Stephen Day profile photo

Stephen Day

Gas Safe Engineer at iHeat

Stephen Day is a Gas Safe registered and FGAS certified engineer with over 20 years of hands-on experience in the heating, cooling, and renewable energy industry, specialising in boiler installations, air conditioning, and heat pump systems.

LinkedIn

About Stephen Day

Stephen Day is a Gas Safe registered and FGAS certified engineer with over 20 years of hands-on experience in the heating, cooling and renewable energy industry.

Throughout his career, Stephen has designed, installed and maintained thousands of systems across homes and businesses in the UK. His background on the tools, combined with his directorship role at iHeat, gives him a rare understanding of both the technical and operational sides of the industry.

He has helped to secure Which? Trusted Trader accreditation all with a focus on delivering great service and long-term value for customers. He also writes for the iHeat blog, sharing practical advice and explaining heating topics in plain, helpful language.

Stephen continues to stay up to date with the latest heating technologies, building regulations and low-carbon innovations.

Gas Safe ID: 5910722

Expertise

  • Boiler systems and installation
  • Heat pumps and hybrid heating systems
  • Gas safety and compliance
  • System design
  • Renewable and low-carbon technologies
  • Technical training


Articles by Stephen Day are reviewed by iHeat’s technical team for accuracy and reliability.

Stephen Day's latest articles

Heat Pump Repair - 2026 Guide

29th September, 2026 Guides

Heat Pump Repair - 2026 Guide

Help for when your heat pump is not working properly.

read article arrow Read Article
What Size Air Source Heat Pump Do You Need?

29th September, 2026 Guides

What Size Air Source Heat Pump...

Air source heat pumps (ASHP) are popular for providing efficient heating solutions. These...

read article arrow Read Article
Viessmann F4 fault code: what it means and what to do

29th September, 2026 Guides

Viessmann F4 fault code: what...

A Viessmann F4 fault can indicate an ignition or flame-related problem, but its exact mean...

read article arrow Read Article
Vaillant F23 fault code: what it means and what to do

29th September, 2026 Guides

Vaillant F23 fault code: what...

The Vaillant F23 fault code means the temperature difference between the boiler's flow and...

read article arrow Read Article
Vaillant Boiler Not Working, No Fault Code

29th September, 2026 Guides

Vaillant Boiler Not Working, N...

If your Vaillant boiler isn't working but shows no fault code, check the power, heating co...

read article arrow Read Article
Glow Worm F1 Fault

29th September, 2026 Guides

Glow Worm F1 Fault

The meaning of a Glow-worm F1 fault depends on your boiler model, so check your model's ma...

read article arrow Read Article
Glow Worm Boiler Not Firing Up No Fault Code

29th September, 2026 Guides

Glow Worm Boiler Not Firing Up...

If your Glow-worm boiler isn't firing up and shows no fault code, check the power, heating...

read article arrow Read Article
Baxi Boiler Not Working, No Error Code

29th September, 2026 Guides

Baxi Boiler Not Working, No Er...

If your Baxi boiler isn't working but shows no error code, start by checking its power sup...

read article arrow Read Article
Baxi Boiler E125 Error Code

29th September, 2026 Guides

Baxi Boiler E125 Error Code

The Baxi E125 error code indicates a water circulation fault. Check the boiler pressure fi...

read article arrow Read Article
Potterton Boiler Flashing Green

29th September, 2026 Guides

Potterton Boiler Flashing Gree...

A flashing green light on a Potterton boiler does not always indicate a fault. Its meaning...

read article arrow Read Article
Common Worcester Bosch Boiler Error Codes

29th September, 2026 Guides

Common Worcester Bosch Boiler...

Worcester Bosch fault codes help identify why your boiler has stopped working. Their meani...

read article arrow Read Article
Home EV Charging Costs

29th September, 2026 Guides

Home EV Charging Costs

Electric Vehicle (EV) chargers are quantified by their power output in kilowatts (kW). Ele...

read article arrow Read Article