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Controller for Temperature Difference

Differential Thermostat

Model series DSDP-4PB
With 2 external temperature sensors
Models for 120Vac, 208-250Vac, 
12V and 24V AC/DC
Output load : up to 60 Amp / 250Vac.
Optional Remote Control + Display Panel
Temperature range: -40F (-40C ) to 255F ( 124C )
Higher ranges available up to 960F ( 515C )
Differential range: 0 to 99 F ( 55 C ) 
Programmable Sequence of operation

Temperature Difference Thermostat mounting in 3-gang box

8 push-buttons:
2. STEP ( display scroll ) 
5. MENU ( settings )
6.  AUX1 ( relay 1 control )
7.  ​AUX2 ( relay 2 control )
8.  ​AUX3 ( relay 3 and 4 control )

Programmable Temperature Difference Control DSD-4PB face plate

Installation example 
in 3-gang wiring box

Metal Face
Dim's:  6.5" x 4.5" x 0.3"
165mm x 115mm x 8mm

Black or Custom
labels available

Programmable setpoints for Sequence Algorithm:

  • HOT = Overheat temperature Limit
  • Hi.L =  High temperature Limit
  • Lo.L =  Low temperature Limit
  • ICE =  Freeze temperature Limit
  • d.Hi = Maximum Temp. Difference setting
  • d.Lo = Minimum Temp. Difference setting
  • d.Cn = Center (middle ) Temp. Difference

Programmable Control of Outputs:

  • High Power relay 1 control ( 30 Amp )
  • High Power relay 2 control ( 30 Amp )
  • Medium Power relay 3 control ( 10 Amp )
  • Medium Power relay 4 control ( 10 Amp )
  • Control at Overheat Limit
  • Control at Freeze Limit
  • Control at Difference Lower/Higher


Differential Thermostat for Ventilation

Attic Ventilation

Difference Thermostat as ven​tilation controller

Great energy savings can be achieved when using the DSDP-4PB temperature difference controller.
  The control is set to mainain a preset difference ( differential ) between the outside and inside temperatures. Either uni-directional or bi-directional fan can be used. 
  For instance; air from outside is automatically pumped IN or air from inside is pumped OUT in order to keep the inside within a certain range, as compared to the outside temperature.
  The programmable Upper and Lower temperature limits make sure that the inside is never too hot or too cold.
  This automatic control prevents the humidity condensation and thereby any buld up of mold or fungus is avoided.

DSDP-4PB thermostat for control of solar heating system with two pumps, boost heater, valve and heat exchanger
DSDP-4PB thermostat 
in simple solar heating system
DSD-4 Temperature Difference Thermostat for solar heating system Thermostat for solar heating system
Energy Saving DSDP-4PB programmable difference thermostat to control solar heating systems

DSDP-4PB Programmable Differential Thermostat is capable of controlling simple, as well as most expanded solar heating systems.
  Programmable sequence of operation, programmable temperature difference range and programmable limits like Overheat, High Limit, Low Limit and Freeze Protection, assure efficient solar heat recovery.
  Up to three temperature sensors and four powerful on-board relays can be used to satisfy variety of configurations. High power switching capabilities allow for direct control of Pumps, Valves and Heaters.
  DSDP-4PB Differential Thermostat can accept variety of temperature sensor probes that can be wired up to 500 ft ( 150 m ) away, using any standard inexpensive cable.
  This maintenace free, self calibrating controller allows for reliable, 100% duty, automatic operation without supervision.
  Programmable Upper and Lower temperature limits can keep the system safe from temperature extremes like overhating or freezing, as well as provides low temperature, low efficiency system protection.

DSD-4 Differential Thermostat semi flush mount with remote panel
Semi-Flush face temperature difference control
installation in wall or panel
with optional remote panel
Temperature Sensor Probes
Temperature Controller sensor probes DSD-4 Differential Thermostat flush mount with remote panel
Flush face temperature dufference control
installation with optional remote panel

Example of available models
Wiring e​xtendable
up to 500 ft ( 150M)

Temperature Sensor Protection
Mounting Guard for Temperature Sensor probes Remote Start - Stop button and light Temperature Sensor with flange

Optional Plate-Guard
for standard sensor probes
Plastic model PPP-4
and SS model PPS-4

Plastic guard for temperature sensor probes
Remote START - STOP button
with LED indicator

Optional Plastic Guard
for standard sensor probes
Model PG-5

Temperature Sensor
with Flange

Temperature Difference Controller​ wiring examples

Download more DSD-4 Wiring Examples

DSD-4 Temperature Difference Controller extended wiring with contactor DSD-4 Temperature Difference Controller basic wiring for up to 2 x 30Amps

Basic DSD-4PB wiring
for loads up to 2 x 30 Amps

Extended DSD-4PB wiring with contactor
for very high loads

DSD-4 Temperature Difference Thermostat extended wiring for up to 60 Amps DSD-4 Temperature Difference Controller wiring for up A-C and Heater

Extended DSD-4PB wiring
for loads up to 60 Amps
and with extra relays for light, fan or other

Simple DSD-4PB wiring
for loads up to 2 x 30 Amps
 like A/C and Heater


DSD-4PB Difference Thermostat Specifications

DSDP-4PB is a digital Temperature Difference Controller ( differential thermostat ) designed for applications based on a difference of temperatures rather than an absolute temperature level. However, it is capable of controlling absolute temperature levels as well.
The controller has an internal, accurate, programmable thermostat processor, that is self-calibrating and does not require any maintenance or adjustments.
The internal, programmable sequence processor allows the user to schedule a specific order of events, as necessary for the application. 
Standard models have two on-board, high power relays with contacts rated for up to 30Amp, 250Vac load max. each. 
Optionally an internal alarm buzzer or up to two additional on-board relays can be ordered for special applications to control loads of up to 10Amp, 250Vac max. each.
The high power and the optional relays' contacts can be wired up to control Heaters, Chillers, HVAC and other loads like a Fan, Motor, Valve, Solenoid, Pump, etc...
All relays' contacts can be wired up as completely isolated from the controller's supply, so the supply voltage can be different than the voltages on the loads.
In order to switch very high loads, the relays' contacts can be wired up to control the coils of external contactors.
An additional, dry contact input can be ordered for external ON/OFF control switch or other applications, like for instance a water level sensor switch.
Also, an additional, low voltage output can be ordered for max. load of up to 30mA, 5Vdc, for instance to connect to an external LED indicator lamp.
The controller is operated and the set points are preset by pressing the corresponding keys on the control panel face. All preset values are stored in internal memory.
A variety of the controller's operating features, configurations, temperature ranges and limits are also programmable via the face plate keys.
The 6-digit LED display shows the current temperature readings, the preset values, the status of the relays and other indications of operation. The LED display can be ordered in RED, GREEN or BLUE color.
Another option is an external Remote Control and Display Panel ( DSDPR-4PB ) that can be connected to the main panel via a 4- or 2-conductor cable up to 500 ft ( 150M ) away.
Note, that the DSD-4PB controllers are designed to eliminate almost completely the EMF ( Electro Magnetic Field ) radiation.