Resideo (Honeywell) TMX-00039 Thermostatic Power Element – R404A, MOP −10 °C, Balanced Port, PS 34 bar

Resideo (Honeywell) TMX-00039 is the upper body (thermal head / power element) of TMX series thermostatic expansion valves. It is gas-charged for R404A with MOP −10 °C pressure limiting.

Change the Charge Type Without Removing the Body — Power Element Sold Separately

The TMX series is modular: the valve consists of three parts — the power element (this product), the base (TMXL solder / TMXB flare) and the interchangeable orifice cartridge. The base stays connected to the line; if the charge type or MOP value is to change, only the power element is removed and replaced.

In practice this means: when the application changes to R404A or moves to a low temperature band, the character of the valve can be changed without cutting the line, without brazing and without recovering refrigerant. Operation continues with the same base and orifice.

What MOP −10 °C Does

MOP (Maximum Operating Pressure) does not allow the suction pressure to rise above the set value. During commissioning, start-up after defrost and hot pull-down, the suction pressure rises rapidly; the motor is loaded above its design current. A valve with MOP throttles the flow at that moment and protects the compressor.

In this model the MOP is −10 °C, and according to the official table it operates in the −10 °C … −50 °C evaporating band — a low temperature application: freezers, blast freezing, low temperature cold rooms.

Technical Specifications (Official Resideo Product Data EN0H-1904GE23)

• Model: Resideo (Honeywell) TMX-00039 | Type: TMX series power element (thermal head)
• Refrigerant: R404A (R507A in the same charge band)
• Charge: damped gas charge, pressure limiting — MOP −10 °C
• Evaporating range: −10 °C … −50 °C
• Max. pressure (PS): 34 bar(a) | Test pressure (PF): 37.4 bar(a)
• Capillary tube: 2 m | Bulb diameter: 16 mm
• Static superheat: approx. 3.5 K (factory setting)
• Max. ambient temperature: 100 °C | Max. bulb temperature: 140 °C (gas charge)
• Equalization: external equalization, integrated in the valve body — separate equalizer connection 7/16" UNF
• Body: balanced port — capacity stays constant even if the condensing pressure changes
• Material: body and base brass · thermal head and diaphragm stainless steel (welded under protective gas)
• Weight: approx. 0.60 kg
• Nominal capacity band (series): 17.0 … 75.1 kW (under R22 conditions)

Compatible Bases and Other MOP Options

Bases: TMXL — solder base, straight-through (D) or angle (W) design · TMXB — flare base, straight-through. The base and orifice cartridge are not included with this product and are ordered separately.

• 🚨 Critical rule for gas-charged MOP valves: Resideo's own note — the bulb must always be COLDER than the capillary tube and the thermal head. In the TMX series this condition is structurally met because the thermal head is warmed by the liquid refrigerant; still, do not insulate or cool the head.
• 🔧 Mounting position is free — the valve can be mounted in any position.
• 🔧 Bulb placement: on the upper half of the horizontal suction line, never after a liquid trap. The bulb must always be insulated; otherwise the ambient temperature distorts the reading.
• 🔧 The external equalizing line must be 6 mm or 1/4" in diameter and connected after the bulb. Leave a bend (overbow) so that oil does not enter the equalizing line.
• Superheat adjustment: the factory setting is calibrated for the lowest superheat and best evaporator utilization — do not touch it unless necessary. If adjustment is needed: clockwise = flow decreases, superheat increases. One full turn changes it by approx. 0.3 bar.
• ⚠️ Do not cool the base with water after brazing — sudden cooling cracks the body.