nathanael engine was running at the time . as we drove from my mates to a area he works then back to his house to see what temps were like . on arrival at area he cleans temp had got to 14 degrees . on return it had got to 30 degrees . which over 45 minutes i dont think was bad result .the reason we worked on 45 minutes was that the first time i seen this in action in sheffild was the person i spoke to said it roughly took him 45 minutes to get to his jobs .