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Yes, You Can Still Use HPS! A Guide for Small-Scale & Budget Growers

Small grow tent with HPS light

While LED technology has gained popularity, High Pressure Sodium (HPS) lighting remains a viable and cost-effective option for small-scale and budget growers. This guide shows you how to successfully implement HPS lighting in smaller spaces like 4×4 tents, even for growing vegetables like tomatoes and peppers.

Making HPS Work in Small Spaces

Heat Management: The Critical Factor

The primary challenge with HPS in small spaces is heat management. Here's how to address it effectively:

  • Proper Ventilation: Install an extraction fan rated at least 2x the volume of your tent per minute (e.g., for a 4×4×6 tent = 96 cubic feet, use a minimum 200 CFM fan)
  • Air-Cooled Hood: Use a reflector with built-in cooling to extract heat directly from the light
  • Intake Air: Ensure cool air can enter from the bottom of your tent
  • Temperature Monitoring: Install thermometers at canopy level to track temperatures
  • Strategic Timing: Run lights during cooler periods (night) if possible

Heat Warning

For a 4×4 tent, consider using a 400W or 600W HPS rather than a 1000W to reduce heat load. A 600W HPS provides excellent coverage for a 4×4 space while generating manageable heat.

Light Distribution in Small Spaces

Ensuring even light distribution in a small area:

  • Center Positioning: Mount the light in the center of your grow space
  • Adjustable Height: Use adjustable hangers to optimize distance from plants
  • Wide Reflector: Choose a reflector designed for even distribution in smaller spaces
  • Light Mover (Optional): For maximum efficiency, consider a light rail system to move the light across the canopy

Budget-Friendly HPS Setup for Small Spaces

Essential Components

A complete budget-friendly HPS setup for a 4×4 space includes:

  • 600W HPS Bulb: £30-40 (Philips Son-T Agro or similar)
  • Digital Ballast: £80-120 (dimmable if possible)
  • Air-Cooled Reflector: £50-70
  • Extraction Fan: £60-100 (minimum 200 CFM)
  • Ducting & Clamps: £20-30
  • Timer: £10-15
  • Total Approximate Cost: £250-375

This setup provides excellent value compared to equivalent output LED systems, which typically start at £400-500.

Money-Saving Tips

  • Second-hand Equipment: Look for used ballasts and reflectors (replace bulbs when buying used)
  • Dimmable Ballast: Allows you to run at lower power when full intensity isn't needed
  • DIY Reflector: Simple DIY reflectors can be made for vegetable growing
  • Off-Peak Electricity: Run lights during cheaper rate periods if available

Growing Vegetables Under HPS

HPS lights are excellent for growing fruiting vegetables like tomatoes and peppers, which benefit from the red-dominant spectrum:

Tomatoes Under HPS

  • Light Height: 18-24 inches above canopy
  • Light Duration: 16-18 hours for vegetative growth, 12 hours when fruiting
  • Temperature: Aim for 21-26°C (70-80°F) during the day
  • Varieties: Compact/determinate varieties work best in small spaces

Peppers Under HPS

  • Light Height: 18-24 inches above canopy
  • Light Duration: 16-18 hours for vegetative growth, 12 hours when fruiting
  • Temperature: Aim for 21-29°C (70-85°F) during the day
  • Varieties: Compact varieties like Hungarian Hot Wax or Cayenne work well

Vegetable Growing Tip

For vegetable growing, you can often run your HPS at a lower intensity (if using a dimmable ballast) during the vegetative stage, saving electricity while still providing adequate light.

Practical Setup Guide for a 4×4 Tent

Step 1: Ventilation Setup

Install your extraction fan at the top of the tent, connected to ducting that exhausts outside the growing area. Ensure there are intake openings at the bottom of the tent for fresh air.

Step 2: Hanging the Light

Mount the air-cooled reflector in the center of the tent using adjustable hangers. Connect ducting from the reflector to the extraction fan to remove heat directly from the light.

Step 3: Ballast Placement

Place the ballast OUTSIDE the tent if possible to reduce heat inside the growing area. Ensure it has adequate ventilation and is not covered.

Step 4: Timer Setup

Connect the ballast to a timer and set your desired light schedule. For vegetables, start with 18 hours on / 6 hours off during vegetative growth.

Step 5: Temperature Monitoring

Place thermometers at canopy level and near the top of the tent. Monitor temperatures regularly, aiming to keep them below 28°C (82°F) at the canopy.

Troubleshooting Common Issues

Excessive Heat

  • Increase extraction fan speed
  • Add additional cooling (intake fan, portable AC)
  • Raise light height temporarily
  • Consider running at lower wattage if using a dimmable ballast

Light Burn on Plants

  • Increase distance between light and canopy
  • Ensure adequate airflow across the canopy
  • Consider light training techniques to maintain even canopy height

Uneven Growth

  • Rotate plants periodically
  • Consider a light mover for more even distribution
  • Use training techniques to maintain an even canopy

The Bottom Line

HPS lighting remains a viable and cost-effective option for small-scale growers, particularly those on a budget. With proper heat management and setup, you can achieve excellent results growing vegetables like tomatoes and peppers in spaces as small as a 4×4 tent. The initial cost savings compared to LED can be significant, making HPS an attractive option for those just starting out or growing on a limited budget.

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