Feed-Through Terminal Blocks: PA66 vs PBT vs PC Insulation Housing

Selecting an insulation housing for feed-through terminal blocks starts with four checks: CTI, UL 94 rating, moisture absorption, and impact demand.

• PA66: dry cabinets, CTI 600 V, cost balance.

• PBT: humid areas, low moisture uptake, stable spacing.

• PC: impact zones, transparent covers, lower CTI.

Follow this order:

1. Confirm pollution degree and working voltage.

2. Match CTI to creepage distance.

3. Check UL 94 V-0 against the final assembly.

4. Add conductor heat rise to ambient temperature.

Why Housing Material Affects Safety

The housing on a feed through terminal block keeps live parts separated. It contains arcs and holds shape. Three ratings drive the result.

CTI shows surface tracking resistance. UL 94 shows flame behavior. Moisture absorption predicts dimensional drift. Under IEC 60112, CTI 600 V places a material in Insulating Group I. That rating matters for 800 V circuits at Pollution Degree 2.

Low-CTI plastics may form conductive paths in dust and damp air. Plastics with high moisture uptake shift wire entry spacing after thermal cycling.

Material Comparison

PA66 fits dry industrial cabinets, PBT fits humid and washdown zones, and PC fits high-impact and transparent-viewing positions.

Selection by Scenario

PA66 Conditions

🛠️ Panel air stays dry

⚡ Circuit demands CTI 600 V

💰 Cost target favors a proven material

PBT Conditions

💧 Washdown or condensation occurs

📏 Wire entry spacing must stay fixed

🧪 Mild chemicals touch the housing

PC Conditions

🦾 Tools or cable pulls create impact

👁️ Transparent cover aids inspection

🚫 Strong bases and solvents are absent

Matching Housing to Terminal Structure

Tight wire entries on a feed through modular terminal block need low warpage. PBT limits swelling. Multi level terminal blocks need resistance to stacked compression. Glass-filled PA66 holds tier alignment across thermal cycles.

Multi conductor terminal blocks face deformation risk at adjacent openings. Dimensional stability outweighs raw impact strength in that layout. Feed through terminals in washdown panels also need low moisture uptake to keep clamping force steady.

A Practical Case

A block rated 800 V for 10 mm² conductors, similar to the JHD5-10 layout, uses a lifting cylinder clamp. A humid food-processing cabinet points to PBT. A standard machine cabinet points to PA66. A forklift or tool-traffic zone points to PC.

Verification Checklist

1. Match CTI to pollution degree.

2. Confirm UL 94 V-0 for the finished assembly.

3. Check moisture uptake against the washdown process.

4. Add conductor heat rise to ambient temperature.

5. Run thermal cycling on prototypes before production.

FAQ

Q: Does CTI 600 V suit 800 V circuits?
A: Yes, at Pollution Degree 2.

Q: Does glass fibre lower tracking resistance?
A: It may raise surface roughness. Choose a high-CTI grade.

Q: Can PC go outdoors?
A: Only UV-stabilized grades resist sunlight.

Q: How does housing material affect derating?
A: Low thermal conductivity traps heat. PC needs a higher derating factor than PA66 or PBT.

Q: What wall thickness keeps creepage distance at 800 V?
A: Many blocks use 1.5 mm minimum walls after thermal aging.

Model	Function	Wire IEC cross-section	Wire UL	Thickness	Maximum current	Number of packages	Thickness/Height()/Width mm	Rated voltage/rated current/rated cross-sectior
JHD5-10		10 mm² 6 mm² 10 mm²	6 AWG 10 AWG 6 AWG	10.2 mm	57 A	60	10.2/47/42.5	800 V/57 A/10 mm²

Specfication: 

End cover	D2.5-10
Cross-connection 10-Polo,Separable	ZL2-10 ZL3-10 ZL10-10
Insertion bridge 10-Polo,Separable	BLS2-10 BLS3-10 BLS10-10
Partition plate	FP
Small Partition	CP
Marking tags	ZB10
Screw/Tightening torque(Nm)	M4/1.2
Material	PA
Flame retardant rating UL-94	V0
Dimensions

With universal mounting feet for standard top-hat(Ω profile) and G-profile DIN rail mounting.