Danfoss RT107 Capillary Thermostat

Posizionamento del prodotto: Remote bulb capillary thermostat of RT series for industrial use, ripristino automatico, SPDT contacts. Applied for temperature control / overtemperature protection of industrial equipment, boilers, compressor discharge, marine equipment and ovens, with adjustable differential.

✅ Core Specifications

Note for charging type: Partial charge. The sensing bulb must be the coldest point in the whole system, otherwise temperature drift or false tripping will occur.

📌 Typical Applications

1. Discharge overtemperature protection for screw compressors (widely used in refrigeration industry), triggers liquid injection cooling solenoid valve when overtemp.
2. Controllo della temperatura & overtemperature alarm for industrial boilers, thermal oil heaters and ovens.
3. Monitoring of marine engine rooms, heat exchangers and hydraulic oil temperature.
4. Interlock temperature control for HVAC and heat pipelines.

🛠️ Installation Instructions

1. The sensing bulb shall fully adhere to the pipe wall / thermowell for good thermal conduction; thermowell is recommended.
2. Raggio minimo di curvatura del capillare ≥50mm. Hard bending, squeezing are prohibited. Once ruptured, internal filling medium leaks and thermostat fails permanently.
3. Installation rule: Temperature of sensing bulb must be lower than thermostat housing (mandatory requirement for partial charge type).
4. Cablaggio: Pg13.5 cable gland must be fitted to maintain IP66 protection.
5. Regolazione: Main knob for set temperature; side nut for differential adjustment (ON/OFF temperature gap).

⚠️ Common Troubleshooting

1. No action at set temperature: Capillary rupture & perdita; loose bulb mounting; filling medium failure.
2. Ciclismo frequente: Too small differential; improper bulb location (housing hotter than bulb).
3. Large temperature deviation: Ambient disturbance on long capillary; poor thermal contact of sensing bulb.

📋 Comparison within the Series (for Model Selection)

RT101: 25~90℃, medium-low temperature

RT107: 70~150℃ (questo modello)

RT123: 150~250℃, alta temperatura

🧩 Alternative Options

Alternative domestiche: capillary thermostats with identical construction, match requirements: intervallo di temperatura, adjustable differential, SPDT contacts, Grado di protezione IP.

Import alternatives: Jumo, SOR temperature switches.

RT107 Standard vs RT107E Intrinsically Safe Explosion-proof Version

RT107E = Explosion-proof variant of RT107. Stesso intervallo di temperature, bulb and capillary structure. Core differences in explosion safety, contact material, ambient temperature and certifications.

Identical Basic Parameters

Intervallo di temperatura: 70 ~ 150 ℃

Differenziale: 6 ~ 25 ℃ adjustable

Sensing bulb: Φ9.5×110mm, partial charge

Capillary options: 2M / 8M

Modalità di ripristino: Ripristino automatico

Modulo di contatto: SPDT Single-Pole Double-Throw

Massimo. bulb temperature: 215 ℃

Grado di protezione IP: IP66

Tabella di confronto chiave

⚠️ Critical Engineering Notes

1. RT107E is Ex ia intrinsically safe type, must be wired with intrinsically safe barrier in IS loop. Cannot directly connect to 220V AC power; standard RT107 can directly drive AC solenoid valves.
2. Sensing bulb and capillary are NOT explosion-proof: If bulb/capillary are installed in hazardous zone, risk assessment is required. RT-E certification only covers thermostat housing.
3. Same mechanical adjustment structure: Set temperature and differential adjustment are identical. Installation must comply with the rule: bulb is the coldest point of the circuit.
4. Replacement Warning: RT107 cannot directly replace RT107E installed in explosion hazardous area. Al contrario, RT107E can be used in non-explosive areas but with higher cost and limited low-current contacts.

Guida alla selezione rapida

Ordinary machine room without flammable medium → RT107, conveniente, direct load driving

Ammonia refrigeration plant, oil/gas, flammable solvent environment, Zone1 hazardous area, only temperature switch signal → RT107E plus IS barrier

Danfoss RT107E (Ex ia IIC T6 Intrinsically Safe Thermostat) Installation Specification

Importante: Only the housing of RT107E is intrinsically safe. Capillary and sensing bulb have no explosion protection. Full installation shall comply with EN60079-14 explosion-proof installation standard, only for IS circuit, 220V high voltage connection is strictly forbidden.

1. Thermostat Housing Mounting
2. Metodo di fissaggio

Remove front cover and mount by 2 holes on housing via screw mounting (parete / panel mount). Mounting orientation arbitrary. Add shock absorber pad for heavy vibration sites to reduce impact on contacts.

2. Condizioni ambientali

Housing ambient temperature: -20℃ ~ +65 ℃ (lower upper limit than RT107 standard version). Housing can be installed in Zone1/2 hazardous area.

Outdoor installation needs rain shield to avoid direct rain splash.

3. Ingresso cavi (Pg13.5)

Comes with Pg13.5 explosion-proof cable gland. Matching gland must be used to maintain IP66. Unused cable entry must be sealed with metal blank plug.

Applicable cable OD:6~14mm; minimo. wire cross-section:0.75mm². Terminal with earth terminal, housing must be reliably earthed.

Cablestrain relief required; pulling force shall not transfer to terminals.

2. Capillary and Sensing Bulb (Critico! Partial Charge Bulb)

RT107E partial charge mandatory rule: Sensing bulb must be the coldest point in the whole capillary circuit, otherwise temperature drift and false tripping.

1. Capillary Handling

Minimum bending radius ≥50mm. Repeated sharp bending, squeezing, flattening forbidden. Capillary permanently damaged once medium leaks.

Uncoil slowly, do not pull hard at capillary root (most fragile point at thermostat outlet).

Capillary routing avoid friction with sharp edges. Loose fastening with cable tie allowed. Do not clamp and flatten capillary.

2. Two installation methods for sensing bulb

① Pipe surface clamping installation (common for compressor discharge)

Use metal clamp to ensure full cylindrical contact between bulb and pipe wall. Derust contact surface, thermal grease can be applied. Do not leave bulb suspended.

Insulation wrapping recommended to isolate ambient air interference.

② Thermowell installation (thermal oil, fluid chamber)

Select thermowell with matching inner diameter (well length ≥112mm). Insert bulb fully to well bottom. Thermowell can be filled with thermal oil.

Accessori opzionali: Bulb pocket / capillary stuffing box.

3. Explosion reminder for bulb area

RT107E explosion certification only covers thermostat housing. Capillary and bulb without explosion enclosure.

If bulb is placed in hazardous area, assess ignition risk from medium and surface temperature. Surface temp＞80℃ needs separate hot surface ignition assessment.

3. Electrical Installation (Most critical for Explosion Protection)
4. RT107E gold-plated SPDT contacts only for intrinsically safe circuit. Circuit must use certified Zener barrier installed in non-hazardous area.
5. Circuit capacitance Ci=0.5nF, barrier parameters must match IS energy limitation, barrier cannot be omitted.
6. Cablaggio: SPDT 3 terminali, terminale 1/2/4; terminale 38 for earthing. Reliable protective earth of housing.
7. Cablaggio: Separate routing for IS cable and non-IS cable, no sharing of conduit. IS cable shield single-point earthing.
8. Installer: Must hold qualification for installation in explosive hazardous area, final inspection required after completion.
9. Commissioning Steps after Installation
10. Verify mechanical fixing, capillary free of squeezing/bending, bulb well contacted.
11. Verify IS barrier, earthing and cabling fully comply with explosion standard.
12. Open cover: main knob for set temperature; side nut to adjust differential.
13. Refit front cover, seal with lead seal if needed (anti-tamper).
14. Installation Prohibition List

❌ Do not install thermostat housing at higher temperature than sensing bulb (partial charge characteristic, malfunction)

❌ Capillary bending radius too small, flattening or sharp fold

❌ Direct connection of RT107E to AC220V solenoid / contattore (contact burnout, loss of explosion safety)

❌ Omission of Pg13.5 gland or metal blank plug, loss of IP protection

❌ IS cable and power cable routed in same trunking without separation

❌ Suspended bulb without thermal contact

6. Installation Difference: RT107E vs RT107
7. RT107: Non-explosion-proof housing, can directly drive high-power load, max housing ambient 70℃
8. RT107E: Intrinsically safe housing, must use IS barrier for weak signal loop, max housing ambient 65℃. Same mechanical requirement for capillary & bulb, but stricter rules for explosion-proof cabling, earthing and zoning.

Danfoss RT Series Capillary Thermostat Full Model List

Nota: Suffix E = Intrinsically Safe Explosion-proof Version Ex ia IIC T6. E-version shares temperature range, bulb dimension with standard model, difference only on explosion circuit, contact and ambient temperature. All with SPDT contacts, IP66 (some manual reset types IP54). Capillary options:2m/5m/8m; order code suffix defines capillary length.

✅ Low Temperature Range (Refrigerazione & Cold Storage Unit)

✅ Medium & High Temperature Range (Compressor Discharge, Thermal Oil Heater, Focus Models)

✅ Intrinsically Safe E-Series List (Ex ia IIC T6, Zone1/2)

Installation note: Only housing explosion-proof; capillary and bulb without explosion protection. Must be fitted with IS barrier, weak signal circuit, high power load direct drive forbidden.

|RT9E|-45 ~ -15|RT9|150|

|RT14E|-5 ~ 30|RT14|150|

|RT101E|25 ~ 90|RT101|300|

|RT107E|70 ~ 150|RT107|215|

|RT123E|150 ~ 250|RT123|300|

📌 Key Model Selection Rules

1. Partial charge (unique for RT107): The sensing bulb must be the coldest point of the whole circuit, otherwise drift and false trip. RT101/RT123 use A/C charge with different rules.
2. Reset option: Most auto reset; manual reset Max version available for safety interlock (latch after overtemperature, manual unlock).
3. Capillary length defined by order code, example RT107: 017-513566=2m; 017-514466=8m; RT107E:017-515366=2m.
4. Suffix L: Long bulb version for thermowell mounting.

📎 Quick Application Filter

Freezer low temperature: RT9, RT13

Compressor discharge protection (≤90℃): RT101 / RT101E

Screw compressor discharge 70~150℃: RT107 / RT107E

Thermal oil furnace, high temp exhaust 150~250℃: RT123 / RT123E