Sign up to receive our special offers direct to your inbox. If you have a slightly leaking radiator, if your system is having an intermittent fault, or not working up to standard, t&s offers booked engineer appointments from monday to friday in either morning or afternoon slots. As a general rule, the price of combi boilers. Find local, recommended boiler & heating engineers. Q = rate of steam flow in kg/h. The information in this section is.