Pressure Control

Liquid Level

Control

Temperature

Control

Glycol Pump

ControlValves

Temperature Controllers

Indirect Thermostat

T12

Negative feedback forlinear output 5 to 30 psi air or

gas supply pressure

Stainless steel housing

Bi-metal sensing elementfor accurate control

Output pressure proportionateto temperature at any setting

Single adjustment overWide temperature range: T 12 -30 to 400oF HT 12 -30 to 700oF

? Direct or Indirect ?

Direct Mode Indirect Mode

Rising Temperature Rising Temperature

Rising Output Falling Output

Direct Indirect

Indirect Thermostat

Indirect

Thermostat with Separable Socket

Maximum Working Pressure

Without Separable Socket 500 psiWith Separable Socket 4000 psiWith Special Separable Socket 7000 psi

Direct Acting Thermostat

T 12DASupply Output

Direct

T 12DA Thermostat

Output

Supply

Indirect

Reversed for Indirect Throttle Mode

High Temperature Thermostat

HT 12Output

Supply

Indirect

Direct Snap Thermostat

T 12S

OutputSupply

Direct

Indirect Snap Thermostat

T 12DASOutput

Supply

Indirect

Indirect Throttle Thermostat

T 12T

Output

Supply

Indirect

Direct Throttle Thermostat

T 12TDA

Output

Supply

Direct

Direct Semi-Throttle Thermostat

T 12DAT

Output

Supply

Direct

Indirect High Temperature Shut-Down

T 12MOutput

SupplyIndirect

Direct Low Temperature Shut-Down

T 12DAM

Output

SupplyDirect

High Temperature Pilot Guard

HT 12PG

Output

Supply

Direct

Typical Installation

High temperatureshutdown thermostat

Burner controlthermostat

Safety shutdown

valve

Burnervalve

Main burner

Pilot

Pilot GuardthermostatInstrument Gas

High temperatureshutdown thermostat

Burner controlthermostat

Safety shutdown

valve

Burnervalve

Main burner

Pilot

Pilot Guardthermostat

Instrument Gas

Low liquid shutdown pilot

Typical Burner Control Installation

Trouble Shooting

SYMPTOM CAUSE

• Erratic temperature changes

•Continuous venting

• Bent sensing element (element should be centered in base and should “ring”)

• Incomplete immersion of probe

•Dirty pilot plug seat•Hole in diaphragm•Weak pilot plug spring•Faulty ‘O’ ring

Trouble Shooting

• To check small seat: increase temperature setting several degrees and see if venting stops.

• To check large seat: decrease temperature setting several degrees and see if venting stops.

• Replace pilot plug and seats if unable to stop venting by cleaning seats.