Heat Pipe Technology BKPOOL 300 Owner's manual

MANUAL 8/12/05
INSTALLATION, OPERATION & MAINTENANCE
Commercial High Efficiency
Heat Pipe Dehumidifier
Model BKPOOLTM 300
Model BKPOOLTM 300-AC
Model BKPOOLTM 400
Model BKPOOLTM 400-AC
Model BKPOOLTM 500
Model BKPOOLTM 500-AC
Heat Pipe Technology, Inc.
6904 Parke East Blvd. Tampa FL 33610
Tel: [phone]
http://www.heatpipe.com
E-mail: [email protected]

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Model BKPOOLTM 300, 300-AC, 400, 400-AC 500, 500-AC
INSTALLATION, OPERATION & MAINTENANCE
1. GENERAL DESCRIPTION
The BKPOOLTM s are commercial high efficiency dehumidifiers. They are radically different from other
dehumidifiers because of the proprietary heat pipe used to exchange heat between the warm intake air
and the cold air discharge from the evaporator. This process precools the incoming air and allows more
moisture to be condensed for less energy spent. The heat pipes are passive devices that use no energy.
The BKPOOLTM standard unit comes pre-charged with refrigerant. The BKPOOLTM AC model is shipped
in two sections which must be piped together, evacuated and then charged as a unit.
The BKPOOLTM AC models which are equipped with outdoor remote condensers have a cooling mode
to reject heat to the outdoors.
The BKPOOLTM comes with a dehumidistat and a thermostat for the unit with outside remote
condenser. Condensate water is removed by gravity drain. The unit comes with an intake and supply air
duct flanges. Pleated 2 in. air filters are standard and can be accessed through a separate cover from
either side of the unit.
2. INSPECTION
All HPT products are carefully tested and inspected prior to shipment. Each unit is in good working
condition when packaged. If the package is damaged in any way, check the contents immediately; note
damage on shippers Bill of Lading and have him/her sign your statement to insure prompt claim
processing. Notify the carrier immediately of the damage so he can come out and inspect the product
and packaging. The carrier alone is responsible for handling and settling your claim.
HPT will cooperate in assessing damage if unit is returned to the factory prepaid.
Unpack the unit. The following will be included: BKPOOLTM dehumidifier, dehumidistat, thermostat (for
the unit with outside remote condenser), user's manual and warranty card.
3. INSTALLATION
The BKPOOLTMs can be placed as a stand-alone unit in an environment such as above the ceiling or in a
mechanical room. The BKPOOLTMs are designed to operate in conditioned space with temperatures
ranging from 60°F to 95°F. Special factory options may be ordered for operation above or below these
limits.
3.1 DUCTING
The BKPOOLTMs can be used with suitable metal or fiberglass ducts using approved methods. The ducts
must be sized appropriately for the airflow listed. A good quality air filter of equal or larger size may be
installed in the inlet register and located for ease of maintenance. The duct must not add more than
0.5" E.S.P. inclusive of both supply and return ducts.
When the BKPOOLTM is used to handle outside fresh air, a branch of the intake can be ducted to outside.
The BKPOOLTM is designed to handle as much as 25% fresh air and will remove most of the moisture
from the air before admitting it to the building. Additionally, the supply dry air can be ducted or injected to
the supply duct of another air handler for the space, providing the back pressure from the other air
handler does not reduce the air flow through the BKPOOLTM . The blower of the main air handler may also
need to be interlocked to the BKPOOLTM so that the blower runs when the BKPOOLTM runs to distribute
the air. A back draft damper will also be needed for the BKPOOLTM to prevent the main AC from blowing
back through the BKPOOLTM when it is not running.

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3.2 CONDENSATE DRAIN
The BKPoolTMs are supplied with a condensate gravity drain outlet. For the gravity drain, the pipe must
have a downward slope for the entire distance to the outside. If installed above the ceiling, the pipe must
be supported every 3 or 4 feet to prevent sagging. If the line has any level runs or dips, it will not drain
properly. Ensure that the drain line has a trap to prevent outdoor air from being aspirated into the
BKPoolTM and prevent draining. If the piping goes underground and back up outside, this is considered an
adequate trap. Do not double trap. This may prevent the condensate from draining due to the air pocket
between two traps. Due to the high static pressure across our dehumidifier coils, a 2 inch minimum trap is
required.
BKP BKP
Min. 2 in.
This will not drain!
Fig 3.2 Condensate trap
For installation above the ceiling or above the ground floor, it is recommended that the BKPOOLTM be
installed over a separate drain pan, which is piped to a separate drain point.
3.3 UNITS WITH A REMOTE CONDENSER
Install the remote condenser in an outdoor, well ventilated and preferably well shaded area. Ensure that
the hot air discharge is not obstructed. Install on a concrete pad or as required by local codes.
CAUTION: Coil is pressurized with a few PSI of nitrogen. Punch hole in copper to relieve pressure before
cutting off end to connect line.
3.4 CONDENSER PIPING
The BKPOOLTM with remote condenser is shipped with a holding charge of dry nitrogen. Release the
pressure before un-sweating the caps from the tubing connection. Connect the BKPOOLTM to the remote
condenser using refrigerant tubing of the sizes listed in Table BKPOOL01. The tubing needs not be
insulated except in exposed areas where the hot gas line might cause harmful burn. Solder the
connections with suitable silver brazing alloy and leak check. An additional Refrigeration charge will have
to be added to the nameplate charge depending on the liquid line size and length. See section 4.
Charging the BKPoolTM
Table BKPOOLTM 01
Model
300-AC 400-AC 500-AC
Liquid
3/8 3/8 3/8
Vapor
1/2 1/2 1/2

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Note:
This BKPOOLTM -AC remote line sizing applies to most applications, up to 50 feet horizontal, and within 10 feet
vertical (ACR OD line sizes).
3.41 Long Line Sets (50 ft or Longer)
For line sets where there are no vertical sections greater than 10 ft. and for lengths up to 150 ft. increase
the vapor line one size larger but leave the liquid line size as is. Also add 4 extra ounces of refrigerant oil
(3GS or Equivalent) to the system for every 50 ft. over 50 ft.
3.42 Vertical Line Sets
When the BKPOOLTM -AC remote condenser is installed either on a roof above the BKPOOLTM Unit, or on
the ground where the BKPOOLTM unit is on an upper floor or attic, special consideration needs to be taken
to insure that Oil will return to the compressor. Unlike a split system air conditioner, the compressor is in
the indoor unit.
If the remote condenser is above the indoor unit, special P-Traps need to be installed in the vapor line at
the bottom of the vertical section and every 10 ft. above that. Small particles of oil that circulate with the
Vapor will accumulate in the traps until they are large enough to be carried up the pipe by the velocity of
the refrigerant. Vertical sections of tubing should not be enlarged beyond that specified in table
BKPOOL01. Pre-manufactured traps are available at the air conditioning supply houses or traps can be
made up using long radius ells of the same size as the tubing.
If the remote condenser is below the indoor unit no special changes are necessary. The oil will travel
down hill with the vapor to the condenser and return with the liquid refrigerant to the indoor unit.
Fig 3.42 P-Traps must be added to vertical lines over 10 ft. where remote condenser is higher
than the indoor unit.
10ft.
BKPool
Indoor Unit
Remote
Condense
r
Vapor Line
Li
q
uid Line
Trap

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4. ELECTRICAL WIRING
CAUTION: Units with three phase compressors can be damaged by running backward. Verify
correct compressor rotation by observing refrigerant pressure gauges at startup. Little or no gauge
movement indicates reverse rotation. Reverse any two leads in the power junction box.
Note: Fan blower motor is single phase and not affected by lead connections.
4.1 Power Supply
Use properly sized wire. Install and connect unit in accordance with local codes. Unit must be grounded.
Size separate circuits to the BKPOOLTM and to the Remote Condenser.
4.2 24 VAC Control Wiring
Units Without Remote Condenser
A dehumidistat is supplied with the unit. It should be placed in the conditioned space away from heat
sources, entrance doors or any sources of humid air. Do not mount it directly on the side of the unit, as
the vibration may adversely affect it. Place the dehumidistat at a location where it could sense the
average relative humidity of the space.
The dehumidistat is of the 24 V type and should be wired with T-stat 18 gauge, 3 conductor low voltage
wire. (See wiring diagram in unit control panel.)
Units with Remote Condensers
For operation of units with a remote condenser, both temperature and humidity are controlled. A 24V
thermostat and a 24V dehumidistat are supplied with the BKPOOLTM AC. Wire the controls with
Thermostat 18 gauge low voltage wiring in accordance with the wiring diagrams.
NOTE: The operation of the remote condenser is by an internal pressure switch. No control wiring is
needed to the outdoor condenser.
5. CHARGING THE BKPOOLTM
The BKP™ is charged with refrigerant 22. The charge amount is listed on the nameplate. It is important to
have exactly the right charge in the unit or damage to the compressor or refrigerant components may
occur. Due to the wide range of operation of the BKP™ it is highly recommended that the charge be
weighed in to the ounce.
5.1 Standard Unit
Standard units (Non AC Models) are factory charged and ready to run after installation and wiring. If the
charge is in question, first, recover the refrigerant in the system and weigh in the proper charge. If it is
determined that the unit has a refrigerant leak, the leak must be repaired. Even though the unit appears to
operate, as the refrigerant level drops the compressor will over heat and be damaged before the condition
is recognized. Repair the leak and replace the liquid filter dryer. Evacuate the system using a Micron
Gauge down to 400 microns. Valve off the vacuum pump and insure the vacuum does not rise above 700
microns. Then weigh in the charge using a scale accurate to 1 once.
5.2 AC Units
The BKPoolTM AC model is shipped in two sections which must be piped together, evacuated and then
charged as a unit. Evacuate the refrigerant system to 400 microns or below. Valve off the vacuum pump
and insure the micron level does not increase above 700 microns. For BKPoolTM -AC units the system

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must be evacuated from all three ports. This is due to the check valves used in the remote condenser. A
1/4 in. flair Tee and an extra refrigeration hose can be used to double up the discharge hose. Remove
the extra hose from the remote condenser tap after charging and before running the unit. Weigh in
the refrigerant charge using the suction and discharge ports. The proper charge of refrigerant 22 for the
unit and the remote condenser can be found on the nameplate. It is important to have the proper charge
of refrigerant. The preferred method of charging is to weigh in the charge from the nameplate with a
scale, which can be accurate to plus or minus one ounce. Additional refrigerant needs to be added for the
length of the line set. The liquid line (the smaller line) is full of liquid in both the heating and cooling
modes of operation. Measure the length of the line set one-way and add to the charge as follows:
3/8 in liquid line add 0.8 oz per foot
1/2 in liquid line add 1.5 oz per foot
5.3 Alternate Charging Method
NOTE: This method will only work if enough load can be maintained on the BKPTM that the suction
pressure does not fall below about 65 PSIG while charging. It will be necessary to fabricate a cover
out of cardboard the same size as the front cover (use the cover as a template) in which a small flap can
be cut for observing the sight glass. Do not run the unit without a cover in place. With the BKPTM
turned off, charge the unit with liquid until the unit can be run without shutting down on low pressure. Start
the unit in the heating mode and charge vapor into the low side port until the sight glass almost clears.
Run the unit for 15 minutes and then slowly add vapor until the sight glass just clears.
6. OPERATION
The dehumidistat controls the operation of the dehumidifier.
6.1 Units Without Remote Condenser
Set the dehumidistat at the desired level, the dehumidifier will run and remove humidity until the set
humidity is reached, at which time the dehumidifier will shut off. For normal operation, a range from 50%
to 60% will provide the best comfort. Settings below 50% will make the unit run longer and less
economical. Settings above 60% which may be required in certain situations will be more economical,
but may not provide adequate human comfort.
6.2 Units with Remote Condensers
The BKPOOLTM-AC with remote condenser is designed to control space temperature as well as humidity.
Therefore, they are controlled by both a dehumidistat and a thermostat. This design allows the
BKPOOLTM-AC to switch from normal operation to remote condenser operation automatically when extra
cooling is needed in the space. In the remote condenser mode, the BKPOOLTM-ACs dehumidify and
provide additional cooling to the space at the same time.
The thermostat should be set 2 to 3°F below the setting on the building thermostat so that the BKPOOLTM
operation will not interfere with the operation of the building A/C. The latter will continue to cycle on and
off to maintain the building temperature. When the building A/C cycles off, with the lower thermostat
setting, the BKPOOLTM continues to run in the thermostat cooling mode until the temperature drops to its
onset point. The BKPOOLTM then shifts to its normal mode, discharging dry warm air.
When the temperature rises to its thermostat set point, the BKPOOLTM again shifts to the additional
cooling mode. Therefore, it will cycle back and forth to maintain the inside temperature at its set point and
the building A/C will not cycle on unless the temperature has risen up to the building's higher thermostat

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set point. In this manner, the building A/C cycles on only when the cooling by the BKPOOLTM is not
sufficient. When the relative humidity is down to the desired setting, the BKPOOLTM -AC will shut off and
the building will be back to its normal A/C operation.
During the wintertime when the space must be heated, the BKPOOLTM thermostat should be set 2 to 3
degrees above the main heating thermostat. This will use the BKPOOLTM normal dehumidifying operation
mode to provide additional heating to supplement the building's heating system. It will continue in this
mode until its dehumidistat is satisfied.
NOTE: The BKPOOLTM is not designed to cool when the outdoor temperature is below 50°F.
Refrigerant Migration will occur and the unit will shut down on low pressure.
7. MAINTENANCE
It is essential that the air filter on the inlet of the unit be kept clean in order to prevent excessive power
consumption and possible damage to the unit. Check the filters routinely to determine the frequency of
replacement.
Keep the outdoor remote condenser free of leaves and grass clippings which may impede air flow.
Check condensate drain regularly to ensure that the condensate is draining properly. If installed with an
auxiliary drain pan under the unit, check that it is dry.
It is recommended that the BKPOOLTM be serviced annually by an authorized HPT certified technician to
provide maximum efficiency and insure long life equipment.
8. SERVICE DIAGNOSIS
The BKPOOLTM is equipped with safety controls which will shut down the unit if a problem occurs. The
BKPOOLTM will remain locked out until it is reset.
If The Unit Locks Out:
1. Check the air filter in the inlet of the unit. A dirty air filter will cause an increase in power consumption
and in the long run may cause damage to the unit.
2. Check the remote condenser. If the air is blocked or the hot air discharge is not free to dissipate, a
high discharge pressure will result and may cause damage to the BKPOOLTM.
3. Check the power supply to the remote condenser. It will be on a separate breaker and if tripped will
cause the BKPOOLTM to shut down.
4. Check refrigerant charge as described above.
To reset the BKPOOLTM
Reset the BKPOOLTM by either turning the humidistat all the way up and then back down or turning the
power to the BKPOOLTM off and then on. Allow 5 minutes for the BKPOOLTM to restart. If it locks out
again after restart, have the unit serviced by a qualified service technician to determine the cause of the
shutdown and correct the problem. See Troubleshooting section below.
.

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9. SEQUENCE OF OPERATION FOR STANDARD UNIT
The BKPOOLTM is controlled, on or off, by a dehumidistat which senses the relative humidity of the space.
The BKPOOLTM is shipped with a remote mounted De-Humidistat. The AC models also have a
Thermostat. Both are designed to be used with a duct system having a total external static of 0.5 in H2O
or less.
(SEE WIRING DIAGRAM) On a call for dehumidification the contact in the dehumidistat is made sending
control power through the safety shutdown switches, through the lockout relay and to the blower relay.
Control power is also sent through a recycle time delay to the compressor contactor.
The safety shutdowns consist of a high and low refrigerant pressure cutout. If either of these cut-outs
open, the current path from the dehumidistat to the contactor is shifted through the coil of the lock-out
relay. The normally closed contact in the lockout relay opens and the normally open contact closes,
essentially shorting across the coil of the compressor contactor and providing full control voltage to the
lockout relay coil.
The contactor will remain off as long as the lockout relay receives voltage from the dehumidistat. Turning
the dehumidistat up and then back down, mechanically opens the contact in the dehumidistat, dropping
the power from the lockout relay.
After reset, voltage can now go through the normally closed contact of the lockout relay to the
compressor contactor and blower relay, provided the safety shutdown has cleared. Control power to the
contactor will be resumed through the off-cycle time delay when the machine has been off for the
selected number of minutes (factory set to 5 minutes for single phase units 3 minutes for 3 phase units).
The refrigerant system is a R-22 (Chlorodifluoromethane) system consisting of a compressor, condenser
coil, sight glass, filter dryer, Thermal expansion valve, and an evaporator with dehumidifier heat pipes.
The coil section contains both the evaporator and condenser coils. The airflow enters through the precool
heat pipe then through the evaporator then the reheat heat pipe and the condenser.
9.1 Remote Condenser Units
The BKP-ACTM series operates similar to the standard unit except that it has a liquid receiver and
employs a separate outdoor condenser. Since the standard unit discharges air through the condenser
coil, the discharge air temperature will always be warmer than the inlet air and can reach temperatures
above 100F. The BKPool-ACTM unit, on the other hand has an outdoor condenser as well an indoor
condenser.
These units use a separate remote mounted thermostat along with the dehumidistat to control the BKP-
ACTM. The dehumidistat operates the unit on and off as described above. The thermostat controls a
reversing valve that diverts the refrigerant flow between the indoor and outdoor condensers. When the
temperature is below the set point, the valve sends the refrigerant through the indoor condenser. This
has the effect of warming the space temperature. When the temperature is above the set point the valve
sends the refrigerant through the outdoor condenser. The BKPool-ACTM then acts as an air conditioner,
bringing the space temperature back down. The BKPool-ACTM will switch back and forth between indoor
and outdoor condenser until the dehumidistat is satisfied.
The thermostat gets its control power from the red wire going to the dehumidistat. On a drop in
temperature, the thermostat contact sends control power directly to the reversing valve coil.
The outdoor condenser is powered from a separate power supply. No control voltage wiring is
connected. A head pressure switch inside the outdoor condenser controls the fan. The fan comes on
when the pressure in the outdoor coil reaches 240 psig and shuts off when it drops below 190 psig.

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The refrigerant flows from the compressor to the reversing valve inlet. In the de-energized state the flow
is sent to the indoor condenser. The line going to the outdoor condenser is internally connected to the
reversing valve's center suction port, which is connected to the suction line coming out of the evaporator
by a 3/16" tube. This tube has a check valve installed in it. Any refrigerant in the outdoor condenser will
be pulled back through this 3/16" tube as the compressor runs. A check valve in the leaving liquid line of
the outdoor condenser prevents refrigerant from being pulled backward through the condenser coils.
When the reversing valve shifts to the outdoor condenser the indoor condenser is connected to the
suction by the 3/16" line. The indoor coil also has a check valve in the liquid line out.
The 3/16" line to the suction header provides a smoother transition when shifting. A hissing sound for 10
to 20 seconds is normal while the machine equalizes after shifting.
The BKP-ACTM also has a liquid receiver in the common liquid line.
If the BKPool-ACTM is installed in an application where it may need to run in the winter when outdoor
temperatures will be below freezing, special provisions need to be made in the installation. An outdoor
thermostat must be installed to prevent the BKPool-ACTM from shifting to the outdoor mode when
temperatures are below 50°F. If the unit is allowed to shift to the outdoor condenser when the
temperature is below that of the evaporator temperature, the compressor will not be able to pull the
refrigerant back when it shifts to the indoor coil and the unit will shut down on low pressure. A check
valve in the liquid line and in the small suction return line prevent refrigerant from migrating to the outdoor
coil during cold whether, while the unit operates in the Heating Mode.
9.2 OPTIONAL EQUIPMENT
9.21 Phase Loss Monitor for Three Phase Units
Units with a Phase loss monitor are provided with fuses which feed the phase loss monitor and the
control transformer. The monitor has an adjustable setting for operating voltage which determines the trip
settings. This voltage must be set at startup to the measured line voltage. This monitor samples the
voltage between all three phases and closes a set of normally open contacts when the voltage and phase
rotation is correct A red LED lights up to indicate the contact is closed. The contact will open if line
voltage on any phase drops by 10% of the adjusted line voltage setting or an unbalance of 4% occurs
between phases. The contact will open to drop the 24 V control power to the control system.
9.22 Cooling Priority Relay
Units with a cooling priority relay will energize the BKPoolTM in the cooling mode on a call for cooling from
the thermostat even if the dehumidistat is satisfied. Control voltage from the thermostat to the reversing
valve is used to energize the cooling relay. Normally open contacts 2 and 4 close to supply control power
directly from the transformer to the yellow wire coming from the dehumidistat. When the thermostat is
satisfied, the BKPoolTM will shut down again.
is used to energize the cooling relay. Normally open contacts 2 and 4 close to supply control power
directly from the transformer to the yellow wire coming from the dehumidistat. When the thermostat is
satisfied, the BKPool-ACTM will shut down again.

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10. SPECIFICATIONS
BKPoolTM 300, 400, 500
Models 300 400 500
Capacity (lbs/day) at
85°F & 60% RH (AHAM) 302 422 532
Capacity (lbs/day) at
80°F & 50% RH (ASHRAE) 214 299 377
Air Flow Rate (cfm) 700 1000 1200
Operating Range All models can operate from 60°F/100% RH to 95°F/55% RH
Dimensions (WxHxD) (in.) 45 x 22 x 24 45 x 22 x 29 45 x 22 x 34
Net Weight (lbs) 250 300 350
Filter Size (WxHxD) (in.) 16 x 20 x 2 16 x 25 x 2 2 - 16 x 16 x 2
Electrical (60 Hz)*
Voltage/Phase 208/230 V/ 1 ph 208/230 V/ 1 ph 208/230 V/ 1 ph
Max. Fuse or HACR Circuit Breaker (A) 30 40 45
Min. Circuit Ampacity (A) 20 26 29
Normal Operating Power (W) 2500 W 3000 W 3500 W
Compressor Scroll Scroll Scroll
Blower Motor Power (hp) 1/3 1/2 3/4
Condensate Pumps Optional Optional Optional
BKPoolTM 300-AC, 400-AC, 500-AC
Models (Outdoor Unit) 300-AC 400-AC 500-AC
Dimensions (WxHxD) (in.) 24 x 25 x 20 24 x 25 x30 24 x 25 x 30
Net Weight (lbs) 65 95 95
Air Flow Rate (cfm) 800 1800 1800
Electrical (60 Hz)*
Voltage/Phase 208/230 V/1 ph 208/230 V/1 ph 208/230 V/1 ph
Fan Motor 1/4 1/4 1/4
Normal Operating Power (W) 350 W 350 W 350 W
*50 Hz models available on custom order.
265V and 460V also available on custom order
Specifications subject to change without notice.

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BKPOOLTM and BKPOOL-ACTM SERIES TROUBLESHOOTING CHECK LIST
Company: ________________________________
Phone: (____) ________ Fax: (____) __________
Job Name: ________________________________
Model # : __________ Serial # : ______________
Test performed by: ______________ Date: ______
Test Dehumidification Air Conditioning
Air
Return Air Flow CFM CFM
Return Air Temperature °F DB °F WB °F DB °F WB
Return Air Static Pressure (Negative) in. WG
Return Duct Size " Depth " Width
Supply Air Temperatures °F DB °F WB °F DB °F WB
Supply Duct Air Pressure (Positive) In. WG
Supply Duct Size " Depth " Width
Condensate after 15 min (see Note below)
Refrigerant
High Discharge Pressure / Sat. Temperature psig °F psig °F
Liquid Line Temperature / Sight Glass °F SG Clear? °F SG Clear? 
Low Suction Pressure / Saturated Temperature psig °F psig °F
Suction Line Temperature (@coil outlet) °F °F
Suction Superheat °F °F
Elec.
Compressor Volts / Amps at outdoor °F Amps at °F DB Amps at °F DB
Indoor Blower Lo Med Hi Volts/Amps Volts Amps
BKPOOL-AC
Outdoor Fan ________ Volts / Amps
Amps
Outdoor Fan Pressure Switch set at ON: _______ psig
OFF: _______ psig
Vapor Line Length / Size ft "OD
Liquid Line Length / Size ft "OD
Note: To perform condensate flow test, run the unit for 15 minutes, then capture condensate for 5 minutes in a
graduated container. Air side conditions must be measured during this time.
Is condensate TRAP properly installed? Yes. No.
Does condensate pump cycle properly? Yes. No.
Remote Condenser
Return
Air Supply Air
BKPOOL

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THE BKPOOLTM TROUBLESHOOTING
Follow each applicable section in order from top to bottom.
Note 1 - Acceptable control voltage range 22 volts to 30 volts.
1) The unit does not start.
Possible Cause Solution
No power to the unit. Check the voltage to unit at the top of contactor.
Humidistat set above space humidity level. Lower the humidistat setting.
If the unit is locked out Reset by turning the dehumidistat up and then down, then wait for time delay. If it locks out again, Follow
Procedure #3 “Unit locks out before starting”
Check for 24V at the transformer. (see note
1) If no, replace the transformer
Check for 24V at lockout terminals 3 & 2 If no, make sure the dehumidistat and field wiring are
OK.
Check for 24V at lockout terminals 1 & 3. If yes, Follow Procedure #2 “Unit locks out before
starting”
2) Fan runs but compressor doesn’t
Possible Cause Solution
Check for 24v across time delay If yes wait 5 minutes. If compressor does not start,
replace the time delay
Check for 24v at the compressor contactor
coil
If yes and the contactor does not pull in, then replace
the compressor contactor
If no check wiring
Check Voltage at bottom of compressor
contactor If no, Replace contactor.
Check for proper voltage at compressor
terminals If no, Repair wiring from contactor to compressor.
Compressor is hot Compressor off on internal overload. Let it cool down.
Check capacitor Replace if bad.
Check compressor ohms Replace if bad.

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3) Unit locks out before starting.
Turn power off to unit for this section. Put gauges on high and low refrigeration ports.
. Possible Cause Solution
If both gauges are below 40 psig, the unit
has a refrigerant leak Repair and recharge the unit.
Low pressure gauge below 40 psig and high
pressure gauge at saturation pressure Replace expansion valve and filter dryer.
If Low pressure is above 40 psig, and high
pressure is below 250 psig, Remove wire from terminal 5 of lockout relay. Continue below.
check continuity from wire to terminal 3 of
lockout relay. If there is continuity, replace the lockout relay.
No continuity across low pressure cut out. Replace low pressure cutout.
No continuity across high pressure cut out. Replace high pressure cutout.
If there is continuity across all cut outs then
the wire between cutouts is open. Replace or repair the wire.
4) Unit runs a short time then locks out.
It will be necessary to construct a cardboard cover the same size as the front cover. Use the front cover
for a template. Make sure the cardboard lays against the diagonal drip rail on the coil. Any leakage of air
around the coil will affect the pressure readings. Cut a small flap in the cover that can be opened and
closed to observe the sight glass while charging. Do not run the unit with the cover off.
Start unit and observe the refrigerant pressures. The low pressure cutout is 15 psig. The high pressure
cutout is 350 psig. If the unit tries to shut down on the low pressure switch, try to observe the sight glass
just before it shuts down.
Do not run the unit with any cover(s) off except the filter cover.
4a) Unit shuts down on low pressure.
Possible Cause Solution
Insure inlet air conditions are above 70°F
and 45% humidity Do not run if conditions are too low.
For BKPool-ACTM units check that unit does
not shift into cooling if outdoor conditions
are less than 50°F.
Do not run in cooling if outdoor temperature is below
50°F. if necessary install outdoor thermostat to prevent
cooling operation below 50°F.
If there are bubbles in sight glass just before
shut down, the unit may have a refrigerant
leak.
Leak check, Recover refrigerant and repair. Replace
filter dryer. Evacuate and weigh in charge.
If there are no bubbles in sight glass just
before shut down, Replace expansion valve and filter dryer.

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4b) Unit shuts down on high pressure.
Possible Cause Solution
Check for proper airflow. Replace filter, clean coil, duct and blower.
If air flow is low, check that the coil is not
icing up. Let ice melt and check for too low temperature for operation. Check Hot Gas Bypass.
For BKPool-ACTM, if the outdoor fan does
not come on at 240 psig in cooling mode Check if there is power to outdoor condenser. Restore the power.
Pressure switch operation does not work. Replace the pressure switch.
Fan motor not running. Repair wiring to the motor and/or replace the fan motor.
If pressure is still high, unit has probably
been overcharged.
NOTE: Proper charge cannot be
determined by refrigerant pressures,
Recover all refrigerant and weigh in proper charge.
5) Unit shuts down occasionally.
Follow the procedure under (4) "unit runs a short time then locks out". If unit shuts down, follow the
outlined procedure. An occasional shut down can be a very difficult problem to diagnose. It usually
involves some trial and error and multiple trips back to solve. If everything looks normal while the machine
is running, consider whether there could be any environmental changes taking place during the day.
Such as the air conditioning or heating being shut down at night while the BKPoolTM runs continuously. If
it is a BKPool-ACTM, the unit could be tripping on cold nights when it shifts to the outdoor condenser.
These units should be prevented from running in the cooling mode if the outdoor temperature is below
50°F.
Small trip indicators are available from local AC supply houses to help in diagnosis. These are attached
across each safety cut out and will tell you which control is shutting the system down. This will narrow
down the possibilities. Do not permanently bypass any safety control unless directed by the factory.

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6) BKPoolTM runs but does not dehumidify.
Follow the procedure in (4) "unit runs a short time then locks out" to observe the sight glass and attach
refrigeration gauges to the BKPoolTM. Using thermometers and hygrometers, take the dry bulb
temperature and relative humidity readings at the air inlet to the BKPoolTM.
Possible Cause Solution
High and low pressure gauges did not move
when the unit comes on.
Check compressor wiring, and capacitor. If compressor
is hot, allow to cool completely before condemning
compressor. OHM compressor to determine winding
condition. Replace compressor if bad.
If the compressor runs, but low pressure
reads too high and high pressure reads too
low. Check Hot Gas Bypass
If HGBP is leaking by, replace valve. If reversing valve is
leaking by replace reversing valve. IF both of these are
OK, replace the compressor.
If the compressor runs, but both low and
high pressure reads low Check if the evaporator coil is frosted up. If frost is present, allow the frost to melt completely.
If pressures are still low, and there are
bubbles in the sight glass, the unit may
have a refrigerant leak.
Check for leak, recover refrigerant, repair leak, replace
filter dryer, evacuate and weigh in proper change.
If pressures are still low and there are no
bubbles in sigh glass. Replace expansion valve and filter dryer.
If high press reads high and low pressure is
ok or high. Check air flow through the unit. If it is low, check filter and ductwork. External static should not exceed 0.5“
Check that air inlet temperatures are not too hot or too
humid.
For AC units, if a hissing noise can be herd
from the reversing valve, feel the check
valve on the small tube from the center port.
If the check valve is hot while running then the reversing
valve is leaking. Shift the unit from heating to cooling
several times and then retest. If it is still hot, replace the
reversing valve.
If high pressure is still high, unit may be
overcharged. Recover refrigerant. Evacuate and weigh in proper charge.
For BKPool-ACTM
7) BKPool-ACTM runs in either dehumidification or cooling mode only but does not
change mode (reversing valve does not shift).
Remove the cover from the thermostat. Turn the temperature setting all the way up then all the way
down. Observe the mercury in the glass bulb. If the mercury does not move from one end of the bulb to
the other, replace the thermostat. If the bulb does not “rock over” at the current temperature, replace the
thermostat.
Remove either wire from the time delay to
keep the compressor from starting. With the
thermostat all the way down, check for 24 V
at the reversing valve coil. Do not run the
BKPoolTM compressor without a cover.
If yes, then the reversing valve coil or the valve itself is
bad.
If no, check the wiring between the thermostat and the
BKPoolTM
If you have voltage to the reversing valve
coil, have someone turn the thermostat up
and down as you listen for a definite "click"
in the reversing valve.
If The valve clicks but does not shift, replace the
reversing valve
If the valve does not click replace the solenoid coil.

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Wiring Schematic BKPool and AC

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Wiring Schematic BKPool AC With Cooling Priority

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AC Only
Wiring Diagram BKPool and AC 208/230V 1 Phase

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AC Only
Wiring Diagram BKPool and AC 208/230V 3 Phase

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Wiring Diagram BKPool AC With Cooling Priority 208/230V 1 Phase