerant pressure or refrigerant temperature. To test the temperature type,
check for electrical continuity while heating the sensor to its closing set point temperature. Once the
thermostat closes (reads electrical continuity) remove the heat source from the sensor. While testing for continuity allow the sensor to cool, measuring
the temperature at the opening point. Compare the
actual operation temperature with the desired operating temperatures and adjust or replace the control
as necessary. To test the pressure operated control
(fan cycle) requires raising and lowering the head
pressure above and below the
19
MAINTENANCE AND TROUBLESHOOTING
Refrigerant Leak Test
If a leak is suspected in an HRU, a leak test
must be performed. There are two methods for testing that are effective on HRUs that are encased in a
two-part foam such as the Enviro-Temp unit. They are
pressure –drop test or leak soap (or bubble) test. Since
the foam insulation gives off a gas that fools halide detectors, they are of little or no use in testing for leaks. The pressure-drop test involves pressurizing the HRU
with nitrogen to the working pressure (450 psi) and
sealing the system for 24 hours. If there is a loss in
pressure, a leak can be presumed. The bubble test
involves pressurizing the HRU and testing for leaks
by covering the suspect areas with an approved leak
soap and searching for the sign of bubbles. Since every Enviro-Temp unit is pressure-and leak-tested at the
factory, the chance of a leak is very remote. Be certain
to properly test the system prior to removal or replacement.
Cleaning, Descaling Water Tubes
There are two methods of cleaning the water
tubes of the E$P units, depending on the type of unit
used. The mechanically-cleanable unit (E-341-XX-C-*,
the “C” means mechanically cleanable) can be brushed
with a wire brush. This can be done by isolating the
water supply to the HRU, relieving the water pressure,
and removing the access plugs at the rear or the unit. Once the tubes have been brushed and all scale materials have been loosened, flush the water tubes with
fresh water, re-install the access plugs and return to
service. The circulator pump should be shut off during
this operation and all air must be bled from the water
circuit when returning the unit to operation. Be certain
to use an approved pipe sealant on the threaded access plugs when re-installing to prevent water leaks.
equipped with isolation and access valves. The isolation valves should be shut off and the access valves
opened. The chemical descaler can be pumped
through the water tubes until the tubes have been thoroughly cleaned. Once the tubes have been properly
cleaned the system should be thoroughly flushed with
fresh water to remove any descaler and sediment. Again, upon returning the system to operation, all air
must be bled from the water circuit, so that pumping
action can be resumed.
The need for cleaning of the water tubes can
be determined by testing for heat exchange (see Performance Testing in this section). The frequency of
cleaning required will depend upon the hardness of the
water, hours of operation, and the temperature of the
water. Periodic monitoring and testing of the system
is usually the best method of establishing a cleaning
schedule.
Chemical de-scaling of the HRU can be accomplished using a metal-safe descaler. If this method
is used, the “water in” and “water out” lines must be
Winterization for Freeze Protection
If the HRU is mounted in a non-conditioned
space subject to freezing conditions, and is connected
to an air conditioner or other unit that will not be operated during the winter months, it must be protected from
freezing. Since the HRU is a water filled appliance, it
is subject to freeze damage. Be certain the HRU is
equipped with a freeze protection control that has been
properly tested prior to anticipated freezing conditions
(See Freeze Protection Thermostats in Electrical and
Controls section). Remember, if a power outage occurs, the freeze protection control system will be rendered useless.
NOTE: THE SUREST METHOD OF FREEZE PROTECTION IS TO DRAIN THE SYSTEM. BE CERTAIN
THAT ALL AIR IS REMOVED FROM THE SYSTEM BEFORE RETURNING THE SYSTEM TO OPERATION.
IF THE SYSTEM IS DRAINED FOR FREEZE PROTECTION, THE PUMP SHOULD BE ELECTRICALLY DISCONNECTED AS A SAFETY MEASURE, TO PREVENT THE POSSIBILITY OF DRY RUN.
20
This manual is produced by Turbotec Products, Inc., and is intended to be used as an aid to
installation of Enviro-Temp Heat Recovery Units. Various applications may require installation
designs or methods differing from those described in this manual. For special applications consult Turbotec or other qualified personnel for assistance.
Tu r b o t e c P r o d u c t s , I n c .
651 Day Hill Road
Windsor, CT 06095
Tel: 860.731.4200
Fax: 860.683.2133
Headquarters
914-916 25th Street, SE
Hickory, NC 28602
Manufacturing Plant
1-800.394.1633
www.turbotecproducts.com
[email protected]
ETIOM-1108