Keeprite ThermoSaver Installation Manual
ThermoSaver
02/12/10
Hot Gas
TM
PRODUCT DATA,
APPLICATION &
INSTALLATION GUIDE
Bulletin K40-THERM-PDI-13
1069130
Supplement to Condensing Unit
Installation & Maintenance Manual
Defrost System
For use on select Air, Remote or
Water-cooled Condensing Units
matched with Low, Medium or High
Prole Evaporators
R22 - R404A 2-30 HP
-30°F to +34°F Room Temperatures
CONTENTS PAGE
Application Guideline..............................
ThermoSaver Operation Cycle...............
Wiring Diagrams.....................................
Installation..............................................
ThermoSaver Control Settings...............
Troubleshooting Guide...........................
Service Parts List...................................
Warranty.................................................
2
3,4
5-7
8
8,9
10
11
BACK
● Provides fast, efcient evaporator
defrosting.
● Complete factory pre-piping of all
controls and valves.
● Utilizes existing liquid line as hot gas
pipe.
● Reduces installation time and provides
maximum savings during operation.
● Ensures maximum compressor
protection using large capacity
suction accumulator and outlet
pressure regulating valve.
APPLICATION GUIDELINE
K40-THERM-PDI-13
- 2 -
02/12/10
ThermoSaver Hot Gas Defrost systems provide for a
fast defrost alternative over comparable electric defrost
systems. They can be used on any freezer or cooler
application ranging in room temperatures from –30°F to
34°F, with capacity ranges of 2 – 30HP , available as an
Indoor Air Cooled, Outdoor Air Cooled, Remote or Water
Cooled Condensing unit.
The basic piping, layout and design concept are covered in pages 3 and 4 of this manual. These should be
reviewed rst to understand the refrigerant ow and to
identify the special defrost components used.
Important design points are:
1. Concept is similar to a “three-pipe” hot gas bypass
system yet only uses two pipes (shares the liquid line
and reduces eld piping and labour cost). The main
difference is the third shared pipe does not need to
be oversized. During the initial hot gas cycle Liquid is
fed rst, then a mixture, only at the latter part of the
cycle is it all hot gas. (so high pressure drops are not
realized)
2. The defrost is very fast - less than 10 minutes and
uses pressure controls (not temperature) for termination and fan delay functions. (results in faster
response time)
3. The evaporator used must be included together with
the Condensing Unit (i.e. sold/supplied as a complete system package) as it must be properly selected and piped with the correct defrosting components.
Line runs and sizes need to be reviewed. (keep
within 100 feet) Electric heat drain pans (using time
–delay relay function) are recommended in place of
hot gas loops.
4. This unique defrost system can be used with either
one or multiple evaporators (regardless of the application, freezer or cooler) and all can be defrosted
at once.
5. There does exist added suction pressure drop across
the outlet pressure regulator (CPR) and suction
accumulator so for load calculation purposes do not
undersize (keep adequate added safety margin).
6. Excessive system refrigerant charges (from long
runs, oversized evaps, oversized receivers) must be
avoided. During the latter portion of the defrost cycle
and post defrost refrigeration cycle, refrigerant will
ood back to the suction accumulator. Keeping the
overall system charge low will reduce the amount of
oodback.
To ensure maximum design benets:
1. Review the line runs and sizes (use short and
properly sized liquid lines -do not oversize).
2. Use minimal refrigerant charge. Use only enough to
satisfy the condenser ooding valve (low ambient
control), receiver seal, liquid line and evaporator
charge requirements.
3. Field adjust these ve critical defrost components to
proper initial settings:
(a) Outlet Press Regulator (CPR) Valve- Must be set
to the lowest possible setting (approx 10-15°F
above evap temp design) without compromising post defrost pull-down time. This valve is not
primarily set for motor compressor motor overload
protection, it’s main purpose is to keep a pressure
differential during the defrost .
(b) Defrost Termination Control- Must not be set too
high. Keep to lowest possible setting (as soon as
ice and frost has melted and pressure then starts
to rise). Higher settings result in longer defrosts
(over 10 minutes) and excessive oodback.
(c) Fan Delay Control- Must not be set too low (as
will promote ooding of the evap resulting in increased amount of refrigerant ood back after the
defrost)
(d) Timeclock - Fail safe Time should not be set
greater than 20 minutes. If the defrost is taking too
long then an issue exists with the control settings
or application. (This must be identied and resolved.)
(e) Time –Delay (Hot gas cycle) – Must be set at
least for two minutes (up to 5 min) in order to (i)
pump out all remaining refrigerant in the evaporator and (ii) Pre-heat the drain pan prior to the hot
gas entering the coil. This timer setting must be
longer than the compressor anti-short cycle setting (if equipped)
Important initial set points are covered on pages 8 and 9 in
this manual and must be followed. Further adjustments can
then be made to suit local eld conditions.
THERMOSAVER OPERATION
K40-THERM-PDI-13
- 3 -
02/12/10
The ThermoSaver defrost cycle system provides a
quicker defrost period (up to three times faster) over the
conventional electric defrost system. This minimizes the
rise in box temperature during the defrost which reduces
product deterioration and increases the system efciency.
This results in lower running times and reduced energy
costs. When using more than one evaporator on the
same condensing unit, all the evaporators can be defrosted
simultaneously.
All ThermoSaver components are completely factory
installed, pre-piped and pre-wired. An extra third pipe
(hot gas line) is not required.
REFRIGERATION
L M
Suction
Accumulator
Condenser
C
D
Compressor
This signicantly reduces the overall installation time
and cost. Factory installed standard components include
the evaporator distributor nozzle, thermostatic expansion
valve (TXV), liquid line solenoid valve, hot gas solenoid
valve, liquid check valves, three way solenoid valve,
defrost regulating valve, suction accumulator, defrost
termination / fan delay pressure controls and drain pan
heater and timeclock. Room thermostat and suction
lter are optional to be eld installed.
The following diagrams explain the ThermoSaver operation
during both refrigeration and defrost cycles.
N
H
Filter
Evaporator
FB
Boil Out
Drier
Receiver
A - Room Thermostat
B - Liquid Line Solenoid Valve
C - Dual Hi / Lo Pressure Control
D - Three Way Hot Gas Solenoid Valve *
E - Liquid Line Check Valve
* On larger (15 HP & up) systems, a separate N/O and N/C solenoid valve is used in place of 3-way valve
As the box temperature rises, the room thermostat (A)
energizes the liquid line solenoid valve (B). This allows
refrigerant to enter the evaporator, build up pressure,
cause the low pressure control (C) to energize the
compressor contactor and start the compressor. The
compressor’s hot discharge gas is piped out to the
condenser through the de-energized 3-Way valve (D).
or seperate N/O and N/C solenoid valves. The hot
refrigerant gas is condensed by the condenser. The
liquid then ows to the receiver through the opened
check valve (E) and on through the coiled liquid line
within the suction accumulator (this performs the function
as a suction to liquid heat-exchanger). The subcooled
liquid then ows through the liquid line solenoid valve
(energized/open) and on to the TXV (F)
(Thermostatic expansion valve).
E
F - Thermostatic Expansion Valve
H - Defrost Regulating Valve
I - Timeclock
Heat Exchanger
I
LEGEND
The refrigerant is then directed through the distributor
at a lower pressure and ows into the evaporator. The
refrigerant liquid / vapour mixture is then boiled by the
warmer box air from the evaporator fan. The refrigerant
vapour then ows though a defrost regulating valve (H)
preventing a motor overload from high suction pressures
and enters the suction accumulator and on to the compressor.
The cycle continues until the room temperature is satised. This de-energizes the liquid line solenoid, initiating a
pumpdown cycle that reduces the suction pressure to the
cut-out setting on the low pressure control which de-energizes the compressor.
A
J - Drain Pan Heater
K - Hot Gas Solenoid Valve
L - Three Way Hi Pressure Control
M - Defrost Termination Pressure Control
N - Fan Delay Pressure Control
K
J
THERMOSAVER OPERATION
K40-THERM-PDI-13
- 4 -
02/12/10
DEFROST
C
Condenser
D
Compressor
L M
Suction
Accumulator
H
N
Evaporator
Filter
FB
Boil Out
Drier
Receiver
A - Room Thermostat
B - Liquid Line Solenoid Valve
C - Dual Hi / Lo Pressure Control
D - Three Way Hot Gas Solenoid Valve*
E - Liquid Line Check Valve
* On larger (15 HP & up) systems, a separate N/O and N/C solenoid valve is used in place of 3-way valve
E
F - Thermostatic Expansion Valve
H - Outlet Pressure Regulator
I - Timeclock
Heat Exchanger
I
LEGEND
Third
K
A
J - Drain Pan Heater
K - Hot Gas Solenoid Valve
L - Three Way Hi Pressure Control
M - Defrost Termination Pressure Control
N - Fan Delay Pressure Control
Pipe
J
The refrigeration cycle results in frost formation on the
surface of the evaporator. This frost will eventually build
up to the point where it will restrict the air ow causing a
loss of refrigeration capacity. To prevent this, a timeclock
(I), usually set to repeat every 6 or 8 hours, initiates a
defrost cycle which melts the frost.
The clock de-energizes (closes) the liquid line solenoid
valve which causes the compressor to pumpdown and
shut off from the low pressure control. The clock also
energizes the drain pan heater (J) in the evaporator and
timer relay which after a two or more minute delay energizes (opens) the 3-way valve and hot gas solenoid valve
(K) which then builds up pressure in the evaporator causing
the low pressure control to close and start the compressor.
The hot discharge gas from the compressor ows through
the 3-way valve forcing all the liquid left in the liquid line
into the evaporator. If pressure builds up too high the
3-way valve safety pressure control (L) will de-energize
the solenoid valve and allow pressure to relieve through
the condenser.
Pressures within the evaporator will increase during the
defrost. The outlet pressure regulator (H) maintains a desired pressure differential in the system, as well as reducing the amount of liquid refrigerant back to the accumulator.
The regulator also minimizes any high suction pressure
avoiding compressor motor overloads.
Once all the frost has melted the pressure will continue to rise until the defrost termination pressure
control (M) energizes the timeclock’s internal solenoid terminating the defrost cycle. The 3-way valve,
hot gas valve solenoids are then de-energized. The
liquid line solenoid valve opens and the compressor
continues to run. The evaporator fans do not start
up until the pressure in the evaporator is low enough
to close the Fan delay control (N). By delaying the
fans this allows any moisture left on the coil to drain
away or freeze. As soon as the evaporator fans are
energized the system will then resume back to the
refrigeration cycle.
The cycle continues until the room temperature is
satised.
This de-energizes the liquid line solenoid, initiating a
pumpdown cycle that reduces the suction pressure to
the cut-out setting on the low pressure control which
de-energizes the compressor.
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